BA038 (B777) Thread
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GasPath
Then I see a problem. See Machaca's provided pictures of the Heat exchanger specifically the dozens of narrow tubes in the large cylindrical case. Any transfer of energy requires time, hence the narrow (large surface area) multiple passages. Adding time to passage transit requires restriction. I submit it is a logical place to consider a constriction. Though there are two systems, I refer to an earlier post of mine showing that when independent systems rely on common Fuel (Though stored separately), the possibility is enhanced for failure when certain parameters are shared, and possess an insurmountable extreme, (Temp. Viscosity, restriction, contamination, ambient energy, etc.). This possibility is well within consideration given the seven second delay.
#1159 Machaca, See also Arcniz#1160 for a good interpretation of my
point about heterogeneity in standard and duplicative systems.
Airfoil
#1159 Machaca, See also Arcniz#1160 for a good interpretation of my
point about heterogeneity in standard and duplicative systems.
Airfoil
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Just read this in an aviation e-mag: wonder if some such thing could have happened in the case under discussion in this forum>>
UPDATE: B-2 CRASH CAUSED BY WATERLOGGED SENSORS
click for video
The crash on takeoff of a 509th Air Wing, Air Force B-2 Spirit bomber, February 23 operating at Andersen Air Force Base, Guam, was caused by water in the aircraft's sensors, according to an Air Combat report issued Thursday. Specifically, moisture in three port transducer units "distorted data introduced by a B-2 Spirit's air data system" which led to flawed information entering the bomber's flight control computers. The aircraft was reacting to inaccurate airspeed and a "perceived" negative angle of attack. This resulted in an "uncommanded 30 degree nose-high pitch-up on takeoff," according to the Air Force.
Major Ryan Link and Captain Justin Grieve, the aircraft's two pilots and the only two aboard were unable to regain control and safely ejected just as the aircraft stalled and mushed into the ground and its left wing impacted the ground. The $1.4 billion aircraft crashed just off the left side of the runway and exploded. It was the first-ever B-2 crash and followed 75,000 hours of loss-free service. Link and Grieve both suffered injuries during ejection, with Grieve suffering compression fractures to his spine.
The report points to the inaccurate readings as contributing factors, adding that ineffective communication of critical information about a technique used to remove moisture from the sensors also contributed. It's possible that all the pilots had to do to avert the accident was turn on the pitot heat prior to performing air data calibrations. But the suggested technique was not part of checklist procedures.
click for video
The crash on takeoff of a 509th Air Wing, Air Force B-2 Spirit bomber, February 23 operating at Andersen Air Force Base, Guam, was caused by water in the aircraft's sensors, according to an Air Combat report issued Thursday. Specifically, moisture in three port transducer units "distorted data introduced by a B-2 Spirit's air data system" which led to flawed information entering the bomber's flight control computers. The aircraft was reacting to inaccurate airspeed and a "perceived" negative angle of attack. This resulted in an "uncommanded 30 degree nose-high pitch-up on takeoff," according to the Air Force.
Major Ryan Link and Captain Justin Grieve, the aircraft's two pilots and the only two aboard were unable to regain control and safely ejected just as the aircraft stalled and mushed into the ground and its left wing impacted the ground. The $1.4 billion aircraft crashed just off the left side of the runway and exploded. It was the first-ever B-2 crash and followed 75,000 hours of loss-free service. Link and Grieve both suffered injuries during ejection, with Grieve suffering compression fractures to his spine.
The report points to the inaccurate readings as contributing factors, adding that ineffective communication of critical information about a technique used to remove moisture from the sensors also contributed. It's possible that all the pilots had to do to avert the accident was turn on the pitot heat prior to performing air data calibrations. But the suggested technique was not part of checklist procedures.
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Well Airfoil.
I think it is quite important to discover whether GA was called. Don't you think to retract the flaps at that moment was 'unusual'? There wasn't an opportunity to discuss the matter with the handling pilot presumably.
Fancy this being overlooked by all you amateur theorists?
I think it is quite important to discover whether GA was called. Don't you think to retract the flaps at that moment was 'unusual'? There wasn't an opportunity to discuss the matter with the handling pilot presumably.
Fancy this being overlooked by all you amateur theorists?
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PoofBoot
I think you're confused; a look at the history of the thread would do you well. The Donks conked @ ~800 no power from then on. No one knows whether F/O Coward was attempting GA or simply trying to throttle up while short. The Flaps issue was aggressively dealt with by mods, who diverted all discussion of Flap reselect to JB. Ordinarily one would want a Positive ROC prior to flap retraction, very little is known except the A/P flew up to I think 17 degree AoA and 108 knots at 200 feet AGL. It's not difficult to look like an "amateur" with very little Data, as you now must know. One can Attempt a Go around with no power; One can attempt a HOVER with no power. (Down is Down).
