# When is it appropriate to be scared of turbulence on a commercial flight? **URL:** \ **Category:** Factual Questions\ **Created:** [December 6, 2013, 12:36pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664 "2013-12-06T12:36:30Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 7, 2013, 6:22pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/61 "2013-12-07T18:22:34Z")
> [@Rick](#): > > Wait, what? Are we talking about American Airlines, the outfit that ignored the airplane maker’s instructions to remove a DC-10 engine and pylon in two steps, but instead they flatrated it using a forklift in one step, cracked the pylon and this was the result [File:Aa191 ohare.jpg - Wikipedia](http://en.m.wikipedia.org/wiki/File:Aa191_ohare.jpg) > > Or my personal favorite these guys went to service a 767 at LAX a number of years ago, forgot to chock the wheels, depressurized the brake system and went home for the day. The next day they came in to work only to find their nice shinny 767 through the fence on Aviation Blvd. oops. > > You buddy might be the greatest A&P guy on the planet, but as a group AA is very underwhelming with their maintenance and why in over 750,000 miles of airline travel I can count on the fingers of one hand my trips on AA. I don’t trust them. Yepper, they are the ones. I have had better experiences with them than you have so I am not so against them. Now if we talk about fords, I give many reasons why I don’t like them. I bet there are some Ford lovers that can do the same. Oh, many other airlines contract with AA to do their maintenance. Other lines are contracting with both in country & over seas company’s to do their work. A lot use unskilled labor with just a few A&P inspectors. Gives ma a warm fuzzy feeling, how about you? Actually, I am pretty much a, “If it ain’t Boeing, I ain’t going.” type of guy. I have not liked any Douglas airliners since the DC -7. Just my preferences. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 7, 2013, 7:10pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/62 "2013-12-07T19:10:00Z")
> [@](#): > > Originally Posted by Richard Pearse View Post > It wasn’t that he used excessive input, it’s that he used alternating full left and right rudder in quick succession. NO airliner will handle this. There was, and still is because some pilots refuse to learn the lesson, a misconception that the manoeuvring speed on an aeroplane, known as Va, is the speed at which you can do anything to the controls and you won’t break the aeroplane. This is not true and has never been true. Va is the speed at which the aeroplane will stall before the wings would be stressed if you pull back on the control column, it gives no protection from excessive rudder input. In a jet with a yaw damper there is no reason to touch the rudder except to keep it straight on the ground during take-off and landing, to maintain directional control following an engine failure, and for very very gentle inputs to maintain balanced flight in a turn if you are exceptionally pedantic about balanced flight. > Airbus made changes to the A300-600 over it’s predecessor that significantly changed the feel of the rudder pedals. 1.2" of pedal travel > [@Magiver](#): > > Airbus made changes to the A300-600 over it’s predecessor that significantly changed the feel of the rudder pedals. 1.2" of pedal travel and 32 lbs of force versus older models that had 4" of travel and 125 lbs of force. [NTSB cite](http://www.ntsb.gov/news/events/2004/belle_harbor_ny/presentations). > > according to the same cite: Compared to other airplanes: > A300-600 has lightest pedal forces. > A300-600 has among the shortest pedal travel. > > The [vertical tail plane on this aircraft](http://i298.photobucket.com/albums/mm262/ferpe_bucket/AA-587_Airbus%20A-300-600R%20_tail.%20assembly.schematic_NTSB_zpsde2fe18c.jpg) is attacked with 6 composite tongues fitted into mating receivers. These failed. > > IMO the plane was poorly designed and destined for the structural failure that occurred. The pilots had no pedal feel relative to allowable inputs and the airplane did not sufficiently limit rudder travel in reference to air speed. The pedal feel they did have varied substantially from earlier models and other commercial aircraft. About the rudder input and VA speeds ( maneuvering speed ) & what you can & what you should not do. In many years of receiving instruction, I have never heard this. I was told that I could not hurt the airplane with any primary control input. When my sister got her ATP, she was not taught this. I do not know about you but without extensive retraining, in a 'Oh Shit" flying moment I will revert back to my oldest & strongest habit. So, a pilot with a lot of years & many thousands of hours is suddenly put into an airplane that can be broken by something he has learned & practiced & expect & you expect him to be cured of that habit in ‘frightful’ circumstances, not ‘fearful’ which takes time but fright which is sudden with no time for thought has you relying on your training… & good habit patterns. How do you change a long and trusted habit? Much retraining & PRACTICE… ( we can have a fun discussion about fear, fright & the human responses to each if you think I am wrong, always willing to learn ) Why is this not in big red letters in the instructors book, the AOPA magazine, Flying magazine and taught & practiced at all levels all the time everywhere? Good God, all those years & hours flying Pipeline patrol I was trying to kill myself with rudder, and aileron inputs. And throwing the C-310 around the sky doing aerial photo work. Do all airliners have this restriction? If not, why not. Also, metal airplanes are watchable by maintenance because of the cracks & stuff as mentioned up thread. Composites, no so much. They look great right up to failure. Even XRAY is of limited use. Plus it is new and apparently not over built like in the history of metal airplanes. ( Computer programs got that pesky problem all solved has it? ) You guys know much more than I ever will about big iron but crew training & knowing that humans & their frailties need to be engineered around, that airplanes designed & built by committee might be lacking in several areas. Time will tell. Human however, are pretty well known. So either the total training of pilots needs to be fixed or the planes need to be. Mother nature disregards ‘normal & predictable’ just enough that we ignore the possibility at our own peril. Fun stuff. Fix my ignorance please, always willing to learn… 😃 🆒 ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 8, 2013, 5:14am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/63 "2013-12-08T05:14:45Z")
