Saturday, January 16, 2021

Pilot Report: 737 MAX Return to Service Simulator Ride

It has been nearly two years since the 737 MAX was grounded in the aftermath of several crashes. After the redesign of a flight control system, the aircraft has been re-certified by the US FAA and EU EASA and is returning to the skies. Several US and international airlines have already returned their MAX aircraft to scheduled service with others to quickly follow.

One of the requirements for the return to service of this aircraft is that pilots undergo a training session in a simulator. The purpose of the sim ride is to familiarize pilots with the behavior and possible failure modes of various flight control and indication systems. The ride included demonstrations of the normal function of the speed trim system (STS) and Maneuvering Characteristics Augmentation System (MCAS) during a stall and failure scenarios of angle of attack (AOA) and airspeed indicators. Runaway stabilizer trim malfunctions and flight with manual trim were also included. Failures of the MCAS subsystem, which is unique to the MAX, were implicated as contributing causes in two crashes prior to the aircraft being grounded.

Preparation for the ride included an extensive computer based refresher course on MAX systems and procedures and a detailed pre-brief on the planned simulator training events. Flight in high fidelity flight simulators is considered equivalent to flight in an actual aircraft, but superior as a training device as many maneuvers and failure scenarios can not be safely accomplished in an aircraft. That said, the devices cost tens of millions of dollars and training time is scarce and valuable. My airline has procured nine MAX simulators for the purpose of re-qualifying all their pilots in as short a time as possible.

Stabilizer Trim: What Is It?

The events surrounding the grounding of the MAX center on the stabilizer trim system. I am going to attempt to keep my explanations in reach of a general audience with some basic understanding of the dynamics of flight. There are many online resources available for those who wish for a more in depth explanation of aerodynamics.

The horizontal wing on the tail of a conventional aircraft is known as the horizontal stabilizer (stab). The elevator is attached to the back of the horizontal stabilizer and is a primary flight control. It moves to change the pitch of the aircraft. The horizontal stabilizer itself also moves a bit to “trim” the aircraft for a particular airspeed. Change the speed of the aircraft, and the trim will need to be changed to prevent the pilot (or autopilot) from having to hold constant force on the controls. A pilot can release the controls of a well-trimmed aircraft without it wanting to climb or descend. This condition is also the most aerodynamically efficient configuration resulting in a smaller fuel burn.

On the 737, stab trim is normally controlled electrically by switches on the control column which are activated with the thumb. The switches (two for redundancy) control an electric motor which spins a large wheel next to the pilot’s knee on the center stand. This wheel is mechanically connected to a jack screw which physically moves the stab. The motor has two speeds determined by flap position. The slow speed is used for flaps up and the fast speed activates when the flaps are extended. This wheel also serves as a manual crank to be used if the electric motor fails. Accidentally leaving the crank handle extended is a self-critiquing error as the handle hurts like heck when it hits your knee (so I’ve been told).

It is impossible to miss this wheel turning as it has stripes painted on it. While flying manually (without the autopilot), the pilot will use the thumb switches to activate the electric trim, but when the autopilot is engaged, the autopilot keeps the aircraft in trim using the same system. Therefore, the trim wheel will be seen moving on occasion in automatic flight as the autopilot adjusts the trim.

Starting in the 80s on the “Classic” version of the 737 (models 300 through 500), Boeing introduced a trim subsystem known as “speed trim”. Speed trim would operate in manual flight under certain conditions should the aircraft deviate from the trimmed airspeed. As mentioned above, trim correlates to airspeed. This system would make trim inputs in opposition to any speed deviation to encourage a return to the originally trimmed airspeed. The important thing to note here is that the trim wheel might now be seen moving in manual flight un-commanded by the pilot.

MCAS: What Is It?

MCAS or Maneuvering Characteristics Augmentation System, is another trim subsystem which was introduced on the MAX aircraft. It was found during certification of the MAX that the aircraft had some unwanted handling characteristics when approaching a stall. Specifically, just before stall entry, and well below any normally encountered airspeed, control column pitch forces became lighter when they are required by certification rules to become heavier. MCAS was designed to run the trim forward under these specific conditions to counter this tendency. It uses the high speed rate of the trim motor regardless of flap position. 

Why did the MAX handle differently than its predecessors? The aerodynamics is complex, but the larger engines on the MAX had to be placed further forward on the wing to ensure ground clearance. This and other design factors likely caused the handling differences. This is the source of some controversy about whether the MAX should have been given a separate type certificate, but reviewing that subject is not the purpose of this report.

One point I’d like to make about flight control augmentation systems in general is that they are ubiquitous and date back to the 1950s. The existence of an augmentation system does not ipso facto indict the underlying design, but rather is an engineering solution that enhances the flight characteristics of nearly all modern high performance aircraft. I have experience flying aircraft which were virtually un-flyable without augmentation. Even fly-by-wire aircraft flight control systems, which are common today, can be thought of as augmentation systems with 100% control authority.

Lastly, the most important part of the entire electric stab trim system is that it can be deactivated at any time through the use of two stab trim cutout switches located on the center stand directly behind the throttles. These switches remove power from the electric trim system and all subsystems including speed trim, autopilot trim, and MCAS. Following deactivation, the aircraft can still be trimmed by manually cranking the trim wheel.

The MAX Return to Service (RTS) Simulator Ride

The simulator session was scheduled for a two hour training event preceded by a one hour pre-brief. The session was designed to cover both normal and non-normal flight profiles. The normal profile included a demonstration of the speed trim system on a routine departure and the expected annunciations and flight control behavior during an approach to stall. 

The non-normal profiles demonstrated trim system failures and angle of attack (AOA) and airspeed indicator failures. The trim system failures included the use of the Runaway Stabilizer non-normal checklist and immediate action items, and subsequent flight using only manual trim. The AOA and airspeed failure profiles were designed to replicate the startle effect and confusion that can manifest from multiple annunciations and aural warnings during this type of malfunction. Subsequent use of the Airspeed Unreliable non-normal checklist and known pitch and power settings were required.

The simulator used was a CAE 7000XR series high fidelity simulator with full motion and daylight wrap-around visuals. All of the training events were flown from SeaTac airport in VFR conditions. The sim was initialized for takeoff on RWY 16L with all preflight items having been accomplished. I was paired with a line first officer for the training event.

Speed Trim Demonstration

A normal takeoff and RNAV departure to 10,000 ft were accomplished. During the climb in manual flight, deviations from trimmed flight were purposely introduced through the use of increased or decreased pitch inputs on the control column. The speed trim system was then observed to make trim inputs opposite of the speed deviations to encourage the aircraft to return to its originally trimmed airspeed. Once the originally trimmed airspeed was re-achieved, the speed trim inputs were automatically removed by the system.

The speed trim inputs were accomplished by the slow rate of the trim motor as the flaps were already up. The effect of these inputs was subtle and easily overridden if needed. 

Approach to Stall/Stall Demonstration

After level off, we each were directed to pull the power to idle but to maintain altitude in manual flight through pitch control to observe the annunciations and flight control behavior during a stall. The approach to stall maneuver has been a staple of airline training for many years, but typically the maneuver would terminate with the activation of the stick shaker stall warning followed by a recovery. It was felt that exploring actual stall characteristics was unneeded and possibly negative training as this situation would never theoretically materialize in actual line operations. A recovery would always be made upon the activation of the stick shaker.

In the aftermath of the Colgan and some other crashes which served to highlight concern about deficiencies in manual flight skills, the FAA introduced extended envelope training (EET). This training went beyond traditional airline flight training to explore flight handling characteristics in areas of the flight envelope that would never be expected to be seen in line flying. The new thinking was that having some experience in these unusual situations might be of use in case one ever developed.

We were asked to make nose up trim inputs down to the lowest flaps up maneuver speed and afterward to continue to maintain altitude through control column pressure alone. A number of visual and aural alerts displayed and sounded as airspeed continued to decrease. The aural "Airspeed Low" alert sounded followed by the "Buffet Alert" FMC advisory message. The pitch limit indication appeared showing that we were within 5 degrees angle of attack to stick shaker activation. The stick shaker activated upon reaching the airspeed where natural stall warning buffet is computed to commence by the stall warning yaw damper (SWYD) computer.

During this demonstration, rearward control column forces continued to increase. As airspeed decreased below minimum maneuver speed, the speed trim High AOA mode activated thereby adding nose down trim at the slow rate of speed (because the flaps were retracted). This served to increase the necessary force to maintain altitude. Note that the high AOA speed trim feature is not unique to the MAX, but is included on older 737 models.

Eventually, the trim wheel made an abrupt twitch forward at the high rate, but only for a fraction of a turn. This, our instructor told us, was the MCAS system becoming active or "waking up". What was happening behind the scene was the MCAS logic took a "snapshot" of the existing trim position when its threshold AOA was reached. It then calculated a maximum amount of trim that could be added. Should the trim ever meet this computed limit, the speed trim and MCAS system becomes inhibited for the remainder of the flight. A short time later, MCAS activated adding additional nose down trim at the high rate of trim motor speed. The control forces were now heavier, but still manageable. 

Finally, the Elevator Feel Shift (EFS) module increased the system 'A' hydraulic pressure to the elevator feel and centering unit as the AOA approached its stall value. The elevator feel and centering unit is how any elevator force is transmitted to the pilots through the control column. Changes in trim go through this unit before they are felt by the pilot. This hydraulic pressure increase dramatically increases forward pressure on the controls and felt like someone was trying to jerk the controls out of my hands. Again, it should be noted that the EFS module is not unique to the MAX but is also included on earlier 737 models.

At this point the aircraft was in a full stall with strong buffet being felt. The controls could still be held aft, but only with two hands on the yoke and significant effort. We were then instructed to release back pressure and to let the aircraft recover and accelerate. The aircraft recovered quickly. The inputs previously made by MCAS and speed trim were automatically removed as airspeed increased and AOA decreased.

This was the end of the demonstration. Both of us ran through this event several times so that we were familiar with the sequence of alerts and flight control inputs. 737 stall behavior is benign with no significant roll or wing drop being noted. Recovery was prompt with back pressure release and flying airspeed was quickly reestablished.

