Qantas A380 uncontained #2 engine failure
bear Question, what has +1 to do with anything?
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If there was an engineer with his panel on the Qantas A380 maybe he could have figured out how to shut down the No. 1 engine!
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No-Hoper....
You have truely missed the point here....
I'm not advicating putting an FE into the A380 flight deck, I'm advicating changing the A380 flight deck to suit a flight engineer, as it should have been in the original design!
As in the adding of the FE into the B767 flight deck some years ago, it didn't work simply because the flight deck was not designed for it, and was never going to work.
Having the FE simply monitoring a couple of screens is not going to work, he needs to have indications of the various system controls, together with suitable ways of controlling those systems, in effect, sidelining the computer from total contol.
That's the problem, the computerized system operation, with no common sense or forethought being applied.
The chances of this happening, virtually zero, the manufacturers have been convinced the computerized systems control is the way to go, and changing it now, unfortunately is beyond financial reality...see, there it is again, flight safety dependant on financial capability.
I personally would be absolutely overjoyed to glance into the A380 (or any other large pax jet) flight deck on the way onboard (sometimes the door is left slightly ajar), and see a modernized version of a B747-300 flight deck!!!
But I remain afraid those two things will never happen, me onboard, and a real flight deck!
Cheers,
EW73
You have truely missed the point here....
I'm not advicating putting an FE into the A380 flight deck, I'm advicating changing the A380 flight deck to suit a flight engineer, as it should have been in the original design!
As in the adding of the FE into the B767 flight deck some years ago, it didn't work simply because the flight deck was not designed for it, and was never going to work.
Having the FE simply monitoring a couple of screens is not going to work, he needs to have indications of the various system controls, together with suitable ways of controlling those systems, in effect, sidelining the computer from total contol.
That's the problem, the computerized system operation, with no common sense or forethought being applied.
The chances of this happening, virtually zero, the manufacturers have been convinced the computerized systems control is the way to go, and changing it now, unfortunately is beyond financial reality...see, there it is again, flight safety dependant on financial capability.
I personally would be absolutely overjoyed to glance into the A380 (or any other large pax jet) flight deck on the way onboard (sometimes the door is left slightly ajar), and see a modernized version of a B747-300 flight deck!!!
But I remain afraid those two things will never happen, me onboard, and a real flight deck!
Cheers,
EW73
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727 spirit
Somebody wiser than me has covered the Landing Distance some time ago:
http://www.pprune.org/tech-log/21117...ml#post2393979
Generally, the landing distance even at Max Takeoff Weight will be less than the the required takeoff distance on the same runway....assuming everything is working.
Qantas had multiple failures of high lift and retardation devices, giving a much higher than normal approach speed (at their reduced weight) and requiring all of the 4000m runway length. I guess an immediate landing at a few tonnes below their actual takeoff weight may have required more than 4000m.
From 747-400 FCTM
http://www.pprune.org/tech-log/21117...ml#post2393979
Generally, the landing distance even at Max Takeoff Weight will be less than the the required takeoff distance on the same runway....assuming everything is working.
Qantas had multiple failures of high lift and retardation devices, giving a much higher than normal approach speed (at their reduced weight) and requiring all of the 4000m runway length. I guess an immediate landing at a few tonnes below their actual takeoff weight may have required more than 4000m.
From 747-400 FCTM
Overweight landings may be safely accomplished by using normal landing procedures and techniques.There are no adverse handling characteristics associated with overweight landings
Landing distance is normally less than take-off distance for flaps 25 or 30 landings at all gross weights.
However, wet or slippery runway field length requirements should be verified from the landing distance charts in the FCOM 2
Brake energy limits will not be exceeded for flaps 25 or 30 landings at all gross weights.
Landing distance is normally less than take-off distance for flaps 25 or 30 landings at all gross weights.
However, wet or slippery runway field length requirements should be verified from the landing distance charts in the FCOM 2
Brake energy limits will not be exceeded for flaps 25 or 30 landings at all gross weights.