> [@GusNSpot](#): > > Why is this not in big red letters in the instructors book, the AOPA magazine, Flying magazine and taught & practiced at all levels all the time everywhere? because it’s not a problem in all aircraft. Look at the Gimli Glider. The PIC put a 767-200 into a forward slip in order to land. I can’t honestly say I understand Airbus’s thinking on the change they made with the A300. The pedal travel was ridiculously short. I’d be afraid to touch them. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 8, 2013, 6:30am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/64 "2013-12-08T06:30:27Z")
> [@Magiver](#): > > because it’s not a problem in all aircraft. Look at the Gimli Glider. The PIC put a 767-200 into a forward slip in order to land. > > I can’t honestly say I understand Airbus’s thinking on the change they made with the A300. The pedal travel was ridiculously short. I’d be afraid to touch them. The difference with the A300 accident was that the pilot made multiple, alternating, rapid, full rudder inputs. No aeroplane is designed to withstand that. Va only gives you protection against a single full application of a single control surface. It does not give protection against rapid control reversals. The sideslip used by the Gimli pilot was nothing like what the AA pilot did. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 8, 2013, 6:58am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/65 "2013-12-08T06:58:13Z")
> [@Richard\_Pearse](#): > > The difference with the A300 accident was that the pilot made multiple, alternating, rapid, full rudder inputs. No aeroplane is designed to withstand that. Va only gives you protection against a single full application of a single control surface. It does not give protection against rapid control reversals. > > The sideslip used by the Gimli pilot was nothing like what the AA pilot did. Va does not specify multiple inputs. It refers to a single input. The Airbus design should not have allowed full deflection above a given speed. That’s the first design flaw. The second is a rudder pedal travel of 1". that would be the equivalent of a gas pedal with 1" of travel to full input. If the pilot just touched the pedal in response to hitting the vortex of the aircraft in front then the plane would have lurched sideways causing the normal reaction to correct with opposite rudder to straighten it out. This wasn’t the pilot’s fault. It was the engineer who redesigned a normal pedal input into something dangerous. ---
**Author:** ![williambaskerville](https://avatars.discourse-cdn.com/v4/letter/w/f14d63/32.png) [@williambaskerville](https://boards.straightdope.com/u/williambaskerville)\ **Post date:** [December 8, 2013, 8:35am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/66 "2013-12-08T08:35:01Z")
> [@Magiver](#): > > Unless it was another pilot who recognized the situation then the answer is no. > > It wasn’t a function of a stall warning indicator being ignored. What happened is that they lost ALL their airspeed indicators. All the pitot tubes froze due to a rare occurrence of rapid icing. The pitot heaters could not keep up with the situation. Without any indication of airspeed the plane can only be flown at that altitude by applying specific engine input against specific trim settings. They had a limited time frame to work with after recognizing the situation. We’re talking seconds and minutes before things get out of control and the pilots would have no feedback from gauges to tell them what’s going on. What’s this limited time frame you’re talking about ? What, exactly, did they have to achieve in those seconds ? They were in control of an aircraft in stable flight, with both engines and all control surfaces working perfectly. The BEA report discussed 13 other episodes where an Airbus 330 lost air speed indicators :- in 4 of them it wasn’t even diagnosed correctly, the pilots did, essentially, nothing and it worked out fine. Finally, what do you think Bonin, the pilot at the controls, was trying to achieve by pulling hard back ? What was in his mind, what problem did he think they had ? Because what he did is frankly bizarre, and if you have some insight into what problem he thought he was trying to solve, I’d love to hear it. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 8, 2013, 12:22pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/67 "2013-12-08T12:22:03Z")
