radimz
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B 747-400 Engines Off

Fri May 25, 2007 12:12 am

Hello,
I have a question: what happens with the generator on a B 747-400 when the engine is shuted down due to a flameout or a engine malfunction? Can it generate power with windmilling engines?
Thanks
 
CFMTurboFan
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RE: B 747-400 Engines Off

Fri May 25, 2007 12:35 am

The generator which is typically reffered to as an IDG (Intergrated Drive Generator) is mounted on an engines accessory drive gearbox. Gearboxes are driven by the HP and in some cases the IP compressor spools via a radial drive shaft to the accessory drive gearbox. The IDG is driven by the gearbox.

IDGs normally need to rotate around 7000rpm output to the internal generator (not sure if this is correct, correct me if it's not) to produce the required electrical frequency for the aircraft. This power is fed into the aircraft main buses via 4 heavy duty wires running to the IDG.

If an engine flames out, or is shut down, then it will not provide the required rotation via the gearbox to the IDG to produce the required power and therefore will not supply power.

[Edited 2007-05-24 17:36:34]

[Edited 2007-05-24 17:41:08]
 
777wt
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RE: B 747-400 Engines Off

Fri May 25, 2007 12:47 am

Then if that's the case, then howcome 747's don't need RAT since 4 windmilling engines is more than enough to provide hyd power?
 
PhilSquares
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RE: B 747-400 Engines Off

Fri May 25, 2007 1:10 am

Quoting 777WT (Reply 2):
Then if that's the case, then howcome 747's don't need RAT since 4 windmilling engines is more than enough to provide hyd power?

Providing windmilling hydraulic power and having the IDG work are two different things. First windmilling hydraulic will get you the pressure needed but it might not get you the volume. That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out. You will most likely get the gear and some flaps out, but as you slow the windmilling will also be less reliable.

The IDG acts as a transmission. It provides a constant RPM range to the generator thus allowing it to operate over a very narrow volt and frequency range (115v +/-2 and 400HZ +/-5). The problem is the generators don't come on line until just about at the end of the start cycle. In a windmilling situation, you won't have even that rotation. So, no IDG.


As for no RAT, the odds of losing all 4 electrical systems is fairly remote. Even on one generator, with selective equipement off, the aircraft will fly all day.
Fly fast, live slow
 
zanl188
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RE: B 747-400 Engines Off

Fri May 25, 2007 1:23 am

Quoting PhilSquares (Reply 3):
That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out.

 Smile

Like Boeing or the pilot has a choice in the matter.......
Legal considerations provided by: Dewey, Cheatum, and Howe
 
DH106
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RE: B 747-400 Engines Off

Fri May 25, 2007 1:26 am

Quoting ZANL188 (Reply 4):
Quoting PhilSquares (Reply 3):
That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out.



Like Boeing or the pilot has a choice in the matter.......

Exactly - LOL
Next time I have a quad failure in a 747 - I must remember to stay up there until the problem's solved !!  rotfl 
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SilverComet
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RE: B 747-400 Engines Off

Fri May 25, 2007 1:43 am

Quoting PhilSquares (Reply 3):
That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out.

On a more serious note though, what does Boeing recommend in that situation? I imagine attempt restart, but other than that (if restart fails)?
 
Arniepie
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RE: B 747-400 Engines Off

Fri May 25, 2007 2:07 am

If you loose all engines wouldn't the APU be able to do the job?
Dumb question maybe but can't it be used in flight to power the hydraulics and give electricity?

Quoting SilverComet (Reply 6):
I imagine attempt restart, but other than that (if restart fails)?

Pray, or let all passengers drink Red bull (gives you wings!!!).
[edit post]
 
radimz
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RE: B 747-400 Engines Off

Fri May 25, 2007 2:15 am

I think the APU cant be started in flight so it wouldnt supply nor electricity nor bleed air
 
DH106
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RE: B 747-400 Engines Off

Fri May 25, 2007 2:37 am

Hmmm - so say, if the 'Gimli Glider' had been a 747 (i.e. run out of fuel with no hope of a restart) - what would Boeing recommend? It's clearly an envisagable circumstance.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
Bellerophon
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RE: B 747-400 Engines Off

Fri May 25, 2007 2:39 am

Radimz

...what happens with the generator on a B 747-400....Can it generate power with windmilling engines?...

