Friday, January 23, 2015

The First Clues from AirAsia 8501 are Emerging

Now that both the digital flight data recorder (DFDR) and cockpit voice recorder (CVR) from AirAsia 8501 have been recovered from the Java Sea, a picture of the fate of the aircraft is starting to emerge. 

The Airbus A320 with 162 passengers and crew was enroute from Indonesia to Singapore when it went missing in an area of heavy thunderstorms over the Java Sea. Just prior to the disappearance of the aircraft, a request was made for a climb which was denied by air traffic control.

Two pieces of information which have been obtained from the recorders are that the aircraft climbed at a rapid rate and that multiple alarms were sounding in the cockpit including a stall warning. At this point it is still too early to speculate exactly what happened to the aircraft but some pieces of the puzzle are available.

Data from the DFDR indicate that the aircraft at some point was climbing at a rate of 6000 feet per minute (FPM) which is considered excessive. This is generally true, especially for a fully loaded aircraft at altitude. A modern transport aircraft actually can achieve such a climb rate under normal circumstances when it is lightweight and closer to the ground, but certainly couldn't sustain such a climb rate without quickly bleeding off airspeed.

The question yet to be answered is whether the climb was initiated by the pilot as an emergency measure to avoid a looming storm cell, or rather caused by the aircraft inadvertently entering a storm and being buffeted by the strong updrafts in the cell. Or perhaps it was a combination of both storm action and pilot input.

A rapid climb for whatever reason appears to have caused the loss of airspeed to a point below the stall speed for the aircraft, which would explain the stall warning being heard on the CVR.

Investigators will need to correlate the position of the aircraft at that time with radar and satellite imagery to determine if the aircraft was actually in a storm cell. Acceleration data from the DFDR will also help determine if the aircraft was experiencing high G forces or severe turbulence which would indicate whether it had entered a storm cell. I don't know if the DFDR on the A320 records imagery from the aircraft's airborne radar, but if it does it will be helpful.

Climb or Turn?

If the rapid climb was initiated by the pilot, another question that needs to be asked is why did he choose to climb as opposed to turning to avoid the storm? 

A common misconception among the public concerning storms is that aircraft can simply climb over them. There is some truth to this. As with most things in aviation, the answer to this question is it depends. Storms come in many shapes and sizes and smaller ones can be topped. The biggest ones however can easily exceed 40,000 ft and should be deviated around and not over.

Even should a storm not exceed the altitude capability of an airliner, (about 41,000 ft for most) it's not a good idea to try to top the larger ones as turbulence can exist well above the actual storm cell. Larger storms with strong updrafts can even eject hail out of the top which can then travel for many miles. Hail will ruin your day.

Presumably, the captain of 8501 knew all this. One possible scenario might have been if they had been searching for a hole in the storms to fly through which then closed in front of them, or they flew into a radar shadow and were confronted with an unseen storm. In this case choices are limited.

The turn radius of an airliner at altitude can be five miles or more depending on speed. If the crew needed to immediately avoid a storm cell but were too close, climbing is the only option. You may not top the storm but it might be less turbulent higher up. Ideally, this is a situation to be avoided by early planning for storm avoidance.

What is a Stall Anyway?

I'm going a bit down the rabbit hole here but please bear with me.

Airplanes can fly through the application of fluid dynamic principles first discovered by Daniel Bernoulli and enshrined in his Bernoulli Principle:

\tfrac12 \rho u^2 + P = \text{constant}  

For the math-phobic, this equation means that as the velocity of a fluid increases, its pressure decreases. As applied to an airplane wing, the air (a fluid) travelling over the top of the wing must travel faster than the air travelling beneath. The faster moving air above the wing then has a lower pressure than the slower moving air beneath and hence lift is generated.

There is one caveat to this process and it's a biggie. Lift is only generated when the airflow over the top of the wing remains laminar meaning smooth. Should the airflow become turbulent, the relationship no longer exists and lift is destroyed. This is known as boundary layer separation and is the technical definition of a stall.

A stall will happen when the airflow over the wing is too slow to generate enough lift to support the weight of the aircraft. When this happens the boundary layer separates, the laminar flow is disrupted by turbulent flow, lift is destroyed and the airplane drops like a stone.

