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I think that when a plane fails from flutter it is
actually caused by a combination of speed and vibration.
The indicated speed can be thought to be what
causes a "load" or frontal pressure. This is the pressure on your hand
when stuck out the car window and is what your airspeed instrument
sees.
The vibration or flutter is more dependent on
true speed and would be the rate of flutter of a handkerchief held out that
same car window.
In the aircraft structure, it's the true speed that
establishes the rate of flutter and is what must be considered to be exciting a
natural harmonic. To cause damage, there must be also enough load to drive the
amplitude up. Consider the space shuttle. It operates at what -
25,000 MPH but in such thin air that the combined effect of load and vibration
is tolerated.
I expect that to get an exact cockpit reading of
Vne, you would need a computer with a formula to weigh components of both true
and indicated speed and it would change with altitude, temperature and other
variables like fuel loading.
High and fast military pilots are taught not to
ever open their parachute too soon after bailing out. One reason is that
the chute pops open at the true airspeed. The jolt can break your bones
and has even been reported to have ripped off someone's combat
boots.
Mark Ravinski
----- Original Message -----
Sent: Thursday, December 03, 2009 10:13
AM
Subject: [LML] Re: Vne is NOT a
meaningless number
Concerning
the discussion of whether VNE is a function of indicated or true airspeed, I
recall reading that U2 pilots operated in the “coffin corner” of some 5-10 MPH
where stall was lower limit and VNE and wings come off the upper. To me
that seems like true air speed would be limit on VNE.
Chat
Daniel
Super
ES
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Skip
Slater
Sent: Thursday, December 03, 2009 6:21 AM
To:
lml
Subject: [LML] Re: Vne is NOT a meaningless
number
"One IVP was lost
years ago when it exceeded Vne."
Gene Long's ES also
broke up in flight when it exceeded VNE during it's inexplicable descent from
cruse altitude a year an a half ago.
The fact it
this: No amount of pilot skill will save a plane once flutter begins to
break it apart. If you knowingly exceed VNE, you are a test pilot and
the only way you'll know you went too fast is as your plane is going down in
pieces. Pilots who willfully ignore manufacturer established limitations
are accidents looking for a place to happen. Pilots who brag about such
exploits deserve a very wide berth.
I have to wonder
what the instructors from HIPAT and LOBO would have to say on this
subject. If they're listening, I hope they'll chime
in.
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