Russian Metrojet A-321 Crash in Sinai (Update)

STR/EPA/Picturedesk

A Russian Metrojet A-321 with 224 passengers and crew crashed in the Sinai Peninsula Saturday after being lost on radar. The aircraft was enroute to St. Petersburg from Sharm El Sheikh and was climbing through about 31,000 ft when radar contact was lost. There were no survivors found. The flight data and cockpit voice recorders have been found in good condition.

There were preliminary reports of the pilots having made distress calls but those were later rescinded. The wreckage was found in two major pieces spread over an area of about 8 km. Such a dispersal of debris suggests that the aircraft may have suffered an inflight breakup.

This has led to speculation concerning either a terrorist missile, MANPAD or structural failure. A terrorist group claimed credit for downing the aircraft but these reports have been dismissed as not being credible as has a video that the group released.

Intelligence reports claim that the terrorist organizations known to be operating in the area did not have missiles capable of reaching the altitude at which the aircraft was flying. A notice to airmen (NOTAM) had been released advising aircraft in that area to not operate below 26,000 feet due to terrorist activity. Likewise, analysis of the wreckage will confirm whether or not a bomb had been placed on board.

The aircraft itself, an Airbus A-321, was one of the oldest of the type in operation having been delivered in 1997. While the age of the aircraft should not be a factor in the crash, the aircraft had suffered a tailstrike in 2001 which resulted in significant damage while it was owned by Lebanon's Middle East Airlines. The aircraft was repaired and returned to service.

There have been several instances of airliners suffering structural failure which was due in part to repairs done after tail strikes. The most notable of these was Japan Airlines 123, a Boeing 747, which crashed in 1985 after a faulty tail strike repair failed resulting in a rupture of the pressure bulkhead.

Speculation and conspiracy theories are as usual expected to run rampant. Cutting the wheat from the chaff when an airplane goes down amid geopolitical unrest is always a challenge. Hopefully the truth behind this tragedy emerges unscathed.

UPDATE: The crash area is now being reported as 350 x 500 meters, smaller than initially reported.

UPDATE 2: Analysis of the cockpit data recorder now suggests that the crew had no warning before a catastrophic event brought down the aircraft. Further analysis of the wreckage should be able to discern the nature of the failure and whether it was a bomb or structural failure possibly due to an old tailstrike repair or undiscovered corrosion.

UPDATE 3: While no evidence of a bomb on board the downed Metrojet airliner has yet been publicly produced, David Cameron, PM of the U.K. has  gone on record stating that a bomb was the likely cause of the crash. US officials have also said that they suspect a bomb was the cause. The U.K and now the Netherlands have suspended flights to the Sinai Peninsula in the wake of the announcement.

New Post: You may also be interested in how a bomb can bring down an airliner: Falling Out of the Sky

MH370 Found?

MH370 found?

No, but an airplane part and a suitcase have washed up near Madagascar. The part will be tested to determine if it came from the Malaysian jet. If it's determined that the part is from MH370 it won't be of much help finding the rest of the wreckage. Ocean currents are quite random and will provide little help as to where to look other than the places already being searched.

The theories that will be put to rest if the part is genuine are the conspiracy theories positing that the aircraft was hijacked and flown to a secret base somewhere. My opinion is that the captain committed murder-suicide with his own airplane for political and other reasons.

Stay tuned.

Germanwings 9525

Airliners are not supposed to just drop out of the sky.

For the second time in nearly as many months, an Airbus A320 has fallen from altitude and crashed resulting in the deaths of all aboard. The latest accident occurred over the south of France.

Germanwings 9525, enroute from Barcelona to Dusseldorf with 144 passengers and 6 crew, had just levelled off at 38,000 ft when after a minute or so it started a descent. In the 8 minutes between the start of the descent and the impact of the aircraft into the Alps, no communications were heard from the cockpit crew in spite of multiple air traffic control attempts.

The descent, which averaged about 3300 ft per minute is not unusually steep for an airliner. The aircraft also maintained it's flight planned course during the descent suggesting that some measure of automation was still functioning. 

The wreckage is in a remote mountainous area in the French Alps and will present serious difficulties in recovery efforts. There are no expectations of finding survivors due to the violent nature of the impact into steep terrain.