> [@Magiver](#): > > Va does not specify multiple inputs. It refers to a single input. I know, did I say anything about multiple inputs? > [@](#): > > The Airbus design should not have allowed full deflection above a given speed. That’s the first design flaw. The second is a rudder pedal travel of 1". that would be the equivalent of a gas pedal with 1" of travel to full input. This is rubbish. A. The A300 did not allow full rudder deflection above a given speed. At 135 knots the available rudder deflection was 30º while at 250 knots the maximum deflection was 9.3º. by comparison the B767 allows 26º at 135 knots and 6º at 250 knots. B. The rudder pedal movement is very similar to other types. The A300 had 1.2" of rudder pedal movement available at 250 knots (the speed the incident happened at) while the Boeing 737 has only 1.0" of rudder pedal movement at the same speed. Do you have the same opinion of the B737 rudder system? Some aircraft progressively restrict rudder pedal movement in proportion to the rudder deflection available, others don’t. There is nothing unique to the A300 about that. The main difference between the A300 and other types was the force required to move the pedal to full deflection. It has the lowest force required at 32 pounds, the next lowest is the A320 at 36 pounds. The B737 by comparison requires 50 pounds of force. So yes the rudder control was light and that was a contributing cause to the accident, but everything you’re saying about the small pedal movement and max rudder deflection being available is without merit. > [@](#): > > If the pilot just touched the pedal in response to hitting the vortex of the aircraft in front then the plane would have lurched sideways causing the normal reaction to correct with opposite rudder to straighten it out. If the pilot didn’t touch the rudder at all there wouldn’t have been an issue (why use the rudder at all? Because American Airlines trained them to). If the pilot had not used rapid alternating rudder movements that caused an ever increasing amount of slip in opposite directions there wouldn’t have been an issue. If the piloting community in general had properly understood Va there wouldn’t have been an issue. > [@](#): > > This wasn’t the pilot’s fault. It was the engineer who redesigned a normal pedal input into something dangerous. This was a combination of poor training, poor handling, and a sensitive rudder system. To put the blame solely on the rudder design is missing the point and pilots who refuse to learn the lessons from this are doing themselves and their passengers a great disservice. ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [December 8, 2013, 2:34pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/68 "2013-12-08T14:34:33Z")
When the lights flicker, when the overhead compartments start opening and the baggage starts flying everywhere, I give you permission to be afraid and start making peace with your demise. I’ve been through some scary turbulence out of Houston in thunderstorms, but I think of it as a fun adventure and never take it too seriously. Flying through lightning is cool 😃 ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [December 8, 2013, 4:06pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/69 "2013-12-08T16:06:09Z")
I think of myself as a pretty relaxed guy, but taking off from Antalya Airport, Turkey a few years ago was a bit scary. We boarded, Me, wife and two small children, in pouring rain, taxied to the end of the runway, then sat there for ages in the rain, thunder and lightning. We thought we would be taken off when all the lights in the airport went out and the whole place went dark. The captain came on the speaker in a laconic voice. “We seem to have a bit of weather,” he said. “We are going to sit for a while and see what happens.” A little while later the airport lights came back on. “Things seem to be happening,” he said again, sounding quite relaxed. “There is an Air India plane leaving now, We’ll wait and see how he gets on.” Then - “Well - he seems to have got away all right. Buckle up tight please, it may be a little bumpy.” A little while later we took off through black clouds up and down like a roller coaster with lightning flashing all around. Several people were sick and quite a few were praying. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 8, 2013, 6:59pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/70 "2013-12-08T18:59:27Z")
> [@williambaskerville](#): > > What’s this limited time frame you’re talking about ? What, exactly, did they have to achieve in those seconds ? They were in control of an aircraft in stable flight, with both engines and all control surfaces working perfectly. The [Nova program](http://video.pbs.org/video/1685933496/) about this flight would give a better explanation but at the altitude they were at the flying envelope is by default narrower. It takes specific power and trim settings to stay within this envelope. Without air speed input this is a problem. Prior to losing air speed information the computer pulled back engine power. What the computer does not do is pull the power levers back so there is no physical indication that this happened. The plane was not in stable flight at this point and the time frame to correct it was measured in seconds and minutes. The situation as the pilots experienced it was a cascade failure of the automated systems. It was nothing but a series of alarms going off. They experienced information overload during the short window of time needed to stabilize the plane. > [@williambaskerville](#): > > The BEA report discussed 13 other episodes where an Airbus 330 lost air speed indicators :- in 4 of them it wasn’t even diagnosed correctly, the pilots did, essentially, nothing and it worked out fine. If the plane was trimmed out then they have time to assess the situation. If it’s not trimmed out then they have a really big problem. The computer had pulled back power in this case. > [@williambaskerville](#): > > Finally, what do you think Bonin, the pilot at the controls, was trying to achieve by pulling hard back ? What was in his mind, what problem did he think they had ? Because what he did is frankly bizarre, and if you have some insight into what problem he thought he was trying to solve, I’d love to hear it. No idea. Loss of altitude? I’m not making excuses for the crew. Some pilots can land a disabled plane in the Hudson River after losing all engines and some can’t land at San Francisco on a clear day with a check ride pilot. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 8, 2013, 9:23pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/71 "2013-12-08T21:23:26Z")
