B747, double engines lost...

[ckhy]

For a B747-200, or just 747s in general, if engines 3 and 4 were lost (seperated from the wing totally), what systems would be affected?

For a start i know the hydrualics and hence control problems, but what are the other ones because serioulsy i cannot think of anything else .

Any input would be greatly greatly greatly GREATLy appreciated.

Cheers

and safe flying

[18-Wheeler]

A clean separation?
You wouldn't lose anything at all, apart from a large chunk of mass and thrust on one side.
All the electrical busses would remain powered (with a little switching) and you'd also keep all your pneumatics and hydraulics.
It's a very reliable aeroplane.

[ckhy]

this is actually based on the crash of the 747-200F El Al cargo flight 1862 in 4/10/1992.

no.3 engine seperated from the wing and it took out no.4 as well. so both engines are lost, and the crew did experience control problems.

i gotta write an essay on what systems are affected by losses of two engines, i knew for a fact that the crew experienced controlling problems and eventaully lost control and crashed so it must be linked to the hydrualics since some flight controls are only powered by hydraulics system 3 and 4, so if they're gone the flight controls will either be degraded or lost.

but what are the other stuff that would be affected?

i seriously couldn't think of anything else and the books i have and the internet aren't helping much

i'm risking that my lecturer will actually see this post but oh what the hell where else am i suppose to get good info then.

hope u guys can help me a out a little bit, just need some hints that's all.

cheers

[potkettleblack]

Did you find this website - its got a searchable database?

http://aviation-safety.net/database/...1004-2&lang=en

Down the bottom it quotes its sources so presumably you can then go and grab the full reports from the NASB & NTSB websites etc.

[lomapaseo]

Originally Posted by ckhy

.............. i knew for a fact that the crew experienced controlling problems and eventaully lost control and crashed so it must be linked to the hydrualics

i seriously couldn't think of anything else and the books i have and the internet aren't helping much

........

somewhat of a leap in assumptions above.

When engines are lost under power (nothing wrong with the engine) they do not always tear away cleanly. They have a tendancy to behave like a gyroscope does when you suddenly tilt it (inlet lift on a B747) The end result is that the # 3 engine goes up and to the right and takes out the #4 as well as some critical leading edge surfaces of the wing. Sure with enough speed the aircraft will fly but when you slow it down for approach it comes out of its stable operating envelop, regardles of how well the hydraulic controls and/or electric motors push and pull.

[ckhy]

yah i have got that website already

i have to find out more than what they already have on there, like i have to go quite in depth

most investigation reports didn't state what systems were lost etc

thanks for the tip lomapaseo!

[MagentaLine]

two engine separation

You didn't mention in what phase of flight and your problems are directly related to configuration. The most critical phase would be immediately after V1 and the a/c (B747-100, -200, -300) would typically be very heavy due to enormous fuel and cargo loads (worst case scenario 750,000# to 835,000# max t/o). With the loss of #3 & #4 hydraulics, pneumatics, generators, etc. many things aren't going to operate normally but will via alternate means. You'll be returning to the airport and a heavy cargo classic will most likely need to begin immediate fuel jettison. The leading edge flaps will still be extended so no need to worry about them. This IS a problem if you were to lose both right engines late in the flight (cruise configuration) and have ruptured pneumatics on one wing (right) and go to configure to flaps 5. If you fail to arm the alternate leading edge flaps (electrical override) the left wing leading edge flaps will extend pneumatically while the right ones won't (flap asymmetry). This can require large aileron correction and increased drag (speed brakes) if greater than 8 degrees. Since we are in t/o configuration we also don't have to worry about not having hydraulics on 3 & 4 for outboard gear extension (they'd still be down & locked). If you were in cruise during the ME out, you simply need to be 230-250 knots for proper alternate outboard gear extension. Back to our t/o situation and the outboard trailing edge flaps would be set to flaps 10 or 20 for t/o. Normal landing flaps are 25 or 30 but electric extension only takes about 5 minutes from flaps up to flaps 10. We'd already be at least at flaps ten so it wouldn't take long to drive them electrically to a landing configuration. Because we wouldn't have #3 hydraulics we don't get to use the A autopilot and the stabilizer trim rate & spoiler capability is reduced. Because we lost both #3 & #4 hydraulics, some flight control response will be slower than normal but redundant systems keep us ok otherwise. The primary brakes are also on #4 hydraulic system but we can use #1 instead and still have a third option with #2 hydraulic reserve brakes but they won't hold the parking brake. The loss of #4 hydraulic also means we can't arm the speedbrakes for landing. Boeing builds an incredible plane and the B747 is the definition of redundancy. Just don't try to pull a UAL and use ailerons to compensate for yaw - that's what a rudder is for. Other simple tricks to remember for B747 classics are the #1 hydraulics are for inboard gear, inboard flaps, body gear steering and secondary brake source. The #4 hydraulic system is for the outboard gear, outboard flaps and primary brake source.

