Whats the logic here?
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Whats the logic here?
Will repost my question here as there was no response in the accident and close calls section. My question relates to the multiple tail strike incident in italy in 2009.
Not an Airbus driver, but can anyone in the know explain to me why the Airbus degrades its flight controls to alternate and direct law in a situation like this where there obviusly is nothing physically wrong with the aircraft (all probes, vanes and FLCC's working as they should), and the only issue is an CG well aft of the approved?
Degrading the flight controls, removing the protections and changing the way the aircraft handels and feels in a situation like this is IMHO only going to stress the pilots more and reduce the chances of a safe recovery.
Whats the logic here?
With its high nose-up attitude of 15° the aircraft, having gained sufficient lift, became airborne at an airspeed of around 110kt. The pitch increased to 23° and, at 125kt, a stall warning sounded for 5s. The jet switched from direct to alternate flight-control law and a cabin altitude warning, indicating pressurisation problems from the damaged fuselage, sounded as it climbed through 9,750ft.
(source: FlightGlobal - http://www.flightglobal.com/news/art...ntinue-444260/)
(source: FlightGlobal - http://www.flightglobal.com/news/art...ntinue-444260/)
Degrading the flight controls, removing the protections and changing the way the aircraft handels and feels in a situation like this is IMHO only going to stress the pilots more and reduce the chances of a safe recovery.
Whats the logic here?
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Full report available on ANSV website
It’s in Italian but g@#€*e translate might be of help. You find details of flight control logic at page 35
http://www.ansv.it/cgi-bin/ita/Relazione%20LZ-BHC.pdf
It’s in Italian but g@#€*e translate might be of help. You find details of flight control logic at page 35
http://www.ansv.it/cgi-bin/ita/Relazione%20LZ-BHC.pdf
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I am unable to read the report but assuming the aircraft did not encounter any faults ( aside from the tail strike), it’s possible that alternate law was triggered due to an abnormal attitude.
When an extreme attitude is encountered ( and the speed, pitch etc quoted is actually not extreme enough), alternate law is triggered to ensure the normal law protections don’t prevent a normal flight attitude being resumed.
That’s my best guess based on the limited info quoted.
When an extreme attitude is encountered ( and the speed, pitch etc quoted is actually not extreme enough), alternate law is triggered to ensure the normal law protections don’t prevent a normal flight attitude being resumed.
That’s my best guess based on the limited info quoted.
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RUMBEAR
Wrong guess: the alternat law was triggered due to the stall warning activation at take off resulting in the FCS discarding at least two of the three AOA output through the ADIRS; then, due to the prolonged flight time with gear down, the direct law was triggered; when the gear was raised the alternate law was reinstated again and kept till the autopilot was on; with AP off (and gear down) the direct law was triggered again. Not let me get involved in this never ending talk about Airbus flight laws: as an Airbus pilot I like the aircraft and by the way it flies as a normal aircraft in direct law; controllability problems in direct law are related to other issues, like faults that leave the aircraft with partial flight control surfaces.
Wrong guess: the alternat law was triggered due to the stall warning activation at take off resulting in the FCS discarding at least two of the three AOA output through the ADIRS; then, due to the prolonged flight time with gear down, the direct law was triggered; when the gear was raised the alternate law was reinstated again and kept till the autopilot was on; with AP off (and gear down) the direct law was triggered again. Not let me get involved in this never ending talk about Airbus flight laws: as an Airbus pilot I like the aircraft and by the way it flies as a normal aircraft in direct law; controllability problems in direct law are related to other issues, like faults that leave the aircraft with partial flight control surfaces.
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What's the logic here? What logic did you find in such a dangerously ignorant crew occupying pilot seats? If the nose pitches 15* at 50kts and after playing with thrust levers they continue the takeoff after multiple tail strikes they should be jailed and Airline's operating license should be cancelled. They manoeuvred the aircraft in such impossible manner that the computer was forced to reject the input as faulty and it went in alternate law and since gear was down direct law. There is no protection against ignorance and stupidity. Dangerous killers at large.
Last edited by vilas; 29th Dec 2017 at 09:06.
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vilas,
While it’s obvious to me what they should have done in that situation, I don’t believe that blaming the pilots is the answer. The logic behind the captain’s decision to continue the T/O after the first power reduction, was that he was more concerned with the damage that might be done to the aircraft if the nose was slammed onto the runway. Obviously he did not consider the dangers of flying with a CG well aft of the design limit.
There is protection against ignorance and stupidity. Its the regulators and airlines responsibility to ensure that only qualified and well trained crews are allowed into the cockpit. But since those protections are under pressure from economical interests, those protections are sometimes out of order….
Another question for joe and others in the know about the Airbus FCS.
Will the fact that the aircraft changes control laws give the pilots better or worse control response/control effectiveness in the pitch axis (in this situation), thereby increasing their chances of successfully avoiding a stall due to aft CG?
While it’s obvious to me what they should have done in that situation, I don’t believe that blaming the pilots is the answer. The logic behind the captain’s decision to continue the T/O after the first power reduction, was that he was more concerned with the damage that might be done to the aircraft if the nose was slammed onto the runway. Obviously he did not consider the dangers of flying with a CG well aft of the design limit.
