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Fed Ex And Why No Winglets For MD-10  
User currently offlinestuckontarmac From United States of America, joined Jul 2013, 11 posts, RR: 0
Posted (1 year 1 month 2 days 13 hours ago) and read 4499 times:

Greetings, I know that in the early 80s a Continental DC-10 was tested with winglets, that led to them being used on the MD-11. From what I understand they were never certified for the DC-10, but with all the testing I don't see how it would have been to difficult to get the paperwork done. Fast forward to the 2000s, with FedEx acquiring a huge fleet of DC-10 10/30, gas prices really jumped off the charts for the first time to sky high numbers. My question is why FedEx did not look into the winglets for their fleet, I figure the cost for certification would have been quite a bit less because of the early 80s test. I know the fleet is on the way out now and it would not be feasible, but would there have been a substantial savings in fuel usage if the winglets had been applied 10 years ago?

[Edited 2013-08-18 09:58:15]

[Edited 2013-08-18 09:59:02]

8 replies: All unread, jump to last
 
User currently offlineLH707330 From United States of America, joined Jun 2012, 782 posts, RR: 0
Reply 1, posted (1 year 1 month 2 days ago) and read 4221 times:

Quoting stuckontarmac (Thread starter):
From what I understand they were never certified for the DC-10, but with all the testing I don't see how it would have been to difficult to get the paperwork done.

I think you answered your own question there. The initial winglets on the DC-10 were only good for a few percent because they were gen 1 winglets, and there was insufficient demand to justify the STC. Same story with the 734, 736, RR 763ER, and a few other designs.


User currently offlineRussianJet From Belgium, joined Jul 2007, 7703 posts, RR: 21
Reply 2, posted (1 year 1 month 1 day 15 hours ago) and read 4117 times:
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Quoting LH707330 (Reply 1):
The initial winglets on the DC-10 were only good for a few percent

Yes, but isn't 'a few percent' actually an awful lot over time?



✈ Every strike of the hammer is a blow against the enemy. ✈
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 3, posted (1 year 1 month 1 day 12 hours ago) and read 4044 times:

Quoting RussianJet (Reply 2):
Quoting LH707330 (Reply 1):
The initial winglets on the DC-10 were only good for a few percent

Yes, but isn't 'a few percent' actually an awful lot over time?

Yes, but you need to weigh this against the cost of certification and purchase. It may seem like a good idea today, but probably didn't seem so at the time.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineRussianJet From Belgium, joined Jul 2007, 7703 posts, RR: 21
Reply 4, posted (1 year 1 month 1 day 10 hours ago) and read 3984 times:
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Quoting Starlionblue (Reply 3):
It may seem like a good idea today, but probably didn't seem so at the time.

I suppose it's all relative - both to fuel costs then vs. today, and to the relative competitive advantage gained in the market then as opposed to now.



✈ Every strike of the hammer is a blow against the enemy. ✈
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 5, posted (1 year 1 month 1 day 9 hours ago) and read 3959 times:

Quoting RussianJet (Reply 4):
Quoting Starlionblue (Reply 3):
It may seem like a good idea today, but probably didn't seem so at the time.

I suppose it's all relative - both to fuel costs then vs. today, and to the relative competitive advantage gained in the market then as opposed to now.

Absolutely. Also we don't know if there were particular issues with the wing. There's more to it that designing the winglets and bolting them on. The lift distribution changes, which means the stresses on the spars and stringers change, which means the fatigue "pattern" changes. There might have been a strongly negative maintenance cost impact.

On the 737 or 320, where you expect to sell quite literally thousands of frames after the introduction of winglets, the economics of modifying the manufactured wing to take winglets into account are quite favorable. FedEx's MD-10 fleet, while large as these things go, is only about 60 frames, and frames well into their life at that.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinewarreng24 From United States of America, joined Nov 2005, 707 posts, RR: 0
Reply 6, posted (1 year 3 weeks 2 days 13 hours ago) and read 3350 times:

Quoting RussianJet (Reply 2):
Yes, but isn't 'a few percent' actually an awful lot over time?

Most companies (mine included) use a 5 year pay-back period to justify investments.

At the time the projected fuel expenses in a 5 year future did not outweigh the benefits of the "few percent" reduction in fuel burn.

Remember that FedEx might only fly a few hours a day with the MD-10. It's not a very high utilization rate at all, so fuel burn of a "few percent" really isn't a big deal.


User currently offlineprebennorholm From Denmark, joined Mar 2000, 6451 posts, RR: 54
Reply 7, posted (1 year 3 weeks 2 days 5 hours ago) and read 3192 times:

Quoting stuckontarmac (Thread starter):
...in the early 80s a Continental DC-10 was tested with winglets, that led to them being used on the MD-11. From what I understand they were never certified for the DC-10, but with all the testing I don't see how it would have been to difficult to get the paperwork done.

Certification of the DC-10 with winglets would likely mean a lot more than just paperwork.

The tests on the CO bird 30 years ago were aerodynamic tests. They were likely done with lightweight load so the wing would never be stressed more than an un-wingletted plane at MTOW. And in conditions where the risk of strong turbulence could be ignored. Data was gathered and used for producing the quite substantially modified MD-11 wing.

Quoting Starlionblue (Reply 5):
There's more to it that designing the winglets and bolting them on. The lift distribution changes, which means the stresses on the spars and stringers change, which means the fatigue "pattern" changes.

Exactly! And in cruise flight in calm air there is a strong inward force on the winglets, which means bending the wingtip substantially more than an un-wingletted wingtip. Add to that strong lateral turbulence. For instance flying through wake turbulence from another plane taking off or landing in front of you may substantially increase those forces.

Wings with winglets must be designed with those forces in mind. The DC-10 wing wasn't.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25332 posts, RR: 22
Reply 8, posted (1 year 3 weeks 2 days 5 hours ago) and read 3177 times:

Quoting warreng24 (Reply 6):
Remember that FedEx might only fly a few hours a day with the MD-10. It's not a very high utilization rate at all, so fuel burn of a "few percent" really isn't a big deal.

Good example of that was the 10-year-old UPS A300 that crashed at BHM. It only had 10,000 hours, or slightly less than 3 hours a day over its 10 years in service. Had it been a passenger aircraft it would have flown 3 or 4 times as many hours.


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