Air France 447

This is a case of two pilots unable to recognize a problem for what it was as it was unfolding, and of a third pilot who couldn't solve the problem in the limited time he had. I agree with Mr. Langewiesche, automation has made flying easier but it has also made pilots less able to deal with the unexpected.

The days of pilots who are well schooled at dealing with all manner of things going wrong are coming to an end. That generation of pilots has long ago started retiring and pretty soon they will all be footnotes in history. You cannot train this kind of thing in a simulator, where the absent risk of real injury and death cannot be simulated. But I think pilots can train themselves to remain calm in stressful situations. We can also train pilots to realize when things are not as they should be, and how to return a situation uncertain into a situation recognizable.

I think many modern aircraft accidents could have been saved had they been flown by pilots from generations before all this automation. As damning as that may sound, modern aviation is safer than it has ever been because automation has removed much of the guess work, because aircraft are better designed, because we know how to better maintain them, and, yes, because our pilots are better in many ways. So how can I stand by my statement that many modern aircraft accidents could have been saved by earlier generations of pilots? Because these pilots were practiced with dealing with things coming apart at the seams, and they have a few bag of tricks for saving the day. I'll provide those techniques in a bit, but first we need to dive into what happened with Air France 447 to illustrate just how quickly things can go from perfectly normal to catastrophic. In this case, less than five minutes.

• Date: 1 June 2009
• Time: 0014
• Type: Airbus A330-203
• Operator: Air France
• Registration: F-GZCP
• Fatalities: 12 of 12 crew, 228 of 228 passengers
• Aircraft fate: Destroyed
• Phase: En route
• Airport (departure): Rio de Janeiro-Galeao International Airport, Brazil (SBGL)
• Airport (arrival): Paris-Charles de Gaulle Airport (LFPG)

1 — The pilots

2 — The weather

3 — The airplane

4 — Narrative: What happened

5 — Analysis: How to prevent recurrence

6 — Technique: communicate as if your life depends on it

7 — Technique: known thrust and pitch settings

The pilots arrived in Rio de Janeiro three days earlier, on May 28, 2009. Their return flight to Paris was scheduled to depart about 2000 Brazil local time, arriving about 1200 France local time; they would be flying through the Window of Circadian Low (WOCL). (For more about that: Fatigue.) Because the flight was scheduled to last 12 hours, 45 minutes, the crew was augmented with a third pilot.

Captain Marc Dubois

Captain Dubois was the pilot monitoring for the first three hours, then went to crew rest, and returned to the cockpit for the final moments, standing behind the two first officers in the pilots' seats.

First Officer Pierre-Cédric Bonin

First Officer Bonin was the pilot flying for most of the flight. He was the least experienced of the three.

Relief First Officer David Robert

First Officer Robert was the relief pilot who assumed pilot monitoring duties when the captain left the cockpit. He was a management pilot and had very little time in the previous three months.

Air France ab initio and other low-time pilots

First Officer Bonin was an ab initio (Latin: "from the start") pilot, hired with virtually no applicable experience and put into large jet aircraft without having gained significant experience in smaller aircraft.

Airlines will tell you that ab initio pilots learn quickly in the simulator and on the line, ignoring the fact that these highly automated aircraft require pilots train to use the automation and leaves little time for building basic skills.

Old tech / new tech, old pilots / young pilots

In my opinion, there is a paradox with modern, highly-automated aircraft that wasn't present with the barely automated aircraft of the past. I base this on my experience flying the oldest models of KC-135As and Boeing 707s before they had autopilots that could be used for climbs, descents, and approaches, as well as engines that could be trusted not to explode at regular intervals.