> [@Richard\_Pearse](#): > > I know, did I say anything about multiple inputs? Well, yes, you did: “The difference with the A300 accident was that the pilot made multiple, alternating, rapid, full rudder inputs”. > [@Richard\_Pearse](#): > > This is rubbish. > > A. The A300 did not allow full rudder deflection above a given speed. At 135 knots the available rudder deflection was 30º while at 250 knots the maximum deflection was 9.3º. by comparison the B767 allows 26º at 135 knots and 6º at 250 knots. So the Boeing aircraft has lower limits at the speed you listed and the Airbus comes apart at the speeds you listed. Add to that the extremely short pedal travel and force needed to hit full deflection. And by full deflection I mean the travel available at any given time. > [@Richard\_Pearse](#): > > B. The rudder pedal movement is very similar to other types. The A300 had 1.2" of rudder pedal movement available at 250 knots (the speed the incident happened at) while the Boeing 737 has only 1.0" of rudder pedal movement at the same speed. Do you have the same opinion of the B737 rudder system? Some aircraft progressively restrict rudder pedal movement in proportion to the rudder deflection available, others don’t. There is nothing unique to the A300 about that. yes on the 737 and oh hell yes on the transition between older A300’s and the dash-6 with the lower pedal pressure. > [@Richard\_Pearse](#): > > The main difference between the A300 and other types was the force required to move the pedal to full deflection. It has the lowest force required at 32 pounds, the next lowest is the A320 at 36 pounds. The B737 by comparison requires 50 pounds of force. So yes the rudder control was light and that was a contributing cause to the accident, but everything you’re saying about the small pedal movement and max rudder deflection being available is without merit. the results speak for themselves. > [@Richard\_Pearse](#): > > If the pilot didn’t touch the rudder at all there wouldn’t have been an issue (why use the rudder at all? Because American Airlines trained them to). If the pilot had not used rapid alternating rudder movements that caused an ever increasing amount of slip in opposite directions there wouldn’t have been an issue. If the piloting community in general had properly understood Va there wouldn’t have been an issue. you’ll have to cite that alternating loads are worse than single input loads. I’m not disagreeing with you entirely on this but side to side rudder input is a regular event when flying. This plane combined extremely short rudder travel with less pedal feedback. It naturally lends itself to creating the situation that occurred and that was too much rudder input followed by too much rudder input to correct the situation. > [@Richard\_Pearse](#): > > This was a combination of poor training, poor handling, and a sensitive rudder system. To put the blame solely on the rudder design is missing the point and pilots who refuse to learn the lessons from this are doing themselves and their passengers a great disservice. We differ on opinion. A properly engineered plane would limit control surface inputs to the structural limitations. This is not 1950. Computers are driving the systems and are easily programmed to stay within the safety envelope. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 8, 2013, 11:57pm UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/72 "2013-12-08T23:57:45Z")
> [@Magiver](#): > > Well, yes, you did: “The difference with the A300 accident was that the pilot made multiple, alternating, rapid, full rudder inputs”. That’s right, sorry I thought you were talking about multiple control surfaces e.g., rudder and elevator. What I was saying is that Va does not give protection against multiple inputs either of one surface in alternating directions or two surfaces in one direction, however the pilot made alternating rudder inputs and therefore was no longer protected by Va. > [@Magiver](#): > > So the Boeing aircraft has lower limits at the speed you listed and the Airbus comes apart at the speeds you listed. Add to that the extremely short pedal travel and force needed to hit full deflection. And by full deflection I mean the travel available at any given time. The Boeing also would not withstand rapid control reversals. The Boeing has lower limits at the speed listed because it has lower limits at all speeds which is probably because it has a more powerful rudder and doesn’t need as much deflection. The Boeing B747 has its rudder limited to 12º at 250 knots which is more than the A300 limit. The point is that the ratio of deflection available at 250 knots compared to that available at 135 knots is similar in both aircraft and that the rudder deflection is designed to be limited as speed increases. In addition to this, the pilot used well in excess of the pedal force required in any airliner to hit the pedal stop. It was calculated that the maximum force used was 140 pounds and that the rudder cables were stretched each time the pedal hit the stop. > [@](#): > > On April 8, 2004, Airbus issued a technical note, titled “AAL 587 – Pedals Force Analysis,” that provided Airbus’ estimate of the rudder pedal forces during the seconds before the vertical stabilizer separated from the airplane … > > The technical note indicated that, during the accident sequence, the forces applied by the first officer to the rudder pedals were much higher than the forces required to reach the rudder travel limit for 240 knots. Airbus found that the highest force applied by the pilot during the accident sequence was about 140 pounds but that the pedal force required to reach the rudder travel limit during that time was about 30 pounds. The note further indicated that the rudder control cable was stretched each time that the