Last edited by ZimmerFly; 29th Nov 2010 at 12:19. Reason: changed 2 words..plus FCTM quote
Having the FE simply monitoring a couple of screens is not going to work, he needs to have indications of the various system controls, together with suitable ways of controlling those systems, in effect, sidelining the computer from total contol.
As for the incident at hand I'm pretty sure that it will make the 380 much safer on the long run once lessons are learned (and all considered it did pretty well, flight engineer or not
)
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Shouldn't we also have a radio operator, to reduce the loads on the pilots? I mean, they have to fly and talk on the radio, that can't be safe!
Perhaps also a navigator, to cross-reference the flight routing, and check that the GPS/INS has not got confused by using his watch and sextant?
Perhaps also a navigator, to cross-reference the flight routing, and check that the GPS/INS has not got confused by using his watch and sextant?
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What the Qantas crew had left to fly with - Learmount
the official position is that the crew "modulated braking in order to stop close to emergency services".
If that turns out to be correct (it is still a "leaked" document at the moment), then actual landing distance required could have been much less.
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I am highly entertained by the discussion on axial forces on the three-rotor system of the Trent.
Having done the analysis a time or two on various engines, let me state some basic truths:
1) the compressor (or fan) rotor is always pulling forward.
2) the turbine rotor is always pulling aft.
3) there is no way one can tell, by inspection, which of these two forces is the greater. It's analogous to two teams of elephants in a tug-of-war.
In fact, the net load on the thrust bearing may be forward at one operating condition, and aft at some other condition. If such a crossover occurs, it's less than desirable; it causes chatter in the lightly-loaded thrust bearing. Designers will make every effort to move the crossover to some sub-idle point.
Having done the analysis a time or two on various engines, let me state some basic truths:
1) the compressor (or fan) rotor is always pulling forward.
2) the turbine rotor is always pulling aft.
3) there is no way one can tell, by inspection, which of these two forces is the greater. It's analogous to two teams of elephants in a tug-of-war.
In fact, the net load on the thrust bearing may be forward at one operating condition, and aft at some other condition. If such a crossover occurs, it's less than desirable; it causes chatter in the lightly-loaded thrust bearing. Designers will make every effort to move the crossover to some sub-idle point.
In fact, the net load on the thrust bearing may be forward at one operating condition, and aft at some other condition. If such a crossover occurs, it's less than desirable; it causes chatter in the lightly-loaded thrust bearing. Designers will make every effort to move the crossover to some sub-idle point.
It seems to me that you could always plan on a pressure rise across the high comp even at windmill and might even bleed some of this to a low rotor cavity to ensure that thrust bearing doesn't float when you don't want it.
But at some sub-idle there ain't any pressure to fool with.
I am highly entertained by the discussion on axial forces on the three-rotor system of the Trent.
Having done the analysis a time or two on various engines, let me state some basic truths:
1) the compressor (or fan) rotor is always pulling forward.
2) the turbine rotor is always pulling aft.
3) there is no way one can tell, by inspection, which of these two forces is the greater. It's analogous to two teams of elephants in a tug-of-war.
In fact, the net load on the thrust bearing may be forward at one operating condition, and aft at some other condition. If such a crossover occurs, it's less than desirable; it causes chatter in the lightly-loaded thrust bearing. Designers will make every effort to move the crossover to some sub-idle point.
Having done the analysis a time or two on various engines, let me state some basic truths:
1) the compressor (or fan) rotor is always pulling forward.
2) the turbine rotor is always pulling aft.
3) there is no way one can tell, by inspection, which of these two forces is the greater. It's analogous to two teams of elephants in a tug-of-war.
In fact, the net load on the thrust bearing may be forward at one operating condition, and aft at some other condition. If such a crossover occurs, it's less than desirable; it causes chatter in the lightly-loaded thrust bearing. Designers will make every effort to move the crossover to some sub-idle point.
