Rick
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MD 88's Taxi On 1 Engine

Fri Aug 30, 2002 11:46 pm

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
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 2:11 am

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!

Long live the MD-80.

Randy
 
deltairlines
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 3:18 am

This has been a Delta policy used on all of its flights for a while. It was created by a Delta Express captain who thought this would be a way to save fuel as well as creating faster turnaround times.

Jeff
 
Captain.MD-11
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 3:36 am

I had a jump seat ride in a British Midland DC-9 about 7 years ago, and the Captain chose to taxi using one engine only.
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redngold
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 3:43 am

Many airlines/aircraft taxi on 1 engine. It's just harder to see with jet engines as opposed to props.

redngold
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Marcus
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 3:49 am

Does this apply only to airliners whose engines are close to the centerline like the DC-9/MD/717 and 727's?
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United_fan
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 4:57 am

When I flew on a Canadiar last month,the f/a announced that it would be a little warm in the cabin until they started the #2 engine near the runway.
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ATA L1011
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 5:36 am

Well DL alot of times use to do the L1011 like that start one engine up during taxi with 2. Alot of this was alos due to the fact that the 1011-1/100 is very slow to spool up.
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Squigee
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 5:45 am

DC-10 pilots are told that they can leave the second (middle) engine off until they approach the runway to save fuel and mx costs.
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gotAirbus
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 6:21 am

Question i was meaning to ask for a long time

Wouldn't it be hard if most airliners (especially turboprops) taxi only on one engine. That engine alone would veer the aircraft off the taxiway and the pilot had to compensate using the tiller wheel?

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sllevin
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 8:36 am

On the CRJ, I know that they tend to taxi on one engine because two engine taxiing tends to be too fast, and they have to ride the brakes. On bigger aircraft, I assume it's mainly for fuel savings.

Steve
 
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United_fan
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RE: Sllevin

Sat Aug 31, 2002 9:06 am

That makes sense...I remeber when I flew American^Eagle in '94 on a Shorts 360 , they didn't start the port engine til we were near the runway.
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Dalmd88
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 8:05 pm

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
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RE: MD 88's Taxi On 1 Engine

Sat Aug 31, 2002 8:13 pm

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.
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lmml 14/32
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RE: MD 88's Taxi On 1 Engine

Sun Sep 01, 2002 5:09 am

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.
 
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RE: MD 88's Taxi On 1 Engine

Sun Sep 01, 2002 5:52 am

On newer aircraft such as the 717, If there is a fuel leak, they will be able to see it on the EICAS. Now I think the MD88s have that too, but you do have a point with the DC9s.
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ThirtyEcho
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RE: MD 88's Taxi On 1 Engine

Sun Sep 01, 2002 6:20 am

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.
 
sllevin
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RE: MD 88's Taxi On 1 Engine

Sun Sep 01, 2002 7:34 am

I've only got a few hours in DC-3's, but I gotta say that I can't picture doing much taxiing on just one engine...

Steve