Rick From United States of America, joined Dec 1999, 129 posts, RR: 0 Posted (12 years 6 months 1 week 1 day 5 hours ago) and read 1682 times:
I fly on a lot of Delta Airlines MD 88's, love em', and over the last few years, I have noticed that they only use 1 engine to taxi. The plane pushes back from the gate and the flight crew starts 1 engine, then about 3/4 of the way out to the runway, I hear a slight popping sound as the 2nd engine fires up. I heard some years ago that airlines did this to save fuel with the old DC9's and 727's, but would they really be saving that much fuel with the newer model planes?
AA737-823 From United States of America, joined Mar 2000, 6017 posts, RR: 12
Reply 1, posted (12 years 6 months 1 week 1 day 2 hours ago) and read 1625 times:
Okay, consider this.
Yes, it's a fuel-saving measure, more recently implemented by American Airlines as part of their "let's not go bankrupt" scheme.
Here's what's to consider though.
The MD-88 is no longer a terribly efficient airplane. It was, in it's early day, more efficient than the DC-9s and 727s it replaced. But now, we have high bypass ratio 737s and A320s that are quite a bit more efficient than the Pratt JT8d-217's on the MD-80s. Even the -219s are not as efficient.
It not only reduces fuel, it also reduces the number of hours put on the engine. That reduces maintenance costs. Think, if they save ten minutes of running per taxi time, that's two taxi's per flight... if the plane makes 5 flights a day (which is a smaller number than I would expect) that's an entire hour of jet engine running you have cut out.
It really does save money. Now think- on a fleet of 400 MD-80s that American has, or even just the 150 (?) that Delta runs, that's quite a bit of fuel saved every day. That's maybe 400 hours per day (at one hour reduction per aircraft) saved!
Dalmd88 From United States of America, joined Jul 2000, 2641 posts, RR: 14
Reply 12, posted (12 years 6 months 1 week 8 hours ago) and read 1267 times:
Taxing on one engine saves fuel and wear on the engine but not time. Operating time on engines doesn't start until the plane takes off. You only record flight time not block to block. Maintenance runs also don't count as use hours or engine cycles.
As a side note Delta recently posted a memo to the mechanics about excessive use of the apu's. These hours and cycles do count and the fuel use adds up. Using the apu's to power lights while working or cabin cleaning is using up the warranty time on some of the apu's in the 777 and 767 fleet.
L-188 From United States of America, joined Jul 1999, 29895 posts, RR: 58
Reply 13, posted (12 years 6 months 1 week 8 hours ago) and read 1253 times:
A lot of times it is easier to maintain a slow taxi if you aren't fighting the idle thrust that is put out by all of your engines.
A lot of airlines will shut down the right hand motor. That way the engine has time to stop spinning before they are parked, makes it a wee bit safer for the ground crew that is going to be working around it since the luggage bins are on that side.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
LMML 14/32 From Malta, joined Jan 2001, 2565 posts, RR: 6
Reply 14, posted (12 years 6 months 6 days 23 hours ago) and read 1196 times:
So this can also be done after landing too this time by shutting down one engine after landing. There is one problem with starting on the taxiway: you have no ground engineer to monitor the exterior and if there is a fuel leak there is nobody to tell you about it.
ThirtyEcho From United States of America, joined Dec 2001, 1679 posts, RR: 1
Reply 16, posted (12 years 6 months 6 days 22 hours ago) and read 1174 times:
This has been a common practice for a long time in aviation, going back to DC3s, 4s, 6s and 7s. In the recips, it was more common taxiing in than taxiing out as the outbound taxi time was sometimes used to warm the engines and perform mag checks, set fuel flows, etc. My uncle was a B24 pilot and they usually taxied out on 2 inboard engines as it cut fuel usage on the ground.