In this respect I think your 3rd point, which could be read to suggest that in e.g. various flight conditions the fan may not produce a forward thrust on the LP shaft, could be somewhat misleading for some readers.
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barit1
The Fan has no power without the LPT being pushed aft. It is the force of the gases that spin these power turbines that rotates the Fan. As such, the LPT has a pull aft, always when the Fan is producing its thrust. I mentioned the tug of war before, the Fan pulls forward, the LPT pulls aft. (actually it is "pushed aft" by the gases.)
The gases under pressure that are producing the Fan's rotation happen between the IPT and the LPT. Following the "creation" of the power, then, is it safe to say that the "Power" is acting on the IPShaft's dual thrust bearings? It is this stationary point on the engine that pushes forward the Pylon, and hence the a/c?
is that it?
The Fan has no power without the LPT being pushed aft. It is the force of the gases that spin these power turbines that rotates the Fan. As such, the LPT has a pull aft, always when the Fan is producing its thrust. I mentioned the tug of war before, the Fan pulls forward, the LPT pulls aft. (actually it is "pushed aft" by the gases.)
The gases under pressure that are producing the Fan's rotation happen between the IPT and the LPT. Following the "creation" of the power, then, is it safe to say that the "Power" is acting on the IPShaft's dual thrust bearings? It is this stationary point on the engine that pushes forward the Pylon, and hence the a/c?
is that it?
Last edited by bearfoil; 29th Nov 2010 at 21:20.
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bear -
Per the diagram, the IPT DOES NOT have "dual thrust bearings". Look closer in the second bearing box area:
The aft ball bearing supports the HPC front end, and is the thrust bearing for the HP system.
The center ball bearing supports the IPT front end and the IPC aft end.
The forward ball bearing is "inside out"; the outer race spins with the fan shaft, and the inner race is rotating with the IP system. A typical differential bearing.
The LP axial load - be it fwd or aft - is thus added algebraically to the IP axial load, and this algebraic sum is reacted through the center bearing.
And remember - it's not only the gas path loads on the airfoils that are considered in the thrust balance equation. There are some large piston areas - fwd/aft faces of discs, air seal areas, etc. - that have LARGE static pressures on them creating large forces. (Remember F = P*A). One must work the summation of all these forces - perhaps dozens - to determine the bearing thrust loads. This is why one cannot glance at a sketch to determine the net loading.
Per the diagram, the IPT DOES NOT have "dual thrust bearings". Look closer in the second bearing box area:
The aft ball bearing supports the HPC front end, and is the thrust bearing for the HP system.
The center ball bearing supports the IPT front end and the IPC aft end.
The forward ball bearing is "inside out"; the outer race spins with the fan shaft, and the inner race is rotating with the IP system. A typical differential bearing.
The LP axial load - be it fwd or aft - is thus added algebraically to the IP axial load, and this algebraic sum is reacted through the center bearing.
And remember - it's not only the gas path loads on the airfoils that are considered in the thrust balance equation. There are some large piston areas - fwd/aft faces of discs, air seal areas, etc. - that have LARGE static pressures on them creating large forces. (Remember F = P*A). One must work the summation of all these forces - perhaps dozens - to determine the bearing thrust loads. This is why one cannot glance at a sketch to determine the net loading.
Last edited by barit1; 29th Nov 2010 at 21:28.
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barit1
At the front of the I/Shaft I locate two thrust bearings running in two channels of the I/Shaft. They belong to the Shaft, not the Turbine, but they serve as impingements for forward mechanical energy. I am merely following the path of return of thrust to the engine/pylon.
I think the Fan is not pulling so much on its shaft, as it is pulling on the LPT, which is being pushed by the IPT, which is pushing forward on its shaft, which is thrusting on the I/Shafts Thrust bearings, pushing the a/c forward. The translation of the Fan's thrust follows back to its final anchor, the Bearings in the center of the Engine?