• The old. Training for these pre-automation aircraft emphasized dealing with systems that were prone to failure, so you got to know the systems very well. Stick and rudder skills were also emphasized, because these aircraft did not always behave well. Things like Dutch Roll, behind the thrust curve approach speeds, and narrow low- and high-speed buffet margins at altitude demanded pilots be trained to know how their aircraft behaved at high altitudes. Simulators were very basic, so flight training was required.
• The new. Simulators have become so good that pilots normally leave the simulator fully typed and ready to fly the line. A lot of training time is taken over by having to learn the automation, so less time is devoted to systems. That usually isn't a problem, since the systems themselves have become so reliable. But those systems are so complicated, that few pilots really understand them unless they devote extra time to learn, away from the classroom. Flight training is practically nonexistent. It is quite likely that many modern airline pilots have never hand-flown large aircraft at altitudes above 29,000 feet because of Reduced Vertical Separation Minima.

The weather for departure and arrival were good, but the flight crossing the equator would be over the Intertropical Convergence Zone (ITCZ), where the north-easterly trade winds in the northern hemisphere converge with the south-easterly trade winds in the southern hemisphere.

The conditions were conducive to condensation at high altitude. One thing to note about convective activity over the oceans is that updrafts can force very small water droplets upward where they become "supercooled." These supercooled water droplets will instantly freeze if they encounter a hard surface, becoming clear ice.

The aircraft was less than five years old and had no outstanding write ups. In my opinion, however, there were issues with the pitot-static, fly-by-wire, and sidestick systems.

The pitot-static system

Depending on where the static ports are located, the reported static pressure is subject to errors which varies with aircraft speed.

Loss of pitot pressure can have a great impact on display altitude:

Ice Crystals

Ice Crystal Incidents

Air France's Airbus A330 and A340 were delivered with Thales C16195AA pitot tubes.

Airbus indicated later that year that BF Goodrich probes appeared to be more reliable in icing conditions, which seemed to prompt Thales to further review their C1619BA probes, concluding:

Air France decided to change the pitot probes across their entire A330/A340 fleet.

The change wasn't considered a time critical upgrade because the ice crystal problem didn't happen often, when it did happen it only lasted a few minutes, and there were procedures to deal with it. The procedure, called "IAS douteuse," which translates to "airspeed doubtful." The procedure was a highlighted training event in simulators at Air France.

The fly-by-wire system

If you've never flown a fly-by-wire airplane, the fact things are managed by "control laws" may be confusing. That is understandable, because this terminology is foreign to conventional aircraft. I found the easiest way to grasp what a control law is, is to think of it as a set of rules the flight control computers use when making decisions. In "normal law," the airplane flies conventionally but the computers interceded on behalf of the pilot to prevent bad things from happening. You cannot stall, for example, in normal law.

I've flown several fly-by-wire aircraft and one of the demonstrations is to try to stall the aircraft with the thrust reduced and full aft stick. The nose comes up and the speed falls, but once you get to a certain Angle of Attack, the fly-by-wire system holds what you have and the aircraft descends. The aircraft does not stall. The problem with this demo, however, is it plants into the pilot's mind that the aircraft cannot be stalled. That is only true in normal law. That begs the question, when do you lose normal law?

In the Airbus fly-by-wire system, there are three Air Data Inertial Reference Units (ADIRUs). As long as two of the three agree on their inputs, you will probably have what you need for normal law. If two of the three have problems, you can have a cascade of issues, such as the autopilot and autothrottles disengaging, flight directors removing guidance, and ending with a degrade to alternate law.

Of critical importance: if one of the airspeeds deviates, it gets thrown out. If the other two speeds differ too much, you go to alternate law and lose your stall protection. You still get stall warning, but it will be up to you to break the stall. An Alternate 2 Law, you can stall the aircraft and your roll inputs, instead of resulting in a roll rate with bank angle limits, will result in a direct connection to the roll creating flight controls.

Inactive Sidesticks: "Who has control of the aircraft?"

