a380900
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Taking Off On One Engine...

Fri Aug 30, 2013 3:35 pm

Let's assume the runway lenght is illimited. I assume any twin could take off on one engine. Is that a reasonable assumption? Or does it take two engines to unstick the plane?
Any particular plane that has done it?
 
wilco737
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 3:40 pm

Quoting A380900 (Thread starter):
Let's assume the runway lenght is illimited. I assume any twin could take off on one engine. Is that a reasonable assumption? Or does it take two engines to unstick the plane?
Any particular plane that has done it?

A twin engined airplane needs to be able to take off if an engine fails at or faster than V1. Then you accelerate on 1 engine to Vr and start rotating and climb away with at least V2. It is part of the certification process.

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KPWMSpotter
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 3:54 pm

Supposedly, Aero Commander once performed a demonstration flight in one of it's early 520 models (twin engine, high wing, six passenger) where the propeller was removed and placed in the cabin before takeoff. The airplane took off from Oklahoma City and flew to Washington DC with the propeller stowed in the back. Reportedly the flight was performed at maximum takeoff weight to boot.

The US Navy is currently operating a Cessna Skymaster (O-2A Pelican) which has been permanently modified to remove the forward engine and replace it with a large radar system.


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Some airplanes wouldn't do so well. Many older low-performance twins (like the DC-3 and the Piper Apache) can't even maintain level flight with an engine out; I don't think they'd fare very well taking off. Then again, I once heard a story of an impatient pilot who decided to fly his Aztec home on a single engine rather than wait for a mechanic where he was...

Modern airliners and general aviation twins would have no problem taking off, just make sure there's a long (and wide) enough runway to get up to flying speed, and no big obstacles in the way...

[Edited 2013-08-30 08:57:36]
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vikkyvik
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 5:10 pm

Quoting A380900 (Thread starter):
Is that a reasonable assumption?

For airliners, I'd say that's a reasonable assumption. One engine has to provide enough thrust to get the airplane airborne. The only thing I might surmise is that you probably don't want to go directly to TOGA thrust on only one engine from a standstill. Not sure the nosewheel would provide enough authority to keep the airplane on centerline.
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Klaus
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 5:25 pm

And of course you would have no redundancy any more – if that sole engine should have a problem, you'd be screwed.
 
wilco737
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 5:49 pm

Quoting vikkyvik (Reply 3):
The only thing I might surmise is that you probably don't want to go directly to TOGA thrust on only one engine from a standstill. Not sure the nosewheel would provide enough authority to keep the airplane on centerline.

No, you shouldn't do that. Neither the rudder nor the nose wheel steering will keep the airplane on the runway.

On the other hand, why would you perform a single engine take off on lets say a 777   

I know that the MD11 can be ferried with one engine inop, but if it is one of the wing engines, you shouldn't go to full thrust right away...

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Starlionblue
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 6:07 pm

The problem with using one engine only (not losing it a Vef) for most multi engined planes is Vmcg, the minimum control speed on the ground. If you set take off power on one engine and leave the other one off while standing still, you'll veer off the runway due to insufficient rudder authority. That's why V1 has to be over Vmcg. You have to be able to continue the take-off on one engine from V1, which of course assumes you won't careen off into a ditch. If you lose an engine under V1, you have to cut power within the regulated 2 second reaction time. If you're under Vmcg and don't do this, you may very well veer off the runway.

When Vmcg is tested, by the way, nose wheel steering is not permitted and the aircraft may not deviate more than 30 feet from centerline.
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timz
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 6:30 pm

Two different questions;

Can a twin-eng airliner take off with one engine shut down? Yes, without a doubt.

Can it take off at its maximum takeoff weight, given all the runway it needs? Any reason to doubt that it can, if thrust is initially kept low enough to maintain control?
 
vikkyvik
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 6:57 pm

Quoting timz (Reply 7):
Can it take off at its maximum takeoff weight, given all the runway it needs? Any reason to doubt that it can, if thrust is initially kept low enough to maintain control?

I see no reason it couldn't. After all, it can certainly continue a takeoff past V1 with one engine inop, even at MTOW. So the only question is if it can accelerate to V1. And I'd say, as long as you add thrust in increments in order to stay on the runway, it should certainly be possible.
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prebennorholm
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RE: Taking Off On One Engine...

Fri Aug 30, 2013 11:18 pm

Quoting KPWMSpotter (Reply 2):
Many older low-performance twins (like the DC-3 and the Piper Apache) can't even maintain level flight with an engine out;

It depends.

