c5load
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Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 4:41 am

I remember reading long ago that the FAA requires airplanes to be able to climb to a safe altitude should something go wrong and be able to land with half the engines that the airplane is equipped with. So a four engine plane could fly and land with two, and obviously a twin engine plane on one. Is this true? Can a fully loaded 744 or 777 safely climb and circle to land with half its engine power gone?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
flyingturtle
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RE: Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 9:53 am

Quoting c5load (Thread starter):
So a four engine plane could fly and land with two, and obviously a twin engine plane on one. Is this true? Can a fully loaded 744 or 777 safely climb and circle to land with half its engine power gone?

No. It is a requirement for twin engine A/C to climb from V2 on one engine left - but it is a requirement for a quad to climb from V2 on three engines left.

A fully loaded 777 can climb on half the engines (it's a requirement), a fully loaded 744 cannot.


David
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Pihero
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RE: Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 11:34 am

There is no certification requirement for a quad to lose two engines at takeoff.
In real life, you would have a good chance of making the climb unless yopu're well above standard temperature.
There are, though, requirements for en-route performance, with a small (5% IIRC) penalty in terms of climb gradient for the loss of two engines.
Landing with three engines out is trained for... takes a lot of planning ahead and dumping as much as you can because on final, you're commited to landing as a go-around, with the gear down is out of question.
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bueb0g
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RE: Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 12:14 pm

Quoting Pihero (Reply 2):
Landing with three engines out is trained for... takes a lot of planning ahead and dumping as much as you can because on final, you're commited to landing as a go-around, with the gear down is out of question.

Did you mean 2 engines? I would have thought a 3 engined go around wouldn't be too problematic.
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Pihero
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RE: Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 12:25 pm

It' " three engines out", i.e a single engine approach to land.
That's an altogether different kettle of fish.
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rcair1
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RE: Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 5:59 pm

Quoting Pihero (Reply 2):
Landing with three engines out is trained for... takes a lot of planning ahead and dumping as much as you can because on final, you're commited to landing as a go-around, with the gear down is out of question.

Isn't this true even with 2 out? Can you do a gear down go-around on 2 (in a quad)? Maybe if rally light?

What about control ability - Isn't there a limit on Vmc for 2 out on 1 side - how would that Vmc relate to landing speeds.
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bueb0g
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RE: Flying On Half The Engines The Airplane Has

Fri Feb 08, 2013 10:12 pm

Quoting Pihero (Reply 4):

It' " three engines out", i.e a single engine approach to land.
That's an altogether different kettle of fish.


Ahh, got you. That certainly sounds like a challenge. Has this ever happened on a quad in real life (probably some 707/DC-8 stories out there)?
Roger roger, what's our vector, victor?
 
strfyr51
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RE: Flying On Half The Engines The Airplane Has

Sat Feb 09, 2013 12:59 am

Quoting flyingturtle (Reply 1):

I beg to differ with you, A 747-400 has and Did climb out on 2 engines out of San Francisco. the #2 engine failed on takeoff and the pilot flying chopped the #1 engine by mistake. The airplane JUST mssed San Bruno Mountain but it Did climb out. and it was at 870,000 Lbs when it did it.
 
Pihero
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RE: Flying On Half The Engines The Airplane Has

Sat Feb 09, 2013 2:21 am

Quoting rcair1 (Reply 5):
Isn't this true even with 2 out? Can you do a gear down go-around on 2 (in a quad)? Maybe if rally light?

Yoiu can go around on two engines, and there is no controlability problem I can remember. It's a handful, but manageable.
IIRC on the 744, the speeds are superior to Vmc '-2".
On the 340, its even better as the min speed displayed (Vls) is automatically computed above Vmc "-2" and displayed on the PFD. ( The logic makes the difference between two engines "same side" out and two engines" both sides" out ).
If you have a gear retraction impossibility, of course you are committed to landing.
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BoeingGuy
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RE: Flying On Half The Engines The Airplane Has

Sat Feb 09, 2013 3:35 am

Quoting strfyr51 (Reply 7):
Quoting flyingturtle (Reply 1):

I beg to differ with you, A 747-400 has and Did climb out on 2 engines out of San Francisco. the #2 engine failed on takeoff and the pilot flying chopped the #1 engine by mistake. The airplane JUST mssed San Bruno Mountain but it Did climb out. and it was at 870,000 Lbs when it did it.

