Uncommanded thrust reverser deployment in flight
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Uncommanded thrust reverser deployment in flight
What would you do if you encountered this situation?
Have you trained for it (procedures or simulator)?
Has anyone here experienced it?
I was reading a very interesting and sad NTSB report about a Lear 35 which had this problem last year. The crew apparently was clueless and had a lot of doctored logbooks and certifications, so their fate was sealed, but I still wonder how the average crew would handle this situation if it happened to them.
In your aircraft, are there definite indicators that the reverser has deployed, or do you have to hunt down what may be causing the problem?
Have you trained for it (procedures or simulator)?
Has anyone here experienced it?
I was reading a very interesting and sad NTSB report about a Lear 35 which had this problem last year. The crew apparently was clueless and had a lot of doctored logbooks and certifications, so their fate was sealed, but I still wonder how the average crew would handle this situation if it happened to them.
In your aircraft, are there definite indicators that the reverser has deployed, or do you have to hunt down what may be causing the problem?
a very interesting and sad NTSB report
Occurrence date/time - November 19, 2013, at 1956 eastern standard time.
https://www.ntsb.gov/_layouts/ntsb.a...14FA045&akey=1
Multiple Failures Put Learjet into the Atlantic | Business Aviation content from Aviation Week
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For the B737 Classics, the thrust lever for that engine will close to idle immediately without pilot action. This takes place so that only idle reverse is experienced and is easily countered. There will be some buffet. Follow the QRH once you have the aircraft under control. If roll is severe due to high power on the good engine, immediate closing of the thrust lever on the "good" engine should minimize the severity of the roll
I understand in the B737 NG series the engine also automatically goes to idle reverse but the thrust lever doesn't move until you go through the QRH and take the published action.
I recommend you Google the report (see link) on the Lauda Air Boeing 767 that experienced an uncommanded in flight thrust reverser during climb. On that accident the aircraft rolled rapidly and control was lost. I recall reading that investigation showed the crew had four seconds to take corrective action before loss of control would occur. That corrective action was not specified but I presume would have included immediate closing of both thrust levers and knowledge of unusual attitude recovery on instruments.
See: https://en.wikipedia.org/wiki/Lauda_Air_Flight_004
Depending on the type of simulator, the uncommanded in-flight thrust reversal should be selectable on the simulator instructor station
I understand in the B737 NG series the engine also automatically goes to idle reverse but the thrust lever doesn't move until you go through the QRH and take the published action.
I recommend you Google the report (see link) on the Lauda Air Boeing 767 that experienced an uncommanded in flight thrust reverser during climb. On that accident the aircraft rolled rapidly and control was lost. I recall reading that investigation showed the crew had four seconds to take corrective action before loss of control would occur. That corrective action was not specified but I presume would have included immediate closing of both thrust levers and knowledge of unusual attitude recovery on instruments.
See: https://en.wikipedia.org/wiki/Lauda_Air_Flight_004
How could you practice for a catastrophic event in a simulator?
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I still wonder how the average crew would handle this situation if it happened to them.
Lauda Air B767 Accident Report
Since then, we have always had a QRH / ECAM procedure.
Basically it says to reduce thrust (Idle), Reduce Airspeed, Shut the engine down, control the aircraft with full rudder trim and sufficient bank to maintain heading.
Also happened to a Fk100 (Brazil I think). Affected side thrust lever automatically slams closed (will take your fingers off if in the way). Believe the crew were unaware of this function with disastrous consequences.
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So do all boeing and airbus aircraft have reliable indicators that the reverser is indeed the problem?
The reason I asked this question is because the problem-solving you have to do is nightmarish if you don't have any clear cockpit indicators of what is happening. The big trouble is if you or the other guy shuts off the engine and that turns out not to have been what was causing the problem. I suppose that is why the checklists say to return the suspect engine to idle rather than shut it down, as I have seen some people do in incident reports.
Imagine you've just taken off, a little bit beyond V2 maybe, flaps start coming up, then BAM you experience severe yaw or roll and your airspeed starts decreasing. Is a thrust reverser the first thing that comes to your mind? What other possibilities are there that could cause this state? Severe flap asymmetry and/or uncommanded spoiler deployment?