The cockpit voice recorder (CVR) has been recovered and while damaged, has been able to have audio files retrieved by French accident investigators. The flight recorders have not as of yet been located.

At this point, speculation is running rampant but generally pointing in the direction of some sort of loss of cabin pressure resulting in the incapacitation of the crew. This would explain the lack of communication with the pilots. Loss of pressurization at 38,000 ft (FL380 in airline jargon) would result in what's known as a "time of useful consciousness" or TUC of about 20 to 30 seconds. 

That means that the pilots would have about 20 seconds to get their oxygen masks on and to start a descent before succumbing to hypoxia. Loss of cabin pressurization was the cause of the crash of Helios 522, a Greece based airliner in 2005, and also the death of golfer Payne Stuart when the Lear Jet he was riding in lost pressurization. 

Currently there appears to be no suspicion by investigating authorities of terrorism or foul play. Witnesses have reported that the aircraft appeared intact and flying normally except for its low altitude. This would seem to at least preclude an on board explosion.

Any theories given at this early stage in the investigation will be grounded in speculation at least until the CVR transcript can be analyzed or the flight data recorder is found. 

UPDATE: The New York Times is reporting tonight that the CVR indicates that the first officer exited the cockpit at cruise and was not able to re-enter. This development changes the fundamental nature of the investigation.

Germanwings A320 Down

A budget European airline A320 has crashed in the south of France in mountainous territory.  As of now, no survivors are expected. More to follow.

AirAsia 8501 May Have Entered a Spin Over the Java Sea

As of today, 93 bodies have been recovered from the fuselage of QZ8501 with 68 of them being identified. There have also been reports of a body being recovered wearing a pilot uniform from the cockpit area.

The mystery that still remains is the exact nature of the events which caused the aircraft to stall and to apparently depart controlled flight. As detailed in an earlier post, the aircraft climbed at a very high vertical speed to nearly 38,000ft followed by sounds of stall warnings being heard on the cockpit voice recorder.

Additional data released indicate that the aircraft changed heading twice during this climbing event and then started a rapid descent after which two more heading changes occurred. Data then indicate that the aircraft entered a "spiral" according to an article in the Wall Street Journal. (Paywall)

Modern airliners are not supposed to stall. All transport category aircraft certificated for commercial service are equipped with elaborate stall warning systems which are designed to give clear audio and tactile (stick shaker) warnings for even an approach to a stall.

Some aircraft manufacturers have gone even further in designing flight controls and other automated safety systems which will not even allow an aircraft to be flown into a stall. Airbus, the manufacturer of the A320 flown as QZ8501, is one of those aircraft builders. Airbus, a consortium of European aircraft manufacturers, revolutionized the industry by introducing the first "fly by wire" commercial airliner, the A320, in 1987. 

"Fly by wire" means that there is no mechanical connection between the controls in the cockpit and the wings as has historically been the case. With this aircraft, the cockpit control stick merely provides electronic signals to a computer (actually a series of computers) which interpret the pilot's intent. The computers then generate commands for the hydraulic servos which actually control the ailerons, elevators, and rudder. 

A Brief History of Flight Controls

The world's first successful heavier-than-air powered airplane was the Wright Flyer. The Wright brothers developed a system to steer the aircraft which actually warped the wood and cloth wings using cables fastened to the body. They later developed and patented a system of hinged flight controls which still provides the basis for aircraft control today.

As aircraft size, speed and complexity grew, new systems of mechanical linkages were employed to connect cockpit controls to flight control surfaces. Hydraulically powered flight controls were introduced in the post WWII era when aerodynamic forces became too great for human strength to overcome. These controls were, however, still controlled through direct mechanical linkages to the cockpit.

An ongoing objective of aircraft designers over the years has been to find ways to reduce the weight of their designs. A lighter aircraft can carry more payload, more fuel, has increased range and is more economical to operate. 

In the 1980s, Airbus felt that computer technology was mature enough for them to design a commercial aircraft with a fully digital flight control system. This system would replace all the pulleys, cables and other mechanical linkages between the cockpit and the wings with electronically controlled servos to command the hydraulic flight controls. There would be no direct mechanical linkage between pilot and wing. It would also save thousands of pounds of weight.