You may have noticed tiny fins and tabs attached to the top of the wing on an airliner. They are there to facilitate laminar flow. Look for them next time.

This means that all airplanes have a minimum speed below which they cannot fly and stay airborne. And as you might suspect this airspeed, called stall speed or Vs, is dependent on aircraft weight. (It is also dependent on many other things such as the width and length of the wing and even the smoothness of the paint, which is why we deice for even a coating of frost.)

It sounds scary but it really isn't. Stalls need not be feared but they should be respected. Once in a stall, every pilot should know how to get out of it. The first step is recognition. A stall may feel very similar to turbulence but a glance at the airspeed indicator will be an immediate tell.

The next step is to simply reestablish laminar airflow over the wing by lowering the nose and trading some altitude for some airspeed while helping with added thrust. Low altitude stalls are the most dangerous as there may be no altitude to trade with. Empty bank account as it were. In this case airspeed must be regained through thrust alone. (In thrust we trust!)

All airline pilots routinely practice stall recovery in the simulator and as an instructor pilot I personally stalled or had my students stall and recover a real airplane on a daily basis for years. It's a basic aviation skill.

Making the Tradeoff

So getting back to AirAsia, why would the pilot climb at such a high rate of vertical speed knowing that there was a possibility of stalling the aircraft? He was possibly trading his available energy for altitude in hopes of avoiding a storm cell.

A major component of flying airplanes is what is known as energy management. This means being aware of and managing the aircraft's mix of potential and kinetic energy. Anyone who has ever ridden a roller coaster or perhaps played with Hotwheels cars and track will understand.

As a roller coaster tops the first big hill, kinetic energy is low (in speed) yet the potential energy stored (in height above the ground) is high. This situation is reversed at the bottom of the hill with high speed thrills and then reversed again at the top of the next hill.

Trading speed for altitude can also be done in an aircraft. Only unlike a roller coaster, an airplane has to maintain a speed above stall speed to stay airborne. The energy available to trade is expressed in the difference between current airspeed and stall speed.

This type of energy tradeoff is also done routinely in airline operations. Say for instance we're cruising along at 280 kts and are given instructions to climb. Air traffic control may also ask for an expedited climb for converging traffic or some similar reason. 

Advancing the engines to climb thrust and climbing at 280 kts is the normal climb profile, but by also pulling the nose up somewhat more and letting the speed bleed off to say 250 kts, the airplane will climb quite smartly, trading the energy in that extra 30 knots of airspeed for a higher vertical velocity. Then once level, you accelerate back to your original 280 kts in level flight.

Be Careful When Slow

If an assumption is made that the captain climbed rapidly by trading his airspeed for altitude but then unsuccessfully avoided a storm cell, the situation might be potentially worse than entering the storm with lots of airspeed. Once available airspeed is traded for altitude, the aircraft is closer to stalling and the gusts found inside a storm can easily cause the airspeed to fall below stall speed.

Once stalled, control of the aircraft can also be compromised by gusts preventing a successful stall recovery. In the case of Air France 447, the pilots never recognized that they were in a stalled condition and never applied the correct recovery procedures.

What happened in the AirAsia cockpit is as yet unknown or unrevealed, and the situation may well have been unrecoverable by any method. Concern for the families of the deceased and other political considerations may impact the timing and method of the release of more information.

Hopefully further analysis of the DFDR and CVR will eventually reveal the actual events surrounding the fate of QZ8501.

Thursday, January 15, 2015

Thunderstorms in Action

Here's a cool little video showing Atlanta Intl arrival radar tracks with some thunderstorms passing through the area.

Notice how the aircraft at first deviate around the storms followed by going into holding for a while.

Wednesday, January 14, 2015

Pilot Shortage: Solved!

Automation may just mean less competition on the layover!

I jest with the title of this post, but only slightly. Automation is here, and in the future, jobs will be either heavily involved with automation or simply replaced by it.

This trend will present some new social problems concerning what to do with all the displaced workers as explained in this video. It's also the reason that efforts to increase the minimum wage will simultaneously succeed and fail at the same time: Those workers who remain will make more. The rest will make nothing.

