Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Thu, 03 Jun 2004 19:16:32 -0400
Message-ID: <redirect-122926@logan.com>
From: bob mackey <nospam@pure-flight.com>
Subject: Re: Unsafe at any speed
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Some people say Lancair IVs are inherently unsafe and people are crashing
and dieing as a result.

Some people say that Lancair IVs are the finest aircraft ever built
and they crash only because the pilots or builders are not up to the task.

You're both right, and you're both wrong.

By the admission of many on this list, various models of Lancairs
have agressive stall-spin characteristics. Adequate pilotage can avoid
stalls and spins, but so can design changes.

Those who insist that better training is required are correct as
any pilot who dies in the plane clearly needed more training to
deal with whatever deadly situation he found that day.

Those who say that the airplane is unsafe are also
correct -- the stall/spin characteristics could undoubtedly be tamed
by modifications to the airframe. Larger tail, forward CG shift, stall
strips, wing twist, airfoil modifications and so on are all common
and well understood engineering approaches to the taming of nasty stall
properties. Properly done, these changes would have little or no
detrimental effect on the high speed cruise that we love, and would
probably improve the low-speed handling.

Those who say that the plane is safe and would only be crashed by
bad piloting are wrong. There are clearly good pilots that are still
managing to get in trouble. A more forgiving airframe might have kept
them alive.

Those who say that the airframe is unsafe and can't be flow safely
are also mistaken. There are situations in which the pilot and the
plane are up to the task and arrive at the destination swiftly and
and proud to be flying in one of the best airplanes ever built.

We are experimental aviators. We can make ourselves safer through
pilot training, engineering, or both.  If we do neither, then we
earn our smoking craters.

----------------------

The segment of this discussion that has been lacking so far (IMO)
is consideration of *how* to make the airframe safer. In my experience
with the design of ultralight sailplanes, it is possible to design
for extreme spin resistance while also maintaining high performance.
One method that could be adapted here would be to change the aileron/flap
mixing schedule. With the flaps down, I'm not too concerned with high-speed
cruise. The wingtips could be made more spin resistant by allowing the
ailerons to deflect up more as the flaps go down. This effectively increases
twist, lowering the tip angle of attack. This in turn helps to prevent
tip stall, and maintains aileron authority when the midwing begins to stall.

Would this help? I don't know without testing. I would start with
modelling in Mark Drela's Xfoil software, then build RC models
with electronically controlled flap-aileron mixing, then build a
full-size mechanical mixer for testing in life size. The testing with
a human on board would require a skilled test pilot as well as a
spin 'chute and/or whole-airframe parachute.

How about some other suggestions for building safer Lancairs without
giving up the performance that we love?


- bob mackey
  flying a 235
  building a 320
  103MD -at- pure-flight.com
  [use this email address, the one at the top is spam bait]