Bertie the Bunyip wrote:
Dudley Henriques wrote in
news
Bertie the Bunyip wrote:
Dudley Henriques wrote in news:1dCdnWn-
:

Bertie the Bunyip wrote:

OK, I think I have it. There're (roughly) similar problems with the
transonic stuff I fly but for some different reasons. Surely there
are some buffet isssues with the ailerons at large displacements as
well?




Bertie
I've not noticed aileron buffet in the 38 even at max deflection.
The ailerons are extremely effective on the airplane.
About buffet; you actually work high performance jets like the 38 by
using the buffet boundary. You can pull the pole and feel the buffet
onset in pitch. It's a highly effective warning when maneuvering
hard.

you're talking mach buffet now, right? not normal flow seperation..

I would have thought you might get buffet problems with large
deflections in and around transonic flight. We can, certainly, but
our airplanes aren't desingned for supersonic flight, of course..

bertie

The buffet limit is actually the subsonic buffet limit and defines the
lift limit line for the 38. In other words, below corner speed, you
are aerodynamically limited in maneuvering room by the lift limit line
which basically means you can pull to the buffet.
In effect, the tactical buffet line defines the left side of the T38's
flight envelope.


Yeh, OK I understand buffet in relation to loading but the control
deflections have no effect on the onset of buffet? Is that not why you
have a limit when close to mach 1?

Bertie

The roll restriction is totally unrelated to tac buffet. For all
practical purposes you can forget aileron buffet as a problem in the
T38. The issue with the roll limit is divergence through inertia roll
coupling. In other words, at the q found at .9 Mach and above, max
aileron throw will generate a roll rate high enough that the roll axis
changes from pure roll and couples either in pitch or with yaw or even
both under specific angles of attack as the roll is initiated; and this
NEW roll axis is so unstable due to the IYMP that departure is a real
possibility.

--
Dudley Henriques