I'll add my two cents to what Ed & William have said....
When I was in the Aeronautics program at SJSU, we watched a film of an in
flight flutter test on a horizontal stabilizer. If memory serves, I think it
was performed by the FAA using a Piper Comanche.
The key was a few fractions of a second of time recorded using a special high
speed camera, that enabled us to clearly see how quickly flutter developes and
what occurs to the structure during flutter.
I still recall the film vividly some 25 years later. The physical displacement
of the horizontal stabilizer and obvious stress to the structure scared the
daylights out of me even though I was just watching a film. It was amazing
that the structure remainined intact even for the deliberately very short
duration flutter test.
I've given the Coupes aerodynamic redline a wide margin, as I would with any
plane, particularly older ones. Like Ed ("response pre-queuing"), I've
pre-programmed my response to anything that feels remotely like flutter (a
slight increase in back pressure / load and reduce power).
Ed is correct and makes an excellent point about defensively anticipating
potential threats, and "response pre-queuing" or preprogrammed responses to
specific situations, particularly those requiring quick response. It's
important in flying and other activities. That same important habit pattern
has also been essential to help avoid accident & injury during 30 years of
motorcycle riding.
Good points gentlemen....
Dan Hall
N3968H
---- Ed Burkhead <[email protected]> wrote:
>
> Bill,
>
> Again, great points.
>
> Perhaps it was that pre-programming that saved me when I had aileron
> flutter. I knew I was approaching Vne and I knew that flutter was a killer
> when Vne was exceeded. I probably had those thoughts as I was slowly
> speeding up toward Vne.
>
> I blew away the Army's driver's testing reflex device with a similar method.
> I call it response pre-queuing.
>
> It's been demonstrated that, if you are thinking about what your response
> will be under a specific stimulus, your response time is lots faster than if
> you have to make the response decision after you see the stimulus.
>
> In driving, as you approach an intersection, you can pre-decide what you'll
> do if the car approaching from the side road doesn't stop. Will you drive
> into the left ditch, the right ditch, slam on the brakes, slam on the gas or
> ram the idiot? Just having those thoughts and making some pre-decisions can
> change an accident into an incident.
>
> By pre-loading my response to the Army driving test's queues, I had about
> half the response time of anyone they'd tested.
>
> I learned about this 35 years ago from a professor who was researching this
> topic. I've practiced it since while driving and, gosh, it sure improves
> your defensive driving. The only bad drivers who've managed to tag me in
> the last 750,000 miles have caught me when I was stopped or moving too slow
> to DO anything.
> ___________________________
>
> My only difference with you, Bill, on your post is in this comment you made:
> > It is likely that the great majority of flutter encounters
> > begin slowly (with the pilot wondering "what is going on") . . .
> > and will cease as soon as power is reduced and speed drops.
>
> That rule may apply to a lot of other things, but I suggest it doesn't
> always apply to flutter. Flutter is, as I understand it, a resonance
> phenomenon. When the conditions are right and the disturbing stimulus hits,
> the resonant vibration often goes to full intensity almost instantly. It
> was so when I had aileron flutter.
>
> If you get slow onset, great. I hope it happens. Wheel bounce from an
> unbalanced wheel on your car can start with low amplitude and slowly rise to
> a peak at the optimum speed.
>
> But, if while flying, you feel that driving-on-a-washboard-road vibration or
> wheel badly out of balance vibration, LOAD the control surfaces instantly.
> It doesn't take a huge load. (i.e. I wouldn't have yanked full back
> pressure on the elevator at high speed.) But loading the control surfaces
> causes them to press between the air forces and the control rods/cables. It
> stops resonance vibrations very quickly.
>
> In the SECOND half of the first instant, chop power and reduce speed.
>
> That driving on a washboard road is a distinct and dramatic thing that
> should never happen in the air. If you are not familiar with it, go find
> busy gravel roads and drive around for a while.
>
> Ed
>
>
> ------------------------------------
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