The fog lifts, and in San Francisco, that is rare. Thank you for your patience. I see the "cavity" in the space between IPT and LPT as a large sphere of extremely energetic gases. These gases exhaust through the LPT, spinning the fan, and also expand against the IPT I merely was trying to "see" the path of thrust back to its "origin", the ultimate fixed point that sends the thrust to the Pylon/a/c. That includes a vector through "Gas", Turbine, and bearings. I think I am seeing it at a very basic level, so good place for me to start. Thanks again.
bear
At the front of the I/Shaft I locate two thrust bearings running in two channels of the I/Shaft. They belong to the Shaft, not the Turbine, but they serve as impingements for forward mechanical energy. I am merely following the path of return of thrust to the engine/pylon.
I think the Fan is not pulling so much on its shaft, as it is pulling on the LPT, which is being pushed by the IPT, which is pushing forward on its shaft, which is thrusting on the I/Shafts Thrust bearings, pushing the a/c forward. The translation of the Fan's thrust follows back to its final anchor, the Bearings in the center of the Engine?
The fog lifts, and in San Francisco, that is rare. Thank you for your patience. I see the "cavity" in the space between IPT and LPT as a large sphere of extremely energetic gases. These gases exhaust through the LPT, spinning the fan, and also expand against the IPT I merely was trying to "see" the path of thrust back to its "origin", the ultimate fixed point that sends the thrust to the Pylon/a/c. That includes a vector through "Gas", Turbine, and bearings. I think I am seeing it at a very basic level, so good place for me to start. Thanks again.
bear
Last edited by bearfoil; 29th Nov 2010 at 21:48.
At max take off power, there is a constant force on the pylon, created by the thrust of the engine. For an A380 this is about 30 tonnes of force.
As stated above, approx 80% comes from the fan, 20% from the core efflux.
In simple terms....
24 tonnes of this thrust comes from the fan, hence there is a force of this amount acting on the LP bearing.
6 tonnes come from the hot high pressure gases exiting the combustion chamber through the turbines. The turbines don't create any forward thrust. All the HPT and IPT do is compress the inlet air. All the LPT does is turn the fan. The turbines just absorb the heat & pressure energy of the combustion chamber gas and turn it into rotational force.
(there is an axial drag force on the turbines, but this serves no useful purpose)
Hope this helps.
As stated above, approx 80% comes from the fan, 20% from the core efflux.
In simple terms....
24 tonnes of this thrust comes from the fan, hence there is a force of this amount acting on the LP bearing.
6 tonnes come from the hot high pressure gases exiting the combustion chamber through the turbines. The turbines don't create any forward thrust. All the HPT and IPT do is compress the inlet air. All the LPT does is turn the fan. The turbines just absorb the heat & pressure energy of the combustion chamber gas and turn it into rotational force.
(there is an axial drag force on the turbines, but this serves no useful purpose)
Hope this helps.
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This cutaway of the area in question, while being a RB-211-526g version, may possibly help.
The LP thrust bearing #28 is identified in red.
NOTE: The resolution of the above drawing will allow its magnification, and a closer look can be had by using Ctrl + as many times as required, and re-centering the image in your browser to view. Use Ctrl 0 to restore your page to normal size.
mm43
The LP thrust bearing #28 is identified in red.
NOTE: The resolution of the above drawing will allow its magnification, and a closer look can be had by using Ctrl + as many times as required, and re-centering the image in your browser to view. Use Ctrl 0 to restore your page to normal size.
mm43
Last edited by mm43; 30th Nov 2010 at 00:10. Reason: typo!
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It seems this thread has evolved into 2 different topics revolving around one incident.One topic is why the engine disintegrated and the other how the crew handled the situation. Both are valid discussions.
