Tag Archives: AF 447

New Ideas on AF 447 Stall Recognition & Stall Recovery Procedures

AF-447 Stall Recognition:

Were the Air France 447 Airbus 300-200 flight crew members trained in stall recognition by:

A) Angle of Attack (AoA) based stall warning alarm system or

B) Loss in altitude, as displayed on the altimeter, due to loss of lift?

C) Both A and B

D) Neither A nor B?

1. A stall of relative wind flow over the Airbus 330 wing occurred at Stall AoA, setting off the flight crew cockpit stall alarm system. The stall warning signaled that the AoA had increased above the Relative Wind Flow Stall AoA, and by aerodynamics, the wing was no longer producing enough lift for flight, and so the altimeter was unwinding rapidly, telling the flight crew that the aircraft was descending. But did the flight crew see the loss of altitude as a symptom of trouble, or the exacting cause of the trouble and their cue to enact stall recovery procedures? If they understood the loss of altitude as their cue that they were in a stall, why did they not immediately begin stall recovery procedures, such as lowering their nose attitude? I do not think that the other multiple alarms and warnings confounded the flight crew. I think that they did not see the unwinding altimeter as the stall recognition cue. If they did, they would have lowered the nose at 37,000 feet and resumed level flight. What was the confusion therefore, that confounded the AF 447 flight crew?

2. Is not the altimeter a very good and reliable indicator of a stall? Along with the AoA Stall Warning system, didn’t the flight crew have this very reliable and verifiable stall indicator, all the indication that they needed to solve their problem? Without a doubt, a rapidly decreasing altimeter is a very good stall indication, especially when the crew has nose up control inputs. Acting on that information alone, the crew would have been able to carry out published stall recovery procedures of lowing the nose to lower the AoA.

Altimeter in Stall Recognition

3. I would argue that, as the Air France Airbus descended from above 37,000 feet to the surface of the sea, loosing its altitude due to loss in lift,  the flight crew never recognized that the loss of altitude was their stall recognition cue. As a result, the crew never attempted standard operating procedure stall recovery by lowering the nose. Was the reason that the flight crew never realized that they were in a stall, due to the fact that they did not understand that the decreasing altitude as displayed on their altimeter, was the stall indication? Why was that the case for AF447? Is that still the case today at many commercial airlines around the globe?

4. From their stall recognition and stall recovery training at Air France Airbus training program, were the flight crew trained to recognize and recover from stall based only on the installed AoA-based stall warning system? Did AB and AF not require the altimeter as the next instrument to be checked for decreasing altitude, in the stall recognition and recovery procedure? How many other commercial pilots are their out flying the line, that do not understand stall recognition and stall recovery procedures?

5. Once a stall is recognized by observing the decreasing altitude on the altimeter, wouldn’t the next procedure in stall recovery be the same procedure of decreasing the nose attitude, just as in the case for stall recovery for AoA based stall warning? In the altimeter case, doesn’t the altimeter substitute for the AoA-based stall system for the stall recognition? Since the AF 447 flight crew never attempted stall recovery procedures, is it correct to conclude, that they never recognized that they were in a stall at all?

6. Should Air France, all airlines flying Airbus, and Airbus Training, and perhaps all commercial airlines, shift stall recognition and stall recovery procedures from focusing solely on AoA-based stall warning for recognition and reaction, and rewrite procedures and redirect training to include scanning the altimeter for loss of altitude, as part of the procedures for stall recognition and stall recovery? Is this a new idea that should be considered by all airlines and training facilities?

Perhaps you could pass this procedural good idea on to your airline’s training department and your pilot association’s training committee? By understanding aerodynamics, you can enjoy safe flying. Remember that $afety Pay$.

International Captain Paul Miller

Air Asia 8501 Crash: Cause is No Mystery-Thunderstorms Can Kill

Captain Paul Miller in cockpit

Captain Paul Miller, Night Flight

In the 1931 novel “Night Flight” by Saint-Exupéry, we learn that even intrepid pioneering aviation heroes in the end are not match for thunderstorms in Patagonia.  We find out that thunderstorms can and will kill. We loose the wonderful hero of this timeless novel, a story of some of the earliest commercial night mail pilots. It is a book that professional pilots and readers the world over have kept popular for over 80 years.

Now we see the crash of Air Asia 8501 as the latest dreadful and inglorious chapter in the story of commercial aviation. Thunderstorms can kill.

Thunderstorms can kill with hail, turbulence, lightning and icing.

