On Thu, 08 Apr 2004 00:49:00 GMT, "Doug \"Woody\" and Erin Beal"
wrote:

On 4/7/04 10:52 AM, in article ,
"Mary Shafer" wrote:

This discussion is going round and round, but my point is... that the stick
forces do not change whether in CAS, MECH or DEL--i.e. any "break out" force
in the cockpit is incidental to what the pilot normally experiences when
pulling on the pole.

I thought the feel system changed in the spin recovery mode, with more
surface deflection per inch of stick displacement, but there's a good
chance that was either a non-standard F-18 or some other airplane. I
mean, I could have been thinking of the F-16 deep stall recovery mode,
you know.

Don't get me started on stick force shaping, as I spent some serious
flight time and money looking at a variety of schedules for pilot
cueing. I can probably tell you more than you want to know about how
pilots perceive the cues, although the most interesting part is how
they can fail to consciously notice a major cue, even when it affects
their technique.

I wouldn't dare even attempt to discuss it with you, Mary unless I were in
receive only mode. |:-)

Did you know, for example, that you have a different tolerance for
time delay in the feel system than you do for time delay in the flight
control system? If asked, you probably don't even know you can tell
the difference, but you can.

Keep it that way. The Plastic Bug flies miserably in MECH. It was a
big deal when they finally trapped in MECH, in fact. Before that, it
had meant diverting to land. When Tom McMurtry had to land one of
ours in MECH he cheerfully declared it to be one of the worse control
modes he'd ever flown, not counting those he'd flown for me when we
were doing the PIO work.

That's what I've heard. I had no idea that a trap in MECH had actually
occurred. It must have been MECH in one axis only. Eh? Sea story?

I honestly don't know if it was one axis or more. It's not a sea
story, because we got the notification from the class desk (or
whatever they call it). You know the thing I mean, the telex to all
F/A-18 squadrons and Dryden, with time-critical information.

I thought DEL was a reversionary mode for more than spin recovery,
though. Doesn't the Bug drop into DEL when the MC faults? It's the
spin recovery mode that overrides the surface limits for spin recovery
when the yaw rate goes over some limit (40 deg/sec, maybe?), isn't it?

It is. You are correct that's DEL, but the only time *I'VE* ever
experienced flying in DEL is when I do Spin Recovery Mode (SRM) checks on
FCF's (only on the A profiles now).

The way I had it explained to me years ago (by some dude at China Lake) is
that SRM is a subset of the DEL mode (with the LEF's at 33-34 degrees and
the TEF's at 0 +/- 1 degree). The nose gets a bit "slicy" coming out of 30K
in with SRM engaged, and the AOA must be kept between 10-20 degrees
(although I know from personal experience that the jet won't explode if you
fall outside of that limit for transitory periods).

I think this is all exactly right, except that my crummy memory for
numbers means I can't say about them. I don't think you can get the
jet to explode on transient excursions outside the limit, although I
know that no one should ever underestimate the fleet pilots, but you
can get it to depart again if you botch the recovery (usually by being
a little too enthusiastic too soon). If you do it just right, you can
get it to depart into a worse mode, like oscillatory instead of flat.

I'll give you my standard stall-departure-spin warning, which I give
to every fighter pilot and test pilot I know. Be careful if you're
flying a two-seat version with a centerline tank. It will depart and
spin much more easily than a single-seat jet or a clean jet. You're
not guaranteed to depart and spin, of course, but you're at greater
risk. It also probably won't recover as well or as quickly and it may
have more spin modes.

I used to have a couple of plots that really made this point clear,
but I left them with one of the flying qualities engineers when I
retired. I wasn't sure if all the data was generally available.

It's kind of a squirrelly deal to fly in. Nauga, where are you?

They're all squirrelly in stall-departure-spin. Maybe it's because
it's all forebody flow so there's a lot of moment arm or something.
The F-16 deep stall procedure is odd, to say the least, because you
get out of the stall by pulling up the nose and increasing the stall
angle before you push over and "rock" the airplane out of the stall.

Yo, Nauga, over here!

Mary

--
Mary Shafer Retired aerospace research engineer