rudder travel limit was contacted. > [@Magiver](#): > > you’ll have to cite that alternating loads are worse than single input loads. I’m not disagreeing with you entirely on this but side to side rudder input is a regular event when flying. Not flying jets it’s not. It has a yaw damper that coordinates turns, there is no p-factor, and there is no spiralling slipstream from a propellor. As I said earlier the only reason to use the rudder in a jet is for take-off and landing, and for an engine failure. Anyway, here is the cite, from the investigation. > [@](#): > > During this accident investigation, the Safety Board learned that many pilots might have an incorrect understanding of the meaning of the design maneuvering speed (VA) and the extent of structural protection that exists when the airplane is operated below this speed. > > From an engineering and design perspective, maneuvering speed is the maximum speed at which, from an initial 1 G flight condition, the airplane will be capable of sustaining an abrupt, full control input limited only by the stops or by maximum pilot effort. In designing airplanes to withstand these flight conditions, engineers consider each axis (pitch, roll, and yaw) individually and assume that, after a single full control input is made, the airplane is returned to stabilized flight conditions. **Full inputs in more than one axis at the same time and multiple inputs in one axis are not considered in designing for these flight conditions.** > > The American Airlines managing director of flight operations technical told the Safety Board … that most American Airlines pilots believed that the airplane would be protected from structural damage if alternating full rudder pedal inputs were made at an airspeed below maneuvering speed … However, as evidenced by flight 587, cyclic rudder pedal inputs, even when made at airspeeds below maneuvering speed, can result in catastrophic structural damage. > > As a result of the flight 587 accident, the industry-developed Airplane Upset Recovery Training Aid now states, **“it is important to guard against control reversals. There is no situation that will require rapid full-scale control deflections from one side to the other.”** > > The Safety Board has no reason to believe that the misunderstanding about maneuvering speed is limited to A300-600 pilots. As a result, the Safety Board concludes that there is a widespread misunderstanding among pilots about the degree of structural protection that exists when full or abrupt flight control inputs are made at airspeeds below the maneuvering speed. **Therefore, the Safety Board believes that the FAA should amend all relevant regulatory and advisory materials to clarify that operating at or below maneuvering speed does not provide structural protection against multiple full control inputs in one axis or full control inputs in more than one axis at the same time.** And here is some information from Boeing about their aircraft design limits. > [@](#): > > Boeing aircraft are not designed to a requirement of full authority rudder reversals from an “over yaw” condition. **Sequential full > or nearly full authority rudder reversals may not be within the structural design limits of the aircraft, even if the airspeed is below > the design manoeuvring speed.** There are no Boeing Procedures that require this type of pilot input. It should also be pointed out > that excessive structural loads may be generated in other areas of the aircraft, such as engine struts, from this type of control input. > In addition, large sideslip angles may cause engine surging at high power settings. It is important to note that use of full rudder for > control of engine failures and crosswind takeoffs and landings is well within the structural capability of the aircraft. > [@Magiver](#): > > This plane combined extremely short rudder travel with less pedal feedback. It naturally lends itself to creating the situation that occurred and that was too much rudder input followed by too much rudder input to correct the situation. The extremely short rudder travel that is shared by many other aircraft. There was no reason to use such large rudder inputs. There was no reason to use any rudder at all. We do jet upset recovery training in the simulator and we don’t touch the rudder, it’s not necessary. By comparison American Airlines upset recovery training was found to be “deficient”. > [@](#): > > As discussed in section 2.3.2.2, the Safety Board’s investigation found deficiencies in the American Airlines AAMP, including the following: > > • ground school training that encouraged the use of rudder for roll control; > > • a simulator exercise in which pilots were encouraged to employ large rudder inputs without being fully trained in the operating properties of the specific rudder control system or fully understanding the structural loads that might be imposed on the airframe by certain inputs; > > • a simulator exercise that provided unrealistic portrayals of an airplane response to wake turbulence and significantly suppressed control input effectiveness to induce a large rolling potential that was unlikely to occur with an airplane as large as an A300-600; and > > • a simulator exercise that encouraged the use of rudder in a highly dynamic situation without portraying the large buildup in sideslip angle and sideload that would accompany such rudder inputs in an actual airplane. > [@](#): > > We differ on opinion. A properly engineered plane would limit control surface inputs to the structural limitations. This is not 1950. Computers are driving the systems and are easily programmed to stay within the safety envelope. Except your opinion is based on faulty knowledge. The aeroplane _was_ engineered to limit control surface inputs to the structural limitations. Computers are not driving the systems, unlike later fly-by-wire Airbus models, the A300 