Dl757md From United States of America, joined May 2004, 1560 posts, RR: 18 Posted (8 years 9 months 3 weeks 6 days 2 hours ago) and read 3286 times:
Reading the other thread about wing tanks, a question came to mind. Does anyone here know how the tanks on the 787 will be sealed to hold fuel?
Fuel and composites don't exactly get along. Carbon fiber probably does the best of the aviation composites but over time problems do occur.
Will they have bladders? A special sealer applied to the inside of integral tanks? I can't really see that working too well as every sealer I've used in tanks fails eventually due to the flexing of the wings. Unlike composites, this isn't a structural problem in aluminum wings as the fuel doesn't adversely affect the metal. Perhaps they have developed a fuel proof resins?
"Boeing has announced that the majority of the primary structure including the fuselage and wing on the 787 will be made of composite materials."
While it's not specific about the spars it does say the majority of the primary structure. Even if the spars are aluminum the skins, ribs, and stringers are the only other primary structure in the wing. If they are composite they will also be in contact with the fuel. The structure of the wings that forms the integral tanks in modern airliner's wings IS the primary structure of the wings. There are composite components of current wings but they are limited to flight control surfaces and secondary structure(closeout panels and such). If Boeing states that most of the PRIMARY structure of the 787's wings will be composite how do you figure it won't be. Is the Boeing site misleading us?
Dl757md From United States of America, joined May 2004, 1560 posts, RR: 18 Reply 7, posted (8 years 9 months 3 weeks 5 days 18 hours ago) and read 3103 times:
If it works on these aircraft, why should the 787 be any different?
Good point OldAeroGuy but I never said it wouldn't work. I merely asked if anyone knows how they will make it work. I have every confidence Boeing has addressed the issue, just was wondering how.
I didn't realize the A330 and A340 horizontal stabs are composite and wet. I forgot about the B-2. So I'm sure this has been addressed and somebody out here has the answer as to what methods are used in these aircraft.
To answer your question, one reason the 787 would be different from the B-2 is that commercial aircraft are utilized far more greatly than military aircraft. I'm sure that operational readiness is very important with the B-2 but I highly doubt that it could come close to delivering a 98% dispatch rate if it were operated 8+hrs every day as airliners are expected to. Basically it has much more ground time with which to correct the technical difficulties I envision with a composite integral tank.
AUAE I like your signature. Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
A point of view I'm sure a lot of airline CEOs have these days. They just don't have the balls to say it publicly.
OldAeroGuy From United States of America, joined Dec 2004, 3340 posts, RR: 67 Reply 8, posted (8 years 9 months 3 weeks 5 days 15 hours ago) and read 3063 times:
I do appreciate the utilization differences between military and commercial airplanes, but the B2 has been around for a long time so I threw that in as example of how problems would have been recognized and corrected.
By the way, I agree totally with your thoughts on the 757. One of the best examples of "Looks Good, Flies Good".
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Dl757md From United States of America, joined May 2004, 1560 posts, RR: 18 Reply 9, posted (8 years 9 months 3 weeks 5 days 14 hours ago) and read 3045 times:
I guess where I was coming from in my remarks about the B-2 is that due to the military's lower utilization of the airframe, they might be more willing to repetitively maintain a problem inherent with an aircraft rather than demand a permanent solution as the airlines would because their planes need to fly more.
Put another way the military might accept 10% of a fleet down at one time for mtc. whereas the same situation would kill an airliner. I know it's a tough generalization to justify but it's how I feel.
I'm glad we share the same fondness for the 57. Just wish someday when I'm doing a takeoff power run at the run-up area at the end of the runway I could release the brakes and see what it's like to fly one!