Hagic
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Taking Off With Just One Engine

Wed Jul 05, 2006 7:05 am

Hello Folks,

Even though I can consider myself as a frequent flyer, the part of the entire flight that I still do not enjoy as much is the take off. As engineer, I always believe that during such critical moment, all electromechanical and electronic systems have to work with 100 % reliability. I always have the feeling that any minor system flaw will lead to a serious incident.

In my last trip I was wondering whether the regulations or design procedures stipulate that a two-engine aircraft must be able to completely take off and reach a controllable altitude with just one engine. If this is true, I guess I would be able to enjoy take offs more, which is definitely the best part of a flight.

Any comments would be appreciated.
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rikkus67
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 7:11 am

All dual engined aircraft have to be able to takeoff with one engine in the event of a single engine failure. It is a STANDARD requirement of ANY twin engined aircraft!

In other words, relax...with the reliability of todays engine, a failure at takeoff is quite rare! Enjoy your next flight!

Rik
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BDKLEZ
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 7:26 am

Aircraft take-off performance data is always calculated in the worst case scenario with the assumption made that an engine will fail during the take-off roll. This being the case, you've got nothing to worry about because the aircraft can then complete the take-off procedure and maintain a positive rate of climb with an engine out. The fact that this only very rarely happens and as such you'll more than likely have both engines available, I wouldn't worry about it.

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comairguycvg
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 8:00 am

I will just add that the aircraft can still take off if reaching the V1 speed and then an engine fails. But prior to V1, if an engine fails, the aircraft has time to stop on the remaining amount of runway. As far as getting to a controllable atltituide, the first priority in an engine out is getting to a controllable airspeed. Then get some altituide for the return to the airport.
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BradWray
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 10:08 am

If one engine was to fail during take off, wouldn't the aircraft go wide of the runway, because of obviously more power to one side of the aircraft then the other?

Thanks, Bradley! Big grin
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Amazonphil
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 10:18 am

THis is where a pilots multi-engine rating comes into play
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VirginFlyer
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 11:21 am

Quoting BradWray (Reply 4):
If one engine was to fail during take off, wouldn't the aircraft go wide of the runway, because of obviously more power to one side of the aircraft then the other?

The aircraft has to be able to maintain controlled flight in the event of an engine failure - it is not allowed to veer off course uncontrollably in an asymmetric thrust condition. This requires control input (primarily from the rudder) to keep the aircraft pointing the right way. This is why you have a minimum control speed (Vmca or the bottom red line) - below this speed, the control surfaces will not have sufficient authority to overcome asymmetric thrust, and the aircraft will become uncontrollable with an engine out. If you are airborne, below Vmca, and you have an engine failure, you are in a lot of trouble. I'm not multi-engine rated, but I believe you are required be above Vmca before getting airborne.

V/F
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jspitfire
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RE: Taking Off With Just One Engine

Wed Jul 05, 2006 5:15 pm

Quoting VirginFlyer (Reply 6):
If you are airborne, below Vmca, and you have an engine failure, you are in a lot of trouble. I'm not multi-engine rated, but I believe you are required be above Vmca before getting airborne.

It is a very good idea to be above Vmc before getting airborne, and most aircraft are designed so that this is not a problem. I just finished my multi rating last year in a Piper PA-30 Twin Comanche. The PA-30 is different, in that it rotates about 5 to 8 knots before Vmc. This isn't a good situation, but in this aircraft it is what has to be done. If you wait until Vmc to rotate, the aircraft will start wheelbarrowing on the nose wheel, which isn't very safe. After rotating, we level off for a couple seconds, get above Vmc, and then continue on our way.

Also, I know all aircraft must be controllable with one engine out, but that does not mean they are able to maintain altitude in all parts of the flight. For smaller twins, most of them will not maintain altitude with the gear and / or flaps down. So, if an engine failure occurs right after takeoff, the aircraft may start descending back to the runway until the gear and flaps are brought up. I'm not sure if the same applies to large commercial aircraft; they have a lot more power available that might be able to overcome the drag of the gear and flaps.

Jason
 
timz
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 1:06 am

Quoting Hagic (Thread starter):
I was wondering whether the regulations or design procedures stipulate that a two-engine aircraft must be able to completely take off and reach a controllable altitude with just one engine.

By "completely", you mean they accelerate from a standing start, and take off, all on the power of one engine? What would be the point of such a requirement?
 
speedbird128
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 2:13 am

Quoting Timz (Reply 8):
By "completely", you mean they accelerate from a standing start, and take off, all on the power of one engine? What would be the point of such a requirement?

