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RA offered:
A safer Lancair "record"?
I would think that - by now - it would be obvious that what is needed is a
safer "Lancair." We all know that Lancairs are neat planes, but they are
also very hot to fly, with virtually no allowable margin for error.
One only has to look at the statistics and the independent research to know
it is an issue with the plane. In fairness, this is not unique to
Lancairs... My very first plane (which I still have) is a Piper Comanche
that is very difficult to insure because it doesn't have a good record (with
cause)... And there are many others, both certified and experimental. It all
comes down to static and dynamic stability and controllability designed into
the plane during engineering - something that the Lancair series (and most
experimentals) have never done. Probably the same reason that the Columbia
was so difficult to certify.
Yes, stability, and controllability. I'd add some comments.
CAFE flew Fred Baron's N9BF at fwd CG, aft CG, and measured elevator stick forces per G, and graphed htat and compared it to similar results from a Cessna 150 and a Wittman W-10 Tailwind. They found the L320 at aft CGs had a greatly diminished stick force required. He also added "Momentary distractions cause the plane to wander more in pitch attitude." Two conditions often related to unintentional entry into stall-spins. Somewhere also I think a former AF test pilot did a simmilar analysis of the flight controls and he commented that the elevator forces were lighter than those programmed into prsent-day fighters. So, here's an area that could be improved. I'm trying to do that with my L235, adding anti-servo trim tab area to the aft part of the elevator... which will increase the pilot's required pounds of pull per G. Will report on the results.
When all is said and done, design stability (verified by proper flight
testing) is the only way to make a plane safe with great performance... It
is difficult, but not magic.
A partial disagreement abouot 'only way'... you also mentioned 'maneuverability'. We should not ignore the pilot-factor ... what he is able to see and do, and what his reactions are ablet o correct or accomp-lish./ Consider the importance of being able to quickly recover from 'unintended events' like 'unintentionally caused-by-pilot stalls'. I found in flight testing the AristoCraft II, and Magnum, and others, with a simple AOA vane, that
1. I could SEE that the AOA vane moved instantly with pitch control movements,
2. that the pitch trim as set, itself held the AOA fixed, if my hands were off the controls,
3.that the Pilot was the cause -- the cause -- of stalling the wing ... it would not stall itself, hands off, no matter what the attitude excursion,
4. that as long as the horizontal tail was unstalled, I still retained control of the wing's AOA below and above the stall AOA, and
5. with that, I could then move the wing's AOA to just below the marked stall AOA and immediately unstall the wing.
This is all without regard to the plane's attitude to the horizon , the airspeed. angle of bank, or whatever... all aerodynamically irrelevant.
In short, besides stability, giving the pilot a wing-AOA vane can save his ability to correct by maneuvering, and this also contributes a lot to make a plane safe, with great performance. The Navy's been doing it for fifty (50) years!
I guess most of us in GenAv and the FAA are just slow learners.
Again, the Lancairs are a neat plane, and though maybe not "un-safe", they
are definitely "not-safe", a reality that everyone that buys or builds one
should recognize and be comfortable with.
One final comment, a speculation, is about being able to control the airplane's pitch in a stalled AOA: I experimented with tufting and with slotting the horizontal tail on the AristoCraft II, and found that when I stalled it to higher AOAs (on the AOA vane) than say 5or 10 dcegrees higher than wing satll, the horizontal tail also stalled. When that happened, I noticed that pushing the wheel forward resulted in a much slower nose-down to recover.. because when a horizontal tail stalled it lost half it's pitching power.
So I made slots on the h-tail's leading edge, and the tufts showed that slots kept the h-tail unstalled to pretty higih AOAs, and then I got a fast, powerful nose-down reaction to pushing the wheel forward, and could bring the wing-s AOA down to just a few degrees below stall AOA, and recover with very little altitude loss, even from pretty deep stalls.
I don 't see why this wouldn't work on my Lancair, and have sketched out some 'spats' to try ... when I get the thing flying. There might be a one or two knot speed penalty, but it'd be okay to only go 199 instead of 200, if that gave me instant unstalling control in case I'd make a mistake. .. I've made a lot of those, and will again.
Anyway, hope this is of some interest to Lancair folks. Any comments are welcome.
Fly fast, but fly safe,
RA
Don;t see why not.
Terrence N211AL
L235/320
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