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If flaps were raised to less than landing position before GA was selected with unresponsive engines (and EAI was not ON), the engine EECs would have automatically reverted from approach idle to minimum idle, aggravating the situation in this particular case. However, there is no mention of raising flaps or GA selection in the AAIB reports.
Green-dot
Green-dot
Controversial, moi?
....the engine EECs would have automatically reverted from approach idle to minimum idle, aggravating the situation in this particular case.
Even if the flaps had been reduced to less than F25 the idle speed would be irrelevant unless the thrust levers were closed, therefore, I fail to understand how the situation would have been aggravated.
Pitot Heat in the B-2
Seekayess, I've never flown a B-2, but chances are that pitot heat is ALWAYS on unless selected otherwise. It may well be that they couldn't even select it off except by pulling a circuit breaker and I can't imagine their doing that.
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To M.Mouse:
There is no mention made about selecting F25 in any AAIB reports i have read sofar. If there was an anticipation to GA, flap selection would have been less than F25, at least to F20, taking the flaps out of the landing position which would mean (as explained earlier) engine EECs would be set for minimum idle. If the thrust levers were even momentarily moved to idle, to minimum idle they would have gone.
Same as for the flap scheduling, there is also no mention if the thrust levers had been retarded to idle, even if only for a short period. Thrust levers in idle, same as your claim flaps were selected to F25, are not mentioned in the AAIB reports but it it does not necessarily mean it did not occur.
Green-dot
The flaps were reduced from F30 to F25. Approach idle would have been minimum idle speed had the thrust levers been closed, which they weren't anyway.
Even if the flaps had been reduced to less than F25 the idle speed would be irrelevant unless the thrust levers were closed, therefore, I fail to understand how the situation would have been aggravated.
Even if the flaps had been reduced to less than F25 the idle speed would be irrelevant unless the thrust levers were closed, therefore, I fail to understand how the situation would have been aggravated.
Same as for the flap scheduling, there is also no mention if the thrust levers had been retarded to idle, even if only for a short period. Thrust levers in idle, same as your claim flaps were selected to F25, are not mentioned in the AAIB reports but it it does not necessarily mean it did not occur.
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It seems obvious to me that the flap retraction to 25 was only to clear the fence and maybe make the runway. Nobody in that situation with two sick engines would attempt a go around. No pilot on the face of the earth would have attempted a go around. Why even bring this up? If they had enough power to go around they would have just landed.
Controversial, moi?
Green Dot you are correct here is no mention in the AAIB report of the flaps being moved.
The flaps were retracted from F30 to F25 and the thrust levers were not selected to idle. Your hypothesis is flawed.
The flaps were retracted from F30 to F25 and the thrust levers were not selected to idle. Your hypothesis is flawed.
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To M.Mouse:
Could you kindly provide a source to back up your statement?
I agree, from a procedural point of view, that it would not be logical to retard the thrust levers to idle in this situation but with unresponsive engines and no thrust increase with the thrust levers fire-walled, would it not be a natural reflex to retard the thrust levers to idle in an attempt to try a last ditch effort to spool up the engines manually, an attempt to initiate a thrust increase from idle conditions?
(Somewhat like gunning your car engine when the engine stalls and you try to recover by letting go of the accelerator and pushing it back in, in an attempt to recover from a stalling engine.)
Regards,
Green-dot
The flaps were retracted from F30 to F25 and the thrust levers were not selected to idle.
I agree, from a procedural point of view, that it would not be logical to retard the thrust levers to idle in this situation but with unresponsive engines and no thrust increase with the thrust levers fire-walled, would it not be a natural reflex to retard the thrust levers to idle in an attempt to try a last ditch effort to spool up the engines manually, an attempt to initiate a thrust increase from idle conditions?
(Somewhat like gunning your car engine when the engine stalls and you try to recover by letting go of the accelerator and pushing it back in, in an attempt to recover from a stalling engine.)
Regards,
Green-dot
Controversial, moi?
Could you kindly provide a source to back up your statement?
If I know something for a fact I post it to avoid pages of tedious and inaccurate speculation developing.
It really makes no difference to me whether you believe what I post or not. The final report will show whether any statement I have made is right or wrong.
...would it not be a natural reflex to retard the thrust levers to idle in an attempt to try a last ditch effort to spool up the engines manually, an attempt to initiate a thrust increase from idle conditions?
