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To the best of my knowledge
these were the only Lancair's that ever came apart in the air. I also heard
sometime back that the outback ( large tail ) was susceptible to tail flutter at
high speeds. Some builders added a bid or two of carbon across the tail
sections in anticipation of that known issue. But not one of those came
off.
Does anyone remember the wing
tests Lance did, the picture of sand or cement bags stacked from one end to the
other over the wing? He said the plane would take 9+ & 6- G's. But during
the stress tests he never was able to break the structure. He under quoted the
what the structure could actually stand.
I believe Lance, like other
designers, always sets the safe limits to the lowest common denominator. They
take into consideration the worst builders that cut corners, use to much resin,
build heavy or not straight, etc. Under these conditions Vne would be an unsafe
speed, but a light quality built, straight aircraft would be safe beyond
the published limits. Again, these are published numbers in a POH that covers
multiple models of aircraft. Not from the "Builder" but the kit maker. I wonder
what the Vne was on the actual test plane Lance built? It would be my guess the
Vne was much higher then the POH.
The ironic part of this whole
discussion is that I stated that I fly my 360 past Vne but the lion share of
crashes in this model ARE from slow airspeeds. There's the IAS side I don't push
the limit. This design loves to go fast.... Slow.. not so much..
Randy
Stuart
LNC-2
----- Original Message -----
Sent: Wednesday, December 02, 2009 6:37
AM
Subject: [LML] Re: Vne is NOT a
meaningless number
Dom old chap (et al),
Y'know, I also have problems with the TAS argument and I read the
report (Flying High and Fast) written for a Van's publication by Ken
Krueger (no relation). No other publication I have ever read discussed
Vne related to TAS. In any event, the emphasis of this report is the
overpowering RVs with big turbo-charged engines and thereby exceeding a
variety of design limited specifications. Vne being one of
them. One way to look at Vne is that it pertains to theoretical
design limits beyond which the concept "unknown consequences" enters the
picture. Flutter is not the only issue as structural limits may also be
exceeded. Remember that aluminum can become distorted (a
hint) before it breaks whilst glass fails explosively when stressed
beyond its limits.
That idea should bring the following into focus. The 320/360 Vne
was set by the designer. From a structural view, the wings were tested
to 9 Gs for a Max Wt of 1685 pounds with the stated load limit of 4.5 Gs - a
100% safety factor. Some have set the MTOW somewhat higher thus
reducing the safety factor. Then we have those that added outer fuel
bays or extended wing tips along with the big/small tail difference.
Flutter can be induced by airframe and flying surface interactions that create
a destructive resonance, a resonance peculiar to the construction
characteristics of the whole system. Thus, the same differences that may
alter original structural limitations may also affect resonance
relationships - i.e. The stiffening of the tail cone may affect the stabilizer
response to prop pulses and maybe even the natural harmonics in the
airframe.
Vne in our Lancairs (200/300 series) may be a conservative value and
exceeding it (IAS) makes one a serious test pilot.
For myself, exceeding 225 KIAS (235 KIAS Vne) requires
conscious work as rudder trim is exceeded requiring the left
foot to exert some pressure to keep the ball centered and the nose down
trim is also exceeded requiring a good push on the stick. Thus, power is
often reduced in a dive (Hmmmm, power used as a trim device).
I looked at NTSB reports for fatal Lancair accidents from 2001 to now (97
total) and could only find 3 where, uh, things came apart, 2 IVs were broken
up in thunderstorms (N29ME 5-16-03 and N241DM 6-6-08) and a
IVP where one aileron couldn't be found among the debris (N299SD
5-15-04). I forgot which one of these raised questions about
re-balancing control surfaces after a paint job.............
Scott Krueger
PS During my review of the 97, it seemed that the most common cause
of a fatal crash was loss of control because of going too slow while too
low.
In a message dated 12/1/2009 7:52:20 P.M. Central Standard Time,
domcrain@tpg.com.au writes:
G’day
Bill,
So Van, of Van’s
is saying that when I was flogging along in my B727 and Airbus at 470 KTAS
each of which had a VMO of 350 KIAS I was exceeding
Vne?
Don’t think
so.
Cheers
Dom
VH-CZJ
From:
Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Bill
Kennedy
Sent: Tuesday, 1 December 2009 10:29 PM
To:
lml
Subject: [LML] Re: Vne is NOT a meaningless
number
Van of Van's
Aircraft wrote about VNE a couple of years ago. Much to my surprise, VNE is
true airspeed, not indicated. It's pretty easy to exceed in my Lancair.
Results can be explosive, meaning onset of flutter to component failure can
be nearly instantaneous. I can't wear a parachute in my plane (Lancair 320),
so I wouldn't screw around with
it.
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