CFMTurboFan and PhilSquares have both answered your question already, but I'd just like to mention a point that follows on from what they have said.

With all four engines operating normally, but at flight idle power - for example during descent from cruise altitude - it can be harder than you might think to spot an engine failure, should an engine quietly just run down. Initially a failed engine will be indicating roughly the same EPR, EGT and Fuel Flow as the other engines, whilst they are at flight idle, there will be little or no yaw or roll affecting the aircraft and the control column will have little displacement from its normal position.

In such a situation, it is highly likely that the first EICAS warning you will get following, say, a #4 engine run-down, will be an Electrical warning, such as "ELEC DRIVE 4" or "ELEC GEN OFF 4", as the IDG drops off-line, because, as has been said, a windmilling engine will not be turning fast enough to keep its IDG on-line.

Odd though it may sound, following an electrical generator type warning, most B747 pilots will first make a quick check that the associated engine is running normally, before actioning the electrical QRH!

Best regards

Bellerophon
 
SilverComet
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RE: B 747-400 Engines Off

Fri May 25, 2007 3:41 am

Quoting Radimz (Reply 8):
I think the APU cant be started in flight so it wouldnt supply nor electricity nor bleed air

APU can be started in flight, and deliver electricity and bleed provided it is within it's operating altitude limits.
 
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Jetlagged
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RE: B 747-400 Engines Off

Fri May 25, 2007 4:02 am

Quoting SilverComet (Reply 11):
APU can be started in flight

Only on the classic. On the 747-400 the APU can be left running in flight, but not started in flight.

As for a RAT, as has been stated on numerous previous threads the primary purpose of a RAT is to supply hydraulic power for flight controls. In aircraft where electrical power is also required for flight controls (e.g. FBW Airbus types) there is also a hydraulically powered generator installed. The VC10 was an exception as it had two RATs one electrical and one hydraulic.

All the 747 flight controls need is hydraulic power and the windmilling engines are enough for that. Standby electrical power is available from the battery for a limited time. So the 747 does not need a RAT.
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BoeingOnFinal
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RE: B 747-400 Engines Off

Fri May 25, 2007 4:13 am

Quoting ZANL188 (Reply 4):
Quoting PhilSquares (Reply 3):
That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out.

Smile

Like Boeing or the pilot has a choice in the matter.......

Obviously they recommend that you stay in the air until someone comes to fix the problem!
norwegianpilot.blogspot.com
 
n8076u
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RE: B 747-400 Engines Off

Fri May 25, 2007 4:27 am

The APU on the 747-400 can't be started in flight. But if it was already running while on the ground and the aircraft takes off, it will continue running, up to a certain altitude. It can provide bleed air while in flight, but as soon as the aircraft goes into air mode, the APU generators cannot be used.


Chris
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KELPkid
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RE: B 747-400 Engines Off

Fri May 25, 2007 4:48 am

Quoting N8076U (Reply 14):
The APU on the 747-400 can't be started in flight.



Quoting PhilSquares (Reply 3):
That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out.

Remind me never to mismanage fuel in a 747-400...  eyebrow 
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
VC-10
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RE: B 747-400 Engines Off

Fri May 25, 2007 5:21 am

Quoting Jetlagged (Reply 12):
The VC10 was an exception as it had two RATs one electrical and one hydraulic.

The BUA '10's only had one RAT
 
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Starlionblue
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RE: B 747-400 Engines Off

Fri May 25, 2007 9:44 am

Quoting PhilSquares (Reply 3):

As for no RAT, the odds of losing all 4 electrical systems is fairly remote. Even on one generator, with selective equipement off, the aircraft will fly all day.

"Ladies and gentlemen, we are going to be turning off the reading lights, the entertainment system and the coffee machines. Don't panic."