is a mechanical aeroplane and was first launched in 1972, so it’s a lot closer to the 1950s than it is to today. This accident was caused by a ham-fisted pilot who had been poorly trained by American Airlines. The light rudder on the aircraft was contributing but not causal. > [@Probably Cause](#): > > The National Transportation Safety Board determines that the probable cause of this accident was the in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design that were created by the first officer’s unnecessary and excessive rudder pedal inputs. Contributing to these rudder pedal inputs were characteristics of the Airbus A300-600 rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Program. The A300-600 had a less than ideal rudder system, however it was still similar to rudder systems in use in other airliners. The pedal travel required and the rudder deflection available were normal for this type of rudder system. It is the aircraft operator’s (airline and pilot) responsibility to learn the aircraft systems and to fly within the limits. American Airlines and the accident pilot failed to do this adequately. As an analogy I think we can agree that a tail-dragger design is less than ideal in terms of the forward visibility and controllability on the ground, however we expect that a pilot who flies a tail dragger will learn the limitations of the design and operate the aircraft accordingly. If they go and taxi into an obstacle it is not the aircraft designer’s fault, it is the pilot’s fault for not operating the aircraft correctly. If we then find that the pilot’s trainer had never briefed them on the lack of visibility or taught them taxi techniques to maintain forward visibility we would say the trainer is also at fault for not training the pilot correctly. The design of the aircraft made it all possible and is a contributing factor, but the pilot should have been aware of the limitations. [Link to accident report.](http://www.ntsb.gov/doclib/reports/2004/AAR0404.pdf) [Link to Boeing article.](http://www.alpajapan.org/news/ifalpabriefing/12ADOBL02%20-%20Use%20of%20rudder%20on%20Boeing%20aircraft.pdf) ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 9, 2013, 12:19am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/73 "2013-12-09T00:19:53Z")
Richard Pearse, a nicely researched post on your part. I’m rereading it a couple of times to see if I’ve missed anything. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [December 9, 2013, 12:47am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/74 "2013-12-09T00:47:33Z")
> [@Xema](#): > > The pitots did indeed ice up. But they de-iced less than a minute later, and worked properly until the plane hit the water, almost 4 minutes later. > > There’s compelling evidence that they never recognized the situation. > > Well, all aircraft systems were functioning normally for several minutes prior to impact. If at any time\* during the descent the pilots had figured out they were in a deep stall (one clue to which would have been the numerous audible “Stall!” warnings), they could have easily flown away from the problem. > > \*Actually, during the final 20 seconds or so they were too low for a recovery. This is highly misleading and partially inaccurate. What happened was, the pitots iced up and the airspeed indication disappeared from the flight displays. One of the pilots panicked and perhaps unconsciously pulled back on his control stick, causing the plane to gain altitude and lose airspeed. Ultimately, he ended up putting the plane into a stall at a very shallow angle, holding the control stick full aft, with the engines at 100% throttle. Because of the design of the Airbus control system, it was not obvious to the other pilots that he was doing this with his control stick, and because the pitot tubes had failed, it was not obvious from the instrumentation either (the other pilots might have noticed the climb, but they could not see the airspeed decreasing, and in the turbulence I doubt they really noticed the climb either). Eventually, the pitots de-iced, and the flight displays began operating again. At that point, the plane was being held at a shallow angle by the one pilot, with the engines at 100% throttle, but was in reality moving so slowly that the airspeed was _too low to register_, and too low for the stall warning system to operate, despite the fact that it was definitely in a stall, dropping vertically at 10,000 fpm. This is the key point. Their airspeed was _too low for the stall warning horn to operate_. The stall warning was not sounding continuously. The pilots could see nothing out their window, but on their control displays they saw no airspeed indication, a shallow climb angle, 100% throttle, and an altimeter and vertical speed indicator that showed they were dropping. There was no display that showed the one pilot had his control stick deflected almost fully aft, just a small light among many that indicated the two pilots were giving conflicting control inputs. Given that their airspeed indications had just failed, and had not re-appeared, and the plane’s attitude (angle to the horizon) was relatively normal, and the engines were working properly, they probably thought that the instrument indicating a rapid descent was faulty. Everything else was consistent with normal flight, except their forward airspeed, which was actually too low for them to register on the one instrument that would actually tell them it was too low. The kicker was that, when one of the pilots guessed that they might be in a stall and took the appropriate corrective action (lowering the nose), the airspeed rose high enough to reach the valid range, thus activating the stall warning system - and causing the stall alarm to sound. They reacted like you’d expect - stopped lowering the nose, thus decreasing their airspeed again and silencing the alarm. It seemed like the