An "Un-stall-able" Airplane

Airbus went even further in their revolutionary design realizing that with computer control, they could design an aircraft that could not be mishandled by an errant or distracted pilot. In effect, the pilot was no longer in direct control of the aircraft but merely got a "vote" in how the aircraft was to be flown. And his vote could be overridden by the computer if a preprogrammed rule was violated.

So should a pilot inadvertently attempt to fly the aircraft into a stall, the computers would intervene to lessen the angle of attack to prevent the wing from stalling. You can theoretically pull fully back on the stick all day in an Airbus and the airplane won't stall. At least that's how it should work.

Faulty Computers

And in a normally functioning airplane that is how it does work. But something was amiss in the cockpit of QZ8501. News reports from the investigation now indicate that there might have been a problem with the aircraft's flight augmentation computer (FAC). There have been unconfirmed reports that the FAC had had recent mechanical difficulties, and that Captain Iriyanto, the pilot in command that night, may have been aware of the problems.

Data from the cockpit voice recorder now indicate that at some point just prior to loss of control of the aircraft, Captain Iriyanto transferred control of the airplane to First Officer Remy Plesel and got out of his seat for the purpose of pulling the circuit breaker controlling power to the FAC. This is considered a highly unusual course of action as a more normal procedure would be to reset the computer from a switch on the overhead panel if it was warranted. For some reason the captain felt that a reset was not appropriate and that the computer should be depowered.

Now as I've mentioned above, the Airbus's flight controls are completely computer controlled. But pulling the breaker on the FAC didn't mean that the airplane was now uncontrollable. There are multiple computers and redundancies in the system, but it does mean that the functions provided by the FAC were no longer available.

Now Vulnerable to a Stall

And one of those functions is what is known as "flight envelope protection" or more simply stall protection. Without flight envelope protection, the aircraft's computers would no longer automatically guard against a low speed condition or stall. Keep in mind that this vulnerability currently exists in all non-digital flight control airplanes flying today including the Boeing aircraft I fly. Their old school philosophy is that the pilot is the best stall protection.

What exactly happened next is still unclear but reports suggest that First Officer Plesel may have been startled by the loss of the FAC. Or he may have been trying to avoid a storm. But whatever the reason for it, he then placed the aircraft in a very steep climb which ran the airspeed down below flying airspeed at an extreme altitude.

At this point Captain Iriyanto was able to retake his seat and assume command of the aircraft, but the aircraft may already have been well into the now unprotected stall regime.

F/O  Remy Plesel

A Spin

Some data that has been made available from the DFDR indicates that there were multiple heading changes both before and after the stall warning sounded. It is possible that the aircraft entered a spin after stalling at high altitude from which the pilots could not recover.

A spin is a species of stall whereupon one wing is stalled and the other is either not stalled or is stalled less severely. When this happens, the more highly stalled wing has more drag than the partially or un-stalled wing and the aircraft starts to auto-rotate and drop.

Many aircraft can enter and exit spins should the correct procedures be applied. Airliners are not counted among those type of aerobatic aircraft. It is doubtful that Airbus even wind-tunnel tested the original design of the A320 for it's spin characteristics. The ability of an aircraft to exit a spin is also highly dependent on it's center of gravity (CG) and beyond certain limits no control input will be successful.

Captain Iriyanto had been a military F-16 pilot and was certainly familiar with unusual aircraft attitudes, and may even have had experience in spinning trainer aircraft. But a spinning airliner would certainly test the mettle of the best pilot ever to fly one even if recovery had been possible.

I've intentionally spun jet trainer aircraft many dozens of times during my instructor days, and it is a violent maneuver. Doing it at night in the weather in an airliner is the stuff of nightmares.

Conclusion

The events I've spelled out here contain a measure of conjecture based on the admittedly sparse data available from various news reports. The reality of what actually happened to QZ8501 may be remarkably different once the full report is made known. It is not yet known what the actual maintenance status of the aircraft was nor its proximity to the nearby thunderstorms. These details should be known when the final accident report is released.

TransAsia Aircraft Lost Power

By now everyone has seen these dramatic images of the TransAsia ATR 72 that crashed into a river shortly after takeoff from Taipei. 15 of 58 passengers aboard survived the crash but neither pilot survived. The data recorders have been recovered and are being analyzed. 

