"1. On a low wind day, glide directly into
the wind, then directly down wind while measuring speed with GPS with the engine
at idle and the yoke back at the stops.
Average the two readings."
Ed I see
a few problems with the suggested method.
1. It
needs to be a standard temperature - pressure
day.
2. Using
ground speed is wind - or no wind depending in this case, better to use
true airspeed.
3. How
do you keep the weight of 1236 pounds in your
trials?
I recall
from my stalls in my Coupe with split elevator, that the airspeed shown in
a power off stall with me alone as pilot and almost empty main tanks was
below 40 Miles, that is way below the 38 knots
requirement.
Calculated
Gross weight here 1248 . Don't recall whether this was a standard temperature
day.
But
there is a better way to see data on that issue. Erco, Forney
and Alon did measure the stalls at certain weights, used in several
versions of the TC for all models. (Source
Juptner)
Stall at
37 miles with a gross of 1125.
Stall at
40 miles with a gross of 1175.
Stall at
48 miles with a gross of 1260.
Stall at
56 miles with a gross of 1400.
Stall at
58 miles with a gross of 1450.
These
are power off stalls at full gross, folks. But one looses altitude usually
before the stall is imminent.
Here is
one misconception. If your plane is said to stall at 56 per TC with a 1400 pound
gross weight, that does not mean it will always stall at 56. It stalls at 56
with a gross weight of 1400. These two data belong
together.
That
said, It becomes clear that when you come in for landing with almost empty tanks
after a cross country and you are alone in your Coupe, the stall speed might be
between 35 and 45, depending on actual weight.
This is
true for all Coupes, 415, Alon , Mooney.
Overloading
the Coupe on the other hand will bring you above that data. I went out for a
nice X-country with my brother last year and gave the load not much
thought. After I had my plane on the scale this spring , I realized that we flew
at around 1600 gross weight, even with empty tanks, not close to designed gross
weight. We did not try a power off stall, but I calculated it to be 64 miles
when being 1600 lb - 65 is my climb out and approach speed.
However
- back to the calculations. If a Coupe stalls at 40 with 1175 lb and at 48 with
1260, one could estimate that it would stall at 45 miles (39kts) when being
1236 - still to high . So, to fit the Sport Pilot requirement, a Coupe
would have to have a max gross weight of 1200
lb.
Not too
bad if the Coupes would weight 600 lbs empty, but mine is 920 lbs empty - end of
game.
Hartmut
----- Original Message -----
Sent: Sunday, October 12, 2003 1:21
PM
Subject: [COUPERS-FLYIN] Flight test
question for LSA Coupes
----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Coupers,
At the
Challenger 20th Birthday Party, Mary Jones, editor of EAA
Experimenter, told us that she was advised by an FAA very-insider she would be
very happy when the final Sport Pilot / Light Sport Aircraft rules were
published. Mary said this phrase
was repeated even when Mary told her source she WOULDNT be happy unless there
was improvement on gross weight and a few other
things.
Im
wondering just how far a Coupe at 1232 lb. and 13° up travel (20° up travel
with the split elevator) comes to qualifying as a LSA under the NPRMs
guidelines. Heres a challenge
for you to try when you are out flying.
Whats
the TRUE minimum flying speed of a 415-C or any Coupe with the split elevator
at 1232 lb. gross weight and engine at
idle?
Ways
to test:
1. On a low wind day, glide directly into
the wind, then directly down wind while measuring speed with GPS with the
engine at idle and the yoke back at the stops. Average the two
readings.
2. Have someone radar zap you as you pull
back the yoke to the stops in ground effect a couple of feet above the
runway. (Please DONT slow down
to this speed between two feet and several hundred feet because the sink rate
is very high and the results might be
undesirable.)
Would
you 415-C and E-and-later pilots who try this please report your results to
us? Inquiring minds want to
know.
Ed
Burkhead
http://edburkhead.com/
[EMAIL PROTECTED] (remove the
QQQ)
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