stall warning was malfunctioning. With more time, they probably would have figured out what was going on (mostly, they key piece of information they were missing is that the one pilot had been holding full back pressure on his stick), but as it was, they had only a few minutes. Remember also that this happened at night, in a thunderstorm, over the Pacific. They would have had to figure out what was happening from the instruments alone, when one of the most important instruments had recently failed and (as far as they could tell) was still inoperative. This was certainly pilot error on the part of the one pilot, who reacted improperly and initiated the stall in the first place. But I hesitate to blame the remaining pilots for failing to recognize the situation in the time available. I view that as primarily the fault of the cockpit user interface in the Airbus. Yes, with specific training for this incident and encyclopedic knowledge of the aircraft systems, an intelligent and skilled pilot could probably have figured it out in the few minutes available. But you cannot staff an entire airline with above average pilots. In any case, your description of it is overly simplistic and significantly downplays how confusing this situation was to the pilots. It was not as simple as “the stall warning horn was sounding the whole time and the pilots ignored it.” ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 9, 2013, 1:08am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/75 "2013-12-09T01:08:56Z")
I’m inclined to agree with the investigating board that a great number of pilots believe that the structural limits of an aircraft fall within the designated air speeds. The quote you gave me regarding Va speed was vague in meaning and useless in flight. Where is the cutoff point between using 2 control surfaces at the same time? And this, BTW, is exactly what was done with the Gimli Glider. That was an extremely stressful maneuver although there was obviously no worry about engine surge. Has me wondering how most vertical stabilizers are attached. As for never using the rudder in a jet (beyond loss of engine) that is counter intuitive when hit with unusual wind forces and that was what happened in this case. That the pilot was trained to do so in a large aircraft is a contributing factor but this goes back to what the Va speed is seen as. Either the plane should restrict movement of the control surface or the rated maneuver speed should be reduced. I have to believe that losing an engine causes a tremendous amount of stress on the vertical stabilizer because that involves maintaining that stress level for a considerable amount of time. If rapid rudder movement causes that much stress I really don’t want to be in the plane with an engine failure. But with that said I better understand your position and agree that the pilots should have been vigorously warned of such a maneuver and trained to avoid it. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 9, 2013, 1:21am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/76 "2013-12-09T01:21:55Z")
> [@Absolute](#): > > This was certainly pilot error on the part of the one pilot, who reacted improperly and initiated the stall in the first place. But I hesitate to blame the remaining pilots for failing to recognize the situation in the time available. I view that as primarily the fault of the cockpit user interface in the Airbus. Yes, with specific training for this incident and encyclopedic knowledge of the aircraft systems, an intelligent and skilled pilot could probably have figured it out in the few minutes available. But you cannot staff an entire airline with above average pilots. > > In any case, your description of it is overly simplistic and significantly downplays how confusing this situation was to the pilots. It was not as simple as “the stall warning horn was sounding the whole time and the pilots ignored it.” the loss of air speed indicators should have triggered a very specific response as to power and trim settings at that altitude. But getting hit with a crapload of failure warnings was certainly a distraction. They are, after all, suppose to react to problems as they are presented with them. People have to remember that this happened at cruise altitude. Flight characteristics are not the same as lower altitudes. The priority list of problems get rearranged. Pilots are trained to react to the various problems thrown at them and in this case the number one problem was not presented to them in the form of a warning horn. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [December 9, 2013, 2:25am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/77 "2013-12-09T02:25:20Z")
> [@Absolute](#): > > This is highly misleading and partially inaccurate. > > What happened was, the pitots iced up and the airspeed indication disappeared from the flight displays. One of the pilots panicked and perhaps unconsciously pulled back on his control stick, causing the plane to gain altitude and lose airspeed. Ultimately, he ended up putting the plane into a stall at a very shallow angle, holding the control stick full aft, with the engines at 100% throttle. Because of the design of the Airbus control system, it was not obvious to the other pilots that he was doing this with his control stick, and because the pitot tubes had failed, it was not obvious from the instrumentation either (the other pilots might have noticed the climb, but they could not see the airspeed decreasing, and in the turbulence I doubt they really noticed the climb either). > > Eventually, the pitots de-iced, and the flight displays began operating again. At that point, the plane was being held at a shallow angle by the one pilot, with the engines at 100% throttle, but was in reality moving so slowly that the airspeed was _too low to register_, and too low for the stall warning system to operate, despite