Runaway Trim Demonstration

All aircraft with a powered trim system are subject to a condition known as runaway trim. Recall that elevator trim repositions the horizontal stabilizer in order to "trim" the aircraft to a particular airspeed. When properly trimmed, elevator stick forces are minimized. "Trim to relieve stick pressure" was the mantra when I was in USAF pilot training in 1982. It is still true.

The converse that a badly untrimmed aircraft is difficult or impossible to fly is also true. An inoperative trim system is sub-optimal, but one that continues to trim after the trim switch is released, or trims on its own can quickly create a dangerous situation. Stick forces will quickly become so unmanageable that continued controlled flight is not possible. This may manifest as either nose down or nose up trim. Neither is good.

Fortunately, Boeing has always included a non-normal checklist (NNC) to address runaway trim. If correctly followed, this checklist will result in the runaway trim malfunction being corrected, or the electric trim system being deactivated. Recall that the electric system, including speed trim, autopilot trim, and MCAS, has always been able to be deactivated through the use of the stab trim cutout switches located on the center stand.

Our demonstration started with the instructor introducing a runaway nose down rapid rate trim malfunction. The most important step of any non-normal event in an aircraft is identifying the malfunction correctly and then applying the correct non-normal checklist. Many an accident has been the result of a wrong assessment of the problem or the application of the wrong checklist. 

Recall that it is now normal for the trim wheel to spin un-commanded by the pilot in manual flight due to inputs by either the speed trim system or MCAS. Since the flaps were up and the aircraft was not in a stall situation, the fast rate trim activation immediately telegraphed a malfunction.This is how an MCAS malfunction might present along with some nuisance alerts. At this point, accomplishing the immediate action items (IAIs) of the Runaway Trim checklist on the Quick Reference Card (QRC) followed by the remaining steps listed in the Quick Reference Handbook (QRH) left us in a situation with the aircraft in manual flight with the electric trim disconnected by the stab trim cutout switches.

Immediate action items are steps on a non-normal checklist that must be performed from memory due to their urgent nature. The Runaway Trim checklist contains several of these steps which include disengaging the autopilot and autothrottles, controlling aircraft pitch and airspeed, and disconnecting the stab trim cutout switches if necessary. This checklist has remained largely unchanged over the many different models of the 737.

At this point, the aircraft had to be flown and trimmed manually using the trim wheel. There is a note in the checklist which emphasizes that reducing airspeed helps to relieve the air loads on the stabilizer which reduces the efforts needed to manually trim. Our malfunction was introduced at about 250 knots. Manual trim at this speed took some effort, but was easily achieved. Slowing to 210 kts allowed the flying pilot to easily fly and trim without assistance from the non-flying pilot.

Close crew coordination is of course required to split the duties of trimming and flying depending upon the situation. Flight in instrument conditions might require the flying pilot to direct the non-flying pilot to manipulate the trim. Instructive to me was the ease with which trim changes through the configuration process were able to be made. We were directed to go around on short final to see the trim changes needed for that maneuver. Using less than full power for the go-around made the maneuver very smooth and controllable.

Unreliable Airspeed Demonstration

One of the most disconcerting and dangerous malfunctions any pilot can face is the loss of reliable airspeed. Airspeed is the oxygen of controlled flight, and loss of reliable airspeed must be quickly recognized and corrected or ameliorated for a successful outcome. The importance of this instrument is why there is a lot of redundancy built in. The 737 has two primary and one auxiliary pitot probes used to measure dynamic air pressure which is then converted to airspeed measurement for the pilot's primary airspeed indicators along with an auxiliary airspeed indicator.

In addition to the direct measurement of airspeed, the 737 has displays of groundspeed derived from the air data inertial reference unit (ADIRU). While airspeed and groundspeed are not the same, at low altitudes, they are close enough to be useful.

Our demonstration simulated a bird strike or similar damage on takeoff which disabled the captain's alpha vane AOA transmitter though we were not informed of this beforehand. Immediately after rotation, a cacophony of alerts sounded accompanied by numerous messages on the displays. The indications included AOA Disagree, ALT Disagree, IAS Disagree, Speed Trim Fail, Feel Diff Press, along with erroneous airspeed, altitude, and flight director indications. The stick shaker sounded and did not cease for the entire demonstration.

As I mentioned above, the most important thing in any non-normal situation is to recognize what has failed and more importantly, what has not failed. A quick scan of the first officer's and auxiliary airspeed indicators told us that it was my instruments that had failed as the other two instruments were in agreement. I transferred control of the aircraft to the first officer who continued the climbout as I then referenced the Unreliable Airspeed checklist.

This checklist is fairly straightforward directing the autopilot and autothrottles to be disengaged if engaged. The flight directors are not to be used as they may also give erroneous information, and lastly for complete airspeed failure, some known pitch and power settings are given which are calculated to keep the aircraft from stalling or overspeeding.

We explored setting these values to see the performance of the aircraft with flaps both retracted and extended. The checklist values will keep the aircraft safe until a more detailed chart in the quick reference handbook, which uses aircraft weight, altitude, and phase of flight to set pitch and power, can be referenced.

Since our situation resulted in useable airspeed indications for the first officer, returning the aircraft to the airport was a matter of accounting for the nuisance stick shaker and other alerts, accomplishing the appropriate checklists and landing. We had been advised to bring ear protection for this segment, and it was worthwhile advice.

Changes Made to the MAX

The changes made to the MAX center around added redundancy to the Speed Trim System (including MCAS), and the Flight Control Computer. Input is now used from both AOA vanes and compared before being routed to the MCAS system. Previously, MCAS received input from only one AOA vane. A difference between input values from the two sensors will inhibit the system. New logic has been added which limits the amount of trim that the MCAS system can add. An exceedance of this limit also inhibits the system. 

Additional safeguards, redundancies and self monitors have been added to the flight control computers themselves to prevent erroneous stabilizer trim commands. The odds of a runaway trim scenario are now effectively nil, but the runaway trim procedures and checklists will remain as immediate action items on the quick reference cards and handbooks.


I published my impressions of flying the MAX back in 2018 after I first flew the aircraft. I thought it was a great flying machine back then and I think it will be better than ever after its return. Was the aircraft as well designed as it could have been? Perhaps not, but then in no human endeavor is perfection ever achieved. I do not mean to denigrate the seriousness of the accidents that occurred nor the memory of those lost. Airline crashes are nightmares for all involved.

That said, underlying causes of any accident are complex and many differing narratives develop, some with agendas of their own. Causal chains behind any accident must be considered in total. A focus upon one aspect of an accident in isolation will inevitably lead to a missed or wrong conclusion. 

Having now flown both the old and newer versions of the MAX, I am more convinced than ever that this aircraft is rock solid, whatever discrepancies there were have been corrected, and that it has a bright future as the preeminent narrow body airliner.

Captain Rob Graves is a veteran airline pilot and retired Air Force officer. He currently flies a Boeing 737 for a major American airline where he has over 30 years of experience. His Air Force career included instructing future USAF pilots in the T-37 primary jet trainer, aerial refueling in the KC-135 Stratotanker, and conducting worldwide logistics in the C-5 Galaxy cargo aircraft. He is the author of This is Your Captain Speaking, an aviation blog. It can be found at

Thursday, March 19, 2020

Dispatch from the Front: Flying in a Pandemic

Yesterday I finished my eighth day of flying out of the past eleven, and to say it's been a bit crazy would be an understatement. The travel industry, having endured the lost decade of the 2000s following 9/11 and finally regaining its footing, is being thrown back into disarray. Entire fleets of aircraft are being grounded and aircrews are being asked to take leave without pay or are being furloughed outright. Several airlines have already ceased operations.

To those of us who lived through 9/11 and its aftermath, this all seems eerily familiar. In a few short weeks we've gone from celebrating a new widebody captain bid (my wife) to investigating how to secure a new home equity line of credit. We'll be fine, but to the new kids who are experiencing their first major industry disruption, I say welcome to the lifeboat party! You will find that an airline career is really just a game of Chutes and Ladders writ large.

The first change I noted back on March 8th was that my commute flight to work was wide open. On a plane which usually has less than ten open seats, there were over a hundred empties. In fact, for those hardy souls who are still out there commuting to or from work by plane, social distancing will be a breeze on empty planes. My flight home from Chicago last night had perhaps a half a dozen passengers and my good friends over at American gave me a first class seat. I felt the thrill of an adrenaline junkie by ordering a glass of water.

Once at work, things seemed more normal. Our first two legs, a Cancun roundtrip, actually had pretty good loads. At the earliest stages of the crisis, it seems that bargaining or denial held sway, making vacationers reluctant to abandon already paid for accommodations. This view rapidly gave way to a desire to not be stuck at a vacation destination should airline service be curtailed, or the fear of becoming sick while away from home. This was evidenced by our last trip, to the Dominican Republic, which carried only a few dozen intrepid souls down, but was full coming home.

Resigned to Illness

Pilots, by their nature, routinely employ a certain insouciance, or gallows humor, when referencing the inherent risks in aviation. Failing to check the terrain charts could "ruin your whole day", or a statement like "it's better to die than to screw up on the radio" has been known to be overheard in a ready room or two. Tied up in this sentiment is a certain fatalism, but also confidence in one's ability to avoid the fate of someone who "bought the farm", even though an outcome might have little to do with ability and more with just lady luck.

These sentiments are in some ways a simple defense mechanism used to ease the knowledge of being at risk. Now that aircrew are being stalked by an unseen menace by virtue of being at work, this defense mechanism has been repurposed from mitigating aviation risks to those of catching the virus. It seemed that most of the aircrew I've spoken to over the past several weeks are resigned to the idea of coming down with the virus regardless of their actions to stay healthy.

Oh, we're all still washing our hands and making herculean efforts to not touch our faces, but we also realize that commercial aircraft, especially with dozens of switches in the cockpit, are flying Petri dishes. From waiting in line at security, to the jet bridge, to sitting in proximity to other people for hours on end, opportunities to pick up a viral hitch hiker seem manifest. Reports that the virus can be spread by simple breathing near an infected individual do little to allay this fatalism.

