NightFlier
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How Stable Is The MD-11 On 2 Engines?

Sat Jul 10, 2004 12:05 pm

I was watching a program on television one day and saw a pilot doing a demonstration with a Falcon 50, were he brought the # 1 engine to idle to simulate an engine failure. When he did this the airplane did not appear to be effected by the idling engine and the pilot explained how well the airplane handled on just 2 engines and how the effects of the #1 engine were not even felt by the passenger's and crew. So I was wondering even though the MD-11 has the #1 and #3 engines mounted below the wings, would it react similar to the Falcon if the MD-11 lost the #1 or #3 engine at any part of the flight ?
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nosedive
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RE: How Stable Is The MD-11 On 2 Engines?

Sat Jul 10, 2004 12:46 pm

Well, I do know my dad had a bat go through his #1, when he landed the mech pointed to the fleshy stuff in the engine, coming out of Subic Bay. He said it felt more like the nose gear wasn't coming up quickly, and that the aircraft dragged a tad. So I guess the MD11 performs decent enough when it loses power to #1 or #3. I'll ask him for some more details later on.
 
Cubsrule
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RE: How Stable Is The MD-11 On 2 Engines?

Sat Jul 10, 2004 12:55 pm

From a merely qualitative point of view, I would imagine the MD-11 would be harder to control with no #1 or #3 engine because the thrust from the 2 working engines would be much further from being symmetric than that of the Falcon 50. I've been out of school for nearly 2 months and am thus far too lazy to do any calculations to give you a better idea of how severe the effect would be.
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RiffedAAMech
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RE: How Stable Is The MD-11 On 2 Engines?

Sun Jul 11, 2004 12:32 am

When I worked at McDonnel Douglas on the MD-11, we would always hear that the cargo carriers who used the MD-11 would shut down the #2 engine in flight to maximize fuel economy. Never verified if this was accepted operating procedure but it did sound like it was possible.
 
MD11Engineer
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RE: How Stable Is The MD-11 On 2 Engines?

Sun Jul 11, 2004 12:47 am

AAMech,

No, you wouldn´t want to shut down an engine in flight without an emergency. Prolonged windmilling will damage the engine due to bad lubrication (You don´t have the internal bleed air to keep the bearing chambers sealed while windmilling). There is even a windmilling inspection in the AMM.
Throttle back, yes, but not shut down.

Jan
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FDXmech
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RE: How Stable Is The MD-11 On 2 Engines?

Sun Jul 11, 2004 1:20 am

In addition, you would have to drift down to a lower altitude.

Reading the engine parameters on ACARS pretty much everyday, I've never seen this done. I suspect the flight crew would have to answer to his chief pilot, FAA, etc on violating established procedures.

I suspect this, urban legend.
You're only as good as your last departure.
 
nightflyer
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RE: How Stable Is The MD-11 On 2 Engines?

Mon Jul 12, 2004 2:24 am

Well, I've only flown it with the engines failed (1 and 2 engines at a time) in the simulator. It yaws a little more than the EMB145 that I used to fly but throw in a little rudder trim and you're good to go.

We don't shut the #2 engine down in flight to save fuel, we don't even shut one down for taxiing.


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MidnightMike
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RE: How Stable Is The MD-11 On 2 Engines?

Mon Jul 12, 2004 8:49 am

I would imagine that it will be very stable, all aircraft goes through a rigorous testing process. Then MD11 would have been tested with the #1 engine shutdown, #2 engine shutdown, #3 engine shut down, #1 & #3 engine shutdown, and so on.

All of this data is recorded and evaluated by the FAA, data is then gone over by the eningeers, and then this data is then uploaded into the databanks when they start building the full flight simulators.

Take for example the A380, they would perform months & months of inflight testing, shutting down the engines in every possible combinations, nothing is left to surprise.
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NightFlier
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RE: How Stable Is The MD-11 On 2 Engines?

Tue Jul 13, 2004 11:27 am

Sounds good to me thanks for the help every one.  Big thumbs up


NightFlier
Airplanes are only as good as the people who fly&fix them.
 
AmericanAirFan
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RE: How Stable Is The MD-11 On 2 Engines?

Wed Jul 14, 2004 10:02 am

Well I read a story about a Delta Airlines Flight 1141 August 1988 and they had up to an hour of taxi delays at DFW and requested to shut of # 2 engine and give thema 2 minute warning before takeoff to start the engine.(that was the Delta flight that crashed due to wrong fuel loads)
_Justin
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nightflyer
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RE: How Stable Is The MD-11 On 2 Engines?

Wed Jul 14, 2004 10:46 am

AmericanAirFan,
If you're refering to the Delta 727 that crashed at DFW, it crashed because they forgot to set the flaps for takeoff.


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AmericanAirFan
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RE: How Stable Is The MD-11 On 2 Engines?

Wed Jul 14, 2004 12:36 pm

I got the story from a book called the black box and they hav all the transmitions and stements of the flight and there was a fuel gauage that did not work and the tanks were not filled equaly if you have a webpage to back it up prove me wrong Im not saying im right
_Justin
"American 1881 Cleared For Takeoff One Seven Left"
 
nightflyer
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RE: How Stable Is The MD-11 On 2 Engines?

Thu Jul 15, 2004 8:32 am

 
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Crosswind
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RE: How Stable Is The MD-11 On 2 Engines?

Fri Jul 16, 2004 9:51 pm

I have heard that in the early 1970s some US carriers experimented with a procedure to throttle back the #2 engine in the cruise, in order to try and save fuel, at the expense of a slower cruise speed. This was during the height of the fuel crisis when oil prices had risen sharply.

It was found to be counter-productive, as intake-drag from the #2 engine being throttled back prevented any increase in efficiency.

Regards
CROSSWIND
 
MD-90
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RE: How Stable Is The MD-11 On 2 Engines?

Sat Jul 24, 2004 12:43 pm

The 727 with the incorrect flap settings (basically, no flaps) was a Northwest aircraft, I believe.

I think that the 727 would be a better example to compare with a Falcon than the MD-11.
 
nightflyer
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RE: How Stable Is The MD-11 On 2 Engines?

Sun Jul 25, 2004 11:40 am

MD-90,
I believe you're thinking of the NW DC9 that crashed in Detroit.

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freshlove1
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RE: How Stable Is The MD-11 On 2 Engines?

Sun Jul 25, 2004 11:41 am

I never recall a DL flight crashing in AUG of 88' due to incorrect fuel loads. I do recall a DL flight crashing in DFW due to the flaps not being set correctly because the crew was to busy joking with the F/A's during the taxi. The NW flight was an MD-80 not a 727 and that did crash due to the flaps not being set.
 
MD-90
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RE: How Stable Is The MD-11 On 2 Engines?

Mon Jul 26, 2004 2:43 pm

DC-9, 727, same difference. Big grin
 
Thrust
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RE: How Stable Is The MD-11 On 2 Engines?

Thu Jul 29, 2004 12:50 am

No matter how fuel-inefficient, you want to all the engines when flying an aircraft...I certainly would...you can fly faster...you are safer...and it is dangerous flying without one of your engines. I would certainly feel uncomfortable, don't know 'bout any of you daredevils though  Laugh out loud
Fly one thing; Fly it well
 
Thrust
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RE: How Stable Is The MD-11 On 2 Engines?

Thu Jul 29, 2004 12:50 am

No matter how fuel-inefficient, you want to use all the engines when flying an aircraft...I certainly would...you can fly faster...you are safer...and it is dangerous flying without one of your engines. I would certainly feel uncomfortable, don't know 'bout any of you daredevils though  Laugh out loud
Fly one thing; Fly it well

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