The reason I asked this question is because the problem-solving you have to do is nightmarish if you don't have any clear cockpit indicators of what is happening. The big trouble is if you or the other guy shuts off the engine and that turns out not to have been what was causing the problem. I suppose that is why the checklists say to return the suspect engine to idle rather than shut it down, as I have seen some people do in incident reports.
Imagine you've just taken off, a little bit beyond V2 maybe, flaps start coming up, then BAM you experience severe yaw or roll and your airspeed starts decreasing. Is a thrust reverser the first thing that comes to your mind? What other possibilities are there that could cause this state? Severe flap asymmetry and/or uncommanded spoiler deployment?
Airbus FBW have a boxed "REV" indication that appears on the respective N1 or EPR gauge - amber while reverser is travelling, green when in correct position.
The FADEC will command idle thrust in the event of one or more reverser doors unlocked in flight or not in commanded position, and/or will command auto restow.
You might also get a ENG 1(2) at IDLE message and ENG 1(2) SHUTDOWN command on ECAM. It tells you to set thrust to idle and engine master off, along with speed limit, max rudder trim, and LAND ASAP amber.
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The FADEC will command idle thrust in the event of one or more reverser doors unlocked in flight or not in commanded position, and/or will command auto restow.
You might also get a ENG 1(2) at IDLE message and ENG 1(2) SHUTDOWN command on ECAM. It tells you to set thrust to idle and engine master off, along with speed limit, max rudder trim, and LAND ASAP amber.
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Last edited by Uplinker; 4th Sep 2017 at 14:27.
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those appear when you command reverse thrust, but i think the most common situation this is going to happen is when maintenance does sloppy work and something goes awry. in this situation, are your indicators still going to show up? and if you've got no indication, are you going to be able to diagnose what the problem is without that indicator?
as you say, the loss of control and utter lack of time you have to solve the situation before it becomes unfixable is a little unnerving.
as you say, the loss of control and utter lack of time you have to solve the situation before it becomes unfixable is a little unnerving.
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In airbus it should not be a problem. There is case from Safety first below, the aircraft was despatched with one reverser deactivated:
the aircraft was dispatched with the thrust reverser unlocked and free to move under aerodynamic forces.
Less than 4 minutes after take-off, the engine N°1 auto-idle was activated. It activates once there is more than 10% opening of the reverser, and brings down the TRA to idle based on the initial TRA position. This reverser opening detection also triggered the Auto thrust disconnection. The Auto re-stow which is also normally triggered was not effective since there was no hydraulic power due to the proper de-activation of the HCU.
As described in the Flight data analysis, there was very little changes on aircraft flight characteristics. Based on the flight parameters evolution it is assumed that the thrust reverser deployed slowly due to the aerodynamic forces (there was no hydraulic power due to HCU de-activation).
The aircraft maintained control with no upset throughout the event.
The engine was shut-down, then the Auto thrust was re-engage, and an IFTB was made followed by an uneventful single engine landing.
Less than 4 minutes after take-off, the engine N°1 auto-idle was activated. It activates once there is more than 10% opening of the reverser, and brings down the TRA to idle based on the initial TRA position. This reverser opening detection also triggered the Auto thrust disconnection. The Auto re-stow which is also normally triggered was not effective since there was no hydraulic power due to the proper de-activation of the HCU.
As described in the Flight data analysis, there was very little changes on aircraft flight characteristics. Based on the flight parameters evolution it is assumed that the thrust reverser deployed slowly due to the aerodynamic forces (there was no hydraulic power due to HCU de-activation).
The aircraft maintained control with no upset throughout the event.
The engine was shut-down, then the Auto thrust was re-engage, and an IFTB was made followed by an uneventful single engine landing.
The uncommanded reverser problem that most talk about is Lauda (there are others)
The pinch point in control of the aircraft for some aircraft is the climb portion where the wing control surfaces are defeated by the reverser eflux.
Yes there are some things that might recover but unless you can act real fast in the right direction ..... I know of one where the PF just continued the aircraft roll through 360 deg and completed the flight without his passengers knowing it happened.
The best corrective action is to act as soon as the reverser unlock light flickers and reduce the engine to idle (no need to shut it down in most cases).
If the discussion is to be about business jets alone, then my comments above may not apply.
