KBUF737 From United States of America, joined Dec 2003, 779 posts, RR: 3 Posted (10 years 3 weeks 1 day 20 hours ago) and read 2762 times:
Are slotted flaps, which used to be considered such a breakthrough more of a thing of the past? I notice more and more newer planes appear to have more "single unit" style flaps which look more blunt and drag enducing imo.
If this is what you meant then you are just mistaken about what a slotted flap is. (no worries, I can easily see why you may make this mistake) It doesn't mean that it comes out in sections but rather there is a gap between the flap and the trailing edge of the wing where some of the air from below the wing can come up and move over the top of the flap.
Right rudder....Right rudder...Come on, more right rudder....Right rudder......Aw forget it, I quit!!
Musang From United Kingdom, joined Apr 2001, 846 posts, RR: 7
Reply 7, posted (10 years 2 weeks 6 days 12 hours ago) and read 2372 times:
Cessnas and pre-NG 737s both had slotted flaps. Cessnas are single slotted, Boeings are up to Triple slotted. As long as there's a slot somewhere.
Its a question of efficiency vs. weight/complexity.
Multiple slotted flaps are traditionally more efficient, but heavy and complicated. Apparently Boeing now have found a double slotted design for the NG 737s which does as well as the original triple slotted types.
The 747SP used a single slotted flap, the other versions used a triple. Less weight, less drag through not needing such large track fairings, but I believe I'm correct in saying it wasn't as efficient. It didn't need to be however, since the same wing (dimensionally) was lifting a much smaller airplane, and reasonable take-off/approach speeds were attainable.
Incidentally the SP flap translation path was interesting. The flap leading edge didn't simply move aft along a track like a Cessna while the trailing edge moved aft/down. The LE moved aft and down on a pivot arm, so it was significantly below the undersurface of the wing. This I recall from the diagrams in a South African Airways 747SP differences manual I read on the flight deck of one over the Indian Ocean, and look forward to a more accurate description from someone who knows what he/she is talking about!!