Quoting DH106 (Reply 9):
Hmmm - so say, if the 'Gimli Glider' had been a 747 (i.e. run out of fuel with no hope of a restart) - what would Boeing recommend? It's clearly an envisagable circumstance.

First of all, I'm sure Captain Squares is aware of the fact that if the engines can't be restarted, eventually the aircraft will touch down whether he wants it to or not.

The Gimli Glider incident would have been one case where Boeing could recommend all it wanted. The landing would have been attempted without any engines on.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
KELPkid
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RE: B 747-400 Engines Off

Fri May 25, 2007 10:08 am

Quoting Starlionblue (Reply 17):
The Gimli Glider incident would have been one case where Boeing could recommend all it wanted. The landing would have been attempted without any engines on.

If I recall correctly, until the Gimli Glider incident, Boeing had no procedures in the manual covering a dual flameout, and hence no best rate of glide speed in the 767 manual (the Gimli Glider flight crew were just guessing on that one...). It was because the engineers figured the possibilities of that happening were very remote...  scratchchin 
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474218
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RE: B 747-400 Engines Off

Fri May 25, 2007 10:51 am

I am sure the 744 has a battery, which should provide essential power for some period of time, in the event of a four engine failure.
 
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HAWK21M
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RE: B 747-400 Engines Off

Fri May 25, 2007 11:27 am

Quoting 777WT (Reply 2):
Then if that's the case, then howcome 747's don't need RAT since 4 windmilling engines is more than enough to provide hyd power?

Chances of loosing all four are remote.Not saying it did not occur  Smile But then the Cause was different.
Then theres the APU & the Main Battery.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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Starlionblue
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RE: B 747-400 Engines Off

Fri May 25, 2007 12:26 pm

Quoting 474218 (Reply 19):
I am sure the 744 has a battery, which should provide essential power for some period of time, in the event of a four engine failure.

It has several. But electrical power alone doesn't do that much good. What is needed is hydraulic pressure to control the flight surfaces. AFAIK the batteries cannot provide drive the hydraulic pumps.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SFOMB67
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RE: B 747-400 Engines Off

Fri May 25, 2007 12:38 pm

[quote=HAWK21M,reply=20]Chances of loosing all four are remote.

I think there have been several 4 engine flameouts on 747's. Most attributed to fuel tank problems. I'm sure it's a busy flt deck when that happens, and I'm sure its not widely publicized.
Not as easy as originally perceived
 
PhilSquares
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RE: B 747-400 Engines Off

Fri May 25, 2007 12:41 pm

Quoting Starlionblue (Reply 21):
It has several. But electrical power alone doesn't do that much good. What is needed is hydraulic pressure to control the flight surfaces. AFAIK the batteries cannot provide drive the hydraulic pumps.

Windmilling engines will provide more than ample hydraulic pressure to the PRIMARY flight controls. The problem is when you have to slow down, the pumps are volumetric and can't power the flight controls and extend the flaps.

I will let all the "experts" on here take it from now on because they have so much more experience flying the 744, oh that was MSFS......


The APU on the 747 could be started in flight, but only after a mod was done. It was not part of the standard 747 delivery package. The 744 APU can not be started in flight. You should have ESS AC and DC for about 25 minutes.
Fly fast, live slow
 
DH106
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RE: B 747-400 Engines Off

Fri May 25, 2007 3:47 pm

Quoting Starlionblue (Reply 17):
The Gimli Glider incident would have been one case where Boeing could recommend all it wanted. The landing would have been attempted without any engines on.

Notwithstanding my earlier comment, I wasn't trying to be facecious here with this one.
Boeing has no contingency/recommendations for getting a 747 down with 4 engines out ?
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
PhilSquares
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RE: B 747-400 Engines Off

Fri May 25, 2007 4:05 pm

Quoting DH106 (Reply 24):
Boeing has no contingency/recommendations for getting a 747 down with 4 engines out ?