And why do the TSA agents need to touch everyone's ID? I used to tell my kiddos to look with their eyes, not their hands. Yuck.

Ten Cities in Eleven Days

My last eleven days of flying included seven domestic cities, three international destinations, and overnights in six hotels. I feel perfectly fine, but let's assume that the virus can be contracted and spread for a few days before symptoms appear. Should this have happened, then I've probably left quite a wide wake of disease behind. Could I have just called in sick and stayed home? Sure, but someone else would've been tapped to fly the trip. Agree or not with whether airlines should be shut down, at least some commercial flights will continue to operate.

The economic pain imposed by this event is going to be far reaching and deep. Unknown is how long lasting it will be. One analogy I overheard is that the economy is not sick per se, but rather has been put into a medical coma until the crisis passes. I'm hopeful that this is true, though it is also possible that after being forced by the virus to conduct more business online and through teleconferencing, business travel may never recover to pre-pandemic levels.

Airlines, of course, are large corporations and do have resources and credit lines to weather the storm, unlike many smaller businesses such as restaurants and hotels. I've been reliably informed that aircrew are the only guests in some of our crew hotels and the only business keeping the doors open. Food venues have been ordered closed which is a problem for overnighting aircrew who have no other ability to eat as my airline serves no meals.

9/11 Redux?

The terrorist attacks of 9/11 were a gut punch to the airline industry which didn't fully get back on its feet until ten years later. Career progression was on hold for many for what is now called the "lost decade". This pandemic has already caused a deeper loss of revenue for the industry than did the brief industry shutdown in the wake of the attacks. When and how a recovery will unfold is an open question.

Life changing or life delaying setbacks are emblematic of a career in commercial aviation. My first officer this trip was lamenting the unfolding events, and while he maintained a great attitude, I could sense his frustration. Let's call him Fred.

Fred has a less conventional background than many first officers with whom I fly. Somewhat of a bon vivant, he grew up on St Thomas and splits his time between the islands, a condo in Chicago, and a farm in the Carolinas. He spent some time on commercial fishing boats where he picked up enough Spanish to be useful in flirting with the waitresses in the Dominican Republic and Mexico. A story he tells of bartering with the crew of a Japanese fishing boat in the south Pacific for some soy sauce for the Korean sailors on his boat was quite entertaining.

He was a captain at his previous airline before it was merged with my airline and as a result he was bounced back to the right seat. Due to several career detours, he is older than I am and is close to having seniority to move back to the left seat for his few remaining years before mandatory retirement. This will now likely be delayed. The fallout for him is real.

Our flight attendants on the trip seemed to have varying degrees of stress due to the crisis. One of them, Bev, seemed to take it all in stride. She has a knack for poker apparently and has played semi-professionally. She was in a good mood having won about $400 in the resort casino, about half being Fred's. I don't gamble and was safely in bed when all this transpired. Tracey, on the other hand, was much more junior and had just purchased a condo. She was quite concerned about financial events though not as much about the virus itself, which makes sense as she is young and hale.

Call Dispatch

Upon arrival at the airport on our last leg home, I received a message to call our dispatch before departing. Given the choice of using the gate agent's dirty and broken screen mobile phone or activating international calling on my phone, I chose the latter.

The control tower at Chicago's Midway airport had been shut down due to three workers there being diagnosed with the virus. The airport was still operating but without a control tower. Think of an intersection where the traffic light goes out. You treat it like a four-way stop sign, but not nearly as much traffic can pass. It's just as safe. I had to get a briefing by a chief pilot concerning the different procedures.

The flight and landing were uneventful, but traffic had been severely restricted due to the closed tower. We were the only aircraft moving on the entire airport after landing. This also meant that my flight home had been cancelled. A quick check on FlightView revealed both an American and United flight were still operating from O'Hare to my hometown.

A Useful Prophylactic

James was my Uber driver from Midway to O'Hare. As I was in uniform, the subject of aviation came up. It turns out that he had been a flight attendant with ATA airlines for 20 years before that airline ceased operations. Family obligations forced his departure from the industry, but he remembered his years fondly. His income from driving has recently fallen drastically as a result of the pandemic. He has applied for a position with Target and has an upcoming interview. I wished him luck.

James was an older gentleman, and I asked if the virus concerned him. He assured me that drinking hot water would serve as an internal cleanse to remove any virus infection. Furthermore, using a hair dryer on the face and nostrils would then remove any offending virus thus ensuring safe passage in our newly infectious landscape. 

The more you know...

Sunday, October 20, 2019

Chemtrails: A Little Truth Goes a Long Way

Proof of chemtrail's existence [Source: the internet]

Running a modest (~3600 follower) aviation themed Facebook page for the past four years has been quite an education in human online behavior. I have a following of fellow professional aviators, air traffic controllers, aviation industry employees and general lovers of aviation. Most everyone abides by the unwritten laws of "netiquette" but there are of course always a few of the usual characters who don't play well with others.

Pedants will pick out a minor mistake or unimportant nuance to trumpet superiority. Last worders must always finish any argument, and reading comprehension aficionados will repeat your point back to you as if it was their idea. Sometimes just not responding to a provocative comment will make the person doing the commenting explode. I don't use the ban hammer often but rather try to talk excitable respondents down off the ledge. But occasionally I get a live conspiracy theorist to happen by. These guys are the most fun of all.

Pick Your Conspiracy

There are many flavors of conspiracies out there from 9/11 "truthers" to flat Earthers to the ur-conspiracy surrounding the Kennedy assassination. Rather than the dissipation of pockets of unknowing as you might expect now that we have the sum total of human science and discovery in our phones, access to the internet only seems to have injected steroids into many conspiracy theories. Confirmation bias kicks into overdrive as whole communities spring up around crazy ideas.

Joseph Pierre, a psychiatrist writing in Psychology Today, makes the point that conspiracy believers venture from a healthy scientific skepticism into nihilistic denialism. Any and all facts are subject to question regardless of any evidence, no matter how convincing, as a matter of principle. I suppose there's an attraction to walking around believing that you have secret knowledge to which few others are privy.


In aviation circles, the conspiracy of choice is known as the "chemtrail" conspiracy. A portmanteau of chemical and contrails, itself a combination of "condensation trails", the chemtrail conspiracy posits that the lines in the sky which originate behind high flying aircraft are not condensation from the moisture in aircraft exhaust, but actually a chemical spray of nefarious origin designed for a sinister end.

These chemicals can be either psychotropic substances which are designed to keep a restive population compliant, or a melange of metallic particles which are used to control the weather or "geoengineer" the planetary climate by blocking solar radiation. This particular conspiracy dates back to the late 90s and appears to have been sparked by a military research paper speculating about a future method of warfare that might include chemical dispersion from aircraft.

A Kernel of Truth

The use of aircraft to spray chemicals, usually fertilizers and pesticides, has a history dating back to the 1920s. The first aerial application of agricultural chemicals took place in 1921 from McCook Field in Dayton, Ohio. More recently, the US military undertook a large scale defoliation effort from 1962 to 1971 during the Vietnam conflict. Dubbed Operation Ranch Hand, Air Force C-123 Provider aircraft dispensed an estimated total of 20 million gallons of herbicides over Vietnam jungles.

Given this history, it isn't too great of a jump for the conspiracy minded to believe that the government has just upped their game and is now using commercial aircraft to poison the population or control the climate. Adherents will often conflate high altitude contrails which are a product of jet exhaust with low altitude wing top mist generation which is a result of the generation of lift in high humidity environments. Entire websites complete with well produced video content exist to promulgate chemtrail theories.

My Very Own Conspiracist

As I'd had thoughts about addressing this subject for awhile, I had the good fortune to have a true believer find his way onto my page. Let's call him Rob (name changed). Rob started out sending me private messages asking how it was that an attitude indicator (artificial horizon) could stay erect to the horizon if an aircraft is actually travelling over a globe.

It's actually a fair question and a real issue. He was unknowingly describing an actual phenomenon called "Earth rate" or "Earth transport" precession. An uncorrected gyro actually would slowly become inaccurate if it stayed true to its starting location as an aircraft travelled the globe. Both of these effects are accounted and corrected for in modern flight management computers. 

This explanation was answered by an angry response that he'd taken an attitude indicator apart and saw no such correction mechanism. This was probably true in that general aviation aircraft don't need such mechanisms due to their high cost and short range. A link to a Wikipedia article was met with a scoff. I didn't really expect him to believe in anything from Wikipedia, did I? How stupid did I think he was after all?

The conversation continued in this fashion. He'd ask why an aircraft travelling in a straight line over a globe wouldn't simply leave the atmosphere as if on a tangent line. The reply that aircraft don't fly in straight lines but use barometric pressure to maintain altitude in the atmosphere which is curved over the planet was also scoffed at. I hadn't "proved" anything.

It then occurred to me that he was a flat Earth believer. Rather than chase him off, I asked how he had come to his views. He mentioned that a ride in a helicopter some years past had provided him with his epiphany. He never did say exactly how that ride convinced him of the flatness of the Earth though. 

I then asked for some reference material. A trove of internet memes and links to videos followed. These memes would show things like graphic representations of an aircraft flying off into space on a straight line course, or a picture of drain or fuel dump vents on airliners as proof of the conspiracy.

Concerning chemtrails, he eventually conceded that rather than a conscious conspiracy of many thousands of commercial pilots and aircraft mechanics, the chemtrail chemicals might actually be added into the fuel directly, thereby limiting the conspiracy to fuel handlers and refiners.

The Pendulum

Looking for a simple way to demonstrate the Earth was not flat which would not rely on technology which he mistrusted, I recalled seeing a heavy four story pendulum hung in a stairwell in the Franklin Institute science museum in Philadelphia. Every morning employees would set up a circle of chess pieces under the pendulum and set it swinging. The pendulum would  knock down the chess pieces as the day progressed thereby demonstrating the rotation of the Earth. There was no way to ignore that!