It is an age-old problem, who has control of the aircraft? When I was in Air Force pilot training, we lost a Northrop T-38 Talon when the front seat pilot thought the back seat pilot had control, and vice versa. Our practice was to wiggle the stick and say "I have the jet." When pilots sit side by side with a yoke in front of them, things become a little easier, since you can see the other pilot's hand on the yoke. With a sidestick, things become complicated.

If the sticks are mechanically linked, you can feel the stick move in your hand when the other pilot moves it. Some fly-by-wire systems have electrical servos to duplicate the mechanical linkage, these are often called "active" sidesitcks. In the Airbus, there is no such linkage, mechanical or electrical, sometimes called "passive" sidesticks. If the other pilot has control, you won't know it by feel alone.

The Airbus solution when both pilots are moving their sticks is a voice warning, "Dual Input," repeated every few seconds, and a green "Sidestick Priority" Light. When one pilot intentionally takes control using the red "takeover" pushbutton on the stick: (1) a red light illuminates on the deactivated stick's "Sidestick Priority" light, (2) a green light illuminates on the active sidestick's "Sidestick Priority" light, and (3) an aural alert announces "Priority Left" or "Priority Right." One pilot can lock the other pilot out by tapping his takeover button twice. If that happens, the other pilot has to press and hold the takeover button to regain control.

Fly-by-wire pilots tend to prefer the system they spend the most time with, and I am certainly guilty of that. Most of my fly-by-wire system time is with the Gulfstream GVII, where the active sidesticks move in concert. If the right seat pilot moves the right stick, the left stick moves. I think this is vastly safer than the Airbus solution because in times of stress, one of your first senses to fail you is your hearing. As with Air France 447, you are unlikely to hear "priority left" or "priority right." So too with the priority lights. In these stressful situations, are you likely to see the lights?

In the Airbus fly-by-wire system, if neither pilot has taken priority, both sticks are active and the inputs are averaged. If one pilot pitches up 10 degrees and the other pitches down 10 degrees, you end up with 0 degrees pitch. If one pilot takes priority, only that stick is active and the other is ignored.

Crew rest area

You could argue that getting the captain back to the cockpit sooner might have made a difference, I'm not so sure. But the absence of a interphone didn't help.

Rumors of fatigue

Palmer acknowledges that these allegations fall short of "factual evidence." But given what happened, this explanation seems plausible.

From departure to the captain's rest period

The least qualified is now Pilot in Command (PIC)

First Officer Bonin (in the right seat) was the pilot flying, Relief First Officer Robert (in the left seat) was the pilot monitoring.

Radar

This Airbus A330 radar was conventional for the time. It was a Rockwell-Collins WXR 700, with manual tilt and gain, and displayed returns in colors from green (least intense) to red (most intense) on the navigation display. The returns would be seen superimposed against the aircraft's position, route, and upcoming waypoints. The gain is normally left in "CAL" position to be able to interpret the display colors in a calibrated mode, so that a particular color represents a particular amount of rainfall. The gain can be adjusted to see beyond return shadows or in conditions where the returns are particularly weak. (See Radar for a deeper discussion about this.) Radar returns from ITCZ weather at this altitude can escape notice when the gain is set to CAL. The BEA interviewed the captain of an A330 which was 37 minutes behind Air France 447:

Relief First Officer Robert selected MAX 8 minutes later in the flight than did the captain on the following flight.

Ice crystal encounter

The loss of airspeed caused the altimeters to drop, perhaps starting First Officer Bonin's perception of a need to climb.

Pilot inputs that were "abrupt and excessive"

Note: The AOA is not displayed in this cockpit.

The first officer's pitch inputs increased to 16° after having been reduced to no lower than 10°. The pitch setting before the event was around 2.5° and N1 was 100%.

The control sticks on each side do not provide any tactile feedback from the opposite side. In this case, the PNF pushing nose down would be unnoticed by the PF, and the PF pulling nose up would be unnoticed by the PNF. The displayed airspeeds and altitudes were now consistent and validated the fact the aircraft was in an aerodynamic stall. Stall warning was the aural voice saying "Stall" and a red band on the airspeed tape. There is no stick shaker.