As far as the crew situation, given the extreme damage to both engine and airframe and the end result of a safe landing, I suspect it is hard to be a critic of the 5 person crew.However as pointed out numerous times, this was not a normal crew in either complement or experience.Experience wise at this stage of QFs ops of the A380, the average line crew would not have anywhere near the experience of the trainers on board.That is not meant to be a criticism of line crew, just realityat this stage in the A380 introduction.
The big unanswered question is how a 2 man line crew would have handled the situation? Another unanswered or even asked question is if the aircraft had a flight engineer with real time instrumentation, if the engine problem would have been noticed and therefore shut down prior to the engine failing?
Certainly in my experience as an B 747 FE, we regularly, very early, picked up minor upward trends which led to early diagnosis, far earlier that computers picked it up, based on parameter variations.
Should there have been an FE on the A380. I believe that there should have been more consideration to a position for someone on the aircraft with engineering experience and knowledge. Its my understanding that there was some discussion on the matter earlier, based particualrly aroung keeping cabin services functioning. The A380, by any consideration is exclusively a long,long haul aircraft and the cost of an air turnback because water or toilets fail is pretty high.However having said that, the cost of fitting screens and controlls that would allow a retrofitted FEs station to operate as per a Tristar or Classic B747 did, is obviously out of the question. The horse has bolted on that one
Those of you suggesting that an FE was, or is, the equivalent to a radio operator or a nav, simply don't know what a good FE did in difficult situations. I for one will be really interested to see what checklist messages came up and how they were handled. At least when a paper checklist is actioned to completion, it goes away.And in the end we FEs always knew where the best and cheapest beers were to be found although in this case I hope that the Company paid so that may not be relevant.
Wunwing
As far as the crew situation, given the extreme damage to both engine and airframe and the end result of a safe landing, I suspect it is hard to be a critic of the 5 person crew.However as pointed out numerous times, this was not a normal crew in either complement or experience.Experience wise at this stage of QFs ops of the A380, the average line crew would not have anywhere near the experience of the trainers on board.That is not meant to be a criticism of line crew, just realityat this stage in the A380 introduction.
The big unanswered question is how a 2 man line crew would have handled the situation? Another unanswered or even asked question is if the aircraft had a flight engineer with real time instrumentation, if the engine problem would have been noticed and therefore shut down prior to the engine failing?
Certainly in my experience as an B 747 FE, we regularly, very early, picked up minor upward trends which led to early diagnosis, far earlier that computers picked it up, based on parameter variations.
Should there have been an FE on the A380. I believe that there should have been more consideration to a position for someone on the aircraft with engineering experience and knowledge. Its my understanding that there was some discussion on the matter earlier, based particualrly aroung keeping cabin services functioning. The A380, by any consideration is exclusively a long,long haul aircraft and the cost of an air turnback because water or toilets fail is pretty high.However having said that, the cost of fitting screens and controlls that would allow a retrofitted FEs station to operate as per a Tristar or Classic B747 did, is obviously out of the question. The horse has bolted on that one
Those of you suggesting that an FE was, or is, the equivalent to a radio operator or a nav, simply don't know what a good FE did in difficult situations. I for one will be really interested to see what checklist messages came up and how they were handled. At least when a paper checklist is actioned to completion, it goes away.And in the end we FEs always knew where the best and cheapest beers were to be found although in this case I hope that the Company paid so that may not be relevant.
Wunwing
Last edited by Wunwing; 30th Nov 2010 at 01:09.
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Here Here!
The only pilots who do not understand the importance of a FE, are ones who either lack the experience of having one on board. Or their egos require the stimulation of their importance over other crew members.
The Bean counters appear to have won this issue, that is until we have a bad disaster and the costs of the accidents overide the costs of having a FE.
A very good friend of mine who has over 22,000 hours just on Boeings alone, stated that the omision of the FE was fine, until things start to go pear shape, and then we see their real worth.
The real cost of safety is difficult to calculate until the bad times come. Let us hope that Airbus will see the need for back up systems that cannot be negated and some SOP's which really address safety in the air.