Hail will shred aluminum leading edges of the wing and tail. Hail will bend, dent and destroy the leading compressor blades of a turbine engine, components spinning at tens of thousand of revolution per minute. Hail will dislodge and destroy the multitude of radio antennae and necessary flight probes sticking out in the free airstream. Hail will pock-mark, crack and puncture flight deck windscreens, windscreens that protect the flight crew from 300 mph winds, minus 60 degree temperatures and air so thin humans can not inhale enough oxygen to live.

Turbulent vertical wind shears will load up a wing with positive two times the acceleration of gravity one moment and slam back in the opposite direction the next with an equal and negative acceleration, and keep doing this over and over again.100_3975

Lightning can burn holes in fiberglass, aluminum and composite components of an aircraft exterior and flight surfaces.

Clear icing can coat an aircraft with a slick covering, increasing its weight beyond the wings ability to sustain flight. Rime ice can build quickly on flight control leading edges, disrupting the airflow needed to sustain controlled flight, raising drag significantly above the engines ability to push forward and again adding weight.

Thunderstorms can and have destroyed numerous aircraft in the history of commercial flight.  The danger to commercial aircraft is so severe that US commercial pilots are required by the FAA and their companies to remain clear of thunderstorm cells and even the overhang of ice crystals, sometimes referred to as the anvil.

Are modern commercial passenger and cargo aircraft safe to operate inside of thunderstorms? This question has been asked numerous times in the week since Air Asia 8501 disappeared from radar screens.  Let’s examine the current FAA standard specifications for commercial transport category aircraft. Are commercial aircraft and engine building companies required to produce aircraft and engines capable of sustained flight in conditions of hail, lightning, icing and severe vertical turbulence?  If so, were any of the current transport category aircraft and engines now flying ever certified by such field tests? Data please?

Are any US certified commercial passenger or cargo airlines currently certified to operate inside thunderstorms in their operation specifications or OpSpecs? I know of none. Are  FAR Part 121 airline dispatchers required to demonstrate their knowledge of thunderstorm avoidance flight planning and flight following by the FAA in order to be certified to operate as a dispatcher?

Are any US certified commercial airmen trained and certified for sustained flight operations inside thunderstorms? Not that I am aware of.

Is FAA air traffic control required by their own regulations to vector commercial aircraft around thunderstorms? Is the national weather service required to keep FAA ATC informed of areas of thunderstorm activity?

So how is it that airlines around the world, operating commercial transport category aircraft, airlines such as Air Asia, in aircraft such as Airbus 320 family, under the direct supervision of a trained and certified dispatchers with access to current up-to-the-minute satellite photographs of, not only thunderstorm cells in the planned flight path of the airline’s flight, but areas and lines of thunderstorms, do not advise their own company flights of safer routes? How is it that the local and enroute air traffic controllers, whose ground-to-air radar is exceptionally good at depicting weather,  might deny a flight’s request to divert around or over a massive area of thunderstorms and then not offer some safe alternative assistance?

Where is the team work, the coordination, the combination of minds needed to improve commercial aviation flight safety?100_0306

Is any of this new information to any certified crew member, airline, ATC, regulator or manufacturer in commercial aviation? Have not thunderstorms been killing commercial flights and flight crew members since the beginning of manned flight. Don’t we find the first popular documentation in the 1931 book, “Night Flight” by Saint-Exupéry. Here our crew members operate aircraft with piston engines, wooden spars and canvas wings.

Now here is the airline industry, more than 80 years since Night Flight with turbine engines, steel spars and aluminum wings. Yet, thunderstorms are still killing commercial flights. Why was Air Asia 8501 the most recent to join the long list?

I wonder if  Saint-Exupéry  would say, “Imagine that? Nearly a century has passed since I wrote my book and this story is still timely in terms of flight safety!”

The chapters are new, the planes are new, the pilots are new, but the story is timeless: Thunderstorms can kill.

Early morning sun rising through clouds.

Early morning sun rising through clouds.

AF 447: High Altitude Stall or Swept Wing Stall? Did the Mishap Investigation Boards Make a Fundamental Aerodynamic Error?

The mishap investigation boards have given a less than
aerodynamically correct presentation of “high altitude stalls” in the 2009 Loss of Control LOC mishap investigation of AF 447 and the  2005 Loss of Control LOC mishap in Venezuela of a West Caribbean Colombian MD82.
The result is that these mishap investigation reports are not putting out satisfactory recommended corrective actions.
Here’s the problem: Swept winged aerodynamics differs from straight winged aerodynamics. Swept wings stall at the tips first. Straight wings stall at the root first. Swept wings pitch up when they stall. Straight wings do not. Swept wings tend to go deeper into the stall. Straight wings do not.