There is protection against ignorance and stupidity. Its the regulators and airlines responsibility to ensure that only qualified and well trained crews are allowed into the cockpit. But since those protections are under pressure from economical interests, those protections are sometimes out of order….
Another question for joe and others in the know about the Airbus FCS.
Will the fact that the aircraft changes control laws give the pilots better or worse control response/control effectiveness in the pitch axis (in this situation), thereby increasing their chances of successfully avoiding a stall due to aft CG?
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"The aircraft, with flaps at 10° and slats at 18°, began to lift its nose at just 30kt and both pilots pushed their side-sticks fully forward as the pitch reached 11°”
That’s amazing insight into stupidity.
Better not risk lowering the nose wheels during a low speed rejected take off - we are better off attempting to get airborne with this uncontrollable pitch up problem.
Words fail me.
Originally Posted by F-16GUY
was that he was more concerned with the damage that might be done to the aircraft if the nose was slammed onto the runway
was that he was more concerned with the damage that might be done to the aircraft if the nose was slammed onto the runway
Better not risk lowering the nose wheels during a low speed rejected take off - we are better off attempting to get airborne with this uncontrollable pitch up problem.
Words fail me.
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That was not my insight though....
The ANSV analysed that obviously the captain intended to reject takeoff when the aircraft began to rotate unexpectedly at 50 knots, both pilots pushed the sticks forward, the thrust levers were moved aft, but then the captain decided otherwise and continued takeoff moving the thrust levers into the TOGA detent. The captain obviously realized following the decision to reject takeoff, that the thrust reduction would result in a rapid de-rotation resulting in a violent impact of the nose gear on the runway.
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F-16GUY
Now come on! Right from the time the load sheet was brought till the time they landed you will be hard put to find any decision by the crew that was not only wrong but insane. At 30kts with full stick forward 11 degrees nose up? screw the nose wheel! Just stop the aircraft would you? Then you reduce thrust and go TOGA then multiple tail strikes are better than nose wheel damage? I hope they tested the crew for drugs.
So who else is at fault? Surely the passengers who travel by such a stupid airline or Unless you are preparing the grounds for some thing equally silly in future .
Now come on! Right from the time the load sheet was brought till the time they landed you will be hard put to find any decision by the crew that was not only wrong but insane. At 30kts with full stick forward 11 degrees nose up? screw the nose wheel! Just stop the aircraft would you? Then you reduce thrust and go TOGA then multiple tail strikes are better than nose wheel damage? I hope they tested the crew for drugs.
I don’t believe that blaming the pilots is the answer
Last edited by vilas; 29th Dec 2017 at 12:47.
With due respect to F16 guy and vilas, I think the control issue is a red herring, and I don’t 100% blame the pilots either, (nor am I excusing them).
We all know that every accident is a combination of more than one factor.
I have not read the full report but in this case we probably had:
A quick turnaround.
A possible language problem or a misunderstanding.
Loading instructions not carried out.
Incorrect CG of aircraft.
Incorrect THS setting entered in FMGS and set for take-off.
Incorrect operation of flight controls on take-off (half pitch-down should be applied until 80 kts).
Incorrect decision to continue take-off following recovery of nose pitching up.
Incorrect decision not to immediately return to airfield.
In an ideal world, the pilots would not have been under time pressure and would have checked the load sheet properly. They would also have insisted that a double check be made of the passenger distribution in the cabin. But it is not an ideal world and turnarounds, slots and general pressure to stick to schedules are causing a potentially dangerous atmosphere these days.
I have never in any SIM been given, or seen a badly out of limits CG, leading to a mis-set THS, leading to a premature pitch-up. These guys/gals probably never had either. By the time they had recovered from the pitch-up situation it might have appeared to them that there was insufficient runway left to stop on - hence the initial power off followed by power back on and decision to continue the take-off.
Some might respond that we are pilots and should be able to handle any eventuallity, but again, we all know that is not how the world is, and unusual things like this should be demonstrated to us in the SIM*
You would not expect a concert violinist to be able to play a piece of music they had never seen before to performance standard first time - they practice, practice, practice - and a similar thing applies to pilots of large complex jet transports.
*without pre-warning, as this will have a much stronger learning value than if the situation is pre-briefed.
We all know that every accident is a combination of more than one factor.
I have not read the full report but in this case we probably had:
A quick turnaround.
A possible language problem or a misunderstanding.
Loading instructions not carried out.
Incorrect CG of aircraft.
Incorrect THS setting entered in FMGS and set for take-off.
Incorrect operation of flight controls on take-off (half pitch-down should be applied until 80 kts).
Incorrect decision to continue take-off following recovery of nose pitching up.
Incorrect decision not to immediately return to airfield.
In an ideal world, the pilots would not have been under time pressure and would have checked the load sheet properly. They would also have insisted that a double check be made of the passenger distribution in the cabin. But it is not an ideal world and turnarounds, slots and general pressure to stick to schedules are causing a potentially dangerous atmosphere these days.