So far it is known that the aircraft reported engine problems at an altitude of 1200ft, 37 seconds into the flight. One of the pilots radioed the word "flameout" shortly before the crash and apparently an automated maintenance reporting system also sent a signal indicating that one of the engines had suffered a flameout according to an aviation investigator.

The term "flameout" is used by pilots to indicate that an engine has stopped producing thrust. While the ATR 72 is a propeller driven aircraft, its engines are technically known as turboprops. This type of engine is actually a turbine, or jet engine attached to a propeller. This means that if fuel is interrupted or some other malfunction occurs, the "flame" in the hot combustion section can go "out", and the engine stops producing thrust.

This particular ATR 72 was relatively new having been delivered in April but had suffered engine problems previously. The malfunctioning engine had been replaced according to reports. News reports did not mention which engine that was.

The latest reports now indicate that the right engine had not flamed out but had inadvertently entered "auto-feather" mode meaning that the propeller blades themselves are rotated on their axis so as to stop producing thrust but that the engine itself continued to run. This was apparently an uncommanded anomaly which would present itself to the pilots in the same fashion as a flameout.

Furthermore, the data recorders also indicate that the left engine was manually shut down. This suggests that there was confusion in the cockpit as to which engine had suffered a loss of thrust and the wrong engine may have been chosen to attempt a restart.

Expect the Unexpected

There was a time in aviation when things would routinely go wrong. Engines were unreliable, instruments were rudimentary and inaccurate, and pilots were pretty much on their own. Those days are decades gone and modern commercial transports almost never suffer the catastrophic failures of the past but that doesn't mean bad things don't happen. 

They still occasionally do, but the odds of say an engine failure on takeoff, one of the most challenging things that can happen, are becoming vanishingly small. At the current reliability rates of aircraft engines, the expected statistical occurrence of any engine failure let alone one at takeoff over a career of flying, is in the low single digits.

This is a really good thing, but it does present the problem of how to keep pilots from becoming complacent. Luckily, modern day simulators have capabilities that are so true in fidelity to actual aircraft that the FAA allows new pilots to complete a full training program and check ride entirely in a simulator. The first time a pilot may fly a newly assigned aircraft is now routinely on a revenue flight with paying passengers. The sims are that good.

You Are Only as Good as Your Training

Not only do all pilots train for normal operations in the sim, but we are routinely checked on emergency procedures such as engine and other system failures. One of the most common (and nerve wracking) events is known as the "V1 cut". In this scenario, during takeoff the instructor will fail an engine almost immediately after reaching our go/no-go decision speed known as V1.

This is the most critical point to lose an engine as you are committed to take off but have barely any flying speed. You won't know which engine will fail or how but you have an idea that something bad is going to happen. You're in the sim after all, and it's a required item, so it's coming. Not so true during everyday flying.

When the engine fails, the first thing you notice is that the aircraft will yaw, meaning the nose will swing towards the failed engine. (The thrust from your good engine on the other side is now pushing the nose towards the failed one.)  What must be immediately done then is to apply rudder to realign the aircraft with the runway so you don't go off the side into the grass. This is also your best clue as to which engine has failed without even looking at the gauges. It's an instinctual response. The nose goes left, you step on the right rudder.

If you're already airborne when the engine fails, the best indicator of which engine failed will more likely be the instruments, especially at night. I always instructed my students to "step on the good engine" and it seemed to work for them.

Don't Shut Down the Wrong One

I should probably also mention now that while an engine failure on takeoff is a serious event, it is also an eminently survivable one. All commercial transport aircraft are designed to fly perfectly well with the loss of an engine. Back in my military days, we'd fail two engines on one side of a four engine plane and get it to the runway with no fuss. In fact with no other system malfunctions, a single engine airliner won't fly as high or fast with a failed engine but landing is not a particular challenge.

The procedures to be followed after getting airborne and cleaned up with a failed engine are to determine what went wrong, attempt a restart of the failed engine if warranted, and to plan a return to the departure airport. Under certain conditions such as no apparent fire, and no internal damage or seizure, a restart may be attempted. If a restart is not warranted due perhaps to a seized rotor, the engine should be secured.

Here is where mischief can occur.

Checklists for both an emergency restart and also for securing a failed engine both usually involve taking the fuel control to off. For a restart attempt, this resets the fuel control unit and for a shutdown, you don't want fuel flowing into the dead engine. 