The answer came back that Franklin was a Freemason and, well, nothing that he touched could be trusted. Interestingly, that was followed by several videos showing Masonic iconography which depicts the sun the same size as the moon with a flat horizon in the background, so it was difficult to know whether the Masons were with him or against him. What was clear was that a thread of mystical religiosity informed his world view and he was not going to let anyone pop the bubble.

What was also clear was that he wasn't going to attempt to address any incongruities that I raised such as how I could video call my wife from China where it was clearly dark at noon. This was just fascinating to me. I clearly didn't want to know the "truth" of his "research" which consisted of internet memes and videos posted by like-minded conspiracists.

Is It Harmless?

By all accounts my interlocutor seemed like a nice guy who got on well enough in society to hold a job and function normally. He mentioned that his job involved some sort of mechanical proficiency, and he did spend quite a bit of time on Facebook, so he wasn't obviously a technophobe. I even admired his inquisitiveness about the world. 

He was thinking about things that many people never consider, but at some point he wouldn't make the leap to the rational conclusion. Many of his positions started with a bit of truth which was then extrapolated to fantasy. The Psychology Today article referenced above noted that a confusion of the notions of  "believe in" versus "believe that" might be part of the cause of these belief systems.

I can't say that walking around believing in a flat Earth or chemtrails is an unalloyed tragedy. If it works for him, then great. In the words of that great 20th century philosopher, John Lennon: "Whatever gets you through the night is alright."

In Conclusion

One of the attributes which is emblematic of all conspiracies is that they're unfalsifiable. Any time an explanation is offered, there will be a counter-explanation which can't be verified. One of the best depictions of this was the scene from the first Terminator movie where Michael Biehn tries to explain to an incredulous prison doctor how robots from the future are coming to kill Sarah Connor.

Of course the joke here is that there actually were robots coming from the future to commit mayhem. But then, it was only a movie. Or was it?

Sunday, October 13, 2019

Did Bad Grammar Doom the Max?

emergency checklist to be used for a runaway stabilizer trim malfunction

As of this writing, the 737 MAX remains grounded with projected return dates now stretching into the first quarter of 2020. Boeing has not as of yet submitted the software fix for the controversial MCAS system to the FAA for evaluation. The European Aviation Safety Agency (EASA) recently indicated that they will seek their own additional testing of the software fix possibly resulting in a staggered return of the aircraft to service.

The post-mortem examinations of what went wrong at Boeing and the assumptions that were made concerning the flawed MCAS software continue. At issue is one assumption made early on that any malfunction in the MCAS system would be immediately recognized by average pilots as a malfunction known as "runaway stabilizer" for which a checklist already exists.

The stabilizer trim system is used by the pilots or the autopilot to keep the horizontal stabilizer in "trim" which means keeping the stabilizer aligned with the slipstream of air. It does this by actually moving the entire stabilizer a through a range of angles which change with airspeed. An "out of trim" stabilizer means the stabilizer is not perfectly aligned with the passing wind. This results in the need to hold force on the control column to maintain altitude. Letting go of the controls in such a condition would result in an undesired climb or descent. A well trimmed aircraft will stay where you put it.

In the 737, the stabilizer trim is normally controlled electrically through a motor, but can also be adjusted manually through a wheel and handle on the center stand. This system has a failure mode known as "runaway trim" wherein the motor runs after the control column electric trim switch has been released most likely due to a sticky or failed switch. This malfunction can result in an unflyable condition if not quickly corrected. It is this failure mode which is addressed by the "runaway stabilizer" checklist reproduced above.

Continuously or Continually?

Boeing engineers were also counting on pilots using this same runaway stabilizer checklist in the event that the MCAS system, which also uses the stabilizer trim, malfunctioned. The problem with this assumption is that the two malfunctions can appear to be very different things. During a classic stuck switch runaway trim, the trim wheel in the cockpit starts spinning and does not stop. That's the definition of "continuously" and is correctly annotated as one of the conditions on the top of the checklist.

An MCAS malfunction, however, presented quite differently. During that malfunction, the MCAS system would spin the trim wheel forward for a specified amount and then stop. If the pilot then used the trim switches to adjust the trim in a nose up direction, a malfunctioning MCAS would wait five seconds and trim forward again after each input by the pilot. This "very often; at regular or frequent intervals"  behavior of the MCAS system is the definition of "continually", not "continuously". 

This is exactly what happened to Lion 610. After reversing the MCAS inputs multiple times, the captain passed control of the aircraft to his first officer who was apparently unaware of the inputs the captain had been making. He never countered the next MCAS input which doomed them.

From Dictionary [dot] com:

In formal contexts, continually should be used to mean “very often; at regular or frequent intervals,” and continuously to mean “unceasingly; constantly; without interruption.”

Is this a minor and pedantic point? Perhaps, but perhaps not. English is the international language of aviation, and all pilots are expected to be proficient in English to be qualified to fly in international airspace. The pilots of both Lion 610 and Ethiopian 302 were likely not native English speakers and were highly unlikely to be aware of such a nuance as the difference in meaning of these two words.

They were, however trained in the various failure modes of their aircraft, and were not likely to be expecting the intermittent behavior of the failed MCAS system. The pilots of Lion 610 had no knowledge of the existence of the MCAS system as it was not included in their flight manuals. The pilots of Ethiopian 302 did have the Emergency Airworthiness Directive (EAD) published by Boeing describing the MCAS system, but were still slow to recognize that their problem originated from a bad MCAS system until too late.

In Conclusion

Aircraft flight manuals should contain all the information needed by pilots to safely operate their aircraft. This information should include accurate descriptions of possible failures, the recognizance of such failures, and best practices on how to solve or mitigate problems that arise. The omission of the existence and description of MCAS from the MAX airplane flight manual only compounded the problems faced by the two mishap aircrews. Faced with a fusillade of warnings and distractions which served to conceal the real nature of their problem, they were defenseless against a poorly designed and undocumented but deadly adversary.

Sunday, May 12, 2019

737 MAX Update

I haven't written about the saga of the MAX lately because there hasn't been much change in the situation concerning the grounded airliner. Progress is being made in fixing the MCAS system implicated in the two 737 MAX crashes, and estimates for the ungrounding of the aircraft range into the July-August timeframe.

The FAA recently convened a multi-agency Technical Advisory Board to review Boeing's proposed software fix for the MCAS system. The results of that review will be needed prior to FAA approval of the design changes.

That said, there have been a number of stories brought to light as to how the MCAS system came to be designed, and some more disturbing revelations about Boeing failing to disclose an inoperative warning feature to its customer airlines.

MCAS: What It Is and What It Is Not

The Maneuvering Characteristics Augmentation System (MCAS) has been routinely described in popular media stories as a stall prevention or mitigation device. It is really neither, but rather is a system designed to make the MAX "handle" just like the older Boeing NG series aircraft it replaces.

During flight testing of the MAX, test pilots and engineers noticed that in a very small corner of the flight envelope: lightweight, aft center of gravity (CG) and approaching a stall, the forces on the stick varied from the NG version of the aircraft. MCAS was introduced in order to counter this divergence in longitudinal stability between the two models to make them "feel" the same. The genesis for the difference in handling is due to the MAX having larger, heavier engines which are set further forward on the wing for ground clearance.

The need for identical handling between the two aircraft was to maintain a common "type rating" on both aircraft thereby allowing pilots qualified on earlier versions of the 737 to fly the new aircraft without extensive training. Airline pilots, unlike, say, flight attendants, cannot fly separate types of aircraft but are generally only qualified on one "type" of aircraft (at a time).

The word "type" has a very specific technical definition in that the FAA designates which aircraft fall under the specific "type rating". For instance, being "type rated" in the 737 allows pilots to operate all the various sub-models of that series (-200, -300, -400, etc) without an extensive course of study for each sub-model. The Boeing 757 and 767 were also given a shared type rating as those aircraft were considered similar enough that pilots could fly both of them under a single "type rating". These ratings are annotated on all pilots' licenses. The same is true for the Airbus A320 series of aircraft.

As we now know, the MCAS system was flawed in its design due to being able to be triggered by a single angle of attack (AOA) indicator, and also by the ability of the system to reset itself and re-engage multiple times without limit. The question of how and why this design flaw happened is the subject of multiple investigations into the certification process.

Inoperative Angle of Attack Warnings

The WSJ has done some excellent investigative reporting on the MAX story and revealed recently that not only did the MAX aircraft not have a specific AOA warning indication which had been included on the earlier NG, models but that Boeing engineers were unaware that the warning on the MAX was inoperative. Furthermore, Boeing delayed notifying their customer airlines of the situation for nearly a year.

Angle of attack cockpit indicators are not known as what are "primary flight instruments" such as airspeed, altitude, and attitude. Pilots use primary flight instruments to directly fly the aircraft. An angle of attack indicator, however, is not required to safely operate most aircraft and is usually not included in cockpit displays. 

An analogy might be to a tachometer in your car. Nice to have but not needed. Much outrage has been vented over Boeing's not including this cockpit indicator as standard equipment, but I don't see it that way. AOA cockpit indicators are simply not needed for safe flight.

Angle of attack sensors, small vanes on the exterior of the aircraft, are traditionally used to send AOA information to an airliner's flight control computers and are used to provide "stick shaker" stall warnings. There are two installed on the 737 and the cockpit warning "AOA Disagree" would display should the two indicators return different readings, indicating a malfunction in one or both.

It was this "AOA Disagree" warning which was inadvertently deactivated on the MAX aircraft. Had the AOA only served its previous function of activating stall warning, this would be no big deal. But because the MCAS system was triggered by a single AOA sensor, not having this warning quickly became a very big deal. 

A single malfunctioning AOA indicator has been implicated as a possible cause for the inadvertent activation of the MCAS system on both the Lion and Ethiopian crashes. Having this alert enabled might have aided the pilots of those aircraft to figure out what was going wrong.

Pinto, Tylenol, MAX?