I have never in any SIM been given, or seen a badly out of limits CG, leading to a mis-set THS, leading to a premature pitch-up. These guys/gals probably never had either. By the time they had recovered from the pitch-up situation it might have appeared to them that there was insufficient runway left to stop on - hence the initial power off followed by power back on and decision to continue the take-off.
Some might respond that we are pilots and should be able to handle any eventuallity, but again, we all know that is not how the world is, and unusual things like this should be demonstrated to us in the SIM*
You would not expect a concert violinist to be able to play a piece of music they had never seen before to performance standard first time - they practice, practice, practice - and a similar thing applies to pilots of large complex jet transports.
*without pre-warning, as this will have a much stronger learning value than if the situation is pre-briefed.
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Uplinker
I read the full report. You are trying to defend undefendable stupidity. Report says there was no time pressure aircraft was ready before time, rather crew wanted to leave early. They were told that passengers need to be relocated the captain didn't do anything. The decision to not abort at 30 kts with nose pointing in the sky was insane and so was everything else. The whole decision making and logic behind it I cannot believe is from a pilot. May be they should stop inquiries into accident. Because no matter what anyone does they are not responsible. Once in a while just clap some Sullenberger's act and move on till another one happens.
I read the full report. You are trying to defend undefendable stupidity. Report says there was no time pressure aircraft was ready before time, rather crew wanted to leave early. They were told that passengers need to be relocated the captain didn't do anything. The decision to not abort at 30 kts with nose pointing in the sky was insane and so was everything else. The whole decision making and logic behind it I cannot believe is from a pilot. May be they should stop inquiries into accident. Because no matter what anyone does they are not responsible. Once in a while just clap some Sullenberger's act and move on till another one happens.
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vilas,
I dont disagree that the decisions made in the cockpit where wrong. My point is only that behind those two pilots there is an organisation (airline/regulators) that has failed big time in allowing those two pilots to end up in a cockpit.
I dont disagree that the decisions made in the cockpit where wrong. My point is only that behind those two pilots there is an organisation (airline/regulators) that has failed big time in allowing those two pilots to end up in a cockpit.
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Welcome to Eastern Europe, especially Bulgaria. People don't get selected/promoted based on ability, but those decisions are based rather on social/policital connections, going back to the era couple of decades ago.
In this part of the world, if you get fired from an airline for whatever reason, you become the prime candidate for the head of CAA. What oversight?
In this part of the world, if you get fired from an airline for whatever reason, you become the prime candidate for the head of CAA. What oversight?
The captain obviously realized following the decision to reject takeoff, that the thrust reduction would result in a rapid de-rotation resulting in a violent impact of the nose gear on the runway.
But reducing the pitch-power couple isn't going to 'slam' the nose into the ground, any more than it causes an uncontrollable pitch-up (and if it is causing an uncontrollable pitch up, all the more reason to low speed abort because you'll have no chance once in the air).
This pilot basically chose a smoking hole over the potential for a slightly bent airplane - that it didn't end up in a smoking hole was little more than dumb luck.
This pilot basically chose a smoking hole over the potential for a slightly bent airplane - that it didn't end up in a smoking hole was little more than dumb luck.
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Uplinker, F16 I wonder if your family was on board this flight would you still say the same things? Actually the stick half forward on A320 is for standardization with other airbuses(wide bodies).It is not critical on A320. The badly out of range CG was the cause. Stick forward wouldn't have prevented the pitch up. Pilots are trained to reject takeoff for anything unusual during low speed phase and that is enough. No one can be trained for RTO with hundred different reasons.
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What's the logic here? What logic did you find in such a dangerously ignorant crew occupying pilot seats? If the nose pitches 15* at 50kts and after playing with thrust levers they continue the takeoff after multiple tail strikes they should be jailed and Airline's operating license should be cancelled. They manoeuvred the aircraft in such impossible manner that the computer was forced to reject the input as faulty and it went in alternate law and since gear was down direct law. There is no protection against ignorance and stupidity. Dangerous killers at large.
Uplinker
I read the full report. You are trying to defend undefendable stupidity. Report says there was no time pressure aircraft was ready before time, rather crew wanted to leave early. They were told that passengers need to be relocated the captain didn't do anything. The decision to not abort at 30 kts with nose pointing in the sky was insane and so was everything else. The whole decision making and logic behind it I cannot believe is from a pilot. May be they should stop inquiries into accident. Because no matter what anyone does they are not responsible. Once in a while just clap some Sullenberger's act and move on till another one happens.
I read the full report. You are trying to defend undefendable stupidity. Report says there was no time pressure aircraft was ready before time, rather crew wanted to leave early. They were told that passengers need to be relocated the captain didn't do anything. The decision to not abort at 30 kts with nose pointing in the sky was insane and so was everything else. The whole decision making and logic behind it I cannot believe is from a pilot. May be they should stop inquiries into accident. Because no matter what anyone does they are not responsible. Once in a while just clap some Sullenberger's act and move on till another one happens.
Fair enough. That does indeed sound shocking.
I was not trying to defend anything, I was trying to understand how this could have happened.
Last edited by Uplinker; 30th Dec 2017 at 14:05.