As I wrote earlier, they recommend against trying to "deadstick" a 747/744 due to the hydraulic problem and eventual reduction of windmilling RPM and subsequent loss of volume in the hydraulics.
Fly fast, live slow
 
Tristarsteve
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RE: B 747-400 Engines Off

Fri May 25, 2007 5:41 pm

Talking of hydraulic pumps on windmilling engines, let me digress a little.
On the A320, we have a common problem of the aircraft flying with the yellow electric hyd pump u/s. This is allowed in the MEL. The problem is that the yellow pump opens the cargo doors. There is a hand pump fitted and we are meant to pump the doors open. What I do is be ready. The crew turn off the engines and as they spool down two of us walk down to the doors, after the anti colls are off, and select open. Both doors open on the hyd pressure from the spooling down engines. And V2500 spool down very quickly.
Its easier to shut them because they are coming down, not so heavy.
 
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HAWK21M
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RE: B 747-400 Engines Off

Fri May 25, 2007 6:43 pm

Quoting Sfomb67 (Reply 22):
I think there have been several 4 engine flameouts on 747's.

I was aware of only one Incident.What are the others.

Quoting PhilSquares (Reply 23):
The 744 APU can not be started in flight

Any reason.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
VC-10
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RE: B 747-400 Engines Off

Fri May 25, 2007 8:35 pm

Quoting PhilSquares (Reply 23):
Windmilling engines will provide more than ample hydraulic pressure to the PRIMARY flight controls.

During internal leak troubleshooting on a JT9 powered 747 I got 3000 psi with 12% N2. Admittedly there was no flow, but the pressure was there.
 
PhilSquares
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RE: B 747-400 Engines Off

Fri May 25, 2007 9:33 pm

Quoting VC-10 (Reply 28):
Quoting PhilSquares (Reply 23):
Windmilling engines will provide more than ample hydraulic pressure to the PRIMARY flight controls.

During internal leak troubleshooting on a JT9 powered 747 I got 3000 psi with 12% N2. Admittedly there was no flow, but the pressure was there.



Quoting PhilSquares (Reply 23):
Windmilling engines will provide more than ample hydraulic pressure to the PRIMARY flight controls. The problem is when you have to slow down, the pumps are volumetric and can't power the flight controls and extend the flaps

As I wrote, they're volumetric pumps... you'll get the pressure long before you get the volume. Just try actuating a flight control with 12%N1!

Quoting HAWK21M (Reply 27):
Any reason.

Wasn't designed that way and no real need.
Fly fast, live slow
 
DH106
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RE: B 747-400 Engines Off

Fri May 25, 2007 9:46 pm

So, not to be too dramatic, but if you run out of fuel in a 747 - there's no real solution
to your erm... problem?

I do appreciate tho, that any deadstick operation with an airliner is fraught with hazard and successful outcomes like the Gimli glider are due to extensive skill of the pilot and perhaps a little luck.
But to balance that - the pilot should never allow the plane to have run out in the first place.

[Edited 2007-05-25 14:50:21]
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
Steve332
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RE: B 747-400 Engines Off

Fri May 25, 2007 11:59 pm

Quoting DH106 (Reply 30):
So, not to be too dramatic, but if you run out of fuel in a 747 - there's no real solution
to your erm... problem?

You could have all the company recommendations in the world, every page ever written on problems on any plane and have a gazillion hours in every aircraft ever built...... But if you run out of fuel there ain't much that can be done apart from doing your best to get the aircraft down safely and as soon as possible.
 
DH106
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RE: B 747-400 Engines Off

Sat May 26, 2007 3:15 am

Quoting Steve332 (Reply 31):
But if you run out of fuel there ain't much that can be done apart from doing your best to get the aircraft down safely and as soon as possible.

Yes, but my point is there appears to be no scenario to achieve this on a 747.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
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Jetlagged
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RE: B 747-400 Engines Off

Sat May 26, 2007 4:34 am

Quoting PhilSquares (Reply 23):
The APU on the 747 could be started in flight, but only after a mod was done. It was not part of the standard 747 delivery package.