There's a Boeing procedure for going-around with 2-engines on a 744, IIRC. So the airplane must be capable of that also.
 
rcair1
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RE: Flying On Half The Engines The Airplane Has

Sat Feb 09, 2013 5:21 am

Quoting Pihero (Reply 8):
Yoiu can go around on two engines

Thanks. I find that pretty impressive.... But so is climb out on 1 in a two with a "just over" v1 failure.

I did find it interesting reading the report on the 707 that crashed in California recently. This is the airborne fueling a/c. The report is on the top of the list on the NTSB site - just too tired to look right now.

Apparently, #2 exited the wing due to a failed mount (that had not be replaced per an AD - though the paperwork said it had been). #2 hit the intake of #1 - dramatically reducing thrust and -I think- increasing drag.

Tho past V1 and actually in the air, the PIC determined the a/c was not flyable (drag/control problems) and put it back down. That decision was described as correct and appropriate by the NTSB.

So- it was one of those rare "abort takeoff after V1" cases that was justified.
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prebennorholm
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RE: Flying On Half The Engines The Airplane Has

Sun Feb 10, 2013 3:23 am

What is certified, and what is physically possible, are two different animals.

Airliners must demonstrate a certain climb gradient with one engine out. If I remember well, then it is 2.75 degrees for twins, and 3 degrees when more than two engines.

Since turbofan engines loose roughly 75% of their power at cruising altitude, then it is no big surprise that a quad can fly straight and level on one engine, and even climb slightly, in clean configuration at sea level when way below MTOW. But forget about the certified minimum climb gradients when more than one engine is lost.

And it gets complicated when we talk "hot and high".

It is fine that quad single engine landing is trained in sims.

Sometimes a quad can successfully climb out on two engines. It depends on the combination of several parameters:
- TOW
- RWY altitude
- temperature
- obstacles (mountains etc.)
- symmetrical or asymmetrical power loss.

But there are no certified criteria for such a take-off.

Quoting BoeingGuy (Reply 9):
There's a Boeing procedure for going-around with 2-engines on a 744, IIRC. So the airplane must be capable of that also.

Sure. But I would hate to try that out at Denver or Mexico City on a hot summerday with two good engines on the same wing. Still that's no reason for Boeing not to tell 744 drivers what to do if it happens on a cold winter day at JFK with #1 and 4 engines lost.
Always keep your number of landings equal to your number of take-offs
 
Pihero
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RE: Flying On Half The Engines The Airplane Has

Sun Feb 10, 2013 12:31 pm

Quoting prebennorholm (Reply 11):
What is certified, and what is physically possible, are two different animals.

That's a very very veryyyy strange statement :
If it is certfied, it is possible without rquiring special skills from the pilots.THAT is the main philosophy of airplane dertification.

Quoting prebennorholm (Reply 11):
Airliners must demonstrate a certain climb gradient with one engine out. If I remember well, then it is 2.75 degrees for twins, and 3 degrees when more than two engines.

That's very optimistic : As a matter of fact, climb gradients are given as percentage of the flight path : so these gradients are, for a twin, 2.4 and 1.2 % for second segment (i.e flaps / slats deployed ) and final segment ( airplane clean ). for a quad, the figures are 3 and 1.7 %. In terms of angle values, taking a radian as 60°:
2.4% ~ 1.4° ; 1.2% ~.7°
3% ~ 1.8° ; 1.7% ~ 1°

Quoting prebennorholm (Reply 11):
But forget about the certified minimum climb gradients when more than one engine is lost.

As said earlier, there is no certification requirement for a second engine loss for takeoff performances. Otherwise we wouldn't have twin-engined airliners.

