B-738 Crash in Russia Rostov-on-Don
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I agree with you that normally autopilots should not do that. If something unusual happens and the autopilot does not know how to deal with it, like power kept on, it will disconnect.
Either due to excessive pitch or overspeed. The question is when it disconnected. But the trim on the Boeing is aparently very fast in trimming when on autopilot. I am not a Boeing guy, but somebody here said it before. Even if the autopilot disconnected early enough, the flight directors would still guide the pilots to nose down. Similar thing happened with many goaround accidents. I still think the autopilot disconnected on them. Could anybody who has access to the Boeing sim try to set a low goaround altitude, or try to do a goaround from intermediate altitude, keep autopilot on, set toga and "sleep through it" with no action? I wonder what it will do. Airbus will pitch down and accelerate and you have to be quick in retracting flaps. I still have to find the accident where airbus test pilots got killed this way. At least that's what I remember hearing in 2008. And of course, violent, or brisk is a question of how we define the words. But at 2am, even brisk can feel violent.
Either due to excessive pitch or overspeed. The question is when it disconnected. But the trim on the Boeing is aparently very fast in trimming when on autopilot. I am not a Boeing guy, but somebody here said it before. Even if the autopilot disconnected early enough, the flight directors would still guide the pilots to nose down. Similar thing happened with many goaround accidents. I still think the autopilot disconnected on them. Could anybody who has access to the Boeing sim try to set a low goaround altitude, or try to do a goaround from intermediate altitude, keep autopilot on, set toga and "sleep through it" with no action? I wonder what it will do. Airbus will pitch down and accelerate and you have to be quick in retracting flaps. I still have to find the accident where airbus test pilots got killed this way. At least that's what I remember hearing in 2008. And of course, violent, or brisk is a question of how we define the words. But at 2am, even brisk can feel violent.
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And Airbus constantly keeps improving the automatics based on previous incident problems.
So may be Boeing is also prone to something like unexpected behaviour in a mismanaged goaround.
So may be Boeing is also prone to something like unexpected behaviour in a mismanaged goaround.
GS capture on a 737 with a wonky GS signal can result in a violent pitch down. Other than that I agree with PJ2's post. I hold on to the flight controls with white knuckles after I press approach mode until the GS is captured. If you haven't experienced one of these it's an eye opener.
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As the autopilot had no other choice than to pitch violently down, to keep altitude, it has probably overdone a parameter in pitch and automatically disconnected itself with quite a pitch down.
Illuminated (red) –
steady for any of following conditions:
ALT ACQ mode inhibited during A/P go–around if stabilizer not trimmed for single A/P operation
The NG doesn't do violent level offs during go around. If it is not trimmed properly, it will fly throught the MCP altitude rather than pitch down violently.
The indication for this is a steady autopilot disengage light.
There is also a Stab Out Of Trim light to tell you if the autopilot is not trimming correctly.
A normal go around on two engines is not a full thrust event. Nothing violent about it.
A wonky GS signal will do things to any aircraft.
It’s a bit of a teaser as the status of the things that are most pertinent, AP in/out and AT in/out, are not given in the update. They must know by now but are not releasing that information.
Given that they say there were no system failures, the scenarios I can think of right now are:
a) AP out - somehow they flew it into the ground, be it from an illusion of some kind and/or trimming so far forward it wasn’t recoverable.
b) AP in & AT out - acquires, then speeds up, AP applying more and more nose down trim until it disconnects or is disconnected.
Option b) would still leave the aircraft wanting to pitch up, as the trim runs reactively, unless the power was taken off suddenly as a reaction to a possible flap overspeed. Would that be controllable using the elevator alone? Not sure but my instinct says yes.
Option a) seems more likely but why was it so different from the first GA? What happened at 3,000’ that caused such a divergence? A bunt to follow the flight director if it acquired 3,000’ followed by a loss-of-control? Can’t think of much else...
Given that they say there were no system failures, the scenarios I can think of right now are:
a) AP out - somehow they flew it into the ground, be it from an illusion of some kind and/or trimming so far forward it wasn’t recoverable.
b) AP in & AT out - acquires, then speeds up, AP applying more and more nose down trim until it disconnects or is disconnected.
Option b) would still leave the aircraft wanting to pitch up, as the trim runs reactively, unless the power was taken off suddenly as a reaction to a possible flap overspeed. Would that be controllable using the elevator alone? Not sure but my instinct says yes.
Option a) seems more likely but why was it so different from the first GA? What happened at 3,000’ that caused such a divergence? A bunt to follow the flight director if it acquired 3,000’ followed by a loss-of-control? Can’t think of much else...
Can icing cause "wonky GS signal"? Sorry, if question seems inappropriate.