AFAIK, all 747-200 APUs, as delivered, can be started in flight. I've never seen anything in the wiring schematics to show an APU variant which had ground/flight logic in the starter circuit. There is logic to limit the intake door opening to about 1/3 in flight. The APU can even be started without a starter motor from windmilling RPM. Not all 747s had APUs which were approved for in flight use. If not approved there is a placard to warn the F/E not to run it in flight.

It seems strange that Boeing deliberately chose to prevent the 744 APU being started in flight. Anyone know the reason?

As for the deadstick landing scenario, some operators do practise this in the simulator. I've tried it myself in -200 and -400 sims. As long as small control inputs are used to limit hydraulic flow it can be done. But it is not easy and any turbulence or crosswind would be disasterous. Presumably Boeing are advising continuing relight attempts for as long as possible, rather than opting immediately for such a hazardous landing. At some point gravity will ensure some kind of landing will occur. Ultimately one would hope the crew would recognise when this was imminent and plan accordingly. Not extending flap would help by increasing Vref and so windmilling RPM.

Quoting PhilSquares (Reply 23):
I will let all the "experts" on here take it from now on because they have so much more experience flying the 744, oh that was MSFS......

I don't think that's called for. I don't know about the other "experts", but my comments about this come from aircraft experience. You don't have to fly the things to understand them.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
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Starlionblue
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RE: B 747-400 Engines Off

Sat May 26, 2007 4:46 am

Quoting DH106 (Reply 32):
Quoting Steve332 (Reply 31):
But if you run out of fuel there ain't much that can be done apart from doing your best to get the aircraft down safely and as soon as possible.

Yes, but my point is there appears to be no scenario to achieve this on a 747.

Well, I guess it's so unlikely that there is no such scenario. So many things would have to break to get to that point,
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Arniepie
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RE: B 747-400 Engines Off

Sat May 26, 2007 5:42 am

How long did it take before the KLM(over ALASKA IIRC) and BA (somewhere near INDONESIA) 747's need to restart their engines after they lost all 4 of them at once?
Did they fly solely on batteries and how much height did they loose before restarting succeeded?
[edit post]
 
KELPkid
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RE: B 747-400 Engines Off

Sat May 26, 2007 6:06 am

Quoting Starlionblue (Reply 34):
Well, I guess it's so unlikely that there is no such scenario. So many things would have to break to get to that point,

That's what I hate about statistics. There's lies, damn lies, and statistics. All it takes it one (albeit, rather unprofessional) aircrew to run a 744 out of fuel...it's not like the statistics against that (fuel exhaustion) are 1,000,000 to one (I guess the assumption is you'd have to press on after the EICAS threw every warning it had in your face before you got to the point of fuel exhaustion...). Throw in some extenuating circumstances (like the fuel system computer malfunctions that the Gimli Glider aircrew were dealing with) and re-run the odds, why don't ya  Wink I wonder if some of the automation like this is now part of the MEL to try and ward off another Gimli Glider-type incident?
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VC-10
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RE: B 747-400 Engines Off

Sat May 26, 2007 9:01 am

Quoting PhilSquares (Reply 29):
Quoting VC-10 (Reply 28):
Quoting PhilSquares (Reply 23):
Windmilling engines will provide more than ample hydraulic pressure to the PRIMARY flight controls.

During internal leak troubleshooting on a JT9 powered 747 I got 3000 psi with 12% N2. Admittedly there was no flow, but the pressure was there.



Quoting PhilSquares (Reply 23):
Windmilling engines will provide more than ample hydraulic pressure to the PRIMARY flight controls. The problem is when you have to slow down, the pumps are volumetric and can't power the flight controls and extend the flaps

As I wrote, they're volumetric pumps... you'll get the pressure long before you get the volume. Just try actuating a flight control with 12%N1!

Phil, I'm om your side! I was just trying to illustrate what low rpm was required to get full pressure
 
PhilSquares
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RE: B 747-400 Engines Off

Sat May 26, 2007 9:36 am

Quoting Jetlagged (Reply 33):
AFAIK, all 747-200 APUs, as delivered, can be started in flight.