The pinch point in control of the aircraft for some aircraft is the climb portion where the wing control surfaces are defeated by the reverser eflux.
Yes there are some things that might recover but unless you can act real fast in the right direction ..... I know of one where the PF just continued the aircraft roll through 360 deg and completed the flight without his passengers knowing it happened.
The best corrective action is to act as soon as the reverser unlock light flickers and reduce the engine to idle (no need to shut it down in most cases).
If the discussion is to be about business jets alone, then my comments above may not apply.
On a twin with most large turbofan engines, if the reverser deploys in flight your chances of a happy outcome are pretty minimal. I was involved in the Lauda investigation - including wind tunnel testing with a reverser deployed. It's not just the thrust asymmetry - the big problem is that the reverser efflux effectively spoils the lift on the wing and that side drops like a rock.
As a result, the cert basis for all Boeing aircraft has changed from 'it's controllable' to 'it'll never happen (3 independent failures, probability less than 10E-10 per flight hour).
It's a regulation that, with the reverser in an uncommanded position, the engine can not provide more than idle thrust. On the pre-FADEC engines this was done mechanically with a fairly complex feedback mechanism that would move the throttle to idle (rather forcefully as sheppey notes - yes it'll break your hand if it's in the wrong place). With FADEC it's all done with electronics and the throttle doesn't move but the engine will still be commanded to idle. The main problem - as Lauda demonstrated - is the transient. When Lauda deployed, the engine was at max climb and the decel characteristics at 24k/Mach .78 meant the aircraft was long since out of control before the engine reached idle.
Paradoxbox, Boeing displays an amber/green "REV" above the EPR/N1 display to indicate the reverser is in-transit (amber) or deployed (green) - and it's a robust indication. IF the reverser has in fact deployed it's not likely to help much.
As a result, the cert basis for all Boeing aircraft has changed from 'it's controllable' to 'it'll never happen (3 independent failures, probability less than 10E-10 per flight hour).
It's a regulation that, with the reverser in an uncommanded position, the engine can not provide more than idle thrust. On the pre-FADEC engines this was done mechanically with a fairly complex feedback mechanism that would move the throttle to idle (rather forcefully as sheppey notes - yes it'll break your hand if it's in the wrong place). With FADEC it's all done with electronics and the throttle doesn't move but the engine will still be commanded to idle. The main problem - as Lauda demonstrated - is the transient. When Lauda deployed, the engine was at max climb and the decel characteristics at 24k/Mach .78 meant the aircraft was long since out of control before the engine reached idle.
Paradoxbox, Boeing displays an amber/green "REV" above the EPR/N1 display to indicate the reverser is in-transit (amber) or deployed (green) - and it's a robust indication. IF the reverser has in fact deployed it's not likely to help much.
The C-5 Ramstein crash was attributed to a TR deployment near lift-off. Yes, the destruction of lift by the TR efflux is probably more a factor than just the TR. On aft-mounted engines, the effect is drag caused by the TR panels and reversed thrust without the lift destruction component. Still the highest yaw of all the engine failure modes and add in a crosswind, control becomes difficult. IAS is usually limited at about 200 KIAS, depending on type.
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Back in the day, a particular nasty trainer gave me a thrust reverser deploy (on the sim) at full power at rotate. (Eng remained at full power) Don't think it was even possible on a 737 but my call of feather it (just come of turboprops) ensured it was shut down by the capt. we were 30 deg off heading but back on track by 200 ft. My point being sometimes s** the qrh just do whatsynecessary.(remember full rudder & full aileron)
During my time on the F70/100, we were sometimes presented this malfunction by the instructor. As has been mentioned by T7A, there is a cable connecting the reverser buckets to the (IIRC) FCU, and on to the power levers, slamming the affected engines lever to the idle position when the buckets open. Although the engine spooled down to a corresponding thrust setting immediately, it was quite a ride and required some work with the controls to keep the aircraft pointed in a good general direction. As soon as the engine was shut down, though, it did not feel much different from an ordinary engine failure except for the affected power lever still remaining stuck in the flight idle position.
I am not sorry I never had to try this in the real aircraft.
I am not sorry I never had to try this in the real aircraft.
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Indications
If I recall correctly, the Lauda 767 did have a number of issues with its reverser on previous flights, indicated by (intermittent?) REV ISLN (reverse isolation) light.