This excessive high angle of attack created a paradox for the remainder of the flight. When the pitch was high enough to cause pitot and static pressures to become invalid, the the stall warning ceased. When the pitch was lowered and allowed the pitot and static pressures to become valid, the stall warning resumed.

The captain's return

The loss of airspeed indications and . . .
panic (avoiding)

The loss of airspeed indications caused the autopilot to disconnect. The loss of airspeed indications isn't announced, but the loss of the autopilot generates a loud "cavalry charge," three musical tones that cannot be missed.

As the report notes, the loss of reliable airspeed caused the position error corrections in the altimeters to drop as well, causing the indicated altitude to drop 300 feet. The report speculates that this may have something to do with the First Officer Bonin's immediate reaction to pull the stick aft. Perhaps he noticed the swing of the altimeter needle down and reacting by pulling up.

The report contradicts itself between "without any inputs of the sidesticks" to "a large initial input on the sidestick under the effect of surprise." I think the latter is more likely than the former.

When the autopilot disconnected, First Officer Bonin immediately said, "I have the controls," which is the correct response. But within two seconds he applied enough back pressure on his sidestick to pitch the airplane up 11° in ten seconds. The BEA report notes that the "salience of the speed anomaly was very low compared to that of the autopilot disconnection." In other words, Bonin reacted in alarm at suddenly losing the autopilot and didn't take the time to ask why it had disconnected in the first place.

The correct response to the surprise of losing the autopilot would have been to do nothing other than lightly cradle the stick without making any inputs, while watching the aircraft's attitude to ensure it remains steady. Then, calmly announce the problem and attempt to collect information to help in your analysis.

That's all well and good, but how does one avoid panic and remain calm in a stressful situation? The conventional answer is to practice in the simulator but that doesn't work for most people, since you know no matter what happens, you are walking away from the simulator in one piece. I can offer two suggestions. First, practice being calm in everyday life. If you are prone to flying off the handle in day-to-day life, try to remind yourself that this kind of behavior on the ground impacts your behavior in the air. The next time the dog soils the carpet or your five-year-old drops her plate from the dinner table, try to avoid raising your voice. With practice, this becomes easier. See: Rule 3 - A Practiced Calm Will Serve You Well. Second, try having a saying ready to go to remind you that you need to keep it together. This is something you can practice in the simulator. I'll go into greater detail, below.

Flight control laws and . . .
systems knowledge (knowing more than you are taught)

Bonin's over-controlling the ailerons was a result of the aircraft degrading to alternate law. In Airbus normal law, aileron inputs are translated to roll rates and pitch inputs to G-loads to make the resulting aircraft movements smoother, limited and protected. In alternate law, these stick inputs go directly to the controls, making it more likely to over bank and pitch erratically.

Relief First Officer Robert mentioned the loss of autothrust and the reconfiguration to alternate law while reading the several ECAM warnings, but the fact they were in alternate law didn't seem to register with Bonin. Having spent all of their flight time in normal law, the affects of alternate law may have been just an academic exercise. When learning a new system — especially something radically different than anything you've experienced before — it is common to focus on what you need to fly the jet and leave everything else for later. Get normal law down, worry about alternate law later. But once you get your type rating and spend every flight in normal law, later never comes. In a stressful situation, saying "you are in alternate law" may not register.

The primary duty of the pilot monitoring is to monitor the aircraft's attitude. Relief First Officer Robert did notice that First Officer Bonin was over-controlling, but didn't do enough to get Bonin to stop. Let's assume that Bonin was in panic, as he appeared to be. Let's also assume that at this point, Robert had not yet panicked. When faced with this situation, you must get the panicked pilot's attention and give him or her direct instruction. Call them by position and name, sort of like when your parents called you with your full name. State the problem succinctly. Then direct the solution. For example: "First Officer Bonin! We are not in normal law anymore! Limit your stick movements to half, no more!"