About the only time you'd think of retarding a thrust lever when you're undershooting, in an attempt to 'cure' an engine problem, would be if it was surging badly - and this is not the case with BA38.
When people talk about manual thrust on the 777, they mean without the autothrottle engaged. All the A/T does is try to move the thrust levers to satisfy demands from from the A/T computer; when you take it out it means you have to move them yourself. The thrust levers have sensors on them which provide position data to the EECs; that's it. The engines are FADEC = Full Authority Digital Engine Control: there is NO 'manual' control; the only thing you can influence is the mode they operate in - the RR Trent has a 'hard alternate' mode you can select from the flight deck that references N1 instead of EPR and removes some of the thrust (overboost) protection.
It seems obvious to me that the flap retraction to 25 was only to clear the fence and maybe make the runway. Nobody in that situation with two sick engines would attempt a go around. No pilot on the face of the earth would have attempted a go around. Why even bring this up? If they had enough power to go around they would have just landed.
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Not for anyone who was a jet pilot
Green-dot put it right, just a human natural reflex for a mopped driver as well as a jet pilot.
Surprise effect + no time to spare !
That's exactly what did Asseline in Habsheim when he realized thrust was not coming.
That's exactly what did Asseline in Habsheim when he realized thrust was not coming.
It's possible to 'rich cut' a carb-fed piston engine by being aggressive on the throttle at a low power setting, on something with an accelerator pump... Maybe people get confused by this and expect jet engines to exhibit the same behaviour.
The only way I know to 'reset' the Trent engine is to momentarily put the fuel control switch into cutoff and hope that it will accelerate up again; even the manual says it could take a loooonnng time. Not a technique I'd apply at 700'.
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To M.Mouse:
Fair enough, patience is a virtue.
To FullWings:
Hindsight has 20/20 vision.
In the case of BA038, the crew were confronted with non responsive engines. They had no time to accurately analyse their engine problems. According to the AAIB reports there were no alerts or EICAS procedures to assist the crew. Could very well be that they perceived engine surging to be their problem at hand at the time.
I am aware of how the system works, including the RR configuration.
In order to select the EEC in the 'hard alternate' mode the pilot has to retard the thrust levers before manually selecting the guarded EEC switch to the 'hard alternate mode' (manual selection is referred to as the 'hard alternate' mode, automatic selection is referred to as the 'soft alternate' mode).
Retarding the thrust levers before selecting the 'hard alternate' mode is necessary because there is no thrust limit protection in the alternate modes (in case of the BA038 situation the thrust levers would have been fire-walled). If the crew had decided to select the 'hard alternate' mode (regardless of an EEC fault or not) they would have retarded the thrust levers before doing so.
To do this, the action is generally triggered by an EEC fault which initially results in a (automatic) 'soft alternate' mode and an EICAS advisory message/procedure. A 'hard alternate' mode selection is the next step in order to acquire a [boxed] N1 reference indication on the affected engine.
Since the AAIB reports explain there is no evidence of EEC faults, hence no alerts such as EEC ALTN light or EICAS messages, logically there would have been no reason for the crew to act and select the 'hard alternate' mode. The only remaining scenario would have been if the crew decided to select the 'hard alternate' mode at their own discretion in an attempt to "wake up" the engines as a last resort. In this scenario they could have retarded the thrust levers to idle although it would not have been necessary to retard the thrust levers that far back.
I stress this probably did not occur or the AAIB would have mentioned it in one of their released bulletins but it could have been a scenario as a last resort attempt to avert premature contact with terra firma in that final minute. If it did occur, it could have resulted in engines reverting to minimum idle if flaps were retracted to less than landing position and EAI not ON. But based on the information that M. Mouse provided (he must have first hand information to back his claim), minimum idle can apparently be illiminated as a factor.
It would have been risky to cycle the spar valves (by selecting fuel control switches from run-to cutoff-to run) which could result in jammed spar valve actuators which would certainly have resulted in fuel flow restrictions.
No but in the BA038 scenario, if this action took place, it didn't either.
Regards,
Green-dot
The final report will show whether any statement I have made is right or wrong.
To FullWings:
About the only time you'd think of retarding a thrust lever when you're undershooting, in an attempt to 'cure' an engine problem, would be if it was surging badly - and this is not the case with BA38.
In the case of BA038, the crew were confronted with non responsive engines. They had no time to accurately analyse their engine problems. According to the AAIB reports there were no alerts or EICAS procedures to assist the crew. Could very well be that they perceived engine surging to be their problem at hand at the time.