You have two engines with two fuel control levers right next to one another. This is the time to be very careful to choose the correct one. Choose unwisely and you're a glider. At my airline, as I suspect at most, this is a two person job with one person designated to guard the good engine lever while the other person shuts down the failed engine.

Again the key to all of this is to not rush. A single engine airplane will fly just fine all day, so rushing will only increase the likelihood of  mistakes.

There is actually precedent for the shutting down of a wrong engine causing a crash. In 1989 a British Midland Boeing 737-400 crashed when the pilots shut down a good engine having misidentified which engine had suffered an internal failure. There were 47 fatalities.

As I mentioned above, things almost never go wrong in commercial aviation, but when they do, you will be presented with multiple alarms sounding and a profound sense of confusion as you attempt to figure out what just happened. Simulator training is invaluable to be prepared but nothing tops a mental preparation to always expect the worst.

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:

 

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.

Found

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.

Debris Found from AirAsia 8501

Floating debris has been found near the site of where the aircraft was last seen on radar. The water has been reported as a relatively shallow 10-30 meters which should aid in the recovery of the flight recorders.

Recovery of the flight data recorder should give a comprehensive picture of what happened to the aircraft and whether the problem was weather related. Reports also describe the debris field as relatively tight possibly indicating the aircraft was intact on impact as opposed to an inflight breakup.

AirAsia 8501

AirAsia 8501, an Airbus A320 aircraft with 162 souls on board disappeared Sunday morning over the Java Sea while enroute from the Indonesian city of Surabaya to Singapore in heavy weather. As of yet there has been no wreckage found nor any signals from the aircraft's emergency locator beacon. The last transmission from the aircraft was a request for a left course deviation and a climb from 32,000 feet to 38,000 feet with weather avoidance given as the reason.

The climb request was denied by air traffic control due to traffic conflicts. There were heavy thunderstorms in the area which are normally associated with the tropical weather in the region. Radar contact was lost with the aircraft several minutes after the denied request.

While it is too early and not enough is known about the fate of the aircraft, a few clarifications about flight near thunderstorms may be helpful.

Don't Mess with Mother Nature

Thunderstorms are dangerous things and can grow to heights above which all commercial planes are unable to climb. Flight through a thunderstorm is also extremely hazardous as the gusts, rain, and turbulence inside can easily bring down any aircraft flying today, including fighters. You simply do not penetrate a thunderstorm.

It may then seem unconscionable that air traffic control (ATC) denied the climb request. What must be remembered though is that the function of air traffic control is not weather avoidance but rather traffic separation. Weather avoidance is the primary duty of the pilot. Most ATC radars are not even equipped to show weather data.

Should a situation arise where a turn away from a large cell needs to be made immediately and ATC denies the request, pilots always retain what is called emergency authority to keep their aircraft free of hazards. In such a case, turning the aircraft away from a storm is always the safest course and should be done while advising ATC of your actions.

The best course of action is to plan your weather avoidance actions as early as possible. Airborne radar has a useable range out to several hundred miles to search for holes in the weather. Should there be no apparent safe passage through the weather, a turnback or diversion to another airport is always possible. As I said earlier, you don't fool around with thunderstorms.

Springtime and summer are the worst seasons for thunderstorms in North America and at times I've seen solid lines of storms stretching from Texas to the Great Lakes. Flying around these storms can take you hundreds of miles off course, even into Mexico or Canada to avoid them.

Stay Out of the Shadows

One of the shortfalls of airborne radar is that it can't see "through" especially thick storms to let you know what is on the other side. The danger is flying towards what you believe is a "hole" in a line of weather only to find a larger cell behind the first one that wasn't apparent. The area behind a thick cell might look clear but isn't. For this reason, pilots are warned to never fly into or towards a radar "shadow" or area behind a strong return.

Modern digital radars now display warning icons on the screen when a shadow is apparent but in the recent past the antenna had to be pointed at the ground to discern shadows. If there were no "ground returns" or reflections from the ground behind the cell, you knew it was a shadow.

Life Inside a Storm

Ok, so what happens if you really screw up and end up inside a thunderstorm? Nothing good. For starters, the ride is going to be really rough. The severe turbulence found inside a thunderstorm means that everything that is not locked, bolted or strapped down is going to fly. This includes carts, lap children and most likely all the luggage in the overhead bins as the doors will pop open. So there will be injuries and chaos.