I think what he meant was the aircraft is able to continue with a controlled take-off once past V1 (Decision speed) and an engine failure occurs....
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krisrockwell
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 5:03 am

I once saw an Airbus video (from Airbus, it was used in flight crew training) where the pilot performed a V2 cut (he brought back the left engine as I recall) and let the aircraft do all of the corrections. He actually just sat there with a pointer and showed what the aircraft was doing on the ECAM. Kind of interesting actually.

Cheers,
Kris
 
ramerinianair
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 5:18 am

Once had an engine failure on an L-1011 during takeoff. It was no big deal. They aborted and tried again. Most people were very upset and un-nerved after the pilots jumped on the brakes. If we continued with the take-off, it would have been fine - we were in a tri-jet and the #2 engine failed. I never get nervous, except when I'm the pilot . . .
SR
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Gary2880
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 5:25 am

Quoting RamerinianAir (Reply 11):
except when I'm the pilot . . .

if the pilot gets nervous i get bloody nervous  Wink
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Caspian27
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 6:37 am

Transport category aircraft in the US are required for certification to be able to able to accelerate the aircraft to Takeoff-Decision Speed(V1) encounter an engine failure at V1, and bring the aircraft to a stop on the remaining runway. This is known as Accelerate-Stop distance. If an engine failure occurs after V1, the aircraft must be able to accelerate to V2 and climb to at least 35 feet above the departure end of the runway. This is Accelerate-Go Distance. These figures are calculated before flight to dtermine whether we have a balanced field length (meaning that we CAN stop on the runway if an engine failed at V1). If we don't have a balanced field length, the aircraft would be weight restricted to achieve a balnced field length.

As others have said, turbine engines are very reliable and rarely fail. However, we practice V1 cuts in the sim to make sure we know how to handle the aircraft if it ever happened in "real life."
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jetflyer
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 6:41 am

A twin engined airliner CAN NOT takeoff from a stand still on one engine unless extremely light. What this means is that they are required to be able to takeoff on one engine if an engine fails after V1 on the takeoff roll in commercial operation, not from the start of the roll.
 
timz
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 7:47 am

Quoting Jetflyer (Reply 14):
A twin engined airliner CAN NOT takeoff from a stand still on one engine unless extremely light.

You mean, assuming a normal runway length? Or, at all?

What if you did have 10000 meters of concrete ahead of you? Maybe at first you can't use full power on the one engine, but eventually you have enough rudder authority ... any reason you couldn't eventually get to V1 and into the air?
 
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Starlionblue
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 9:17 am

Quoting Krisrockwell (Reply 10):
I once saw an Airbus video (from Airbus, it was used in flight crew training) where the pilot performed a V2 cut (he brought back the left engine as I recall) and let the aircraft do all of the corrections. He actually just sat there with a pointer and showed what the aircraft was doing on the ECAM. Kind of interesting actually.

On the 380 if an engine fails the control systems will automatically add rudder and fly completely straight. But the designers added a little "artificial" yaw in the direction of the failed engine anyway since it gives the pilots a better visual cue. I'm sure all sorts of warnings would pop up but any little warning sign is a a good thing.

Quoting Timz (Reply 15):
Quoting Jetflyer (Reply 14):
A twin engined airliner CAN NOT takeoff from a stand still on one engine unless extremely light.

You mean, assuming a normal runway length? Or, at all?

What if you did have 10000 meters of concrete ahead of you? Maybe at first you can't use full power on the one engine, but eventually you have enough rudder authority ... any reason you couldn't eventually get to V1 and into the air?

Maybe. But it's pretty academic. Since nobody has to test it nobody really knows.



As has been said, while there is enough POWER for a twin airliner to take off and climb on one engine, such power when applied at low speeds asymetrically may make rolling in a straight line impossible.

On a triplet or quad, the climb requirement is still calculated based on ONE engine out, so a twin needs more total power than a triplet or quad (50% more than a quad), all other things being equal.
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Tom12
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 9:21 am

I recently red in "pilot" magazine that a 737 only uses 60% of the kebabs actual power. The author also told us that the 737 is more than capable to perform a take-off with only one engine.

As for maintaining flight, I was speaking to one of Ryanair's captains who was telling us that he had to shut down the number 2 engine on his way into STN and he landed fine so i am sure that the aircraft can handle flight with only one engine.

Hope that helps,

Tom  Smile
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Starlionblue
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 9:27 am

Quoting Tom12 (Reply 17):
I recently red in "pilot" magazine that a 737 only uses 60% of the kebabs actual power. The author also told us that the 737 is more than capable to perform a take-off with only one engine.

As for maintaining flight, I was speaking to one of Ryanair's captains who was telling us that he had to shut down the number 2 engine on his way into STN and he landed fine so i am sure that the aircraft can handle flight with only one engine.

This is a certification requirement and has been tried multiple times in flight test before an airliner enters service. Anything else would deviate from the "no single point of failure" doctrine in airliner design. If you can't fly on one engine in a twin, the whole point of having two engines goes out the window. Might as well put a GE90 on the back of your 737 and go single.