It is becoming apparent that the MAX will be back flying at some point, but the question now arises as to how well Boeing will weather the ongoing tsunami of negative PR. Even President Trump weighed in on this question recommending that Boeing rebrand the aircraft.

If you recall, the Ford Pinto never rose above safety concerns after several accident caused fires and the model was eventually terminated. The response to the Tylenol poisonings, however, is now considered a textbook example of how to manage a public relations crisis. One thing learned is that transparency and being forthcoming in light of a tragedy is essential. Boeing has only made matters worse by their perceived lack of candor.

My guess is that once the MAX is back in the air, the crisis will be quickly forgotten. My reasoning is that the public has a notoriously short memory for these sorts of things. Other aircraft have had spotty beginnings and went on to become successful. The MAX, which is still a 737 at heart, has a long and enviable safety record. As the parable states, the dogs may bark, but the caravan moves on.

Sunday, March 31, 2019

Flight Data Results from Ethiopia 302 and the MCAS System - Smoking Gun or False Lead?

737 MAX throttle quadrant showing trim wheel and stab trim cutout switches (lower right).

The Wall Street Journal is reporting that, after preliminary analysis of flight data from the downed Ethiopian 737 (ET302), investigators now believe the controversial Maneuvering Characteristics Augmentation System (MCAS) activated and may have played a part in the accident.  This finding is significant because the MCAS system has now been implicated in both this crash and the Lion Air crash which occurred last year.

MCAS - What is It?

To recap, the MCAS system was installed on the 737 Max aircraft to mitigate some unique handling characteristics of the new model which differed from older 737s. Boeing originally chose not to document this new system in the aircraft flight manual, but has since briefed all Max operators on the existence and function of the system in the aftermath of the Lion Air crash.

Among the reasons Boeing engineers may have had for not including the system in the flight manual are that the system was only supposed to ever activate during aerodynamic stall conditions in manually controlled flight, which in normal operations would never be seen. Entire careers are flown without ever seeing an actual stall, so this rationale might have been thought sound.

The problem for the MCAS system wasn't necessarily its intended operation, which was to be rarely if ever seen, but rather any potential failure modes. Unintended activation of the system due to a mechanical fault has now been suggested as a factor in both Max crashes. Flight data from the Lion Air crash show the pilots repeatedly fighting the inputs from a misfiring MCAS system, and according to latest reports, the MCAS system also activated on the mishap Ethiopian airliner.

Adding to the controversy of the existence of an undocumented system is the revelation that the system can be activated by a single angle of attack (AOA) sensor. Angle of attack sensors measure the angle of the relative wind over the wings. Too great of an angle between the wing and the airflow over it will result in an aerodynamic stall wherein the wing stops producing lift.

The questions being asked involve the engineering decision to use the input of a single AOA sensor to trigger the MCAS system to operate. There are two (or more) AOA sensors installed on all airliners which among other things are used to provide "stick shaker" stall warning to pilots if they get too slow or approach a stall. Again, a stall is something that most airline pilots will never see outside of a training simulator where stall recovery is practiced routinely.

What Did the ET302 Pilots Know about the MCAS System?

Lion Air JT-610 crashed on October 29, 2018. The investigation of that crash first brought the MCAS system and a malfunctioning AOA sensor to light. On November 7th, Boeing released an Operations Manual Bulletin (OMB) to all 737 Max operators. This bulletin mentioned that erroneous AOA signals can cause the trim to run uncommanded by the pilot. The directed remedy is to apply the runaway stabilizer trim checklist which directs the use of the center pedestal mounted stabilizer trim cutout switches. The text of the bulletin is as follows:

The Indonesian National Transportation Safety Committee has indicated that Lion Air flight 610 experienced erroneous AOA data. Boeing would like to call attention to an AOA failure condition that can occur during manual flight only.

This bulletin directs flight crews to existing procedures to address this condition. In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC. It is possible for the stabilizer to reach the nose down limit unless the system inputs are counteracted completely by pilot trim inputs and both STAB TRIM CUTOUT switches are moved to CUTOUT.
Additionally, pilots are reminded that an erroneous AOA can cause some or all of the following indications and effects:

- Continuous or intermittent stick shaker on the affected side only.
- Minimum speed bar (red and black) on the affected side only.
- Increasing nose down control forces.
- Inability to engage autopilot.
- Automatic disengagement of autopilot.
- AOA DISAGREE alert (if the AOA indicator option is installed)

In the event an uncommanded nose down stabilizer trim is experienced on the 737 - 8 / - 9, in conjunction with one or more of the above indications or effects, do the Runaway Stabilizer NNC ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.

A subsequent Emergency Airworthiness Directive (EAD) directed this information to be included in the flight manual of all Max aircraft within three days.

In my view, it is reasonable to assume that the ET302 pilots were well aware of the MCAS system, its possible failure mode due to an erroneous AOA sensor, and the steps to be taken to remedy the malfunction.

Why Didn't They Just Turn it Off?

The investigation of the Lion Air crash has revealed that on the flight immediately preceding the mishap flight, an off-duty 737 qualified pilot was occupying the jumpseat. That aircraft also suffered the same malfunction of the AOA sensor resulting in uncommanded nose down trim. On that flight, however, the guest pilot recommended that the operating pilots use the stabilizer trim cutout switches, which they did. That flight landed uneventfully.

The pilots on the subsequent Lion Air flight fought against the nose down trim commands continually, but never did deactivate the electric stabilizer trim with the cutout switches. The errant automated trim commands eventually trimmed the aircraft into an unflyable condition.

It would seem easy to Monday morning QB the actions of the Lion Air mishap pilots, but it must be remembered that there were many other things happening at the same time. One important thing to note is that the stick shaker activated right at liftoff and continued for the entire flight. The stick shaker is a device that literally vibrates the control yoke when an aircraft approaches an actual stall. It is loud and disconcerting when activated. The pilots were no doubt startled and distracted.

Another point to note is that the MCAS inputs would not "present" like a traditional runaway trim situation. Typically, a runaway trim malfunction in a simulator would simulate a stuck switch where the trim wheel would run continuously in one direction. During the mishap Lion flight, the flight data recorder showed the pilot actively trimming back against the MCAS inputs followed by a few seconds delay when the MCAS system would reactivate and start trimming forward again.

Another system called "speed trim" installed on earlier and subsequent 737 models can also run the electric trim with the autopilot disengaged, so it is not completely unusual to see the trim wheel spinning by itself with the autopilot off. This "negative training" may have contributed to the pilots not focusing on the uncommanded movement of the trim wheel even though speed trim only functions with flaps extended while the MCAS system only functions with the flaps retracted.

What Happened Then on ET302?

The flight data recorder and cockpit voice recorders from ET302 have been recovered and sent to France where they were downloaded and decoded by the BEA, the French equivalent of the NTSB. The data from the recorders have not been released to the public, however investigators have an "emerging consensus" that the MCAS system activated and contributed to the accident. The story also noted that this preliminary finding is subject to revision.

The pilots of ET302, however, had something that the Lion pilots did not, and that is a detailed description and knowledge of the MCAS system and the procedure to disable it by throwing two easily reached switches. Without more information from the accident investigation, it is simply too early to reach any definitive conclusions about the fate of that airliner.

Thursday, March 14, 2019

What's Next for the Max?

As an aviation blogger, the past few days have been simultaneously hope inspiring and depressing. Hope inspiring as many people understand, or make a good faith attempt to understand, the underlying issues surrounding the 737 Max. But also depressing as random fanbois, trolls, and low information, yet self proclaimed experts, happen by my comments section to disgorge their dubious wisdom on things about which they know little or nothing.

Mencken was Right: No One Ever went Broke Underestimating the Intelligence of the Public

One commenter offered, based on no information other than two 737s had crashed, that all of them should be grounded. I pointed out that by that logic, it would be even more beneficial to ground all airplanes everywhere as it would be safer still. The response was "I didn't say all airplanes should be grounded" displaying an ironclad grip on logical fallacies.

When I noted that the MCAS system could be completely deactivated using two switches mounted on the center console, a commenter replied that well, "maybe the switches reconnected themselves". Other than the testing of those switches being a mandatory preflight item, this commenter has obviously confused the Boeing 737 with the SkyNet model T-1000 Terminator which can rewire itself automatically.

Lastly, when one commenter [Hi Scott!] boldly opined that the 737 was the worst airplane he'd ever flown on, I replied that my passenger experience is usually more dependent upon the particular airline and class of service rather than the aircraft type. This big brained person assured me, however, that no, none of that mattered. He apparently would rather sit in a non reclining 28 inch pitch economy seat on a Spirit A320 than a first class seat on a JAL 737.  [Sigh]

Public Relations and Marketing Wins

So the FAA bowed to international and media pressure and grounded all Max aircraft, which is proving to be a minor inconvenience to most operators of the aircraft. I was personally walking out to a Max to fly to Phoenix when the announcement came. Someone somewhere had done some preparations and an -800 was towed to the gate by maintenance about 10 minutes later for a slightly delayed departure.

We of course are now treated to the circular logic of all the "I told you so" stories. The process starts as media sensationalism whips up a gullible and credulous public followed by outraged calls for the aircraft to be grounded. After weather-vaning politicians cave into public pressure, preening media talking heads then get to state that something must have been really been wrong. And so it goes.

Make no mistake: this grounding has more to do with public relations and marketing than safety. As of yet, there is very little evidence that the two Max crashes are in any way related other than the most superficial of circumstances. But the tsunami of media scare stories and sensationalism showed no signs of abatement, so this was the correct decision. 

The FAA cited "newly" discovered satellite data which finally swayed their decision.They are referring to the ADS-B tracking system which relays flight parameters to air traffic control through satellite. This information, however, was publicly available shortly after the crash and it does show some minor altitude excursions, though nothing is conclusive.

The cockpit voice recorder and flight data recorder from the Ethiopian crash have been recovered and sent to France for analysis. Again, prescient commenters noted that this was a good thing because, of course, had they been sent to the US, American investigators would falsify any result finding the US producer of the aircraft at fault. I actually agree with this decision in spite of the slander against the integrity of the NTSB and other US investigators. Having French investigators analyze the data will deflect the inevitable cries of bias should the investigation find fault in anything except the aircraft itself.