In no way should the effort of the crew be overlooked, but it should be understand that in this case the Hand of Fate was most helpful to a happy ending.
Regards
Col
The only pilots who do not understand the importance of a FE, are ones who either lack the experience of having one on board. Or their egos require the stimulation of their importance over other crew members.
The Bean counters appear to have won this issue, that is until we have a bad disaster and the costs of the accidents overide the costs of having a FE.
A very good friend of mine who has over 22,000 hours just on Boeings alone, stated that the omision of the FE was fine, until things start to go pear shape, and then we see their real worth.
The real cost of safety is difficult to calculate until the bad times come. Let us hope that Airbus will see the need for back up systems that cannot be negated and some SOP's which really address safety in the air.
In no way should the effort of the crew be overlooked, but it should be understand that in this case the Hand of Fate was most helpful to a happy ending.
Regards
Col
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JFZ90
It helps a great deal. Here is what I have:
The Qantas 380 has the TRENT 972. 36 tons of thrust available at METO. Six tons come out the tail pipe as direct thrust, 30 tonnes are produced by the Fan. The Fan has to pull on something to offset its thrust, this "something" can be a bearing, or it can be a Turbine. The LPT is powering the Fan with effort that obtains to the Fan as 30 Tonnes.
Its reaction to this 30 tonnes it provides impinges on what? To me, the equal and opposite reaction of the LPT is the drag it creates in spinning up to this level of power, less the six tonnes that leave it out the back. I cannot make the Thrust bearing (#1) at the midsection of the LPShaft work, at least not from the diagram. The #2 TB is the most robust, by mm43's welcome cut/pic. You mention axial drag on the Shafts that is not consequential, I am looking for the spot in the powerplant that receives the entire 36 tonnes of thrust, and pushes the a/c through the air. The six tonnes of gas I see as impinging on the #3 TB, that of the HPShaft. Since thirty tonnes of gas (for discussion's sake) have to be accelerated to spin the Fan, I look at the IPT as half the wall of the Cavity as pushing forward on its bearing, it is the beefiest, and surely absorbs the lion's share? That would leave the Fan Shaft. What is it "Pulling" on?? I see it at this point as pulling on the LPT module, which is locked in the engine by the TB #1. Pursuant to barit1's explanation, the tug of war is won by the LPT, always. If this is so, I can envision the LPT itself as providing the anchor for the Fans motive power.
respect,
bear
It helps a great deal. Here is what I have:
The Qantas 380 has the TRENT 972. 36 tons of thrust available at METO. Six tons come out the tail pipe as direct thrust, 30 tonnes are produced by the Fan. The Fan has to pull on something to offset its thrust, this "something" can be a bearing, or it can be a Turbine. The LPT is powering the Fan with effort that obtains to the Fan as 30 Tonnes.
Its reaction to this 30 tonnes it provides impinges on what? To me, the equal and opposite reaction of the LPT is the drag it creates in spinning up to this level of power, less the six tonnes that leave it out the back. I cannot make the Thrust bearing (#1) at the midsection of the LPShaft work, at least not from the diagram. The #2 TB is the most robust, by mm43's welcome cut/pic. You mention axial drag on the Shafts that is not consequential, I am looking for the spot in the powerplant that receives the entire 36 tonnes of thrust, and pushes the a/c through the air. The six tonnes of gas I see as impinging on the #3 TB, that of the HPShaft. Since thirty tonnes of gas (for discussion's sake) have to be accelerated to spin the Fan, I look at the IPT as half the wall of the Cavity as pushing forward on its bearing, it is the beefiest, and surely absorbs the lion's share? That would leave the Fan Shaft. What is it "Pulling" on?? I see it at this point as pulling on the LPT module, which is locked in the engine by the TB #1. Pursuant to barit1's explanation, the tug of war is won by the LPT, always. If this is so, I can envision the LPT itself as providing the anchor for the Fans motive power.
respect,
bear