Sure, if we are talking about a DC-3 hauling four tonnes raisins during the 1948-49 Berlin Airlift, then you are right.

In 1938 Danish Airlines (later part of SAS) was buying new planes. A committee was set up to choose the right plane. In their report they shortlisted Douglas DC-3 and the four engined German Focke-Wulf Condor. They recommended to buy the Condor, even if it was $18,000 more expensive, because it could take 4 pax more and with one engine inop it would climb at 10 feet/second, while the DC-3 with one engine inop would climb only 2.5 feet/second. They ended up buying two Condors.

We still have one DC-3 flying here in Denmark. Many years ago it was taken off the ordinary aircraft register and put into the "experimental" category. MTOW has been limited so it can operate safely with an engine quitting at any time. It has limited its performance to almost a joke, but it can still take well over a dozen pax on a one hour tour, when the sun is shining all over and it is pointless to talk about alternates. But I am not sure it can today make a Berlin Airlift roundtrip even with an empty cabin.

It is forbidden to take ordinary "pax" on board, only members of the club who support the DC-3 ops. But you can register as a club member on the stairs when you board the plane.

On the other hand, when in 1942-44 a Luftwaffe Condor took off for a marine patrol around Iceland, then I would have hated be on board if one engine had quit during the first few hours of the flight. (Well, I would have hated to be on board in any case).
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KELPkid
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 4:45 am

You couldn't *LEGALLY* do it  And, for the record, Starlionblue is right about Vmcg...how do you get beyond it with only one engine functioning? You'd go off the runway before you'd hit Vmca (the minimum airspeed that gives you the aerodynamic control to control the aircraft with one engine inop and the other at 100% thrust).
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atct
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 6:00 am

I've personally lost an engine in a Dc-3 near gross right after take off and, though very handicapped, flew just fine. I've also flown a 150 Apache on a single engine and yes, it will climb, though very slowly. It wont go very high but it will fly just fine.

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Mir
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 6:43 am

Quoting KELPkid (Reply 10):
And, for the record, Starlionblue is right about Vmcg...how do you get beyond it with only one engine functioning? You'd go off the runway before you'd hit Vmca (the minimum airspeed that gives you the aerodynamic control to control the aircraft with one engine inop and the other at 100% thrust).

You don't use 100% thrust throughout the takeoff - you build it up slowly, adding thrust as the airplane accelerates and you have more directional control. You'll only get to takeoff thrust once you pass Vmcg. This is why the scenario presented includes an unlimited runway - you'll need it. But the airplane will take off on one engine if given enough space to do so.

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Starlionblue
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 7:38 am

Quoting KPWMSpotter (Reply 2):
Many older low-performance twins (like the DC-3 and the Piper Apache) can't even maintain level flight with an engine out; I don't think they'd fare very well taking off.
Quoting atct (Reply 11):
I've also flown a 150 Apache on a single engine and yes, it will climb, though very slowly. It wont go very high but it will fly just fine.

I did my commercial multi training and checkride in a 1957 Piper Apache-150, meaning lots of time with the critical engine out. As atct says, it will climb and fly straight and level on one engine, even in Florida. If it couldn't do that it wouldn't be allowed to fly. Yes, it requires a gentle touch on one engine, but it was by no means very difficult to control. I had to do instrument approaches on one engine. Also simulated engine out on climbout at 600-800 feet. No problem as long as you remember to raise the dead and turn gently.

Now, if you put the gear and especially the flaps out with an engine out, it will sink like a rock. The instructors said the "climb rate" dirty was an estimated minus 1200fpm! The technique was to wait to the last minute to put the gear out, then land flapless.
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airmagnac
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 10:51 am

Quoting wilco737 (Reply 5):
On the other hand, why would you perform a single engine take off on lets say a 777

How about a single-engine ferry flight ?    

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KC135Hydraulics
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 1:42 pm

This is an interesting discussion! I read an accident report a couple years ago about a DC-8 that crashed while trying to perform a 3-engine ferry flight with an outboard engine out. Long story short, they were not able to control the aircraft due to increasing thrust too quickly on the other outboard engine and inadequate directional control at low speed, and it started to veer off the runway. The pilot attempted take off to save the plane from going into the ditch, but stalled and crashed.