The structure of the aircraft may also be in peril. A simple rudder reversal on an Airbus taking off from JFK back in 2001 caused the whole vertical stabilizer (tail) to break off. Forces inside a thunderstorm will be stronger and may cause engines to depart the wing and wings to depart the aircraft. Never good.

But let's assume the engines and wings stay on the aircraft. The next danger is the huge amount of rain that the engines will swallow. Jet engines have a fire burning in the hot section and if enough water gets poured into the engine, the fire will be put out. We call this a flameout. And like trying to restart a campfire in the rain, it won't easily relight.

So now you're a glider in severe turbulence looking for a place to land in heavy rain and wind with limited instruments. This situation is generally one pilots wish to avoid so we are well incentivized to stay out of thunderstorms.

So What Happened?

Getting back to the fate of AirAsia 8501, the Java Sea where the aircraft was last seen on radar is nowhere as large an area as the Indian Ocean where the Malaysian 777 disappeared. Also, the aircraft was in radar contact which really narrows the potential search area.

So while weather may have played a part in the disappearance, it is just too early to know.

As it happens, I've flown on AirAsia. I put my family on an AirAsia flight from Bangkok to Phuket on a vacation a few years back. I found the airline to be modern, professional and a delightful experience.

While our prayers go out to the families who have loved ones on the aircraft, we hope to know more in the near future.

What Will They Find?

After a month of looking for the lost Malaysia 777 with no luck, it appears as if the surface search is coming to an end. There are simply no clues on the surface of the ocean that can be traced to the missing airliner. Efforts now, after having possibly hearing the last calls from the submerged beacon will focus on an underwater search using autonomous submersibles.

 These amazing machines have the ability to search the ocean floor thousands of feet beneath the surface for any clues. The problem is they are painstakingly slow having an underwater speed of only several miles per hour. It may take years of searching to find anything. The missing Air France recovery took several years of search and that was after finding floating debris from the crash.

 The question then arises that should the wreckage of MH370 be found, what clues will it give up as to the cause of its disappearance?

There are two "black boxes" that will need to be recovered to obtain the most complete picture of the fated airliner's last flight. The digital flight data recorder (DFDR) and the cockpit voice recorder (CVR) will both need to be found to have all the information available.

The flight data recorder will reveal most of the details regarding the state of the aircraft itself. For instance, there has been some speculation that the aircraft was tracked at an altitude of 45,000 feet by a military radar. The DFDR will confirm if this happened. If someone flying the aircraft intended to incapacitate the cabin occupants through oxygen deprivation, this theory might be confirmed.

The DFDR will also detail the last moments of the flight and whether it hit the water abruptly or was eased down so as to keep the aircraft in one piece. Had someone intended a soft touchdown to minimize flotsam and debris, that would have been the way to do it.

I believe that the cockpit voice recorder may be of less value. Assuming that the hijacking was carried out by one person, we might expect the last two hours of the CVR to be silent as the flight ventured further south over the ocean. Should conversation be heard, that would mean a team of hijackers in collusion. The act of silently flying the plane hours away from land indicates, though, that the hijackers had no "message" of grievance they wanted to share either.

Most voice recorders are supposed to capture the last two hours of sound in the cockpit and then to overwrite the data. At least that's what we're told. Depending on which conspiracy theories about spook-craft you believe, overwritten data my also be able to be obtained through advanced electronic analysis. Still, it seems unlikely that much useful data on the recorder might be found.

Lastly would be evidence found on the aircraft itself, namely who might be found in the cockpit. If only one pilot is found there, then it will be known that that person incapacitated the other pilot. If both are found there, determining the cause of death will be important, and we add likely impossible. If one pilot had hit the other on the head, only a detailed examination might determine that.

All these details will depend upon the condition of the aircraft should it ever be found. The depths at which the aircraft may lie are at the very limits of salvage equipment. The Bluefin vehicles have no mechanical arms to manipulate any wreckage they may find so that will have to be accomplished by other underwater vehicles.

Questions of how long the various governments are willing to take to find the missing plane also need to be asked. The Chinese will likely finance the continuing search effort for some time as they have the resources but if nothing is found in say two years or more, when will the effort be abandoned?

Malaysia 370 has a secret and is apparently still unwilling to give it up.