Sorry, but that's just incorrect. Most were delivered so the APU could be used in flight, not started. In fact, all 747/744 are certified for inflight operation, that way you can do a bleed off takeoff and use the APU bleed for the packs. I can count on one hand the number of 747 classics I've flown that have hand the APU certified for inflight start.

Quoting Jetlagged (Reply 33):
Not extending flap would help by increasing Vref and so windmilling RPM.

But now you have the problem of stopping with nothing but accumlator pressure. That is where the situation rubs both ways. As far as airlines trying to accomplish this in the simulator, that's great, but it is counter to what Boeing recommends and it certainly wouldn't be accomplished with the FAA/CAA in the simulator.

Quoting Jetlagged (Reply 33):
I don't think that's called for. I don't know about the other "experts", but my comments about this come from aircraft experience. You don't have to fly the things to understand them

That comment was not directed to people who have a technical background or people who really want to have a discussion and learn. Please re-read some of the posts and you'll see where my comments are directed.
Fly fast, live slow
 
zanl188
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RE: B 747-400 Engines Off

Sat May 26, 2007 9:59 am

Quoting PhilSquares (Reply 38):
That comment was not directed to people who have a technical background or people who really want to have a discussion and learn. Please re-read some of the posts and you'll see where my comments are directed.

Sometimes you gotta take a step back and read what you post the way others read it. I have a technical background and have been working with heavy aircraft, operations, and aircrews for decades, yet I can see the absurdity of this comment:

Quoting PhilSquares (Reply 3):
That is why Boeing recommends against an attempt at landing the aircraft if all engines are flamed out.

Assuming the PNF or FE (if available) is going to continue attempting a restart, I would love to hear what options Boeing suggests for the PF, in lieu of a landing, when all four are flamed out.
Legal considerations provided by: Dewey, Cheatum, and Howe
 
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Starlionblue
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RE: B 747-400 Engines Off

Sat May 26, 2007 10:42 am

Quoting KELPkid (Reply 36):
That's what I hate about statistics. There's lies, damn lies, and statistics. All it takes it one (albeit, rather unprofessional) aircrew to run a 744 out of fuel...it's not like the statistics against that (fuel exhaustion) are 1,000,000 to one (I guess the assumption is you'd have to press on after the EICAS threw every warning it had in your face before you got to the point of fuel exhaustion...). Throw in some extenuating circumstances (like the fuel system computer malfunctions that the Gimli Glider aircrew were dealing with) and re-run the odds, why don't ya Wink I wonder if some of the automation like this is now part of the MEL to try and ward off another Gimli Glider-type incident?

Well, true. However the Gimli Glider was caused by failure to follow ALREADY ESTABLISHED procedures. So was Air Transat 330.

In the end, there is risk in life and if we try to eliminate that last 0.0000001% of risk it starts costing more than I want to pay. It's far more risky for me to climb on my ladder to clean the gutters than flying JFK-LHR.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
PhilSquares
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RE: B 747-400 Engines Off

Sat May 26, 2007 1:14 pm

Quoting ZANL188 (Reply 39):
Assuming the PNF or FE (if available) is going to continue attempting a restart, I would love to hear what options Boeing suggests for the PF, in lieu of a landing, when all four are flamed out

This is out of the FCTM.


Multiple Engine Failure
Multiple engine failure is a situation that demands prompt action
regardless of altitude or airspeed. Accomplish recall items and establish
the appropriate airspeed to immediately attempt windmill restart. There is
a higher probability that a windmill start will succeed if the restart attempt
is made as soon as possible (or immediately after recognizing engine
failure) to take advantage of high engine RPM. Use of higher airspeeds
and altitudes below 30,000 feet improves the probability of a restart. Loss
of thrust at higher altitudes may require descent to a lower altitude to
improve windmill starting capability.
The inflight start envelope defines the region where windmill starts were
demonstrated during certification. It should be noted that this envelope
does not define the only areas where a windmill start may be successful.
The MULTIPLE ENGINE FLAMEOUT/STALL NNC is written to ensure
flight crews take advantage of the high RPM at engine failure regardless of
altitude or airspeed.
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Jetlagged
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RE: B 747-400 Engines Off

Sun May 27, 2007 2:42 am

Quoting PhilSquares (Reply 38):
Sorry, but that's just incorrect. Most were delivered so the APU could be used in flight, not started. In fact, all 747/744 are certified for inflight operation, that way you can do a bleed off takeoff and use the APU bleed for the packs. I can count on one hand the number of 747 classics I've flown that have hand the APU certified for inflight start.