Edit: Ninja’d by Aerocat
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Stab ND
When flying the MAP manually with a relativly light B737, one easily might apply to much ND Trim in attempting to capture a low level-off altitude. Since the speed might increase rapidly one can find himself in a condition with Stab Trim at 0 / Full ND and T/L retarding to more or less idle.
What may come next is what the second video shows in its late stages. My company had a very very close shave with a 735 years ago going around, they lost more than 1500ft after the initial level off and were pulling as hard as they could....
It might be difficult to realize the condition one is in and the existing setting. And more difficult to make the next step and increase thrust to get rid of the impressive nose-down moment while retrimming and - probably most of it - being puzzled.
Add adverse weather and gusty conditions.
In any case interresting to see all the speculations above showing a total lack of 737-knowledge, not speaking of experience. Let's all hope those don't come from pilots.
And let's hope none of us ever gets caught flat-footed like this. It's always waiting just around the corner....
What may come next is what the second video shows in its late stages. My company had a very very close shave with a 735 years ago going around, they lost more than 1500ft after the initial level off and were pulling as hard as they could....
It might be difficult to realize the condition one is in and the existing setting. And more difficult to make the next step and increase thrust to get rid of the impressive nose-down moment while retrimming and - probably most of it - being puzzled.
Add adverse weather and gusty conditions.
In any case interresting to see all the speculations above showing a total lack of 737-knowledge, not speaking of experience. Let's all hope those don't come from pilots.
And let's hope none of us ever gets caught flat-footed like this. It's always waiting just around the corner....
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Quick... well, hopefully quick... question from a SLF: would a light-side 737-800 making a high energy go-around into an increasing headwind (35 -> 52 kts) be prone to a negative [longitudinal] dynamic stability state?
With respect, all you non-pilot guys are over thinking it.
Light plane, Manual thrust,increasing headwind, 4am in the morning, haven't gotten up for a pee in six hours, crappy rosters for months on end, trim a bit too much nose down when the somotogravic hits....... that's it IMHO.
And that's why you want a well rested crew.
People in normal jobs have moments when their brain doesn't process information well often, and nothing happens. People driving cars have moments when their brain doesn't process information well and most of the time they get away with it, sometimes they crash, rarely is it headline news.
We know this crew was capable of flying a go around because they did one two hours earlier. When this comes back that there was no aircraft malfunction I hope we all acknowledge that being well rested and in good mental shape is critical to flight safety and crew rostering should be regulated to ensure that profits don't get in the way of the paying passengers expectation that they will survive the flight.
Light plane, Manual thrust,increasing headwind, 4am in the morning, haven't gotten up for a pee in six hours, crappy rosters for months on end, trim a bit too much nose down when the somotogravic hits....... that's it IMHO.
And that's why you want a well rested crew.
People in normal jobs have moments when their brain doesn't process information well often, and nothing happens. People driving cars have moments when their brain doesn't process information well and most of the time they get away with it, sometimes they crash, rarely is it headline news.
We know this crew was capable of flying a go around because they did one two hours earlier. When this comes back that there was no aircraft malfunction I hope we all acknowledge that being well rested and in good mental shape is critical to flight safety and crew rostering should be regulated to ensure that profits don't get in the way of the paying passengers expectation that they will survive the flight.
MAK Update
As the crew were proceeding with another manual approach, they decided to go around again at a height of 220 meters (4 km before the runway) and initiated climb setting the engine to takeoff thrust. At a height of 900 m there was a simultaneous control column nose down input and stabilizer 5-degree nose down deflection, resulting in abrupt descent with negative vertical acceleration of -1g. The following crew actions to recover did not allow to avoid an impact with the ground. The impact occurred with a speed of over 600 km/h over 50 degrees nose down.
Frosch, re:
The reason that too much trim can easily be applied is because leveling-off using the horizontal stabilizer is most certainly not the way to fly any aircraft. The horizontal stabilizer is a very powerful flight control, to be used carefully and appropriately in manual flight. "Trimming-into" a level off, while not unheard of, is not the way to level off. I am well aware that it can be and has been done on the Boeing and perhaps understand why some crews may decide to operate the aircraft this way. However, the autopilot isn't going to anticipate a level off and begin trimming prior to capture.
The challenge of a low-altitude level-off on a go-around is and always has been a challenge because things are happening very fast. You have to be right on top of the airplane's performance, no matter what type you're flying; there's no magic in it - it's just part of the kit. Trimming "into" the level off is a recipe for loss of control.
PBY, others have provided some examples which may or may not be comparable to what happened here. Are you thinking of the Sochi (Armavia) or the Perpignan (XL Airways/Air New Zealand) accident? If so, here are links to the Perpignan report and the Sochi Report.
When flying the MAP manually with a relativly light B737, one easily might apply to much ND Trim in attempting to capture a low level-off altitude.