Obviously it's not a 2-engine aircraft, but it illustrates the importance of Vmcg and asymetrical thrust on any aircraft with wing-mounted engines.
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26point2
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 2:02 pm

Years ago at KPDX a misguided fellow tried a single-engined takeoff in a biz jet. Quite a humorous set of events and some entertaining reading. Here's the report:

http://www.ntsb.gov/aviationquery/br...211X09774&ntsbno=SEA98FA047&akey=1
 
KELPkid
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 7:23 pm

Quoting Starlionblue (Reply 13):
Now, if you put the gear and especially the flaps out with an engine out, it will sink like a rock. The instructors said the "climb rate" dirty was an estimated minus 1200fpm! The technique was to wait to the last minute to put the gear out, then land flapless.

Was the gear electric or hydraulic? I've heard interesting things about really old twins where say, only one engine has a hydraulic pump and the otther engine has the only alternator   Not sure if that was applicable to the Apache or not...
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Starlionblue
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RE: Taking Off On One Engine...

Sat Aug 31, 2013 9:43 pm

Quoting KELPkid (Reply 17):
Quoting Starlionblue (Reply 13):
Now, if you put the gear and especially the flaps out with an engine out, it will sink like a rock. The instructors said the "climb rate" dirty was an estimated minus 1200fpm! The technique was to wait to the last minute to put the gear out, then land flapless.

Was the gear electric or hydraulic? I've heard interesting things about really old twins where say, only one engine has a hydraulic pump and the otther engine has the only alternator   Not sure if that was applicable to the Apache or not...

Hydraulic. If memory serves the left engine, which was the critical one from an aerodynamic standpoint, also held the generator* and drove the hydraulic pump. Well done, Piper designers. Having said that, if you lost the hydraulic pump there was a hand pump so no big deal. In the unlikely event all that failed, there was a nitrogen bottle driven emergency gear extension system. We were told not to use it. It was cheaper to repair the plane after a belly landing than to rebuild the nitrogen pipe system. Good times...


* No alternator. The Apache I flew was not modern enough for AC apparently. 
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Scooter01
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RE: Taking Off On One Engine...

Sun Sep 01, 2013 12:08 am

I found this Convair promo-film

Watch at 04:00


Quote:
"At airline training-school the pilots are tought how to take off and fly the Convair Liner on a single engine".

Scooter01
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ThrottleHold
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RE: Taking Off On One Engine...

Sun Sep 01, 2013 5:56 am

I've done it in the sim with a 77W. Slowly feed in the power on the engine and it works!
 
EGGD
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RE: Taking Off On One Engine...

Sun Sep 01, 2013 2:22 pm

Yes it is possible, like ThrottleHold above I have done it in the simulator. It is just a balancing act between rudder and thrust lever. Full corrective rudder input at low speed and slowly feed in the thrust, when the rudder becomes more effective with increasing speed and take off thrust is attained then back off on the rudder correction to keep the aircraft straight. It is not however, recommended practice in a real aircraft!
 
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Starlionblue
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RE: Taking Off On One Engine...

Sun Sep 01, 2013 2:45 pm

The more important question is of course if it can be done on a conveyor belt.   
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
KELPkid
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RE: Taking Off On One Engine...

Sun Sep 01, 2013 9:48 pm

Quoting Starlionblue (Reply 18):
* No alternator. The Apache I flew was not modern enough for AC apparently.

A real shame that no one thought to come up with an STC for an alternator, as an alternator saves about 75% of the weight of a generator. A generator has two permanent magnets surrounding the rotating armatures, and two brushes that can wear out   I've converted old pickup trucks from generators to alternators  
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Starlionblue
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RE: Taking Off On One Engine...

Mon Sep 02, 2013 6:18 am

Quoting KELPkid (Reply 23):
Quoting Starlionblue (Reply 18):
* No alternator. The Apache I flew was not modern enough for AC apparently.

A real shame that no one thought to come up with an STC for an alternator, as an alternator saves about 75% of the weight of a generator. A generator has two permanent magnets surrounding the rotating armatures, and two brushes that can wear out   I've converted old pickup trucks from generators to alternators

Fair point. However we're talking a plane that is ancient and probably only used for flight training nowadays. No big deal I guess.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
yeelep
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RE: Taking Off On One Engine...

Mon Sep 02, 2013 8:41 am

Quoting KELPkid (Reply 23):
A real shame that no one thought to come up with an STC for an alternator

They did, STC SA334SW.
http://www.shortwingpipers.org/photo...st/data/509/alternator_interav.pdf

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