Hey

Apparently some airlines taxi on one engine till they get to the runway, then they start the other up. Then Once they'v landed they switch the other one off and go back on one!. Apprarently it saves fuel.

But could it be done at say, 35000ft? To save even more fuel, sure you'd fly slower, but the cost would decrease and tickets prices would lower, why don't they do that?

cheers
forfun

i spose, but.... i wouldm't really care but i guess most people just see planes as a tube with wings.

Still, it would save money 

I used to fly 20-series Lears. Mmo was .83. This airplane could  climb directly to 39,000' in about 15minutes and the power must be reduced to avoid exceeding Mmo! I've also experienced two flameouts in these aircraft. What happens when you lose one engine at this altitude? First.....Mach will decay rapidly   Second........the Angle of Attack (AOA) indicator will rapidly approach the yellow(indicating an inevitable stall), if you attempt to stay at that altitude...... As Hagar stated, power on most aircraft is reduced after takeoff and again when cruise altitude is reached but on most jets the output of each engine still remains in the 90%+ range. This Lear can achieve a 10,000fpm initial climb rate but as you approach the flight levels it falls off to less than two thousand. Usually the last two thousand feet are gained at 500-750fpm or less! That's about the same as a Skyhawk/Cherokee isn't it? Imagine losing %50 of your power in one of these airplanes(try it on the sim!).

On the occasion that I did have a flameout a "re-light profile" is in the AOM. What this means is that the "dead engine" won't even re-light until you reach a much lower altitude. So, let's say that you wanted to try your theory at one of these lower altitudes where it's a little safer...... now you have this problem.........
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.......due to the above mentioned adverse yaw, the rudder has to counter the single running engine's desire to turn the aircraft. To accomplish this it must create lift on a horizontal plane but in the process, more drag is created because this large "paddle" is hanging out in the slipstream much more so than the subtle inputs required in more normal flight conditions. ......hope that helps.....

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This is not true. The power required for taxiing is not enough for the assymentric power to affect the aircraft, Only at higher speeds does flying on one engine affect the balance and it certainly wont on the ground.

cheers
forfun

P-3 does long range patrol with 2 of the 4 engines feathered.

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Any pilot who did it would be adding to his/her pysical workload too, particularly in a larger, older type, and even more so if a tailwheel aircraft...


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Like, erm, take off for example... , or worse, land... , if fact just getting in the aeroplane...

Charlie

This topic was started about airlines flying their jets on one engine to save money, lol, i didn't say it rite. o well, its a good little disucssion .

lol

cheers
forfun

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lol. tru

LOL it was informative no arguments there.
As for the other comment, more a generalised one for future referance, although topics may quickly go off in another direction, fear not as the original one will have more than likely been answered:)

KEEP THEM ENGINES RUNNING. ALL OF THEM!

Well, now, if you´re talking about commercial-jets with two, three or four engines, an engine shut-down at 35000 feet - or at any altitude above ground - usually means that you should immediately go through the emergency-procedure list very fast, and - always remember this - very carefully. And then do the right things in right order.

YOU CAN´T AVOID TAXIING... (or death - but that´s not the issue here)

Taxiing an airplane on the ground is basically just like moving any big pile of metal from one place to another, except, instead of dragging or pushing it, you are able to use the plane´s own energy-source to move it around. I don´t think the airlines would mind if their planes were hauled by trucks all the way from the gates to the runways and vice versa, if it was possible - that way they would save quite a lot of fuel (ie. money), but for the time being, the engines are still used.

NOTHING KEEPS YOU FROM FLYING IT FOR REAL!

So, taxiing is just an obligatory thing you must do to get that pile of metal airborne. Once you get airborne, you are FLYING an AIRPLANE! Your plane has then reached its own natural element and it´s not a pile of metal anymore. But you yourself have entered a whole different new world. And in that world the laws of aerodynamics rule above all others.

Your airplane - whatever type she happens to be - has been planned and built by professionals, so don´t worry - she will do her stuff. But remember -  you´ll have to give her a few things, too. Basically, you´ll have to give her three things she really needs to take good care of you.

Those three things are: AIRSPEED, ATTITUDE and ALTITUDE - and they all go hand in hand. For instance: if your attitude is wrong, you will first lose either your airspeed or your altitude, and eventually both of them... etc. - I´m sure you can figure the options out yourself...

Oh well, I sure could go on and on, but maybe some other time. So I let this be "part one", but in the meantime - watch your airspeed and keep them engines running. All of them! 

I found this out on Airliners.net forum of the same topic.
They said that generally taxiing on one engine is not economical for BOEING aircraft.

BUT, they also said, that the power of Airbus engines at idle is sufficient enough to taxi on one engine if need be. Now, for all who are argueing one engine taxiing, it is happenning in the real airliners, Delta for example.

So i don't think taxiing on one engine is as bad for the aircraft as some people are saying. (jets only)

cheers
forfun

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Yes you can - buy a Harrier...


Charlie

LMAO

i didn't read all the replies above, but this is what i know about this...

I heart they do it on the CRJ (i guess any version) because it's a little 'overpowered'. even with one engine on idle, this plane keeps running. on the ground it's easy, but in the air at FL350 it's a whole different story! first of all the asymetric flying. pilots are trained to be able to fly a jet on one engine, but it's not very handy. second it's dangerous. what if the #2 fails? you can start up the other one again, but i think that's not worth the risk and time...