Crash-Cork Airport
Join Date: Jan 2008
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Can any drivers explain what the torque difference in the engines would do?
Is the stated 5% difference enough to possibly cause control problems? Especially in the given scenario where they are performing a go-around in cloud?
Just trying to understand...
Is the stated 5% difference enough to possibly cause control problems? Especially in the given scenario where they are performing a go-around in cloud?
Just trying to understand...
Join Date: May 2011
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APOLOGY plus concern re status of "Ticket seller"
I am of course wrong and this is indeed the new, updated, interim report.
Apologies.
I was partly misled by monitoring the Irish media who seem not to have reacted to this update. Or they haven´t noticed it ? Or it says nothing worth commenting on ??????
The details of the engines and its significance are beyond me but the continued confusion re the status of the oversight by the Spanish authorities AESA of the operators, and the status of the airline Manx2, now described as the ticket sellers or similar does not inspire much confidence in me.
And the Spanish authorities don't now seem to have much confidence in the company which provided the aircraft and crew. A bit late for that however ?
Apologies.
I was partly misled by monitoring the Irish media who seem not to have reacted to this update. Or they haven´t noticed it ? Or it says nothing worth commenting on ??????
The details of the engines and its significance are beyond me but the continued confusion re the status of the oversight by the Spanish authorities AESA of the operators, and the status of the airline Manx2, now described as the ticket sellers or similar does not inspire much confidence in me.
And the Spanish authorities don't now seem to have much confidence in the company which provided the aircraft and crew. A bit late for that however ?
Join Date: May 2011
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Laconic style of Irish Authorities
They state baldly and blandly that the operator was unable to furnish them with the "FDR data frame layout which is required to decode the FDR recording" and that they had to seek this from the relevant US authorities.
Is this unusual ?
Surprising ?
Amazing ?
Worse still ?
Is this unusual ?
Surprising ?
Amazing ?
Worse still ?
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So the question then for the AAIU is:
Was the engine power imbalance big enough to cause the final missed approach / go around to be unstable, resulting in the wing touching the ground (after perhaps an over-correction by PF)?
Was this is what caused the final set of holes to line up?
Was the engine power imbalance big enough to cause the final missed approach / go around to be unstable, resulting in the wing touching the ground (after perhaps an over-correction by PF)?
Was this is what caused the final set of holes to line up?
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What the final AAIU report might say . . .
We will have to wait at least another 6 months before the final report. I would imagine that the torque issue/engine imbalance will be allocated a secondary or tertiary factor in this preventable accident. The error chain started much much earlier, and the inescapable issue is that the crew should not have put the aircraft in that place in any event.
Join Date: Feb 2003
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imbalanced torque
Lurker
For want of anyone more current and/or qualified, I suggest the torque difference would tend always to cause the left wing to drop.
The pilot flying will compensate for this with aileron and rudder, provided that he is not so aware of the real situation that he leads with the left engine all the time. The FDR tells us that he was indeed not balancing the engine output on this approach. The pilot flying will have had mildly crossed flying controls throughout the approach.
Pulling the power off, when that seems to leave the right engine still blowing air over the right wing, probably accentuated the tendency for the left wing to drop.
Earlier contributors have told us that the Metroliner was a brute to fly.
For me, the best explanation at present for the left wing drop turning into an unmanageable roll to the right has to include some stage of stall. The interim report mentions a continuous stall warning but does not give the critical values of angle of attack that the FDR might have recorded, nor any late change of elevator angle that might have worsened the situation.
Different aircraft, in or near the stall, might roll left or right with right aileron applied as was probably true here in the last few seconds.
More certainly, coarse right rudder (applied both to counter the excess thrust of the right engine and additionally to raise the left wing) will tend to reduce the effective angle of attack of the left wing and to delay its impending stall. The right wing stalls first and the aircraft rolls to the right - rapidly or even by way of a "flick".
Honest speculation, good enough till we get the FDR traces in the final report.
For want of anyone more current and/or qualified, I suggest the torque difference would tend always to cause the left wing to drop.
The pilot flying will compensate for this with aileron and rudder, provided that he is not so aware of the real situation that he leads with the left engine all the time. The FDR tells us that he was indeed not balancing the engine output on this approach. The pilot flying will have had mildly crossed flying controls throughout the approach.
Pulling the power off, when that seems to leave the right engine still blowing air over the right wing, probably accentuated the tendency for the left wing to drop.
Earlier contributors have told us that the Metroliner was a brute to fly.
For me, the best explanation at present for the left wing drop turning into an unmanageable roll to the right has to include some stage of stall. The interim report mentions a continuous stall warning but does not give the critical values of angle of attack that the FDR might have recorded, nor any late change of elevator angle that might have worsened the situation.