Also on the accident flight, the REV ISLN light illuminated intermittently.
Position of reverser is properly indicated on engine instruments, probably on every aircraft type, by "no indication" for stowed, amber "REV" for in transit, green "REV" for deployed. In case of uncommanded deployment, warning display may trigger an alert (depending on aircraft type).
For chance of recovery - at low altitude, low speed, high thrust, chances are dim, lack of maneuvering room. At high altitude, improper reaction may come into play: unfamiliarity with unusual attitude recovery (civilian flight training conditions people to maintain positive gee and to pull to get back up to altitude; in case of severe roll this will lead to a pull through the vertical down, which will invariably destroy a jetliner. Proper reaction would be to unload, roll back or roll through, but keep the nose from dipping down too deep).
Many informative postings prior to this one, compliments.
Also on the accident flight, the REV ISLN light illuminated intermittently.
Position of reverser is properly indicated on engine instruments, probably on every aircraft type, by "no indication" for stowed, amber "REV" for in transit, green "REV" for deployed. In case of uncommanded deployment, warning display may trigger an alert (depending on aircraft type).
For chance of recovery - at low altitude, low speed, high thrust, chances are dim, lack of maneuvering room. At high altitude, improper reaction may come into play: unfamiliarity with unusual attitude recovery (civilian flight training conditions people to maintain positive gee and to pull to get back up to altitude; in case of severe roll this will lead to a pull through the vertical down, which will invariably destroy a jetliner. Proper reaction would be to unload, roll back or roll through, but keep the nose from dipping down too deep).
Many informative postings prior to this one, compliments.
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This is turning into a great thread, thanks for the replies everyone.
But I hope someone will answer my question (perhaps it was not clear enough)
I know that under normal circumstances most aircraft (all?) have indicators for thrust reverser deployment -when on the ground-.
But.. When you are in the air, and the reverser has deployed, for example by aerodynamic forces, or mechanical failure (parts falling off etc) - will the indicators still appear in your aircraft? Is there some kind of mechanical or electrical sensor that physically or electronically detects that the reverser door or doors are not stowed completely? Does it detect when the door is only open slightly or do the doors need to open to the stops before the sensor detects it? If the cause of the deployment is due to faulty maintenance, will the sensor (i.e. in the Airbus) still be able to detect that the door is open?
Sounds like some aircraft have a physical link to the throttles which slams the throttle lever down. That sounds like a nasty hospital bill but certainly better than crashing. What about in the Boeings and others i.e. CRJ?
And if for some reason you did not get a cockpit indicator, do you think you would still come to the conclusion that your reverser was stuck open and act appropriately? Or would you be hunting for other possible solutions and miss the obvious as the Lear crew did?
But I hope someone will answer my question (perhaps it was not clear enough)
I know that under normal circumstances most aircraft (all?) have indicators for thrust reverser deployment -when on the ground-.
But.. When you are in the air, and the reverser has deployed, for example by aerodynamic forces, or mechanical failure (parts falling off etc) - will the indicators still appear in your aircraft? Is there some kind of mechanical or electrical sensor that physically or electronically detects that the reverser door or doors are not stowed completely? Does it detect when the door is only open slightly or do the doors need to open to the stops before the sensor detects it? If the cause of the deployment is due to faulty maintenance, will the sensor (i.e. in the Airbus) still be able to detect that the door is open?
Sounds like some aircraft have a physical link to the throttles which slams the throttle lever down. That sounds like a nasty hospital bill but certainly better than crashing. What about in the Boeings and others i.e. CRJ?
And if for some reason you did not get a cockpit indicator, do you think you would still come to the conclusion that your reverser was stuck open and act appropriately? Or would you be hunting for other possible solutions and miss the obvious as the Lear crew did?
Too long ago for me to remember the date (or apparently for Google either), Eastern Airlines had a TR on a DC9(-30 I think) come open right at rotation or immediately after in KATL.
They were dispatched with it inop but MTC didn't properly secure it so it came unlocked and fully deployed while at T/O power. IIRC, they immediately closed the throttle and shut off the fuel and lived to fly another day. If they had any advantage, it was knowing that TR had been messed with but mostly it was superior airmanship.