The piloting profession is ripe for change due to automation. The pilot shortage is real and projected growth rates for the world's airlines far outstrip the projected numbers of pilots being produced. The replacement of pilots with automation is a long term goal of many stakeholders in commercial aviation.

This won't happen today or tomorrow, but it will happen eventually. Boeing's technology cycle runs about 15 to 20 years. The first generation of aircraft automation was introduced in the late 1970s followed by the 777 and 737NG technology introduced in the late 90s. The latest technology cycle for aircraft automation is the newly released 787 to be closely followed by the 737 Max aircraft.

Both of these new technology aircraft still need at least two pilots to be flown so we won't see single pilot airliners until at least the next technology cycle in perhaps 15 years from now at a minimum, but probably many more years than that.

But they're working on it.

In an article in C4ISR, a company called Aurora Flight Sciences has been contracted by DARPA to investigate the feasibility of an automated copilot:

C4ISR&Networks, January 12, 2015 
Aurora Flight Sciences has been awarded a $6 million DARPA contract to develop cockpit automation. 
The contract, for Phase I of DARPA's Aircrew Labor In-cockpit Automation System (ALIAS) program, calls for Aurora to develop "an automated assistant capable of operating an aircraft from takeoff to landing, automatically executing the necessary flight and mission activities, checklists and procedures at the correct phases of flight while detecting and responding to contingencies," said a company news release. "At the same time, the human pilot would be continuously informed through an intuitive interface of which actions the automation is executing, and take back control if so desired." 
Aurora is collaborating with the National Robotics Engineering Center and Duke Engineering Research Institute. "The ability to reassign cockpit roles, allowing humans to perform tasks best suited to humans and automation to perform tasks best suited to automation, represents a potential paradigm shift compared to how flight operations are currently conducted," said Jessica Duda, Aurora's ALIAS program manager. "One of our key challenges is to develop a system that creates trust between the pilot and the automated assistant."

I am actually gratified to read in this article a recognition that future automation should find things for humans to do that they actually can do.

Today's deployment of automation is the worst of all possible worlds as bored pilots are expected to sit on their hands and watch the machine fly the airplane but be ready to jump in and save the day should the machine screw up.

This model is not working. Rusty, bored and distracted pilots are uniquely unqualified to monitor the performance of machines which nearly never screw up but when they do, do so in a big way.

Using the currently flawed model, we should expect to see more accidents such as the Air France crash into the Atlantic by confused pilots and crashes like the Asiana accident in San Francisco made by pilots who weren't competent to fly a simple approach in clear weather, but rather relied heavily on the automation to stay safe.

Automation is here to stay, and overall, that's a good thing. Like any new technology, it needs to be carefully deployed for the maximum benefit and should enhance human capabilities rather than replace them as the current technology attempts to do (poorly).

Sunday, January 11, 2015


One of the black boxes from Air Asia 8501 has been found. It should be a just a short while until the other recorder is found which will give a complete picture of the fate of the aircraft should they yield good information.

My speculation is that the aircraft wandered into a thunderstorm which then either compromised the structure of the aircraft, or placed the aircraft in a position from which the pilots could not recover before hitting the water. A stall scenario similar to the Air France crash over the Atlantic may have occurred.

It should only be a short while until more is known.

Saturday, January 10, 2015

Sometimes Chicken, Sometimes Feathers

As I've mentioned before, I am what is known in airline parlance as a commuter. This doesn't mean that I drive to work, it means that I live in a different city than where I work. It also means that getting to and from work involves a plane ride. I guess it's a little like having to take public transportation because that's actually what it is. It's the waiting at a bus stop for a bus that doesn't come that can be a drag.

The Thousand Yard Stare

Being a commuter and subjecting yourself to the vicissitudes of commercial aviation on a weekly basis necessitates that a certain zen-like attitude be maintained. Any business person who travels on a frequent basis knows exactly what I mean. From parking at the airport to the TSA and surly gate agents who seem to relish keeping you off the plane, it's a miracle that anyone flies at all.

God bless those that do, though, because they're the source of my livelihood.

