Blacksheep
negative dihedral=the downward incline of an aircrafts wing or other supporting surface in relation to the horizontal. Esp. the angle thus formed.(New Webster's Dictionary).
Steamchicken
"Some fighters are deliberately unstable; I think the F16 is one (which cannot be flown without the computer)."
Hhmmmm?
I guess I know what you mean: There are several kinds of stability: dynamic stability, static stability a.s.o. Modern fighter AC ( it began with the F-4 Phantom) have no "built-in" dynamic stability and as you write correctly cannot be flown without computers. So far so fine.
This has nothing to do with the unchanged requirement to fly stable when delivering weapons. Just the opposite, modern computers compensate for the missing"natural aerodynamic stability" and provide the pilot with an unmatched stable platform when firing his gun. Even modern stand-off weapons like be fired by a pilot who is sitting in a nice and steady flying machine.
Back to negative dihedral.
As the gentlemen above post quite correct, there are two main points to note:
1) Neg. dihedral is applied to reduce excessive roll stability. The degrees selected are directly related to the sweep-back angle
A rough theoretical formular: 3° sweep-back are related to 1° neg. dihedral. Practically this value is devided by 2.(ratio than 3 to 0.5)
Works nicely on BAe 146 as BiK_116.80 writes: 15 to 3
2) Neg. dihedral helps to reduce a tendency for dutch roll in AC with swept wings and high T-tails as BiK said.
Everybody who had the pleasure to fly B-727 knows what I am talking about.
There are so many real experts in pprune who could give you better infos than me, but hope it helps.