. . .the only thing you can influence is the mode they operate in - the RR Trent has a 'hard alternate' mode you can select from the flight deck that references N1 instead of EPR and removes some of the thrust (overboost) protection.
In order to select the EEC in the 'hard alternate' mode the pilot has to retard the thrust levers before manually selecting the guarded EEC switch to the 'hard alternate mode' (manual selection is referred to as the 'hard alternate' mode, automatic selection is referred to as the 'soft alternate' mode).
Retarding the thrust levers before selecting the 'hard alternate' mode is necessary because there is no thrust limit protection in the alternate modes (in case of the BA038 situation the thrust levers would have been fire-walled). If the crew had decided to select the 'hard alternate' mode (regardless of an EEC fault or not) they would have retarded the thrust levers before doing so.
To do this, the action is generally triggered by an EEC fault which initially results in a (automatic) 'soft alternate' mode and an EICAS advisory message/procedure. A 'hard alternate' mode selection is the next step in order to acquire a [boxed] N1 reference indication on the affected engine.
Since the AAIB reports explain there is no evidence of EEC faults, hence no alerts such as EEC ALTN light or EICAS messages, logically there would have been no reason for the crew to act and select the 'hard alternate' mode. The only remaining scenario would have been if the crew decided to select the 'hard alternate' mode at their own discretion in an attempt to "wake up" the engines as a last resort. In this scenario they could have retarded the thrust levers to idle although it would not have been necessary to retard the thrust levers that far back.
I stress this probably did not occur or the AAIB would have mentioned it in one of their released bulletins but it could have been a scenario as a last resort attempt to avert premature contact with terra firma in that final minute. If it did occur, it could have resulted in engines reverting to minimum idle if flaps were retracted to less than landing position and EAI not ON. But based on the information that M. Mouse provided (he must have first hand information to back his claim), minimum idle can apparently be illiminated as a factor.
The only way I know to 'reset' the Trent engine is to momentarily put the fuel control switch into cutoff and hope that it will accelerate up again; even the manual says it could take a loooonnng time. Not a technique I'd apply at 700'.
And it helped, did it?
Regards,
Green-dot
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Retarding the thrust levers before selecting the 'hard alternate' mode is necessary because there is no thrust limit protection in the alternate modes (in case of the BA038 situation the thrust levers would have been fire-walled). If the crew had decided to select the 'hard alternate' mode (regardless of an EEC fault or not) they would have retarded the thrust levers before doing so.
What if they had firewalled with such a switching? - It would have saved their day, wouldn't it?
This is some silly behind the desk comment. If you are in a emergency situation without thrust, you really don't care about technicalities, formalities, bulletins, sops or similar: Anything that gives you a notch more is very welcome....
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I believe Green-Dot
is saying closed throttles are necessary because Alt mode is locked out at advanced levers, to prevent over speed, No? Once throttles are retarded and Alt mode select is done, then truly manual Fuel control is obtained.(FAMEC?)
Airfoil
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Mariner9 Quote:
SOMETHING caused this incident
Certainly did, and its clear that the fuel has to be one of the major suspects. However, if it was, I would suspect it was more to do with its fluidity/pumpability in a combined low fuel temperature/lowish fuel quantities (minimising the net positive suction head available) environment than any other quality issues. (Cant recall whether I've mentioned this before, but the viscosity of Jet is specified only at -20C)
SOMETHING caused this incident
Certainly did, and its clear that the fuel has to be one of the major suspects. However, if it was, I would suspect it was more to do with its fluidity/pumpability in a combined low fuel temperature/lowish fuel quantities (minimising the net positive suction head available) environment than any other quality issues. (Cant recall whether I've mentioned this before, but the viscosity of Jet is specified only at -20C)
It is obvious that you know a lot about Jet fuel compliance.
I glean from your response that fuel compliance (or at least production) is as I suspected somewhat of a "Black Art".
Your statement re viscosity measurement only at -20C is interesting.
I still suspect the fuel.
However, I never INTENDED to suggest that the fuel wouldn't burn (although others have suggested this).
I INTENDED to suggest that some property of the fuel caused it to exhibit strange TRANSIENT viscosity characteristics under SUCTION, as in fact you have stated above.
Maybe I didn't express myself clearly enough.
I have NO experience in aviation but as a professional engineer I find it difficult to come to any other conclusion (ON THE INFORMATION AVAILABLE TO US) other than some aspect of the FUEL, conditioned by ENVIRONMENT, and FUEL SYSTEM DESIGN caused a condition that has not been previously considered.