Author: bruce_meacham@... Time: Wed Aug 22, 2001 7:01 am PDT Link
I love reading CAFE results. It's excellent quality data on the
planes we know and love. I was reading throught the Glastar results
and found something interesting. It's the ratio of roll rates to
airspeed. Notice how most aircraft have only a small difference in
roll rate with airspeed, yet the RV has a substancial difference.
What this means is that the RV feels crisp and responsive at
manueving speed yet transitions to a more predictable and safe mooshy
feel at approach airspeeds. This is a very desirable quality. One
which was clearly designed in. Can you believe at Vso an RV-6's roll
rate is comprable to a Cessna 152!
Roll rate vs. Airspeed
Va 1.3 Vso ratio
RV-6A 80 36 2.222222222
Tailwind 47 45 1.044444444
Cessna 152 47 34 1.382352941
RANS S-7C 63 53 1.188679245
GlaStar 52 47 1.106382979
My next question is why? Regardless of how, roll rate is a function
of the difference in lift. So at lower airspeeds the difference is
smaller. I have two theories.
#1 All the other aircraft have high aspect ratio wings. Perhaps this
is a normal effect of low aspect ratio wings. The higher aspect
ratio wings still have effective aelaron control even at 1.3Vso to
overcome thier moment of inertia. Where the low aspect ratio wings
lose the aelaron forces more easily relative to thier moment of
inercia. Fancy way of saying low aspect ratio behave differently.
#2 The wings have started stalling at the root and the aelarons are
operating in parcially stalled condition. Again another effect of
the lower aspect ratio.
At any rate three chears for Van!