vinayak

hey
i was wondering what do u say when someone in an airline interview asks you what is the advantage of sweepback wings?

i know they create less induced drag and are more aerodynamic, and do something to delay the transonic drag rise.

will appreciate your response, other than "try google" :P

thanks,
vin

virgo

You're in the wrong thread, vin. Try "Tech Log"

5150

Try Wikipedia ! I did

vinayak

can someone please move it, and can someone please answer it...

MIKECR

Swept wings increase the Mach Crit value. A swept wind also provides better stability in turbulence. Disadvantages - they dont generate as much lift as a conventional straight wing, hence most turboprops have straight wings and have much better performance for operating from smaller runways etc. Theres a few more advantages/disadvantages but those are the main ones

Swanie

[From "AFT systems"]

In comparison to a straight wing;
+ Delayed compressibility effects
+ Increase MCRIT, MDRAG RISE
+ Flatter CL curve, so less effected by both speed and AOA changes(less gust sensitivity and reduced CL loss with speed decrease).
+ Less induced drag
+ Better lateral stability

- Tip stalling, (there are plenty of good threads on here about this...)
- Generate less lift
- Reduced CL max and a higher stalling AOA (poor low speed lift)
- Can have too much lateral stability = dutch roll
- HIGH induced drag at high angles of attack (high drag at low speed, i.e. approach)

vinayak

thanks... i read something, http://www.adl.gatech.edu/classes/hi...Drag_Rise.html

the figure 0.7M is something that i found everywhere... is this the mach number till which the drag co-efficient remains the same?? whats the funda...

if u put the cruise speed and the sweepback angle of any airplane in the formula M'=M/cos (sweepback) u end up getting 0.7 again.

and whats this compressibility thing. confused about it.

i am kinda confused... have a Air india interview soon and this is their favourite
question and they really hit u hard with this...