Different aircraft, in or near the stall, might roll left or right with right aileron applied as was probably true here in the last few seconds.
More certainly, coarse right rudder (applied both to counter the excess thrust of the right engine and additionally to raise the left wing) will tend to reduce the effective angle of attack of the left wing and to delay its impending stall. The right wing stalls first and the aircraft rolls to the right - rapidly or even by way of a "flick".
Honest speculation, good enough till we get the FDR traces in the final report.
I remember the jetstream 31 was a handful at low speed when the rpm was changed due to the different response time of the left and right engines. Quite a lot of aileron input would be needed during changes of thrust. I guess if all your practice go rounds are single engine, then you know which way it will roll, but a 2 engine go round would produce a roll that may not be predictable.
Different aircraft had different characteristics depending on how well they had been set up by the engineers.
Different aircraft had different characteristics depending on how well they had been set up by the engineers.
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I'm sure it didn't help, but I suspect that being absolutely knackered, stressed, and at the end all said and done, not very experienced, probably had more to do with cocking up your 3rd ILLEGAL go-around from below minimas, than a bit of an imbalance in the engines responses.
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probably had more to do with cocking up your 3rd ILLEGAL go-around from below minimas, than a bit of an imbalance in the engines responses.
An absolute disgrace, that aircraft should never have been where it was in the first place. I know that the investigators have to be painstakingly thorough but it just seems like investigating marginal differences in power output is such a wasted effort in the context of flagrant and repeated busting of minima.
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I remember the jetstream 31 was a handful at low speed when the rpm was changed due to the different response time of the left and right engines. Quite a lot of aileron input would be needed during changes of thrust
beyond that a small mismatch in torque as well a slightly different response time is everyday business, every aircraft has a small mismatch , even with freshly calibrated engines.
for me it seems that they came to high and tried to reduce using beta inflight, lost control and stalled out . the small response difference when they at last second applied power again is not the reason for the crash in my opinion.
best regards
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Originally Posted by telstar
An absolute disgrace, that aircraft should never have been where it was in the first place. I know that the investigators have to be painstakingly thorough but it just seems like investigating marginal differences in power output is such a wasted effort in the context of flagrant and repeated busting of minima.
I note that the report states (from CVR info) that the Captain was handling the thrust levers throughout the final approach - was this the same during the Go Around, giving PF less chance to anticipate changes in the aircraft's handling?
well, thrust ( power) changes on the tpe331 will not result in any rpm changes on this single shaft engine.
for me it seems that they came to high and tried to reduce using beta inflight, lost control and stalled out . the small response difference when they at last second applied power again is not the reason for the crash in my opinion.
I note that the report states (from CVR info) that the Captain was handling the thrust levers throughout the final approach - was this the same during the Go Around, giving PF less chance to anticipate changes in the aircraft's handling?
Both crew should have been capable of performing a missed approach from less than 50', it's part of the skills test.
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short bellows
"The bellows of the No. 2 engine PT2/TT2 sensor, when examined, was found to be considerably shorter than required by the manufacturer’s specification"
Can anyone explain how this could be the case, do they shorten with age or a maintenance issue?
Can anyone explain how this could be the case, do they shorten with age or a maintenance issue?
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I suspect that the sensor issue/5% tq split will have had very little to do with the accident. Find me any 20+ year old turboprop with perfectly matched engines and I'll be surprised. Indeed from experience on TPE J31s I doubt it would be noticeable. Remember we're talking old machines who have lived a hard life here. Even two matched engines could be confused as being not matched due to trimming for bad rigging in the controls, an airframe which isn't perfectly true etc etc.
My concerns are, as alluded to by some folks above:
1. They shouldn't have been there in the first place. Period.
2. The mention of being below flight idle in the interim report. If they went into beta, which would have dropped them from the sky like a brick, And may well have rolled them, They stood no chance of recovery from their self induced error.
3. The captain operating the power levers whilst the FO flew. Ridiculous. Flies in the face of all good practice. If the FO was struggling the skipper should have been handling, especially in the conditions.
Sadly I feel the whole thing still comes down to gross pilot error. The engine issue is just a red herring, which the authority understandably have to report in their thorough investigation.
My concerns are, as alluded to by some folks above:
1. They shouldn't have been there in the first place. Period.
2. The mention of being below flight idle in the interim report. If they went into beta, which would have dropped them from the sky like a brick, And may well have rolled them, They stood no chance of recovery from their self induced error.
3. The captain operating the power levers whilst the FO flew. Ridiculous. Flies in the face of all good practice. If the FO was struggling the skipper should have been handling, especially in the conditions.
Sadly I feel the whole thing still comes down to gross pilot error. The engine issue is just a red herring, which the authority understandably have to report in their thorough investigation.