Pilots of swept winged transport category acft need to know this because many of these pilots received their basic and primary instruction in straight winged trainer
acft, and as such have learned straight winged stall recovery procedures.
Pilots who are now operating swept winged acft, who have not had
specific swept winged stall recovery procedures training per se, may not be adequately trained to handle a swept wing stall.
The various LOC mishap reports of the Colombian MD82 and AF 447 make reference to a problem the boards call “high altitude stall.”  This is really just an explanation that at high altitudes, the spread between true airspeed and indicated airspeed causes longitudinal pitch changes to feel exaggerated. But that extra pitch feel exaggeration is not the problem that keeps the acft stalled from loss of control at FL 370 to impact. What keeps the acft stalled is high angle of attack. The stall is the result of longitudinal controls being in the what is known as the region of reverse control, where the acft is on the back side of the power curve. This means that drag produced by the production of lift, induced drag, is so large, that it is greater in magnitude than the thrust available from the engines, meaning that even at full throttle, the pilots must push the nose down, in order for gravity to add force to thrust, to accelerate the acft forward to a speed great enough, and an angle of attack low enough, to bring the aerodynamic force vector vertical enough so that induced drag is lowered enough so that thrust can now accelerate the acft back into the normal one g flight envelop.

I apologize to all for the very long statement above, especially if it is confusing. In layman’s terms, the pilot has to push forward to get the plane going fast enough to begin flying again.

The boards should have cited swept winged stall and failure to employ swept wing stall recovery procedures as the mishap cause. Recovery procedures for swept wing stalls are different from procedures from recovery procedures for straight wing stalls.
Notice that when both AF447 and the Colombian MD82 descended through lower altitudes, they remained stalled and did not recover. The stall was not a result of high altitude, but high Angle of Attack. In both cases, if the correct swept winged stall recovery procedures had been used, the pilots could have recovered the acft, would have recovered the acft at much higher altitudes than the terrain CFIT and would have recovered the acft immediately, in my opinion. Stall recovery comes by lowering the angle of attack, not by lowering the acft altitude.

This is very important information and needs to be put out.

When a swept wing stalls, the stall emanates at the trailing edge of the wingtip due to span wise flow thickening the boundary layer. The aileron is actually one of the first wing components affected by a swept wing stall. As the stall progresses back up the wing, the aerodynamic center (AC) shifts forward, raising the nose and angle of attack (AoA). This causes the angle of the aerodynamic force (AF) to shift aft, resulting in a rapid and high rise in induced drag (Di), the horizontal vector component of AF. This induced drag opposes thrust, slowing the acft further and raising the AoA, deepening the stall.  This is known as the Region of Reverse Command or the back side of the power curve. Because induced drag rises and rises quickly, there may not be enough power alone to thrust the acft to a higher speed.

The stall is AoA dependent, not altitude dependent. The thrust available is limited by altitude, therefore the thrust deficit above induced drag is altitude dependent. Therefore the only recovery possible is to dump the nose down, reduce the AoA, reduce Di low enough, to where available thrust, as it is added, is sufficient to overcome Di and parasite drag Dp and accelerate the acft Indicated Air Speed (IAS) fast enough to regain lift and therefore one g level flight.

This is the only recovery possible. Swept wing aero is so important to know, that the US Navy has an entirely separate course on it, and it is taught after a flight student has learned to fly straight winged aerodynamic acft. In straight wing aero, the stall begins at the wing root instead of the tip. The AC as a per centage of the mean aerodynamic chord does not shift much, thus AF doesn’t shift aft and doesn’t result in a rapid rise in Di, slowing the acft further. Recovery is quicker with lowering the AoA, adding power and quickly regaining IAS.
Is it possible that the crews of neither of these LOC mishap acft received training in swept wing aerodynamics and the stalls that occur to swept wings?

There is a lot to know in swept wing aerodynamics that is different from straight wing aero, quite a bit to learn (I’ve only touched on it here). This knowledge is critical to understanding swept winged stall recovery procedures and successfully implementing them.

See “Aerodynamics for Naval Aviators,” by H. H Hurt Jr, NAVAIR 00-80T-80, Jan 1965, Naval Air Systems Command,  page 353-354, concerning the “Region of Reversed Command.”


Pilots have got to know this swept-winged aerodynamics if they are going to fly swept winged aircraft safely in all situations, I believe.

In my opinion, this is especially true, if they chose to become test pilots by conducting uncertified operations into FL 600 thunderstorms or operating acft over the certified gross weights indicated for altitude.

Let me know what your thoughts are. Thanx, Paul

Safety Purpose vs the Legal Purpose: Why the Safety Purpose Works: are you looking and leading forward or backward?

Safety Purpose vs the Legal Purpose: Why the Safety Purpose Works: are you looking and leading forward or backward?