I'm pretty sure of my facts. There is a difference between approval for start or use in flight, and being electrically inhibited from starting. The 747-200 APU is normally wired so it can start and run in flight. That does not mean it is approved to do either. The 747-400 in contrast is wired so that in flight start is not possible.

APU bleed for the packs? How many do you think it could run?

BA didn't use to use the APU for no bleed takeoffs. Maybe your airline was different. It's hardly worth the trouble as packs will be turned on in sequence very soon after takeoff.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
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Jetlagged
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RE: B 747-400 Engines Off

Sun May 27, 2007 7:56 am

Quoting PhilSquares (Reply 38):
But now you have the problem of stopping with nothing but accumlator pressure. That is where the situation rubs both ways. As far as airlines trying to accomplish this in the simulator, that's great, but it is counter to what Boeing recommends and it certainly wouldn't be accomplished with the FAA/CAA in the simulator.

As long as you don't pump the brakes and there is no leak in the return line the brakes will work, but at something less than 3000 psi of course. It's not often you will find yourself in the sim with the CAA or FAA, and of course in those cases you would be on best behaviour.  Smile

What you appear to be saying is that because Boeing don't recommend you attempt a deadstick landing, you simply fly into terra firma when too low for further relight attempts. My reading of what you quoted is too keep trying restart procedures whether inside or outside the envelope. In other words, the restart envelope is not a limit. Repeated relight attempts was, after all, is how that BA crew saved the 747-200 which flew into a volcanic ash cloud. However while the F/O and F/E attempted this the Captain was considering what to do if the engines did not restart, to the point where at the time it became clear he wouldn't be able to clear the mountains he was going to head out to sea to eventually ditch.

I doubt Boeing mean don't consider a deadstick landing at all. It would be risky, but it is your last resort. Faced with your own impending demise are you saying you would not attempt such a landing because Boeing don't recommend it? Or would you try to use your own skill to at least have a go at saving the aircraft?

I don't expect deadstick landing is part of any recognised airline training programme, but pilots do practise all kinds of things in the simulator (think Sioux City DC-10). The minimum airspeed for a deadstick landing is mentioned in at least one airline's Flight Manual. 150 knots from memory.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
Qantas744er
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RE: B 747-400 Engines Off

Sun May 27, 2007 8:41 am

This really bugs me...

Some "armchair pilots" here just dont seem to understand that people like Philsquares in this case talking about the 744 are right, and anybody opposing the things they state are are just idiots. Why do some of us always need to absolutely try to prove that what a pilot says is wrong and what we say is right without knowing the actual facts? For sure we play MSFS and we might know stuff bout the 744 but if someone like him tells us where wrong well then for god sake we are wrong.

Now some of you might think im over reacting... but we have lost so many aviation experts (pilots,mech's etc.) with us always telling them the exact opposite of what they say telling them that what we say is absolutely right....

Now who would you rather listen too: me a 15 year old student or rather Philsares an highly experienced airline captain while talking about a 747-400?  Wink

Leo
Happiness is V1 in Lagos
 
Bellerophon
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RE: B 747-400 Engines Off

Sun May 27, 2007 9:55 am

Jetlagged

...BA didn't use to use the APU for no bleed takeoffs...

Yes they did, on the B747-400, until recently.


...APU bleed for the packs? How many do you think it could run?..

Well at least one, although I've no personal experience, in the air, with more.


...It's hardly worth the trouble as packs will be turned on in sequence very soon after takeoff....

A matter of opinion, personally I wouldn't agree, and I regret the fact we no longer use this procedure in my airline.

