It has to do with the thrust vector and the landing gear
geometry. Light twins tend to bind on the asymmetric thrust
and the short coupled landing gear. Turbo props and jets
are generally longer and the engines thrust further from the
nose wheel. On jet aircraft, the engines may be on the tail
and they can taxi just fine on one engine.

The airlines do anything to save fuel, but they do not
take-off with paying passengers aboard to save fuel. They
do start and taxi on one engine, but will start all engines
when nearing the take-off runway so the temperatures has
stabilized and the engine can be verified as running. On
airplanes with 4 engines I do understand that some flights
may be allowed to depart on three engines, but I have no
researched the FAR 25 or 121 to see. Also the particular
OPS manual for an airline would have to allow it.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"RK Henry" wrote in message
...
| On Wed, 18 Oct 2006 19:07:51 +0200, Mxsmanic

| wrote:
|
| Neil Gould writes:
|
| By the time one is rated to fly -- anything, not just
multi's -- one has
| received training in all aspects of the operation of
the plane, including
| engine out. Taxiing with a single engine would be part
of that training.
|
| So why doesn't anyone seem to have done it?
|
| In fact, they do. I often see multis taxiing in to the
ramp with just
| one engine running. Mostly turboprops.
|
| Curious coincidence: I just saw the show on CNBC about
American
| Airlines that they're saving a lot of fuel by taxiing on
just one
| engine.
|
| RK Henry