KC135guy

This may be a dumb question but I'm going to ask it anyways. I'm a student pilot, very close to getting my ticket. I've been doing some research on parasitic drag and what the aircraft manufacturers are doing to try to reduce drag and increase fuel efficiency. Adding winglets is a very effective way to reduce this drag, increase fuel efficiency and also adding lift without increasing the size of the wing. As an engine mechanic in the AF I've worked on several types of planes that have been modified over and over to increase their capability and life to an already old airframe. These planes have been flown long past the manufacturers estimated lifespan due to these modifications. Ok, here's my question. Why don't the airlines modify their older aircraft, which still have alot of life, with winglets in an attempt to reduce fuel costs? It seems to me that it would be a simple modification that would have great financial benefits in the long run.

rickair7777

It looks simple, but in typical aviation fashion is very expensive. I think it is around one million (or more) per airplane. You also take the airplane out of service for probably weeks, all while still making lease/mortgage payments and incurring calendar-based Mx expenses.

You might not save enough to recover the investment on older airplanes, which may only have a few years left in service.

KC135guy

That makes sense. I forgot that in the civilian world every minute a plane is down for mx it's lost revenue for the company. I'm sure that to some extent modifications are done, TCTO's (time compliance techincal orders) or AD's, as long as it doesn't add too much to the mx time frame.

Thank you rickair7777

runge

yeah, it's a combination of time down for maintenance, and return on investment. The airlines don't want to or can't afford to pay for any modification that won't pay for itself within a year or two.

Twin Wasp

The winglets also add weight. Japan airlines has 747-400s without the winglets because on their short legs they wouldn't pay off and they'd take a payload hit. I've heard the wing on the -400 is so twisted when the plane is heavy they actually make drag the first couple hours but as the weight drops they pay off.

ryan1234

Exactly... it was my understanding that not all aircraft even benefit from the winglets they were designed with. Just depends I guess.

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