And I've probably got it a little easier in some respects than the paying customer even if I'm not assured a seat at all. Nearly a decade after 9/11, the TSA finally recognized that crew members aren't really the enemy and have instituted a trusted traveller program for airline crews. This makes security screening a little easier to take.

And in some cases I get to pre board the aircraft if I will be riding in the cockpit. Otherwise I have to board at the end of the line. Even then, knowing that most passengers always head to the back to find the by now non-existent aisle seat, I take the first middle seat I can find which is usually near the front.

But overall, the entire process is somewhat dehumanizing and tedious. The term "thousand yard stare", used by shell shocked soldiers applies when commuting. It's a defense mechanism used to shield your psyche from the inevitable realization that while you got off of work at 3pm, you may not get home until 9pm or perhaps not at all.

No, You Can't Go Home

This was my experience last week.

Finishing a three day trip with a scheduled arrival at my domicile of 1610, I knew making my commute flight home which was scheduled for 1600 was a long shot, but Chicago almost always comes through for me in delaying flights so I thought I had a fighting chance.

We were coming in from the west with a significant tail wind and I wasn't being stingy with the throttles either hoping to arrive ahead of schedule to increase my odds. My F/O was taking a later flight home and agreed to babysit the jet so I could punch out and run for my flight.

Even air traffic control seemed to be on board asking us to "maintain maximum forward" for traffic. Gladly, we said.

Then the plan changed. We were told to slow to 250 and to turn 20 degrees to the right. This is the equivalent of slowing to 55 and then to get off the freeway onto a surface street. Not helping. And this was done several hundred miles out.

Apparently we were to be sequenced behind a Citation. The Cessna Citation, affectionately known as the "Slow-tation" is the slowest business jet in the air. The joke goes that it has bird protection screens installed...on the exhaust to keep birds from flying into the back of the engine. The new Citations are much faster but too many of the old ones still clog up the skies.

This Flight Has Been Cancelled

Eventually arriving, I noticed several jets waiting for takeoff and correctly guessed that one of them was the one I was trying to catch. Oh well. I'll just hang out in the pilot lounge, maybe do some online training and get some dinner before catching the next one at 1850. 

As I listed for the flight, the computer screen said the flight was unavailable. It had been cancelled. OK, I guess I'll get the rest of my training done, get some dinner and catch the 2000 jet to be home by perhaps 2200. Getting home at 10pm after a 4am wakeup is not ideal, but at least I'll be home.

No such luck. As I was clicking through the online training screens on the lounge computer, my phone beeped again. A text message from the airline mentioned a cancelled flight. I thought it must be a repeat message but no, the last flight home was cancelled. Great. Another night in the crashpad.

Well, I was thinking that if I have to do the time, I might as well do the crime and go fly. And sure enough, due to all the cancellations there was some open flying for the next morning. One trip in particular had a late morning show and flew one leg to San Antonio and then deadheaded home. 

I'd fly that leg, get released from the deadhead and be on a plane home in a few hours after that. I'd get home only a few hours later the next day with a decent paycheck to show for the effort. Seniority has its privileges and I got the assignment.

The temperature dipped that night to negative five degrees which probably had something to do with all the cancellations but it made for a chilly hike to the crash pad. On the bright side, when the weather is really awful, I don't worry so much about meeting one of the more vibrant denizens of South Chicago looking for forced charity, so there's that.

More Sand in the Gears

The flight to Texas was uneventful and I was released from having to deadhead back to Chicago, which by then was in a snowstorm, so all was looking good. Then an announcement was made that the flight attendants working the flight were delayed a half hour. No prob. Time for a salad.

We boarded, taxied, and then sat. The anti-skid braking system had a problem which meant a gate return. It also meant that that airplane wouldn't be flying anytime soon. That system almost never breaks but when it does, it isn't a quick fix. My concern now was whether this flight would be cancelled.

Luckily it wasn't cancelled but we did have to wait two more hours for another flight to arrive from Phoenix. Only then would I be allowed to go home. Finally airborne, I arrived home at about 10pm, a day after getting off work.

While I don't necessarily believe in karma, considering that the day before Christmas eve I made my commute flight after an international arrival with 15 minutes on the ground I figured that I was due for a little trouble getting home. The universe is in balance once again.