Flew an Airtran 737-700 and we taxied out to runway with 1 engine all the way until about 3 min before departure.

One generator is able to power the plane and by opening the isol valve you will have pressure on both ducts. Good luck trying, Jeffrey

I'm fairly certain 2 packs - 1 engine is not only a bad joke, but prohibited.

This was an intriguing question since on my recent United flights I recall the number 2 engine being delayed until we were well along in taxiing. So I asked a 777 FO friend of mine of another major carrier about their procedure. He says it's not standard practice to delay start-up of the second engine since the fuel savings is usually very marginal unless at busy airports like JFK or YYZ in winter where waiting for de-icing and time on the ground is pretty long. Plus, he said if there's going to be any problem with the systems it'll probably be at engine start. So it's best to know that before you get too far away from the gate such that if you need to you can just pull back in, versus being in line during taxiing and nowhere to go. But, as in my case, it does happen outside of those conditions, so it's likely very dependent on the airline SoP. Interesting observations that I'll have to pay more attention to the next time I fly.

Particularly on the a330, after arrival, single engine is almost a must. That airplane is so overpowered that at idle you'd have to be standing on the brakes. On departure taxi that happens too, and often pilots complain about the brakes getting too hot before take off. Not all companies allow single engine taxi before departure. In 747s it is also very common not to start the two outboard engines. Having said that, in FSX, single engine taxi is impossible to simulate correctly. Single engine taxi in real world doesn't result in the airplane wanting to turn. The tiller doesn't have to be turned to create momenta opposite to the momentum of the engine. In FSX you have to step on the pedal, as if you were flying with one engine. So... I'm afraid that, until they FINALLY (after years and years) simulate proper nosewheel steering, independent of the rudder, single engine ground maneuvers will not be realistic. I'm suprised with some of the pilot comments here. By their nature, jet engines are ready to go right after startup, especially high-bypass turbofans.

Particularly on the a330, after arrival, single engine is almost a must. That airplane is so overpowered that at idle you'd have to be standing on the brakes. On departure taxi that happens too, and often pilots complain about the brakes getting too hot before take off. Not all companies allow single engine taxi before departure. In 747s it is also very common not to start the two outboard engines. Having said that, in FSX, single engine taxi is impossible to simulate correctly. Single engine taxi in real world doesn't result in the airplane wanting to turn. The tiller doesn't have to be turned to create momenta opposite to the momentum of the engine. In FSX you have to step on the pedal, as if you were flying with one engine. So... I'm afraid that, until they FINALLY (after years and years) simulate proper nosewheel steering, independent of the rudder, single engine ground maneuvers will not be realistic. I'm suprised with some of the pilot comments here. By their nature, jet engines are ready to go right after startup, especially high-bypass turbofans.

Weird... I've never seen an A/C taxiing with a single engine running, including A330, A310, A300 and 747... I tried to simulate the single engine taxiing with NGX and nose steering was OK if GS was about 20-25.

It doesn't really work very well in fsx due to how its coded, you might get some success with it if you fiddle around with the realistic settings, so you get less yaw etc from single engine, but then that would effect ops when airborne. In terms of it being used in real life, it is done now by more and more ailines, including those flying various versions of the 737, it's used more often during taxi in than out,(there be nothing more embarrassing than getting to the hold to find you can't start engine 2) some airlines are still in the process of testing he procedure to see what benefits they get. Airlines are doing everything they can atpresent to save fuel, as fuel now is the single biggest cost to the operation. Ryanair showed that by flying 170 to 5 dme and gear down at 5 to 4 miles saved them 1million euros a year in fuel across their fleet. So flying cdas, and atc redesigning procedures to get continous climb also are all part of a very changing aviation industry now. Company sops and atc procedures are all focussed now on how to make flights greener. Which is interesting how much flack flying and airports get in the media when actually it's probably the most advanced industry when it comes to doing something about it's environmental impact...cruise ships meanwhile are the biggest inefficient poluting one!