What Next?

What happens next is we wait for the data from ET302 to be downloaded and released. When that happens and a likely cause of the accident can be discerned, the Max will be cleared to fly. Notice that I didn't say that this clearance will in any way be dependent on the outcome of the investigation. The aircraft will be flying again in a matter of weeks regardless of the findings.

Why you ask? Should the MCAS system be implicated in this crash (unlikely in my opinion), there will be software fixes and training updates offered. As I've noted many times, the system can be deactivated completely through the use of two center console mounted switches. Even then, the system should only activate in the case of gross pilot negligence resulting in an aerodynamic stall or, as in the case of the Lion crash, an errant sensor input due to a mechanical malfunction. 

The software fixes will preclude the activation of the system due to the failure of a single sensor. The training updates will reemphasize to all operators that undesirable electric trim inputs can be inhibited through the use of the center console mounted stab cutout switches. 

Should the MCAS system not be implicated in the ET302 crash, the Max will be back in the air that much sooner. Make no mistake, all airline crashes are tragedies of the highest order for everyone involved. The object of any investigation is to find out what happened and to take measures to prevent any future recurrence. Commercial aviation is one of the safest, if not the safest means of transportation available. 

What will be left is a mopping up by the lawyers.

Captain Rob Graves is a veteran airline pilot and retired Air Force officer. He currently flies a Boeing 737 for a major American airline where he has over 25 years of experience. His Air Force career included instructing future USAF pilots in the T-37 primary jet trainer, aerial refueling in the KC-135 Stratotanker, and conducting worldwide logistics in the C-5 Galaxy cargo aircraft. He is the author of This is Your Captain Speaking, an aviation blog. It can be found at He also writes for 

Tuesday, March 12, 2019

Is the Boeing 737 Max 8 Safe?

737 Max 8

This past Sunday, an Ethiopian Boeing 737 Max 8 aircraft crashed shortly after takeoff from Addis Ababa to Nairobi with 157 passengers and crew. There were no survivors. This is the second crash of a Max 8 variant of the 737 in five months after the crash of a Lion Air Max 8 last October.

An undocumented system was brought under scrutiny in the Lion Air crash and now questions are being raised as to whether this same system, known as maneuvering characteristics augmentation system (MCAS), might have played a roll in this latest crash. If that is found to be the case, the safety of the aircraft itself will be called into question.

What We Know

At the current time, the cause of both accidents is unknown as the accident investigation is still underway on the Lion Air crash and the Ethiopian Air crash investigation is just getting under way. The flight data recorders and cockpit voice recorders have been recovered from both accidents and are being analyzed.

The flight recorder data from the Lion Air crash suggests that the pilots were having control difficulty due to erroneous inputs from the aircraft's MCAS system which itself received faulty inputs from a malfunctioning angle of attack (AOA) sensor. It is this errant sensor and its maintenance history that investigators are focusing on.

Initial reports from the Ethiopian Air crash suggest that the aircraft experienced control difficulties shortly after takeoff. Data from a flight tracking and reporting system known as ADS-B show highly unstable vertical velocity and airspeed readouts which were similar to the airspeed and altitude excursions of the Lion Air mishap aircraft.

Unconfirmed reports from listeners on the frequency reported that the Ethiopian pilots stated that they had unreliable airspeed indications and were declaring an emergency.

And right now, that's it. There are similarities, but no confirmation that the same system brought down both aircraft.

Is It Safe?

Given that we know little about the cause of the first accident and nothing about the cause of the second, a grounding of this model aircraft is premature. I am qualified and current in this model aircraft and am confident that it is as safe as any aircraft flying. Airplanes sometimes crash. It is always a tragedy when they do, but barring a definitive indictment of the design, there is no reason to overreact.

Even should the MCAS system be found primarily at fault, the system can be completely deactivated by two easily reached switches on the center console of the cockpit. Why the Lion Air pilots didn't take this action is unknown, but the investigation should eventually reveal the cause. A similar malfunction occurred on a previous flight of the mishap aircraft, and those pilots took the correct action and landed uneventfully. Questions as to why the aircraft flew again without being properly repaired should be asked.

In the event of unreliable airspeed, which can happen to any aircraft independent of model, routine practice of this malfunction in the simulator should make it a non-event. I recently underwent this training myself, but the basics of pitch and power date back to Wilbur and Orville. Recognition is the toughest part, but after that, known pitch and power settings will keep the aircraft from stalling and in control.

I don't mention these questions to cast blame, but rather to answer critics who don't understand aviation or engage in magical thinking. The Max is still a 737 at heart and flies nearly identically to the other four models of the aircraft that I have flown. So yes, it is safe, and I'd gladly put my family on one and fly it myself with no reservations.

Captain Rob Graves is a veteran airline pilot and retired Air Force officer. He currently flies a Boeing 737 for a major American airline where he has over 25 years of experience. His Air Force career included instructing future USAF pilots in the T-37 primary jet trainer, aerial refueling in the KC-135 Stratotanker, and conducting worldwide logistics in the C-5 Galaxy cargo aircraft. He is the author of This is Your Captain Speaking, an aviation blog. It can be found at He also writes for 

Saturday, February 16, 2019

It Shouldn't Have Flown

By Steven W. Freimuth, former Captain, USAF


The following is my recollection of the events that occurred during a takeoff and flight on a September day in 1973 while flying out of U-Tapao Royal Thai Navy Airfield (UT) in Thailand.  This was after the war was over.  But we were still flying missions to maintain the peace.  While these events happened over forty-five years ago, most of them were so etched in my mind, that I can still recall them as if it were yesterday.

I am finally following up on my years of “intentions” and reducing this to paper as a result attending two Arc Light / Young Tiger reunions. It was there I met Tommy Towery and acquired the many “We Were Crew Dogs” books which he edited.  He wondered why a KC-135 pilot would be interested in reading these short stories mostly about B-52 crew experiences.  Well, I learned a lot more of the bigger picture in SEA (Southeast Asia) and stateside.  Often we were so busy  in our own activities, and in accordance with SAC’s (Strategic Air Command) “need to know” policies, that we (I) didn’t know much about the details of the roles of my fellow airmen.  And our shared suffering.  But more of that in another article.

I have chosen to use “full width” paragraphs to write the sequence of events as they occurred and what my thoughts were at that moment.  I have included “indented sections” to further explain various aircraft and performance details.  This is to assist the reader who isn’t as familiar with them to gain a better understanding of both what was going through my mind and happening to the aircraft.  Thus, read just the expanded text to get a blow by blow description.

The Aircraft:  I was going to write about the KC-135A aircraft so the reader would have a better understanding of some of its quirks and limitations.  However, I came across the following written by Robert Graves who flew them in the 1980’s.  His description included everything I wanted to say and written better.  He wrote:

The First All Jet Tanker

The KC-135 Stratotanker, produced between the years of 1956 and 1965, was a derivative of Boeing's test bed aircraft, the 367-80. From this early test aircraft, both the KC-135 and 707 were derived which is why the KC-135 has a strong resemblance to the 707, though the tanker was smaller and lighter. Still, the tanker could carry 135,000 lbs of fuel and weighed in at just under 300,000 lbs fully loaded.

Part of the impetus for the Air Force to acquire this aircraft was the cold war. The nuclear arms race was in full swing in the late '50s and the Air Force wanted to have a tanker which could refuel its new intercontinental bomber, the B-52, to allow it to reach Russia. The old KC-97, a derivative of the WWII era B-29, just wasn't up to the task.

In fact, because the angst of quickly fielding a nuclear deterrent was so high during that time, several compromises and shortcuts were made in the design of the KC-135 to get it operational faster. These were compromises which I came to despise acutely nearly thirty years later.

The first compromise was the engines. Engine manufacturer Pratt and Whitney was working on a new engine design at the time known as the bypass fan engine. This new engine was to become the basis for all modern engines and was eventually used on the 707, but it just wasn't going to be ready in time for the tanker. So the KC-135 was outfitted with older engines which incorporated a technology known as water injection to produce enough thrust. Yes, you heard that right...they pumped water into the engine.

Without getting too detailed, high pressure pumps injected water into the engines during takeoff which increased thrust by means of an increased mass flow rate. Still, the airplane was grossly underpowered. While the airplane did usually get airborne, it would take most of the runway to do so when heavy. I have seen the departure end of the runway coming under the nose during rotation more times than I care to remember.
To give you an idea of how puny the engines were, the CFM-56 engines fitted on a 737 today produce about 34,000 lbs of thrust while the tanker's original P&W J-57s produced a mere 12,000 lbs. Due to its underpowered nature, the aircraft gathered unflattering monikers such as "The Silver Sow" or "The Steam Jet". My personal favorite was "Strato-Bladder" for the bladder type fuel cells in the body tanks. 

The KC-135A was eventually re-engined in the 1980s with those same CFM engines and was redesignated the KC-135R. The new "R" models are quite sporty now and even hold some time to climb records for transport category aircraft.

This first compromise of using water injected engines led to the compromise which I came to hate the most. To feed the water injection system, a water tank was needed. Since most of the body of the aircraft where cargo bins are on a normal plane were taken up with fuel tanks, a decision was made to remove one of the two air conditioning units, or packs. This meant that the airplane was hot, and I don't mean hot as in cool, but rather hot as in fetid.

I was stationed in Okinawa, remember, which is in a subtropical climate zone. This means warm and damp winters followed by hot and damp summers. The lack of A/C on the aircraft was most pronounced when flying hour after hour of "transition" training, or touch and go practice. It wasn't uncommon to get off the airplane soaking wet. Boeing didn't even have the courtesy to install an air vent to blow on the pilots' faces. The air outlets were under the seat where what little cool air that did emanate did no one any good at all.