Hope this helps.

[ckhy]

holy molly that's a lot of info to digest and gee it's complicated, i only fly a tiny Cesnna . Thanks heaps MagentaLine this definitely gave me more insight to the operation side of the biggie.

much appreciated

[Willit Run]

CKHY,
We all started in Cessna's. So, I am not belittleing you in any way. Your question is a very broad one. If you want to know what you have lost or not lost, you really need to go through a full systems course on the 747. The systems are so redundant, that you can deal with just about everything in another way. Some of the abnormal procedures are a bit long winded, but they are the approved procedures. When you stack multiple emergencies upon one another in a critical phase of flight, crews need to determine which to do in which order. That can be a crap shoot.
Get ahold of an old sytems book somewhere, study it! Boeing has come up with procedures to deal with just about everything. Posting a systems book or procedures manuel on here is not practical.
Evaluating what happened in the El Al Accident was done by the professional accident investigators.
If you understand the 747 systems, then you can make sense of the report, but untill then, don't even try. You will have more questions than answers.

Hope I didn't discourage you.

Good luck with your project!

[2380]

747 #3 & #4 LOST

As far as I remember this a/c encountered control problems when trying to use flaps. LH worked, RH was damaged by losing it's engines.A/C sort of rolled over due to flap inbalance.

[Right Way Up]

As others have implied apart from obvious performance problems (i.e. heavyweight low level failure) a double engine failure on one side will theoretically still allow enough redundancy to fly safely. However the secondary damage involved will probably decide the survivability of the incident. Having done the 2 eng lost scenario in the sim I found the procedure fairly straight forward. However I am led to believe that the simulators do not realistically reflect even a clean separation. The sim , I am told, reflects a total loss of thrust on one side but does not account for the big loss of weight on the same side. Allegedly!

[Lucifer]

AWACS 707 lost in Alaska due to double engine failure from bird flock ingestion - anyone know why it rolled onto its back, as presumably separation did not occur? Not familiar with that type - is power asymetry such a large problem with 707 series aircraft?

Apologies if causing thread diversion!

[Intruder]

MagentaLine went through a lot of the contingencies. One clarification, though: Loss of #4 hydraulics will not prevent deployment of all the ground spoilers, though manual deployment after touchdown may be preferable to arming them for auto-deployment in some cases.

As others stated, airplane controllability will depend on time of the separation and collateral damage. Loss of the engines and related systems in and of themselves would not cause loss of control. Damage to other systems (LE flaps, bleed air and fuel lines, etc)

For a system summary:

Loss of thrust of #3 & 4 engines: Sufficient thrust from #1 & 2 if starting at reasonable weight and altitude (e.g., NOT right after heavyweight takeoff, still dirty). Once at Flaps 1 and Flaps 1 speeds, should be little problem.

Loss of #3 & 4 generators: Sufficient backup with #1 & 2; no problem.

Loss of #3 & 4 bleed air: IF the separation is between the engine and the pylon valve, and the valve can be closed, air can be supplied to the right wing from #1 & 2. If not, the right Bleed Air Isolation Valve will have to be closed, and Leading Edge Flaps will require alternate (electric) extension and retraction.

Loss of #3 & 4 hydraulic systems: Outboard trailing edge flaps and wing landing gear will have to be extended by alternate means. Wing landing gear cannot be retracted. Primary normal brakes lost, but #1 hydraulic system provides full backup. Some controls (elevators, stab trim, spoilers, etc) will have reduced effectiveness, but airplane is fully controllable. Autopilot 'A' lost; autopilot 'B' still works.

Fuel: If pylon fuel valves are intact and can be closed, crossfeed procedures can be used to maintain balance. Fuel dump is unaffected.

[411A]

The B707 is a conventionally controlled aeroplane (cables, bellcranks, balance panels etc), with hydraulic assist only with the rudder, and of course, spoilers.
LE devices are extended pneumatically.
Trailing edge flaps can be extended electrically, if required.
However, if the aeroplane is very heavy, and a sudden power loss is experienced with two engines on one side (3&4 for example), with takeoff flaps at 14 (used on the B-advanced cowl model), sufficient height needs to be traded for airspeed, until the flaps can be retracted, for it to attain a positive rate of climb.

IE, too low, too slow, can and generally will result in being dead as a doornail.

Clean it up however, and it performs surprisingly well....considering.

PS: a 140 pound push on the rudder is required (rudder boost ON) to keep it straight, at lower speeds, with failed engines on one side.
Boost OFF (or failed), bypass the hospital, and go straight to the cemetary.

To give you an example of the necessity of rudder boost on the B707, with one outboard engine failed, Vmca is 120knots with rudder boost ON, 180knots with boost OFF.

