Air India Crash

Brun said:
However, suctioning alone cannot produce the same high fuel flow as the tank pumps can, hence thrust in the takeoff range is then no longer available."

This seems to contradict what actually happens in the sim.
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No it doesn't. Feek said thrust was reduced, and the manual says thrust in the takeoff range is no longer available. You can limp an airliner up and away from the ground on less than takeoff thrust.
 
squerble said:
No it doesn't. Feek said thrust was reduced, and the manual says thrust in the takeoff range is no longer available. You can limp an airliner up and away from the ground on less than takeoff thrust.
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95% N1 would be a normal thrust setting for a de-rated to-off. (Depending on perf. calcs.)
 
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Only other reason for no thrust other than no engine RPM would be having the reverse thrust engaged or perhaps the sensors detecting it preventing engine RPM in forward flight.
 
NickK said:
Only other reason for no thrust other than no engine RPM would be having the reverse thrust engaged or perhaps the sensors detecting it preventing engine RPM in forward flight.
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We'd have seen them open in flight, which they weren't. In fact, if they had, they'd probably have fallen out of the sky quicker as it would have had a much more decelerating effect.
 
squerble said:
We'd have seen them open in flight, which they weren't. In fact, if they had, they'd probably have fallen out of the sky quicker as it would have had a much more decelerating effect.
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It depends - if they'd partially deployed then air would flow through the engine but the sensor would prevent increased RPM. It would explain no thrust and it could cause the computer to get confused and block the request for RPM to both engines.
 
NickK said:
It depends - if they'd partially deployed then air would flow through the engine but the sensor would prevent increased RPM. It would explain no thrust and it could cause the computer to get confused and block the request for RPM to both engines.
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Doesn’t explain the RAT deployment, and it’s another situation where it would have to happen to both engines at once.

There are also a long list of lockouts to prevent that happening, not least the thrust levers being at idle, but it has happened in the past so it’s not impossible, but both engines is a stretch.
 
NickK said:
It depends - if they'd partially deployed then air would flow through the engine but the sensor would prevent increased RPM. It would explain no thrust and it could cause the computer to get confused and block the request for RPM to both engines.
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Actually, you're not far off. I've just checked the 737 QRH and it has the statement.

"The EEC's prevent power above idle if the related thrust reverser has moved from the stowed position"

Meaning forward thrust lever movement would not result in any increase in N1 if the reverser was detected as unstowed and remain at idle. (Assuming the 787 is has similar protections)

But still, both at the same time? I really can't see it.
 
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esmozz said:
Actually, you're not far off. I've just checked the 737 QRH and it has the statement.

"The EEC's prevent power above idle if the related thrust reverser has moved from the stowed position"

Meaning forward thrust lever movement would not result in any increase in N1 if the reverser was detected as unstowed and remain at idle. (Assuming the 787 is has similar protections)

But still, both at the same time? I really can't see it.
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Two questions if I may:

On the 737 can you actually move the thrust level forward with the reverser lever up, or is there a mechanical lock as well as a software one?

Am I right in thinking that the 737, at least some versions, allow deployment of the T/R below 3ft radar altitude to reduce landing distance as you’re basically committed to touchdown at that point? I think I read it in relation to the Jeju crash.
 
Penfold101 said:
Two questions if I may:

On the 737 can you actually move the thrust level forward with the reverser lever up, or is there a mechanical lock as well as a software one?

Am I right in thinking that the 737, at least some versions, allow deployment of the T/R below 3ft radar altitude to reduce landing distance as you’re basically committed to touchdown at that point? I think I read it in relation to the Jeju crash.
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Regarding the first question, I don't actually know as I've never tried it. There is a mechanical lock which only allows you to pull the reverse thrusters up after the main thrust levers are at idle but I don't know if that then locks the main thrust levers in place until the thrust reversers are stowed again. The 737 doesn't have a software lock on the thrust levers as they are purely mechanical (Just cables connect to the HMUs (fuel metering units) in the engines, unless I'm mistaken). It's not something I would ever try with the reversers deployed when the engines are running just in case you can. I'll try it with the engines off next time I'm at work as I'm kind of curious now as well, although I'd assume it was the case.

Regarding the second question - yes, although it's actually 10' on the Rad Alt, at least on our aircraft (or air/ground logic in ground mode). I'm not sure why to be honest, unless it's some short field landing technique I'm unaware of as it strikes me a recipe for a heavy landing and every airline I've worked for specifically states TL are only to be deployed once the main wheels are on the ground.

Normally thrust reversers don't reduce the field length used during landing as the autobrakes schedule a steady deceleration. It will keep that deceleration regardless of whether the thrust reversers are used or not. It just applies the brakes harder. This helps with brake cooling on short turnarounds (and saves on expensive brake discs). Obviously if you are applying maximum manual braking, they will shorten the distance required a bit but somethings gone a bit wrong if you're having to do that.
 
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I remember getting diverted from Bahrain to Qatar on approach - you could see the super cell over the airport and lightning as we turned.
The onward connect 24 hours later - arrived in Manilla the morning of their military coup - that was fun :D
 
Brun said:
I'm with the above. Just because something is modelled does not necessarily mean it's accurate, even if based on the best available data.
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I’ve been discussing this with a friend who’s been in the sim industry since the mid 1980s, he works at a place very close to a major USA airport right now.

First, he took a 763 from takeoff to FL320 with the pumps off. Thrust was reduced but there was no problem. Then he took a 744 from takeoff to FL320 as well with the pumps off. This was a little different, the outboard engines ran at reduced thrust and the inboard ran at full power. He puts that down to the nearer engines starving the others.

To quote:

“The simulation for that kind of thing is based on data supplied by Boeing, so it's not typically an educated guess.”

PSX does the same.

I would assume that the 787 behaviour is very similar.

I would 100% say that this wasn’t caused by the fuel pumps being off as was suggested earlier. It simply wouldn’t cause this.

For those that don’t believe me, he sent me a video. I’ve got the whole thing up to FL320 in glorious 1080p as well.
 
What weight was that sim running - full cargo and passenger capacity?

I assume that given the 787 has two engines it's going to have full power or at least the power required to take off and climb.

I still think with no lift -> no thrust (captain's words) -> no RPM -> something blocking RPM - - -> sensor trip and confused computer that applies block to both engines.
 
NickK said:
What weight was that sim running - full cargo and passenger capacity?

I assume that given the 787 has two engines it's going to have full power or at least the power required to take off and climb.

I still think with no lift -> no thrust (captain's words) -> no RPM -> something blocking RPM - - -> sensor trip and confused computer that applies block to both engines.
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The 787 has a FADEC computer for each engine (Full Authority Digital Engine Control). Thrust levers send signals to the FADEC and it's that which sets the engine power based on a variety of parameters.

So a software problem with either the FADEC or a subsystem thereof that's part of the overall engine management.

Or vapour lock, which I'm still not convinced about.

Or (most likely) something none of us have figured out correctly.
 
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