It is also probable that neither pilot really understood the ramifications of being in alternate law. Most aircraft qualification training is on a tight schedule with the objective of passing a check ride. Instructors will emphasize the things most likely to be examined and pay only cursory attention to everything else. You may see a question on a test, such as, "how is aileron control affected by a degrade to Alternate 2?" You competently answer, "direct control of ailerons and lift dump, loss of bank angle protection." Job done, as long as you can spit that out when asked. But do you really understand?

How do you really learn something so you understand beyond rote memorization? Your answer may be different than mine, but you need to find that answer. For me, the best way to learn — to really learn — is to instruct. If I don't have a student, then I instruct by writing lesson plans for the day I will have a student. The process of writing cements knowledge for me. For others, it might be talking to others. Back to our aileron control example. I would dive deeper and find out how normal law filters stick movements into aileron deflection, why that doesn't happen in alternate law, and how the pilot takes on that duty. A good exercise is to pretend you are explaining this to an annoying child who always responds with "why?" Answer as many why's as you can, and you will understand well enough to recall that knowledge in times of stress. See: Being a Better Student / Do a better job teaching as well as learning.

Stall recovery and . . .
stall recovery (there is a difference)

We must first address a common misperception about stall angle of attack and then discount a factor that some say delayed the stall warning for the pilots of Air France 447.

We know that parts of the wing can go supersonic well before the airplane because the wing shape requires a longer distance over the same time. This occurs at the "Critical Mach Number," which could be accompanied by Mach buffet. Older, high speed aircraft could experience Mach buffet and Mach tuck, which happens when the redistribution of air flow and/or loss of effectiveness of the tail results in a pitch down. Most of us have never experienced Mach buffet or Mach tuck because our wings are designed to allow for better high speed behavior. These airfoils are called "supercritical," because they are designed to perform efficiently at and just above the critical Mach number. One of the few downsides of supercritical wings, however, is that they stall at lower angles of attack at high Mach numbers, because the shock wave on the wing impacts boundary layer separation.

Is it important to know that the stall angle of attack can change at high speeds for some wings? I don't think so. In fact, I usually ignore that fact because if you respect the stall warning systems of your aircraft, you will never need this information. I bring it up here, only because there are those who say the two first officers of Air France 447 were not warned. An examination of the cockpit voice recorder proves there were multiple stall warnings, but it is unclear if the pilots heard each or fully understood that the aircraft was actually in a stall. I think a stick shaker could have gotten their attention. But later in the flight, they clearly heard the off-again, on-again stall warning. They just didn't recover properly.

The Air France 447 pilots obviously didn't think to aggressively decrease the angle of attack to break the stall, as we are taught today. However, I still hear of instructors teaching to minimize altitude loss as a sign of good airmanship, disregarding the fact the training is done for the approach to stall at low altitude, building poor muscle memory for actual stalls at high altitudes. The fix is obvious: treat all training approaches to stalls as if they were the real thing: aggressively break the stall with a reduction in the angle of attack while adding thrust. Get the airplane flying again before worrying about altitude loss.

Recommendations: two from the BEA and . . .
two more from me

The BEA report lists the causes of the accident:

This BEA report has all the facts, but fails to use them to clearly delineate causes. In this situation, the best window into what really happened and how to prevent recurrence is to look at the recommendations. In this case, these two from Section 4 of the report:

"Consequently, the BEA recommends: that EASA review the content of check and training programmes and make mandatory, in particular, the setting up of specific and regular exercises dedicated to manual aircraft handling of approach to stall and stall recovery, including at high altitude."

"Consequently, the BEA recommends: that EASA and the FAA evaluate the relevance of requiring the presence of an angle of attack indicator directly accessible to pilots on board aeroplanes."