Two engines inop on one side, Vmca 170knots with rudder boost ON, 235knots boost OFF.

A tough old bird, but it needs to be handled with care.

[aidey_f]

Sim engine failures

Originally Posted by Right Way Up

However I am led to believe that the simulators do not realistically reflect even a clean separation. The sim , I am told, reflects a total loss of thrust on one side but does not account for the big loss of weight on the same side. Allegedly!

Depends greatly on your sim, and how much the customer wanted to 'tune' the malfunction. In general however, the engine separation malf should feed into the mass proerties model. Other system effects will depend on where the break in the pylon is modeled - up/down stream of the fuel LP shutoff valves for example. On one I looked at recently, when the engine came off the wing we put a high fuel flow demand into the fuel system for that engine position. However, getting hard data for engine separation effects from the OEMs is like getting hold of hen's teeth.

[Taildragger67]

Chky,

Re the El Al accident, if you can't get anything from the NTSB site or in English from the Dutch air investigations unit, have you tried approaching Boeing directly?

They seem like a pretty approachable lot and personally my first port-of-call would be a letter, providing evidence of student bona fides (eg. writing to them (rather than email) with support from your institution), they may be able to point you in the right direction.

Naturally they could be a bit reserved at first in the current security environment.

Also, maybe it's worthwhile trying to get in touch with some of the senior investigators at the ATSB and seeing if they have any stuff or can provide any pointers.

Just keep in mind that part of the point of doing these sorts of assignments is not just to learn the actual technical aspects, but also your research techniques; a bit of lateral thinking and some interesting stuff in the bibliography can often get an extra mark or two.

Good luck
TD67

[lomapaseo]

Originally Posted by Lucifer

AWACS 707 lost in Alaska due to double engine failure from bird flock ingestion - anyone know why it rolled onto its back, as presumably separation did not occur? Not familiar with that type - is power asymetry such a large problem with 707 series aircraft?
Apologies if causing thread diversion!

Certainly a difficult question to answer with either a simple yes or no, since it didn't roll over on its back.

As one of those that walked the debris field and documented the tree chops and furrows in the ground.

[ckhy]

Thanks guys for your tips and advice it did clear things up a bit for me. I've came to a conclusion that because of the damaged caused by the 2 engines on the leading edge of the right wing, it led to assymetric LE flaps, generating more lift on the left wing and stalled the right wing and in the end the aircraft rolled violently to the right and crashed because there weren't enough roll and yaw control to balance the aircraft etc etc. My lecturer agreed with me and reckons i'm on the right track. so now i just gotta keep writing it

cheers guys

[18-Wheeler]

Originally Posted by ckhy

Thanks guys for your tips and advice it did clear things up a bit for me. I've came to a conclusion that because of the damaged caused by the 2 engines on the leading edge of the right wing, it led to assymetric LE flaps, generating more lift on the left wing and stalled the right wing and in the end the aircraft rolled violently to the right and crashed because there weren't enough roll and yaw control to balance the aircraft etc etc. My lecturer agreed with me and reckons i'm on the right track. so now i just gotta keep writing it
cheers guys

What happened with them is that they lost the pneumatic duct on one side, and they apparently didn't follow the correct procedure with extending the flaps.
There's one switch in the Classic that'll kill you, and it's the Leading Edge Alternate Operation switch. Mr Boeing didn't rig that switch very well, as unlike the Trailing Edge Alternate Operation switch it doesn't disable the movement of the LE flaps in conunction with the movement of the TE flaps.
In the heat of the moment, it's very easy to forget this, it the LE alternate switch and run the flaps. The LE flaps will still work as if the alternate switch wasn't switched, however. The TE alternate switch really does cut out the normal TE flaps operation when switched though.
The trick is to remember to run the LE flaps using the alternate electrical system, all out both sides in one go. Don't bother with the flap scheduling thing, just do them all at once, eitherr in or out and be done with it.

The poor chaps in Europe may well have forgotten this, hit the switch and run the flaps, thus leading to the LE flaps not coming out on one side and so the plane uncontrollably rolling over.

[747dieseldude]

Originally Posted by 18-Wheeler

The poor chaps in Europe may well have forgotten this, hit the switch and run the flaps, thus leading to the LE flaps not coming out on one side and so the plane uncontrollably rolling over.

What killed the poor chaps, is that they did everything in a rush. They did not have time to asses their situation, and do checklists i order, which led to assimetry, reducing airspeed too fast etc.
All this is because engines took with them the fire detection loops, resulting in a false fire warning. Since the crew was not aware that the engines had seperated, and the information was not relayed to them by the tower (who knew of the seperation), they believed an actual fire burning that could not be extinguished. That was the reason they tried to put the aircraft on the ground as soon as possible, without getting organized first.
Without the so-called "fire", they might have kept going, assesing the situation, and getting the very reliable 747, which at the point of flight the failure occured, was very survivable.