The percentage you quote is quite logical in context.
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zeke
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 11:18 am

Quoting Hagic (Thread starter):
As engineer, I always believe that during such critical moment, all electromechanical and electronic systems have to work with 100 % reliability. I always have the feeling that any minor system flaw will lead to a serious incident.

This is incorrect, aircraft during their life successfully and deliberately takeoff and land with systems known to be inoperative at the time of departure. The aircraft have so much redundancy in them that another single failure should not be a big concern.

This is where the sadistic instructors in the simulator have their fun, they may give you a scenario of say a takeoff with an inoperative generator on one engine, then at rotation fail the other engine with the operative generator. Leaving without an engine and no electric generator momentarily, which is not a problem even in a FBW aircraft. A few checklists later and you are back on the runway scenario finished, something we do in the simulator, something I have never heard of in real life.

Quoting Hagic (Thread starter):
In my last trip I was wondering whether the regulations or design procedures stipulate that a two-engine aircraft must be able to completely take off and reach a controllable altitude with just one engine. If this is true, I guess I would be able to enjoy take offs more, which is definitely the best part of a flight.

Airlines are designed so that once the aircraft has sufficient speed on a runway they can continue a takeoff and come back to land in the event of an engine failure or fire.

Before they reach that critical speed the procedure is to stop on the runway.

This exercise is practiced regularly in the simulator, and something due to the reliability of the engines that many pilots go through their entire career never seeing.

Quoting Jspitfire (Reply 7):
It is a very good idea to be above Vmc before getting airborne, and most aircraft are designed so that this is not a problem. I just finished my multi rating last year in a Piper PA-30 Twin Comanche. The PA-30 is different, in that it rotates about 5 to 8 knots before Vmc. This isn't a good situation, but in this aircraft it is what has to be done. If you wait until Vmc to rotate, the aircraft will start wheelbarrowing on the nose wheel, which isn't very safe. After rotating, we level off for a couple seconds, get above Vmc, and then continue on our way.

CAR3/FAR23 aircraft like the PA30 do not have any takeoff performance at all. They guarantee no performance at all with one engine inoperative with gear and flap down. With a light twin close to the runway, you are no better off than being in a single.

In Airlines V1 is always greater than Vmcg, the rotation speed must be greater than 1.05 Vmca, and V2 must be at least 1.1 greater than Vmca, and 1.2 Vs.

Quoting Jetflyer (Reply 14):
A twin engined airliner CAN NOT takeoff from a stand still on one engine unless extremely light. What this means is that they are required to be able to takeoff on one engine if an engine fails after V1 on the takeoff roll in commercial operation, not from the start of the roll.

I am not sure if you could even when very light, you would be well below Vmcg and Vmca making directional control impossible.
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liedetectors
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 11:51 am

First of all, no one is going to dispatch with an engine out. (lets not get into a debate over the exception for fairy flights)

Caspian27 and BDKLEZ are correct in their statements about calculations assuming an engine out. Losing an engine is the major assumption that goes into calculating the magic number for an airplane, the Balance Field Length.
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Starlionblue
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 8:34 pm

Quoting Liedetectors (Reply 20):
First of all, no one is going to dispatch with an engine out. (lets not get into a debate over the exception for fairy flights)

The ones where you sprinkle fairy dust on the plane and it just floats off the ground? Big grin
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pilotaydin
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RE: Taking Off With Just One Engine

Thu Jul 06, 2006 9:05 pm

Quoting Hagic (Thread starter):
a controllable altitude with just one engine

We have takeoff analysis charts for each airport, each runway, under headwind tailwind and temperature variables...these give us our V1, Vr and V2 figures, these figures allow us to clear the climb segments 1-4 even with an engine out...

so nothing to worry about
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SP90
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RE: Taking Off With Just One Engine

Fri Jul 07, 2006 10:48 am

Quoting Starlionblue (Reply 18):
Might as well put a GE90 on the back of your 737 and go single.

That would be so over the top, but I would love to see it, even if its photoshop. The diameter of the engine will be greater than the body of the aircraft.  Big grin
 
Fly2HMO
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RE: Taking Off With Just One Engine

Fri Jul 07, 2006 11:32 am

Quoting Rikkus67 (Reply 1):
It is a STANDARD requirement of ANY twin engined aircraft!

Not true, specially for light GA twins. Hence:

Quoting Zeke (Reply 19):
CAR3/FAR23 aircraft like the PA30 do not have any takeoff performance at all. They guarantee no performance at all with one engine inoperative with gear and flap down.



Quoting Jspitfire (Reply 7):
This isn't a good situation, but in this aircraft it is what has to be done.

Same in the Seminole. And I think it's a pretty common ocurrence in most light twins.

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