The packs now go OFF during the "Before Take-Off Checklist", prior to entering the runway, and only come back ON when CLB power is selected, normally when the flaps have been retracted to Flap 5, a period of several minutes. Whilst this might not sound very long, it can seem like an eternity to those passengers sitting down the back of a hot aircraft.

I departed DXB recently, where the OAT during the day peaked at 45C. Given the choice, whilst driving their car, would anyone here voluntarily turn off their car air-conditioning for 4-5 minutes, whilst keeping the windows shut, in those sort of temperatures?


Best regards

Bellerophon
 
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Jetlagged
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RE: B 747-400 Engines Off

Sun May 27, 2007 10:39 am

Quoting Bellerophon (Reply 45):
Yes they did, on the B747-400, until recently.

Apologies, I should have stressed I was refering to the 747-200, though of course it's years since they operated those. I'm not saying they never used the APU for take-off then either, but it's not a universal practice.

Quoting Bellerophon (Reply 45):
...It's hardly worth the trouble as packs will be turned on in sequence very soon after takeoff....

A matter of opinion, personally I wouldn't agree, and I regret the fact we no longer use this procedure in my airline.

As the 747-200 APU was not approved for in flight use in many cases, the exception for use immediately after takeoff seems strange, that's all. Again the 744 is a different animal and its APU is approved for in flight use. You're right, it can feel an eternity as a passenger while the A/C is off, but it's not much more fun with the A/C on.  Smile

Five minutes with no cooling in a well insulated aircraft cabin is a bit different to 5 minutes in a car, though. I suspect it will get hotter, quicker, on the 744's flight deck than in the cabin.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
PhilSquares
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RE: B 747-400 Engines Off

Sun May 27, 2007 4:37 pm

Quoting Jetlagged (Reply 42):
APU bleed for the packs? How many do you think it could run?

BA didn't use to use the APU for no bleed takeoffs. Maybe your airline was different. It's hardly worth the trouble as packs will be turned on in sequence very soon after takeoff.

If BA used or not, I really don't care or dispute that. However, with a bleed off takeoff, you can still have the packs running via the APU bleed (all 4 on the 400), keep the cabin cool and get extra performance. That's all it is.

As far the classic APU, it was never approved for in flight start until very late in it's life. It was always approved for inflight operation to get the extra performance.

Quoting Jetlagged (Reply 43):
CAA or FAA, and of course in those cases you would be on best behaviour.

You also don't do things that will expose you needlessly! The BA flight you refer to just followed the loss of all engines abnormal. That's is. That is practised in the simulator. Perhaps that's what you're talking about. Of course you as the PIC are going to do whatever it takes. But Boeing's position is there has not been a loss of all engines and a subsequent crash so the odds are you will get at least one engine back. That's all you need.
Fly fast, live slow
 
G-CIVP
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RE: B 747-400 Engines Off

Wed May 30, 2007 5:36 am

Quoting Bellerophon (Reply 45):

"it can seem like an eternity to those passengers sitting down the back of a hot aircraft".

Tell me about it! It isn't too pleasant but bearable. I'm not quite sure what has preciptated the change in policy - could I be enlightened?
 
Meerkat
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RE: B 747-400 Engines Off

Wed May 30, 2007 9:28 pm

Coincidentally there was a programme on NatGeo this morning about the BA009 four engine out incident. It was caused by volcanic ash from an erupting volcano in Indonesia. They were unaware of why they'd lost engines as it was at night and radar returns no signature from ash.
IIRC the crew said that they tried restarting something like 80 times(!) before success. After successfully getting all four back on-line, one of them surged and they ended up landing on three.
Just to make matters even worse, the ash had also trashed visibility through the windshield (imagine a very fine sand-blast) and the glideslope was out at the diversion field - think it was Bali or Jakarta. They still had localiser info though, and managed to look through a sliver of glass at the edge of the shield that wasn't so badly shot to get down safely.
Looking at footage of the state of the engines, it seemed remarkable that they got them back on at all.
Needless to say, the monitoring of volcanic eruptions and their potential to cause problems has been somewhat modified since then!

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