Old Technology

As I flew the airplane in the early 80s, it had undergone a number of technology updates to its original systems but many vestiges of older technology were still on board. We still had a navigator assigned to the crew, but he had at his disposal an inertial navigation system, or INS which made his job more or less obsolete. Airliners were crossing oceans then with similar systems which had their accuracy measured in yards while GPS was still on the design table.

The aircraft also had, however, a sextant and an overhead port with which to view the stars. Celestial navigation dates back to the time of Magellan and was the reason the navigators were still on board. Remember, this aircraft was designed to fight a nuclear war and at the time it was thought that a nuclear detonation might render all electronics useless. Therefore, the navigator was trained to use the ancient technology of celestial navigation with a sextant to determine our course while flying to nuclear armageddon. My one regret is never having had our nav teach me how to shoot the stars with the sextant.

Over-water communications were also rather dated. While we had a high frequency or HF radio which could bounce signals long distances, ours was an old tube-type radio requiring a warmup and without a squelch control. This meant maintaining a "listening watch" on air traffic control frequencies which were always full of static, whistles and pops. Of course this was a copilot duty. When the air traffic frequencies became too unusable, I might have inadvertently tuned the radio to an awesome rock station beamed out of Saipan.

The standard for overseas communications is through the use of satellites today.

Flying the Beast

As I mentioned above, the airplane was underpowered. This meant that it had to be flown very smoothly and deliberately when it was heavy, which was most of the time. There were restrictions on the angle of bank that one could use after takeoff for instance, and multiple warnings concerning what to do or not do should an engine fail on takeoff.
There were so many red warnings on the engine failure pages that I think most of us flying the beast were convinced that an engine failure was pretty much game over. Thankfully I never got the opportunity to test out that proposition. …”

 Another former crew member has described the takeoff in the following manner: “I realize that this was a long time ago but when I was stationed at Robins AFB back in the mid-1960s our KC-135A s would use between 11000 and 12000 on T/O.  It was closer to the latter on hot days.  Sometimes they would return after their missions and still have some pine needles in the intakes from the tops of trees at the end of the runway. Of course these were fully loaded airplanes.  If anyone here ever witnessed a fully loaded “water wagon” they were truly something to behold.”

 And, as an additional piece of information for the B-52 crew members reading this, I have gleaned, your maximum takeoff weight was about 488,000 lbs.  From what I have read in “We Were Crew Dogs” the maximum weight at UT was about 454,000 lbs. (with twice the engines and water).  Half of that weight would be 227,000 lbs.  My takeoff weight in the follow story was about 262,000 lbs. The base weight of a 135 was between 105,000 and 107,000.

 As a final comment before I start my tale, there was a saying in SAC: “If someone could construct a runway that would actually encircle the entire earth, SAC would could come up with a mission plan that would use every inch of it”.


This was to be our second flight of the day.  We were assigned to fly a KC-135A, tail number 59-1475, using a water takeoff with a max fuel load of 156,000 pounds on runway 18.

THE RUNWAY:  Runway 18 is a 11,500-foot runway that ends with the overrun (or approach portion (when landing to the north on 36) followed by a sandy beach and the Gulf of Thailand.  Normal departure after takeoff is to the north.

WATER TAKEOFF AND JET ENGINES:  The KC-135A aircraft had four J-57 jet engines.  These engines were not turbofan jets In order to provide more thrust for takeoff, a 670 gallon tank of water was installed in the belly of the plane.  Electrically driven pumps furnished approximately 80 gallons per minute to each engine.  Accordingly, we normally had about two minutes of water before run out.  This increased the mass flow through the engines providing substantially more thrust.  Each engine (dry) should be able to provide a maximum of about 12,845 lbs. of thrust within a temperature range of -65 to 5 degrees.  The dry thrust would diminish substantially as the temperature rose above 5 degrees.  Water (wet takeoff) should be able to provide a maximum of about 12,925 lbs. within the 20 to 100 degree range.  

GENERATOR LOADS:  Three of the engines had generators to provide electricity while no. 4 had a cartridge start system in its place.  All the normal aircraft electrical loads could be met from the output of only one generator.  According to the charts, it would use about 94% of the rated capacity of a one generator during the highest usage period of a mission - except a wet takeoff.  The water injection pumps, that were needed for the critical two minute period, consumed about 100% of the capacity of a generator.  Thus, during a wet takeoff, about 175% of the available output of one generator was consumed with three available.  Safety and redundancy had been built in.

MAX FUEL LOAD:  According to the charts, the maximum fuel load (capacity) is 202,800 lbs. for aircraft with an upper deck aft fuel tank installed.  However, I recall that at UT, the max load was 156,000.  This lower load was the maximum that we could get airborne given the runway length and warm temperatures.

The Form 781 maintenance log indicated that this was the first flight for this aircraft after going through “corrosion control”.  I didn’t know what that was and believe the crew chief said something about “taking the aircraft apart, looking for corrosion, and then putting it back together”.  I thought about a FSAGA (first sortie after ground alert).

I also need to insert at some point that at a safety briefing, probably within the prior week or so, there was a 135 out of Grand Forks or Minot that kept popping circuit breakers during a flight.  The crew continued resetting them several times and they continued to trip.  The crew found an electrical fire.
The preflight proceeded normally until we got to the Control and Trim Check.  With the control wheel rotated to the left, Ground reported “Left ailerons up, tabs down, left spoilers 40 degrees, right spoilers down, right ailerons down, tabs up”.  (A correct call and indications.)  When I then rotated the yoke to the right I got something like “Left ailerons down, tabs up, left spoilers up, right spoilers 40 degrees, right ailerons up, tabs down”.  Something in the all so familiar call given in a standard cadence seemed wrong.  “Aah Ground, would you repeat that call.”  It was repeated the same and Ground, this time, seemed to realize that something was wrong.  After a short conversation, I believe Ground said something like “Sir, we must have a stuck actuator, let me get a ladder and a hammer to fix it.”

As we waited on maintenance, I believe at some point we may have decided to continue to complete a few of the items left in the Interior Inspection checklist that we could do without Ground i.e. altimeters check, etc.  And we waited on the ramp in the afternoon sun (usually between 84 and 88 degrees).  Think of sitting in an auto in this position with two windows open while wearing a Nomex (a non-breathing plastic bag that provided fire protection) flight suit.  Because of this, we delayed putting on the SAC required inflatable life jackets that were to be worn on all overwater takeoffs.

Maintenance must have had problems finding the appropriate SAC specified hammer as start engine time (30 minutes before scheduled takeoff time?) came and went.  I believe it was between ten and fifteen minutes before takeoff time that maintenance finished “fixing” the problem.
At this point I should point out to those unfamiliar with this fact that takeoff times are important in SAC, almost sacred.  My recollection is that the scheduled time plus up to five minutes was okay.   I never knew if it went all the way up to those under CINCSAC but at least I had been told that everyone at UT got a black mark after their name when there was a late takeoff.  And, as was the custom, one “awe sh*t” wipes out 10,000 at-a-boys.

As a SAC trained professional - and a person whose Mother taught him to “do the right thing”- my crew and I finished the Interior Inspection checklist, and began the Starting Engines and Before Taxiing checklist, and Before Takeoff checklist in record time.  While switches were being thrown and settings made, clearance was requested for taxiing.

I started to taxi as soon as clearance was given.  My co-pilot started the Before Takeoff checklist while we were taxiing.  We continued to run the checklists, throw switches, verify systems, and adjust settings.  Now there is a saying in SAC that there is only one thing worse than having a taxiing accident, that is living through it.  While well aware of that, I must admit that I made a “high speed” taxi.  In fact, a very high-speed taxi.  I think it was about four times faster than I had ever taxied before or since for scheduled flights.  Probably twice as fast as an alert taxi exercise.  I thought we might skid around the corners as we headed to the runway.  But I was going to make an on-time take off if at all possible.

As we approached the hammer head we called and received takeoff clearance.  No stopping before taking the active.  As we turned to the runway heading of 18, I brought the throttles back and my Co started the water injection.  I believe my Nav called that we crossed the threshold between four and five minutes after our scheduled takeoff time.  My crew had saved the day!

As I advance the throttles, water kicked in and we were off.  Air speed slowly increased as we rumbled down the runway.  S1 was called as our takeoff continued.

S1 is a calculated speed (V1 to the rest of the world) where if you encounter a major problem prior to reaching, you can abort and stop within the remaining runway length.

Then, just at the start of rotation, the aircraft became very quiet.  At least very quiet for a KC-135A making a water takeoff.

Water takeoff’s noise was about 126 decibels.  

“The KC-135R is a dramatically quiet aircraft in comparison to the KC-135A, which is one of the worst noise offenders in the USAF inventory. … The noise footprint has been reduced from the "A" model by 95%”

Within a fraction of second later, the boom was out of his seat and standing between the pilot’s and co-pilot’s seats with his hands on each of our head rests.  “Generators!”  I looked up and saw all three had tripped off line.  Later, I found the Nav had attempted to make a similar call but he had crushed his mic switch attached to his flight suit with an alligator clip.

It is a crew duty for the Nav and Boom to monitor the generators on takeoff as the panel is overhead between the pilots.

At this moment in my life, everything slowed and every sense was at its keenest.

My first thought was that there was no way this aircraft would fly.  I thought the loss of water was about the same as losing one and a half engines while making a heavy weight takeoff.  Next, did we have a fire on board that caused the loss of electrical?  At that moment, I caught a glimpse of my Mae West life jacket on the floor next to the center control column out of the corner of my eye.  In the rush to complete the checklists following the maintenance delay, I hadn’t put mine on for the very first time.  I will accept that glimpse as Divine intervention.  Here I was about to crash a 263,000 pound aircraft into the Gulf of Thailand and I didn’t have my life jacket on.  We’re going to fly!!
How to do that? Throttles, I reached over and firewalled them.