IIRC, the reverse component for the -30 was 40% of engine being thrust produced.
We tried the event in the sim during recurrent and if you didn't IMMEDIATELY snap the throttle to idle and shut off the fuel…you didn't make it.
As you said, no time for any book or even thinking about any book.
As for indications, I never flew a TJ airplane where the reverser indications were different air vs ground but I can't speak for all airplane types.
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We tried the event in the sim during recurrent and if you didn't IMMEDIATELY snap the throttle to idle and shut off the fuel…you didn't make it.
As you said, no time for any book or even thinking about any book.
This says a great deal about today's training in some airlines. Glad to hear there is some imagination in some airlines. I was so tired and fed up of the repetitive trivia served up in LPC's & OPC's. It was mind numbing and not very educational after the umpteenth time of a mandatory item. RST's tried to inject some variances, but the emphasis was on CRM, QRH, FDM & SOP's. There was not a lot of thinking outside the envelope. Guys are terrified of having to solve a problem without a checklist: terrified of acting immediately, as the scenario dictates, as a pilot. Their first thought is "what does the SOP say?" Then there is a huge ? mark as they realise there isn't one. OMG, what to do.
I was in RST's given by 2 year F/O's SFI. They had the script. It was quite interesting to remember the times they commented, "I haven't seen anyone do that before, but it worked. Hm?" That was from the enlightened ones. The others just chimed in, "you weren't supposed to do that." Oh dear.
I used to really enjoy the education gained by designing scenarios where there was no checklist; and often derived from real events that went wrong. Sadly, that was stamped out by those who thought it taught a bad attitude.
How many accidents have happened because the crew failed to follow the QRH correctly? Not many. It is the WTF factor that fuddles the brain and needs a knowledge of the a/c & aviation to solve the problem that trips up the majority. The NTSB investigators are sometimes quite bemused as to 'why the heck did they do that'. Often it was because they didn't know any better, but they should have.
In my some of my previous outfits they had one OPC/LPC program and one RST. You could ask your mates what happened and what the sequence was and what they did. Not very educational or confidence building. RST's should be real training and fun. Find out about yourself & the a/c and the way you behave under certain conditions. Checking should be more realistic and less repetitive trained monkey stuff. Ah, but then too many might fail and need re-training and that is disruptive to the roster, especially in the summer. Tick the boxes and smile. XAA happy, CFO happy. HOT? that depends.
As you said, no time for any book or even thinking about any book.
This says a great deal about today's training in some airlines. Glad to hear there is some imagination in some airlines. I was so tired and fed up of the repetitive trivia served up in LPC's & OPC's. It was mind numbing and not very educational after the umpteenth time of a mandatory item. RST's tried to inject some variances, but the emphasis was on CRM, QRH, FDM & SOP's. There was not a lot of thinking outside the envelope. Guys are terrified of having to solve a problem without a checklist: terrified of acting immediately, as the scenario dictates, as a pilot. Their first thought is "what does the SOP say?" Then there is a huge ? mark as they realise there isn't one. OMG, what to do.
I was in RST's given by 2 year F/O's SFI. They had the script. It was quite interesting to remember the times they commented, "I haven't seen anyone do that before, but it worked. Hm?" That was from the enlightened ones. The others just chimed in, "you weren't supposed to do that." Oh dear.
I used to really enjoy the education gained by designing scenarios where there was no checklist; and often derived from real events that went wrong. Sadly, that was stamped out by those who thought it taught a bad attitude.
How many accidents have happened because the crew failed to follow the QRH correctly? Not many. It is the WTF factor that fuddles the brain and needs a knowledge of the a/c & aviation to solve the problem that trips up the majority. The NTSB investigators are sometimes quite bemused as to 'why the heck did they do that'. Often it was because they didn't know any better, but they should have.
In my some of my previous outfits they had one OPC/LPC program and one RST. You could ask your mates what happened and what the sequence was and what they did. Not very educational or confidence building. RST's should be real training and fun. Find out about yourself & the a/c and the way you behave under certain conditions. Checking should be more realistic and less repetitive trained monkey stuff. Ah, but then too many might fail and need re-training and that is disruptive to the roster, especially in the summer. Tick the boxes and smile. XAA happy, CFO happy. HOT? that depends.