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Posted for Sky2high@aol.com:
While the discussion of Lancair's aerodynamic warts was of great interest,
we should all remember that those at the controls of experimental, amateur
built heavier-than-air machines are always test pilots. In any event, I
found that:
1. Lee Metcalf's compilation of crash stats,
2. Mark Ravinski's descriptions of unusual attitudes and
3. Skip Slater's aft CG discussion
most valuable.
So,
1. It was amazing to read so many accidents are loss-of-control. Always
remember that we have a small (to some, teeny even) rudder.
2. These babies demand that you pay attention and understand the craft's
characteristics even if you aren't capable of (or confident in) testing the
extremes of the flight envelope. Geez Mark, any more sky tricks?
3. I have included Skip's comments so that I may comment specifically on the
320/360 Lancairs.
A. It is interesting to note that I have never heard of anyone parachuting
out of a forward-hinge canopied Lancair (built to plans without a jettison
ability). Although I have no direct knowledge, it would seem that the
canopy
would open no further than a few inches in flight - perhaps a tail slide
could
get it open - perhaps. I just dont' know and I don't wear a parachute.
B. Changing CG by lowering Gear. Try this calculation - compute a cruise GC
and then add 500 (approximate change in nose gear weight moment) to the
aircraft moment and re-divide by the weight. Note that the CG moves aft by
1/4 to
1/2 inch. If you are in a flat spin due to rear CG, put out the gear
resulting in added drag and the CG moving forward - of course, you may have
to make
new gear doors especially after the nose gear door tries to act like a
ventral fin but that is much better than the damage caused by smacking the
terra
firma.
C. Using flaps to change the center of lift. In Jan-Feb 2003, I performed
some experiments at 155 KIAS by taking the flaps out of reflex (-7* to 0*).
Besides slowing the aircraft by 12-15 Kts, the Longeron angle came down
(nose
down) 2.5* and the AOA indicator changed 17 points (1.7*?). One should
remember that the flap reflex position (if properly built) is to reduce drag
with
a minimum pitching moment - Hah! How many of you have surprised a passenger
with the dramatic pitch change as you lowered the flaps (or, by raising them
after takeoff)? I don't know if the 320/360 flaps can take even partial
deployment in a flat spin, but it may be one way out. I understand that the
235
POH says that their flaps must be in the reflex position above 197 Kts.
Also, I used the flaperons in my tube & fabric Challenger to trim the craft
in
pitch. Even a "heavily loaded towards the rear" 320/360 could benefit from
taking the flaps slightly out of full reflex. Also remember that the long
engine mount moved the CG forward 1.5 inches with no adverse effects.
Recently, I
have thought that Lancair miscalculated the CG limits - maybe because it was
done for the wing with 0* reflex................
D. P-Factor. We just don't have enough rudder to compensate for the
throttle being slammed to the firewall. Remember that most spam cans are
underpowered and we are not.
Scott Krueger AKA Grayhawk
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL (KARR)
LML, where ideas collide and you decide!
PS. I am not a military pilot but I read a lot.
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