I would add to that list: the Airbus needs a stick shaker. The only thing in the cockpit to indicate a stall is an aural, "Stall, stall" voice. There are several studies about "Auditory exclusion as a stress response," showing that one of the first things to shut down when we are under high stress is our ability to hear and discern. That is also the reason an active sidestick is superior to a passive one.

Highly experienced pilots too often keep quiet with a smug confidence that they are smarter than everyone else. These overconfident pilots may find out they've assumed too much and will miss the opportunity to learn they were wrong, if they were wrong, or to teach others, if they were right. Young pilots too often keep their mouths shut rather than being discovered as being ignorant about something important. They can, as a result, find themselves in critical moments lacking a critical procedure or technique that could have saved them. Even if the pilots had communicated well prior to a crisis, their performance during a crisis will depend on their ability to impart meaningful information in a timely manner.

Share knowledge, ensure understanding

Once the maximum recommended climb altitude increased to FL375 and the first officer asked the captain if it would be okay to climb to FL370, the captain "vaguely rejected" the first officer, saying "it might be bad." He was evidently thinking that with only a 500 foot margin, the aircraft would be thrust limited if the temperature went up. That was a good call, but he should have articulated that to the first officer. It would have helped the first officer understand this critical limitation of high altitude flight, and it may have prevented him from instinctively climbing when the autopilot disengaged on its own.

Admit ignorance

When First Officer Bonin became concerned about the sound of the ice crystals and the way the conditioned air started to smell and become more humid, he asked the Relief First Officer Robert who simply said it was the ozone in the air. Had Robert followed up and asked what ozone had to do with the humidity, he might have provoked a discussion of the many effects of flying in the ITCZ. With those thoughts fresh in his mind, Bonin might have been less prone to panic in the moments to come.

During a crisis, communicate to impart meaningful information in a timely manner

When Bonin was trying to level the wings with the increased sensitivity of alternate law, Robert's job was to handle the ECAM messages, but he did so by just reading them in what seemed a random order. If he had instead zeroed in on the fact they were in alternate law, he might have been able to make Bonin understand why the aircraft was handling differently than he was used to. "We're in alternate law! You no longer have filtered ailerons inputs so you need to be gentle!"

Additionally, neither of the pilots in the cockpit at the time of the stall verbalized the fact they were in a stall. Had either simply said "Stall," it might have triggered the correct stall recovery technique.

Replace panic with a pre-planned thought

It is easy to arm chair quarterback what happened to the two young first officers and criticize their lack of composure when the autopilot disengaged. Perhaps older pilots from earlier generations were well practiced at dealing with sudden crises in the air, but that doesn't do newer pilots any good. I was once flying with a fairly experienced pilot who became completely unglued when our aircraft lost a hydraulic system, forcing us to declare an emergency and use the aircraft's alternate gear extension. I had to talk him through the process and prevent him from panic. When we were on the ground, I asked him how many times he had ever declared an emergency. "Including today, once." So, if you are in that boat and might be prone to panic, what can you do? You should have a pre-planned thought, ready for emergencies.

The idea of the pre-planned thought is one I've been using for a very long time, but I've seen it best articulated by professional race car driver and performance coach Ross Bentley. If you practice having this thought ready to go in the simulator, it might save you in the airplane. More about pre-planned thoughts: Compartmentalization and Flight.

For my pre-planned thought in the event of an emergency, I used to think, "I've tried A. I've tried B. I've tried C. Now what do I try?" This comes from the book "The Right Stuff" and thinking about it makes me smile. More importantly, it forces me to slow down. After a few years, I started saying "Pie-oh-see." Having a structured way to approach a problem is key to avoiding panic. There are various methods out there, here is PIOSSEE:

P – Problem: Identify what’s wrong (e.g., engine failure, abnormal indications).

I – Immediate Action: Perform any critical emergency memory items or boldface procedures that must be done without delay.

