Plane Down in Hudson River - NYC
Joined: Feb 2005
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From: flyover country USA
Where is it and where's it going?
It's at a warehouse somewhere near there now.
Do a Hover - it avoids G
Joined: Oct 1999
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From: Chichester West Sussex UK
Some posters here seem to think that if a jet engine is running at some low power (not flamed out) then increasing the fuel supply by opening the throttle will necessarily give you more thrust.
Sadly that is not how engine fuel systems work. Whether they be earlier generation hydro-mechanical engine fuel systems or modern FADEC (full authority digital engine control) fuel systems their job is to meter the increase in fuel flow asked for by throttle positions (NB whether the throttles are operated by the pilot or the autopilot makes no difference).
This careful metering has to take into account the pressures at the different stages of the fan and compressor combination, especially the compressor.
The probes and ports for measuring these pressures can easily become contaminated by bird remains so sending incorrect information to the fuel scheduling systems.
Therefore a bird strike can cause an engine run down to a low RPM (not a flameout) without any mechanical damage being present to the compressor blades themselves.
Sadly that is not how engine fuel systems work. Whether they be earlier generation hydro-mechanical engine fuel systems or modern FADEC (full authority digital engine control) fuel systems their job is to meter the increase in fuel flow asked for by throttle positions (NB whether the throttles are operated by the pilot or the autopilot makes no difference).
This careful metering has to take into account the pressures at the different stages of the fan and compressor combination, especially the compressor.
The probes and ports for measuring these pressures can easily become contaminated by bird remains so sending incorrect information to the fuel scheduling systems.
Therefore a bird strike can cause an engine run down to a low RPM (not a flameout) without any mechanical damage being present to the compressor blades themselves.
Joined: Feb 2005
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From: flyover country USA
The probes and ports for measuring these pressures can easily become contaminated by bird remains so sending incorrect information to the fuel scheduling systems.
The significant damage in this case is likely in the HP compressor airfoils - bent, twisted, broken, "corncobbed" in airline slang. They were simply unable to pump any significant airflow through the burner and turbines - and it's airflow that makes it go.
A modern high-bypass engine's core is smaller than older donks, and it's coupled to a bigger fan. This means two things:
1) the inlet area of the core is smaller, so it's a smaller target for a bird to attack
2) if a bird successfully attacks the core, it does proportionately more damage!
Last edited by barit1; 5th March 2009 at 20:25.
Joined: Mar 2002
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From: Florida
Barit1
I agree with much but not all subject to some more data.
Again I suspect that the only mechanical damage is in the Low pressure compressor. However I'm afraid that we may have to wait for the public hearing to release the powerplant report unless somebody has some inside knowledge.
At any rate since little fan damage was seen, I'm beginning to wonder how they got through the certification test if they indeed ingested a bird into the core.
I'm equally keen to hear what happened to the same engines in the Rome starling encounter.
I agree with much but not all subject to some more data.
Again I suspect that the only mechanical damage is in the Low pressure compressor. However I'm afraid that we may have to wait for the public hearing to release the powerplant report unless somebody has some inside knowledge.
At any rate since little fan damage was seen, I'm beginning to wonder how they got through the certification test if they indeed ingested a bird into the core.
I'm equally keen to hear what happened to the same engines in the Rome starling encounter.
Joined: Feb 2005
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From: flyover country USA
I have no inside information re 1549. However, my contacts with former colleagues have a unanimous agreement re the likely state of the core compressors.
And I don't know the details of a certification test for birds. BUT-- I seem to recall for a single large bird, it is aimed at a point deemed most critical re: fan blade breakage. That point is probably NOT the fan blade root, where a large amount of debris might enter the core. The objective of that test is more likely to determine if multiple fan blades will break, which could be REALLY bad.
But again, no inside knowledge.
And I don't know the details of a certification test for birds. BUT-- I seem to recall for a single large bird, it is aimed at a point deemed most critical re: fan blade breakage. That point is probably NOT the fan blade root, where a large amount of debris might enter the core. The objective of that test is more likely to determine if multiple fan blades will break, which could be REALLY bad.
But again, no inside knowledge.
Joined: Jun 1999
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From: Oztrailia
rcallahan
I don't fly Airbus but I do know that until you enter a "detent" the throttles work like any jet. Push them forward and they give you more thrust.
So how do you know the crew didn't slowly move the thrust levers forward to see what happened? They don't need to go all the way to TOGA, in fact that sudden burst of fuel as TOGA was selected could have made the stall worse.
I know that in my 777 I'm not going to push TOGA to try and get the engines running again after an event like this. Easy does it until the engine stabilizes. ( if it ever will )
The crew never selected TOGA
So how do you know the crew didn't slowly move the thrust levers forward to see what happened? They don't need to go all the way to TOGA, in fact that sudden burst of fuel as TOGA was selected could have made the stall worse.
I know that in my 777 I'm not going to push TOGA to try and get the engines running again after an event like this. Easy does it until the engine stabilizes. ( if it ever will )
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From: Scotland
Turning corners
DC-ATE
You'd be amazed. Usually done at three on a Monday morning*, a big tractor in front and one guy with two fistfuls of levers on a console clipped onto the last bogie, walking behind, steering the beast, all the steering on the double sets of tyres synchronised. The route's measured out beforehand in 3D but, of course, occasional mistakes do happen as do hydraulic leaks. Usually at seven-thirty in the morning.
*the preference for Monday morning is simply due to the fact that the guy on the levers is not as likely to be obliterated by a Jersey (or Staten Island) driver as he might be on a Saturday night. But that's just hearsay
Edit: in fact, looking at that pic,and having an approximate idea of the several hundred tonnes that assemblage of bogies could handle, I do suspect there might have been a bit of overkill.
You'd be amazed. Usually done at three on a Monday morning*, a big tractor in front and one guy with two fistfuls of levers on a console clipped onto the last bogie, walking behind, steering the beast, all the steering on the double sets of tyres synchronised. The route's measured out beforehand in 3D but, of course, occasional mistakes do happen as do hydraulic leaks. Usually at seven-thirty in the morning.
*the preference for Monday morning is simply due to the fact that the guy on the levers is not as likely to be obliterated by a Jersey (or Staten Island) driver as he might be on a Saturday night. But that's just hearsay
Edit: in fact, looking at that pic,and having an approximate idea of the several hundred tonnes that assemblage of bogies could handle, I do suspect there might have been a bit of overkill.
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Dysag
D8-K, very old-fashioned, just like me. Very little wire, and it would most certainly not float. Actually, it does have a side stick, but only one. I have had six people in the cab, and I have dug more than one goose pond with it.