the fact that it was definitely in a stall, dropping vertically at 10,000 fpm. > > This is the key point. Their airspeed was _too low for the stall warning horn to operate_. The stall warning was not sounding continuously. The pilots could see nothing out their window, but on their control displays they saw no airspeed indication, a shallow climb angle, 100% throttle, and an altimeter and vertical speed indicator that showed they were dropping. There was no display that showed the one pilot had his control stick deflected almost fully aft, just a small light among many that indicated the two pilots were giving conflicting control inputs. > > Given that their airspeed indications had just failed, and had not re-appeared, and the plane’s attitude (angle to the horizon) was relatively normal, and the engines were working properly, they probably thought that the instrument indicating a rapid descent was faulty. Everything else was consistent with normal flight, except their forward airspeed, which was actually too low for them to register on the one instrument that would actually tell them it was too low. > > The kicker was that, when one of the pilots guessed that they might be in a stall and took the appropriate corrective action (lowering the nose), the airspeed rose high enough to reach the valid range, thus activating the stall warning system - and causing the stall alarm to sound. They reacted like you’d expect - stopped lowering the nose, thus decreasing their airspeed again and silencing the alarm. It seemed like the stall warning was malfunctioning. > > With more time, they probably would have figured out what was going on (mostly, they key piece of information they were missing is that the one pilot had been holding full back pressure on his stick), but as it was, they had only a few minutes. Remember also that this happened at night, in a thunderstorm, over the Pacific. They would have had to figure out what was happening from the instruments alone, when one of the most important instruments had recently failed and (as far as they could tell) was still inoperative. > > This was certainly pilot error on the part of the one pilot, who reacted improperly and initiated the stall in the first place. But I hesitate to blame the remaining pilots for failing to recognize the situation in the time available. I view that as primarily the fault of the cockpit user interface in the Airbus. Yes, with specific training for this incident and encyclopedic knowledge of the aircraft systems, an intelligent and skilled pilot could probably have figured it out in the few minutes available. But you cannot staff an entire airline with above average pilots. > > In any case, your description of it is overly simplistic and significantly downplays how confusing this situation was to the pilots. It was not as simple as “the stall warning horn was sounding the whole time and the pilots ignored it.” They were over the Atlantic. Where is it taught that when you get a stall warning you pull back on the stick and increase the angle of attack? I’m not a pilot and even I know that you lower the nose when in a stall. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [December 9, 2013, 2:32am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/78 "2013-12-09T02:32:57Z")
> [@Rick](#): > > They were over the Atlantic. Oh yeah, duh…I knew that. > [@](#): > > Where is it taught that when you get a stall warning you pull back on the stick and increase the angle of attack? > I’m not a pilot and even I know that you lower the nose when in a stall. The Airbus control system simply adds the inputs of each pilot. Pilot #2, the one who panicked, was essentially holding his stick all the way back, commanding full nose up. However, this was not obvious to the other pilots - 1) the sticks are not linked, so the other stick in the cockpit did not move, 2) there was no cockpit display showing control deflections, 3) with the sticks located along the far edge of the cockpit, the stick was not easily visible to the other pilots. When pilot #1 correctly moved his stick forward to break the stall, because the control system just adds the inputs, the net effect was that the flight control system simply _reduced_ the “nose up” input being given by pilot #2. When the stall warning sounded, pilot #1 reacted naturally - when you do X and an alarm sounds, stop doing X - and returned his stick to the neutral position. The airplane then continued to obey the “full nose up” input from pilot #2. As I recall, it is possible that the pilots worried they were actually getting an erroneous “stall” warning caused by an overspeed, which would explain why lowering the nose triggered it. Not totally consistent with the other information, or with the design of plane I think, but again - this all happened very fast, and they didn’t know which instruments and systems to trust. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [December 9, 2013, 2:34am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/79 "2013-12-09T02:34:56Z")
> [@Si\_Amigo](#): > > Never, because there is nothing you can do about it. In fact, if you freak out or try to do anything you more than likely will put the crew at risk as they attempt to get up and clam you down. This was a typo. I think you meant “they attempt to get up and clamp you down.” 😉 ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 9, 2013, 2:42am UTC](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664/80 "2013-12-09T02:42:52Z")
> [@CookingWithGas](#): > > This was a typo. I think you meant “they attempt to get up and clamp you down.” 😉 Well they’ll shoot your ass if you don’t calm down. Not sure about clamping. [Previous page](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664.md?page=3) [Next page](https://boards.straightdope.com/t/when-is-it-appropriate-to-be-scared-of-turbulence-on-a-commercial-flight/675664.md?page=5)