To Steal an F-86

In article ,
Merlin Dorfman writes:
Peter Stickney ) wrote:

...

: You can certainly fly a transonic or supersonic airplane without using
: a slab, but what happens is that your pitch authority (Ability to
: raise or lower the nose) decreases, and, depending on the
: configuration, teh airplane may not be able to be trimmed at all.
: (The pitchup of the F-84s, for example.)

Is this the "control reversal" at transonic speed mentioned in
the British film, "Breaking the Sound Barrier?" (I know that
opinions vary as to whether or not control reversal is real.)

Well, the movie's a movie, and then, well, there's reality.
In the early days of flight into the transonic reagion, airplanes
would display all manner of behavior. Some would pitch down, (Meteor)
SOme would pitch up (F-84) Some would pitch down & then pitch up
(Canberra, IIRC), some would porpoise divergently, eventually risking
breaking up (Vampire), and soem would just keep right on going with
the pilot more passenger than director. (Venom). I suppose it would be
possible for an airplane to pitch up and then pitch down, but usually
the pitchup was so severe that it bled off a lot of speed, and bent
the airplane.
This was due to the various shifts of the Center of Moment of the
airfoil as shockwaves began to form and move along the wing and tail
surfaces. What gets felt in the cockpit is the change in trim force
as this happens, and the perceived feel of what's going on. For
ecample, you're hauling back in the stick, with nothing happening, and
then the airplane pitches up to the extent that holding the stick in
place feels like you're pushing it. Elevators don't work backwards,
or anything like that. It was possible to get situations where
aileron deflection at high speeds would bend the wing in the opposite
direction, reducing and eventually reversing roll control. B-47s were
quite prone to this, which led to the redline limit of 425 kts IAS.
F-86s were somewhat subject to it, and some of the thinner winged
transonic fighters like the FJ-4 Fury and F3H Demon could, it hey had
a tendency to roll a bit be "fixed" by slamming the stick hard over at
high IAS, bending the wings into rig. (Sort of like warping the
wingtip of a balsa glider to make it fly straight)
This concern about bending the wings is what led to the inboard
ailerons of the F-100 and F-8 Crusader.
Nowadays, (Post 1955 or so), we seem to have a handle on it, and
passing through the transonic range is a bit dull. All you notice is
a bit of change in the trim feel on some airplanes, the ASI jumps, and
the fuel goes away fast.

If you get a chance, go check out the NACA Technical
Reports Server, for teh period between 1943 and 1953. There's a lot
of stuff in there on the transonic behavior of a lot of airplanes,
ranging from dive tests of a glider P-51 to the pitchup tendencies of
various swept-wing jets. Most of it is, well, technical, (saves
changing the name), but the abstracts can be rather clear.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster