Hey Guys,I've gotten back into the MD-11 lately and have been flying it a lot. It got my wondering that with all the types of fuel saving going, would it be logical to leave engine 2 idle during taxi or even turned off. I guess when the MD-11 was very active with the passenger model in airlines during the 90's saving fuel wasn't the biggest concern, but these days would it happen? Would a certain airline decide to leave it at idle (probably not turned off).

The MD-11 (from what I read) is really an overpowered twin. During taxi (if at low weights) you can taxi with just 1 and 3. Just start 2 at least 3 minutes before takeoff for engine warm up and to ensure that No. 2 is stabilized and within limits.When you're taxiing, usually the engines are retarded to idle and you just roll down the taxiway using thrust when needed. It would be better for fuel to just turn the thing off.However, you will use more thrust at heavy weights (near 500,000 lbs (give or take a hundred thousand)) to keep rolling. You may use more fuel for taxiing on two engines than you would three. Shut No. 2 down if at a low weight.EDIT: Added last paragraph.

Hi Kenny,I've been testing it out with certain weights and if I'm doing a short/short/medium haul I may leave engine 2 off. But I'm finding when I'm a bit more heavier I need the 2nd engine to get rolling then I can just idle it.

When I was flying DC-10s, the number 2 engine was known for causing damage because of its position. The wing engines have the ground to help dissipate some of the thrust, but the number 2 has a downward angle with full force. We've had a couple jets damage hangers and other buildings in the past with the number 2. Our rule of thumb was this. At weights below 500K, we would start the number 2 when clear of congested areas. For weights 500K and above, we start the number 2 and leave it at idle. In either case, you never take the number 2 above idle.

There was a time I used the number 2 above idle. I stopped in Greenland to grab some passengers, but was forced to over night after a aircraft reported low level windshear. After waiting it out, we entered crew rest due to our duty day limit.

There were no hangers to fit our jet, so we had to leave her outside for the night. The next morning we de-iced and started engines. I was 480K so i used 10% of my weight for breakaway thrust. I set about 48% on 1 and 3 waited for her to move. The 10 was known for taking a moment to roll on initial movement. After a few seconds i added a tad more thrust. She stayed in place and i glanced down to ensure i had the parking brake released. I continued to add more power until the takeoff warning horn sounded. At this point i knew my tires were frozen to the ground. I returned to idle and had the engineer start the number 2. Once started, i slowly advanced 1 and 3 to the takeoff warning horn. I asked tower were there any buildings behind me and he ensured i was clear. At this point i slowly fed in the number 2. Suddenly the aircraft lunged and the nose snapped to the right. I snapped to idle and got on the brakes as the plane moved a few feet. We taxied to the runway, applied the flight into suspected windshear procedure, and off we went.

Rick, thank you very much for this short storry. It was very impressive.

 

John

Nice story Rick. Thanks a lot.

any time gents, though i fly Gulfstreams now, its still a 3 wholer world

Nice story. Very interesting.

Other things for saving fuel..

 

Fly your OFP flight plan (climb when the OFP tells you to not the FMS)

 

Enter the winds to calculate the descent correctly, always try to do a continuous descent.

 

Flap 35 landings (not allowed at our company when the runway is wet or limiting)

 

2 engine taxy

 

A/C packs off on taxy out and in

 

Delayed engine start during the pushback

 

Keeping APU use to a minmum on the ground