O – Options: Consider all feasible courses of action (e.g., divert, eject, continue, troubleshoot).

S – Select: Choose the best available option based on the situation.

S – Start Execution: Begin carrying out the selected course of action.

E – Evaluate: Continuously monitor the results and adjust as needed.

E – Execute Backup Plan (sometimes interpreted as a second evaluation or finalize execution depending on training context).

That doesn't mean I have to go through the PIOSSEE process whenever something goes awry, but saying "Pie-oh-see" slows me down and reminds me I have a better way to approach problems than simply reacting.

If it was you at high altitude, in the ITCZ, and the autopilot suddenly disengaged, how would you prevent panic? If you think, "PIOSSEE," it will give your mind someplace to go rather than panic. In fact, you should speak your thoughts aloud to get the crew's help. "Problem? No autopilot." "Immediate Action? Fly the airplane." "Options? Well, we need to figure out why the autopilot disengaged before we can do that!" Having something to think about may prevent the panic that caused the first officer to pull up into a stall. But once he started down that path, then what? Both pilots should have realized that flying with the pitch up 11 degrees wasn't going to work . . .

You may think the cases of Birgenair 301 and AeroPerú 603 have little to do with Air France 447. In those cases, the pitot tube or static ports were blocked on the ground and the blockage was permanent. In this case, the blockage was momentary. But in all three cases, had the pilots known where to set the thrust levers and the aircraft pitch, they would have survived. This should be required knowledge before being awarded a type rating.

The known thrust and pitch setting technique

If you ever find yourself with uncertain airspeed or altitude information you can sort things out, but it will take time. To buy yourself that time, it is vitally important that you set the pitch and thrust of the aircraft to known settings that will keep the airplane flying. For most aircraft, you only need to know values that will work at maximum weights during initial climb after takeoff, during cruise altitude, and in the approach environment. There are countless aircraft accidents, including AeroPerú 603, where this knowledge would have saved the day.

If your manufacturer doesn't provide this information, you should arrange these three scenarios in the simulator or record them during actual flight the next time you have the right conditions:

• Climb after takeoff, maximum weight
• Cruise at high altitude, after a maximum weight takeoff
• Missed approach, at maximum weight for landing

I've found over the years that the answer for the initial climb tends to be between 10 and 15 degrees of pitch at takeoff thrust, between 2 and 3 degrees at maximum continuous thrust for cruise, and between 10 and 15 degrees at just below maximum continuous thrust for a missed approach. You should record these either in the simulator or the aircraft when the opportunity arises.

Finally, if your aircraft has an Angle of Attack indicator that is usable for flight, you have another ace up your sleeve. Most cockpit AOA indicators are normalized, meaning they don't report the actual angle in degrees, but a ratio of that angle over the stall angle of attack. It is slightly more complicated than that, if you want to get into the nuts and bolts, see: Angle of Attack. You should scour your manuals and record values in the simulator. For many aircraft, you should see 0.66 NAOA on approach at V_REF and something lower when you apply a wind additive. As the NAOA increases, you are getting closer to the stall. In the Gulfstream GVII, for example, the stick shaker occurs at 0.97 NAOA. Also realize that some aircraft give you instantaneous AOA while others dampen the result. In my Gulfstream I can see the AOA on appraoch dance between 0.3 and 0.7 and even higher, but I make sure the average is lower than 0.66. In other aircraft, the instrument dampens out the oscillations for you. Knowing what's about right can save you someday.

Final Report on the Accident on 1st June 2009 to the Airbus A330-203 registered F-GZCP operated by Air France flight AF 447 Rio de Janeiro - Paris, Bureau d'Enquêtes et d'Analyses (BEA) pour la sécurité de l’aviation civile, Published July 2012.

Langewiesche, William, Should Airplanes Be Flying Themselves, Vanity Fair, October 2014.

Palmer, Bill. Understanding Air France 447. 2013.