Quoting prebennorholm (Reply 11):
But I would hate to try that out at Denver or Mexico City on a hot summerday with two good engines on the same wing.

You are missing one of the main points of airplane required performance for certification : it's not only about takeoffs , but also for all phases of the flight.
Lose an engine during cruise and you are required to consider for the remainder of the flight a further loss of an engine, which in actual fact requires you to ensure that you clear all obstacles in your route ( drift-down performance ) and ensure a safe landing at your chosen alternate airport in the actual wx conditions ; In that sort of situation, you'd have plenty of time to prepare, dump fuel to the max you'd chose, allowing ( because you're a wise pilot ) for an overshoot and another go.
In these conditions, Denver in the summertime is no problem.
That's the reason we practice two engines out asymmetrical approaches and landings, and single engine approaches are confidence boosters.
Stop considering that Boeing or Airbus train us for having fun in the sim.

As I said in a previous post, two dead engines on the same wings are a bit of a handful in terms of piloting, but it's within the capabilities of all quad drivers. The only difference with semi - or totally - symmetrical engine configuration is just a question of Vmc, i.e speed at which rudder control authority is guaranteed. That Vmc , which I called Vmc "-2" is beloww the chosen min speed -Vls- displayed on the PFD speed scale on Airbus quads, and the FMS makes the difference between asymmetrical configurations. Very nice.

[Edited 2013-02-10 04:37:47]

[Edited 2013-02-10 04:41:34]
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timz
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RE: Flying On Half The Engines The Airplane Has

Sun Feb 10, 2013 10:28 pm

Quoting strfyr51 (Reply 7):
A 747-400 has and Did climb out on 2 engines out of San Francisco. the #2 engine failed on takeoff and the pilot flying chopped the #1 engine by mistake. The airplane JUST mssed San Bruno Mountain

Sounds like you're talking about that departure for Sydney-- UA 863 or some such thing. San Bruno Mtn is right of the intended departure course-- the radio towers reach maybe 1600 ft. Were they really climbing out on the two right engines?

Or did one of the right engines fail and they climbed on three engines?

[Edited 2013-02-10 14:33:39]
 
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DocLightning
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RE: Flying On Half The Engines The Airplane Has

Mon Feb 11, 2013 12:53 am

Quoting Pihero (Reply 12):
If it is certfied, it is possible without rquiring special skills from the pilots.THAT is the main philosophy of airplane dertification.

Yes. His point, however, is that the opposite is not true. There are many things that airliners have done that was WAY out of any certified specification and normally trained-for events in the sim.

For example, that Aloha Airlines 722 that became a convertible after departing ITO and landed safely at OGG. I don't believe that she was ever certified for an event like that, nor did the crew ever train for it.
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Pihero
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RE: Flying On Half The Engines The Airplane Has

Mon Feb 11, 2013 11:30 am

Quoting DocLightning (Reply 14):
There are many things that airliners have done that was WAY out of any certified specification and normally trained-for events in the sim.

I, of course, agree with you but the idea was certification doesn't translate into the real world ( see the argument on hot and high, two dead engines on the same wing...etc...)
Your example of the Aloha 737 is not that exceptional in terms of handling and survivability : the loss of part of the top of the fuselage had very little impact on structural resistance, that part playing a minor role in load bearing.
A similar incident happend in 1960 to a Caravelle in a collision with a private Stampe, on approach to Orly. The debris caused the engines to flame out ( a wheel of the Stampe lodged itself in the air intake of the right engine ). FE managed to restart both Avons, delivering just a fraction of the necessary thrust. They landed safely.
See here
IMVHO, the most amazing feat of airmanship was displayed by the crew of a DHL A300 hit by a missile in Baghdad, one wing on fire, all hydraulics lost, all flight control surfaces streaming in the wind. Here is an Airbus paper wruitten by Jacques Rosay in tribute to that crew. The diagrams, explanations, pictures... all make me shudder years after it happened. This paper is - in all probability - the best, most graphic report on the actual events.
Download the pdf from HERE
But I digress...
Sorry
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