The Safety Purpose seeks the cause of mishaps and tries to determine procedures to immediately and forever prevent a re-occurrence. The Legal Purpose on the other hand attempts to find fault or blame for injury and damage and assign penalties.

But there is one other very significant characteristic that safety managers need to know in order to do their job successfully, to be winners and lead their organization into a mishap free future. Here it is in a nutshell:

Lawyers only look backwards in time, never forward. When a lawyer says, “The ice crystal icing is new,” what he/she really means to communicate with you is that this subject area before has never shown up in court previously in a negligence case. There is no case history of this type of event.” We have recently heard a statement similar to this in AF 447 reports.

The event of ice crystal formation around the clouds of very tall thunderstorms is as old as the natural history of the earth, that is tens of billions of years old. Scientists of meteorology physics have shown us this in lab experiments and field observations. Teachers of pilots have been warning students to not only stay out of thunderstorms, but to say away from the high overhang of the upper clouds as well. This is nothing “new,” and pilots who desire to have a long career have paid heed to this advice for decades.
This is a good example of why lawyers running safety programs is a flawed concept. In law school, lawyers are taught to only look backwards.

THE SAFETY PURPOSE on the other hand, looks forward. Safety looks forward toward accident reduction, toward hazard resolution and the huge financial savings of mishap-free flight operations. So safety was achieved in flight school by educating pilots in the future to stay clear of thunder storms and avoid the overhangs. Not only can the ice crystal threat of the overhang be a hazard, but often hail showers can be located in these areas.

The flaws in the fostering of the Safety Purpose at BEA, AF, AB and other organizations such as FAA may very well be rooted in this very basic differential theory of management.

It is my opinion that the forward view found in SAFETY THEORY is of much more value to the commercial airline industry that the Legal Theory of finding fault and assigning penalties.

My guess is that airlines with safety people in charge of safety programs do a heck of a lot better than those with lawyers trying to run things. My guess is that the safety people at the regulatory authorities do a daily, albeit losing battle with the attorneys that have taken over positions of upper management.

JMHO, of course.

Air France 447 and Jean-Pierre Otelli, “Piloting Error, Volume 5”

What weather lies ahead of our flight?

Heard about the book today.  Jean-Pierre Otelli  who specializes in aviation safety, publishes his book “Piloting Error, Volume 5” today.

But in my opinion, he only re-analyses the facts collected in BEA’s report.  I believe that the BEA’s report is seriously flawed and the book adds little to mishap prevention.

Would you like proof that BEA’s investigation is flawed?

Simple: there is little if any recommended corrective action contained in the report, that, if followed, would have prevented this mishap. Rather, the book and report appears to center on finding fault, assigning blame and extracting tribute for damages. So, the investigation is really a legal investigation and not a Safety Investigation.  I have explained in the blog that the only value to a Safety investigation is to find ways to prevent a recurrence.
It appears to me training is weak at AF as well. So, that is a managerial responsibility and regulatory duty. Remember that this crew was certified by the airline’s training dept and national aeronautical regulators before they were assigned to operate this flight. If their performance as a crew and as individuals was substandard, as alleged in the BEA’s report, then that would be a direct indictment of the training and certification authority credibility, would it not?

From my background training experience, when we first learned basic and radio instrument procedures in basic jet training, an important segment of that training were procedures to employ when some of the instruments failed. Some of this training focuses on the failure of attitude and/or directional gyro equipment and is called partial panel procedures. Some other procedures focused on loss of pitot-static instruments, some or all, and teach you to remain in stable flight using attitude instruments and standard engine power settings. Other procedures cover magnetic and/or directional gyro or heading instrument failures, still others cover what to do if part of your navigation instrumentation fails.

We practiced all of these procedures right from the beginning of our training. Along the way with every new aircraft, with every new organization, these procedures remained a significant part of regular training. At my last sim/training session a year before retirement, we were required to practice these procedures and focus especially on the loss of pitot-static instruments. We trained heavily on this. After more than 40 years of flying and training, we were reviewing the basics and training on written procedures for loss of instrumentation.
So, were these AF447 crew members trained by AF in this area? There certainly appears to be a question here. However, does the report by BEA or the book by Otelli  investigate this?

So, read over my various blog postings and let me know what comes to your mind.

AF447: What will they find in Black Boxes?

Could new attempts to raise black boxes by investigators of the AF447 disaster be nothing more than attempts to exonerate all responsible parties?

Has Airbus, Air France, the FAA or any other manufacturer or regulator conducted testing inside 70,000 ft thunderstorms?

Have French officials, Air France, Airbus or the FAA been able to explain why the Air France dispatch office, a recipient of regularly updated satellite photography, was unable to inform AF447 of extremely severe weather in the flight path assigned to AF447 by that same dispatch office?