The challenge of a low-altitude level-off on a go-around is and always has been a challenge because things are happening very fast. You have to be right on top of the airplane's performance, no matter what type you're flying; there's no magic in it - it's just part of the kit. Trimming "into" the level off is a recipe for loss of control.
PBY, others have provided some examples which may or may not be comparable to what happened here. Are you thinking of the Sochi (Armavia) or the Perpignan (XL Airways/Air New Zealand) accident? If so, here are links to the Perpignan report and the Sochi Report.
I doubt B is plausible. The autopilot will only trim if the elevator is holding a force. It won't matter how fast the aeroplane is going, the AP will keep itself in trim. I doubt the 737 could accelerate so fast that the AP trim couldn't keep up. If the power comes off suddenly, the aeroplane will be in-trim for that speed, apart from the thrust couple. I wouldn't have thought that that would be so much that a bit of backstick wouldn't correct it; maybe a shallow descent but not a major dive.
Have a read of the Icelandair 757 GA incident at Oslo in 2002. Massive push-forward on stick to -49° and 250KIAS by the captain. Why would he do that? Illusions?
Have a read of the Icelandair 757 GA incident at Oslo in 2002. Massive push-forward on stick to -49° and 250KIAS by the captain. Why would he do that? Illusions?
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Conditions:
Night in clouds, no visible horizon
Low weight with Aft CG
Low speed on final will cause more nose up trim
Manual Go Around with full thrust plus aft trim will lead to an extreme nose up attitude
Pilot will be surprised by the high pitch attitde. 20-25 nose up
high force to put the stick forward will not decrease the pitch attitude
Autopilot ON will not help the situation, except you remember to increase the speed
impossible to achieve a low level off
Nose down stabilizer will help....if you do not apply too much stabilizer, which will cause a dive
another solution:
reduce thrust
bank to get the nose down to the horizon
complete the recovery
There is also a good chance you end up in a dive
Night in clouds, no visible horizon
Low weight with Aft CG
Low speed on final will cause more nose up trim
Manual Go Around with full thrust plus aft trim will lead to an extreme nose up attitude
Pilot will be surprised by the high pitch attitde. 20-25 nose up
high force to put the stick forward will not decrease the pitch attitude
Autopilot ON will not help the situation, except you remember to increase the speed
impossible to achieve a low level off
Nose down stabilizer will help....if you do not apply too much stabilizer, which will cause a dive
another solution:
reduce thrust
bank to get the nose down to the horizon
complete the recovery
There is also a good chance you end up in a dive
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This might be a really stupid idea, but what if he had his thumb on the STAB TRIM button as he initiated the GA? Maybe over compensated or even lost the sensation of pressure due to tiredness, controlling the a/c in the weather? Sorry if its a dumb thought but just throwing it up there
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When flying the MAP manually with a relativly light B737, one easily might apply to much ND Trim in attempting to capture a low level-off altitude. Since the speed might increase rapidly one can find himself in a condition with Stab Trim at 0 / Full ND and T/L retarding to more or less idle.
Here's a similar scenario with a Korean Mad Dog freighter out of SHA in 1999:
After takeoff the first officer contacted Shanghai Departure and received clearance to climb to 1500 metres (4900 feet): "Korean Air six three one six now turn left direct to November Hotel Whiskey climb and maintain one thousand five hundred meters."
When the aircraft climbed to 4500 feet in the corridor, the captain, after receiving two wrong affirmative answers from the first officer that the required altitude should be 1500 feet, thought that the aircraft was 3000 feet too high. The captain then pushed the control column abruptly and roughly forward causing the MD-11 to enter a rapid descent.
Both crew members tried to recover from the dive, but were unable. The airplane crashed into an industrial development zone 10 kilometers (6 miles) southwest of Hongqiao airport. The plane plunged to the ground, plowing into housing for migrant workers and exploded.
When the aircraft climbed to 4500 feet in the corridor, the captain, after receiving two wrong affirmative answers from the first officer that the required altitude should be 1500 feet, thought that the aircraft was 3000 feet too high. The captain then pushed the control column abruptly and roughly forward causing the MD-11 to enter a rapid descent.
Both crew members tried to recover from the dive, but were unable. The airplane crashed into an industrial development zone 10 kilometers (6 miles) southwest of Hongqiao airport. The plane plunged to the ground, plowing into housing for migrant workers and exploded.
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PJ2 I found something about the Go Arounds:
It is study on Airplane state awareness during a go around.
It lists many accidents, including the ones you mention.
http://caa.gov.il/index.php?option=c...id=669&lang=he
It is study on Airplane state awareness during a go around.
It lists many accidents, including the ones you mention.
http://caa.gov.il/index.php?option=c...id=669&lang=he
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It's not rocket science! Fly a GA like a normal take off, TO/GA, accelerate, rotate 2/3' per second and look for 15' pitch. Positive rate..... problem is that you actually have to fly the airplane.
