To Steal an F-86

In article ,
Guy Alcala writes:
Emmanuel Gustin wrote:

"Merlin Dorfman" wrote in message
...

Did the Soviets learn about the all-flying tail from the
captured F-86, and put it on their later fighters

The F-86A did not have the flying tail, this feature was
introduced by the F-86E. This model entered combat in
Korea in September 1951.

The first Soviet fighter with the flying tail appears to
have been the SM-9/2 prototype of the MiG-19, which
was built in 1954.

So it is quite likely that the Soviets were aware of the use
of a slab tailplane on the F-86E when they designed the
SM-9/2. On the other hand, NASA's adoption of the
'flying tail' appears to have been inspired by British
data.

There's a common misconception here. The "all-flying tail" on the
F-86E and F wasn't a slab, it was a movable stabilizer with
separate (but linked) elevator, as developed for the XS-1 (and
credited by Yeager with allowing the a/c to be controllable through
the Mach). The slab came in on the F-100, IIRR. From what I
recall, there'd come a Mach number when the shock wave from
compressibility would make the elevator ineffective (usually
leading to tuck under), but the stabilizer itself would then be
forward of the shock and retain its effectiveness. So the
stabilizer was made movable (i.e. trimmable like a Buff, but
directly connected to the joystick instead of just the trim switch)
and linked to the elevator around a center pivot. The two surfaces
were geared to move in a certain relationship to each other. I
don't know the specific details (whether it was based on IMN or
just a pure mechanical relationship). Hopefully Mary, Pete or
someone else can fill in the details.

F-86D/Ls and Hs had a one-piece slab.
The reason for th all-moving tails (dangit, no chalkboard again! Assume a
chalkboard, and a lot of Fighter-Pilot hand talking)
Think of the stabilizer/elevator combination as a wing (Wich, after
all, it is) At subsonic speeds, deflecting the elevator affects the
airflow over the entire surface, so that the entire are of the
stabilizer is used to control pitch. As the flow over the stabilizer
gets transonic, and the shockwaves form, elevator deflection begins t
only effect the flow over the elevators themselves, greatly reducing
effectiveness. The solution is to move the entire stab (stabilator),
which lets the entire surface develop whatever lift needs to be
created to counterbalance the wing. (It's early yat - I've only had 1
cuppa Coffee) Why doesn't every airplane use this? (The Wright
Brothers did) The problem is that once the stabilizer had to get
above a certain small size, it's danged hard to move manually, no
matter how much you balance it. It took the advent of powered
controls, (The electric screw jack on the XS-1, or the hydraulics on
the F-86E) to make it practical.

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.)

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

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.)

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