Normal takeoff procedures required the pilot to keep his left hand on the nose gear steering wheel (until about 90 KIAS), advance the throttles with his right hand to about takeoff EPR (engine pressure ratio) and then return his right hand to the yoke.  The co-pilot would follow the advance of the throttles with his left hand and fine tune them to about 2.85 EPR.  Takeoff thrust was determined by the EPR setting.  This was normally reached with a 94-98% RPM.  According to the Dash 1, the overspeed limit of 102% RPM should not be exceeded at any time.  If an engine overspeeds between 102-104% consideration should be given to operating on reduced power and shutting down the engine as soon as safety of crew and airplane permits.  If an overspeed exceeding 104% occurs, the danger of complete engine failure is more imminent.   The normal runway distance from the start of rotation to unstick is about 1,000 feet.

I then tapped my Co’s hand that was on the throttles. No electrical, no intercom!  He knew to check the RPM and pull them back if we were over 102%.  We were mushing through the air, over the overrun, sandy beach and then the water.  To this day, I believe it was the ground effect that kept us in the air.

Next, gear!  Normally the flying pilot calls over the intercom for the other pilot to raise the gear.  No intercom.  I immediately reached for the gear handle.  It wouldn’t come up!  We must have a hanging truck.  If I raise the gear using emergency override procedures, the gear will come up.  I will most likely lose all hydraulics as the gear will rip out all the hydraulic lines that are routed through the wheel wells for maintenance purposes.  The gear will be jammed in the wheel wells and may not come down. I can worry about landing later, I need to fly now.  I pulled the emergency override trigger.  The handle and the gear went up.  No loud crunching sounds.

The KC-135 has two main landing gear and a nose gear.  Each main gear has four tires, two forward and two aft.  These four tires are mounted in an assembly called a truck.  Each truck has actuators that level each truck after becoming airborne.  If a truck is not level, it is referred to as a hanging truck.  Raising the gear with a hanging truck using the 3,025 psi hydraulic pressure will cause the gear to be retracted.  Wheel well damage may result from emergency retraction if the main gear trucks are not level, the oleos are not sufficiently extended, or the nose gear is not centered.

According to a chart I just reviewed, the takeoff four engine maximum climb rate at sea level was 1,290 fpm and the three engine rate was 580 fpm.  The emergency procedures section of the Dash 1 states that gear drag lowers the rate of climb approximately 300 fpm at takeoff with flaps down.  An engine failure decreases the rate of climb approximately an additional 900 fpm.  The opening of the gear doors reduces the rate of climb even more while the gear is being raised.  According to this, 300 fpm plus 900 fpm equals 1,200 fpm reduction without considering the door effect.  A chart amount of 90 fpm does not provide a lot of flight cushion. Paper calculations have never provided an iota of actual lift or thrust.  And we had lost water, even worse in my mind than an engine.

The later modifications to the KC-135R designation provided a maximum climb rate of 5,000 fpm even after considering the allowable increase in aircraft and fuel weights.

While doing these procedures, I was looking out my window.  (No flight director system – no electrical power.)  I saw a Thai fishing boat.  It was a small boat with a tiny cabin leading below deck.  As we were about to fly over it, I saw the captain coming up from below deck with a white bucket full of something. He looked into my eyes and I saw the whites of his.  (Maybe you B-52 types are used to this low-level flying, this was a first for me.)  His bucket went up as he dove back down below deck.

Flaps! With the gear up we were beginning to gain airspeed. I reached over and raised the flaps.  On one of the two gauges that monitored the inboard and out board flap position (one gauge and for the inboards, a second gauge for the out boards), both needles went from about the three o’clock position to the twelve o’clock position.  On the other gauge, one needle went to twelve, the other to nine o’clock.  Asymmetrical flaps! Brace for the rolling motion!  No roll detected, bad gauge?

Asymmetrical flaps is a condition where the flaps do not retract or extend at the same rate.  This difference has the same effect as imputing a “turn” using the ailerons via the yoke.  This is extremely dangerous when at very low altitudes.  A bank angle of 30 degrees at climbout speed with flaps down could reduce climb capability by as much as 400 fpm.  As speed decreases, the effect becomes more severe, particularly in the clean configuration.

Assess your flight condition.  Gear up, flaps up, somewhere between 1,000 and 2,000 feet AGL and accelerating to over 200 KIAS.  Okay, now what.

Declare an emergency.  Battery switch emergency.  Listen to the UHF radio “click” as it cycles and tries to lock on the preset frequency.  Not enough power in the battery to lock on a frequency.  Go to “guard” position on the radio.  Still not enough power to lock on.  Dead battery.

The UHF radios had preset frequencies for items like ground control, tower, command post, etc.  To change from one preset to another you would rotate a dial with numbers, similar to an old-fashioned TV dial.  Guard was an emergency frequency that could be both monitored and transmitted on.

Shout at the Co to try and get some generators on line.  He successfully gets number 1 and 2 on line and mated to the bus.  Number 3 is toast.  This provides power to all the equipment. Get a TACAN DME (distance measuring equipment) lock at about 12 miles.  That is a long way to swim! (Even for a Minnesotan used to 10,000 lakes).  “This is _____ declaring an emergency in a left turn to 360 at 2,000 feet”.

So here we are rolling out on a 360 heading and describing to the Command Post the nature of our emergency.  About this point I told the Boom and Nav to go back in the plane and see if we had a fire, etc.  They reported no issues.  When we got back even with the base and are down wind, the Command Post asks me what is our current condition.  “Gear up, flaps up, two generators on line”.  “Roger”, is the response, “that is a go condition”.  I didn’t tell them my legs were shaking on the rudder pedals.  I don’t think that would have changed their opinion.  I was thinking “land, go to bar”.
We are now north of the base climbing through 8,000.  My number two engine oil pressure gauge starts to fluctuate and soon goes to zero.

Because more engines in the 135 were apparently shut down because of faulty oil gauges than actual loss of oil pressure, the fleet was in the process of being modified with a second low pressure sensor and indicator, a red warning light.  This aircraft had been modified.

And the number two oil light was illuminated.  Time to shut down number two engine.  Must have blown an engine seal after going to increase thrust.

“Command Post, this is _____, declaring an emergency.”  A short pause.  “Roger ____, didn’t you just terminate your emergency?”  “That’s a roger but now we are declaring a new one.”  And in addition to shutting down the engine, it caused us to lose a good generator.  We were down to one generator.  We are given clearance to dump fuel and return to land.

But, as I earlier mentioned, my Mother taught me to do the right thing.  Two things would have been wrong if we just hit the dump switch.  First, the JP-4 fuel we would dump, about 60,000 pounds (or about 9,230 gallons) to get down to maximum landing weight for braking limit purposes, would not evaporate prior to returning to earth.  There would be a whole lot of rice paddies covered with a film (or more) of JP-4.  Second, if we dump fuel with the boom up and in trail, fuel gets into the tail assembly and it needs to be cleaned somehow.

So I requested clearance to 21,000 feet.  After being granted, we start the slow, wallowing struggle to climb to that altitude.  It takes quite a while to get there but we finally make it.  “Boom, go back and lower the boom so we can dump”.  I soon get a call back over the intercom. “Pilot, I am having control problems with the boom.  One of the ruddervators isn’t working.  We may have to land with the boom in trail”. 

About this point in the flight, I am beginning to have doubts as to the air worthiness of this plane.  And more specifically, what’s next.  Systems just don’t seem to be functioning as designed.  But we successfully dump the fuel and the Boom is able to get it up and locked.

We now begin our decent.  We lower the gear handle and the gear comes down.  Again, I send the Nav and Boom back to check the visual down and locked stripes that can be seen from inside the cargo area.  I speculated that the gear wouldn’t come up, not because of a hanging truck, but rather to the fact that we must have lost electrical power while we still had the “weight on wheels” (WOW) safety interlock switch in the “on ground” position.  That prevents the gear handle from being raised using normal procedures.

Next, the flaps are lowered.  They extend without an issue. It was a faulty gauge.  This is followed by a successful three engine landing.

Because of the previous events, we are were met by the squadron or wing commander after taxiing in and shutting down.  He was kind enough to present our crew with a six pack of beer for doing a good job.  (Or for saving his promotion?)

We then had to endure a longer than usual maintenance debriefing.  I can’t recall if any of the above qualified for a “red X” in the 781.  But we did make a few entries. Someone brought to our attention that maintenance was aware of a circuit board defect that could cause a generator to trip offline. If this board experienced a vibration equivalent to that of slamming a fist on a table, it could trip a generator.  Because of the location of this board, they were replacing them only when an engine was required to be replaced.  I believe all further recollections of comments made would be censored.


For the next week or so, every evening after a flight we would be in our trailer and my co-pilot would go into the performance charts and say “it shouldn’t have flown!”.

This was very unsettling to my five-month pregnant wife, Melanie, who I had brought over for about six weeks.  She was staying at the Swan Lake Hotel but came to our trailer during the day time.  She found more to do on base as she waited for us to return from flights.  Since the war was over, I wanted to share with her some adventures in Thailand that I had on my prior two TDY’s.  This was NOT one of them I planned on sharing with her.  She did gain a greater appreciation for the risks any airman encounters when they “slip the surly bonds”.

My Co did buy me a nice lobster dinner at Camp Samae San (the Thai Marine Corps Base with US Army units adjacent to UT) with a deep-water port.  I believe the fuel and weapons for the UT aircraft came through this unit.  It was my first and only trip to their O Club, but what a club!  Real linen table cloths and napkins, real (non-plastic) silverware including salad and desert forks, real glass glasses, candle lamps on the tables, waiters, etc.  It was as good or better than any restaurant in Bangkok.  And twelve lobster tails.  Okay, they were one ounce each but tasted wonderful.  And all paid for by my co-pilot because -  even though I didn’t follow SAC policy for over water takeoffs; and whether through luck, skill or Divine intervention - I was at the controls and now we were able to eat the lobsters rather than them eating us.

Shortly after my return to Ellsworth, I put in my paperwork for a January separation.  The war was over, I heard rumors of a RIF (reduction in force), and recalled the two to three weeks of pulling Alert (with the possibility of only one to a max of three flights) a month that seem to happen whenever I was back stateside.  I don’t believe I was notified of the above citation that appeared in the December 1973 issue of SAC Combat Crew magazine until it was sent to me by my former squadron commander several months after my separation.