Drew - Some of your questions I addressed in the email that I just
replied to on the same subject.
I too wonder what VG's would do for me, but first I have to get
accurate airspeed data. If I go that route I will send another email
with well documented data.
I preformed my GRT EFIS air speed calibration incorrectly which an
earlier email caused me to re-review. If I had done it correctly
density altitude would have been automatically taken into account
better than I was able to through writing down numbers.
Aircraft weight was within 20 pounds as that is how much fuel was
used. However, weight should not matter if the LRI (GRT AOA indicator)
were calibrated correctly. All aircraft should always stall at the
same AOA regardless of airspeed, fuel weight, payload, "G" loading,
bank angle, and turbulence.
I have the Fife wingtips and full flaperon, but not the Mackenzie
leading edge cuffs. The installation of a leading edge cuff often
results in some loss of cruise airspeed. So my question to you is
how much loss in cruise speed did you experience and what was the
result that you experienced in reduced stall speed if you put the
MacKenzie cuffs on after your plane was flown some?
I will try some 60-65 knots with 12* flaperon the next time up to
see how it handles. I appreciate the insight.
My pitot is 6" below, outside and just forward of the main spar
with 2 static pickups on each side of the tail cone.
Thank you for your thought provoking questions and information.
-----Original Message-----
From:
mike.davis@dcsol.com [mailto:
mike.davis@dcsol.com] On Behalf Of Ken
Sent: Tuesday, December 14, 2010 10:28 AM
To:
rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Stall speeds
Wonder what VG's would do for you?
These numbers are sometimes a can of worms to compare.
Pitot and static positioning for IAS comparison?
Was density altitude used (true airspeed) for gps verification? Was the
wind properly accounted for in any gps comparison?
How accurate is the aircraft weight? Power setting? Idle speed if power
off? Deceleration rate?
I normally take off in rebel 119 with the Mackenzie drooped leading
edge, Fife wingtips, and full flaperon at 41 knots (46mph) in ground
effect at 1650+ weights. I immediately accelerate before climbing out of
ground effect. At 3000 feet with a ridiculously high nose attitude I can
easily match the 40 knot power on stall. Don't know about unmodified
wings. Power off (500 or less prop rpm) it is sinking at a good rate at
those speeds. The rebel's nose is so high and deceleration so fast that
power off I can't really define on my rebel when the sink starts or when
to call it a stall.
I would not call it stalled, but below 50 knots it can sink out pretty
quick without any power on (or in gusts). The rebel is sure comfortable
at low speeds though. So 60-65 knots with 12* flaperon is what I target
for low altitude inspections. Same speed as for a normal approach on a
long runway or a normal climb out.
The GPS says my cessna pitot 5" below and just forward of the main spar
with cabin static is giving accurate readings.
Ken
Drew Dalgleish wrote:
Seems high Gary. Have you checked your airspeed against a GPS? Is it
possible that your static port is in a low pressure area? My airspeed
indicator always reads higher than my GPS unless I have a screaming
tailwind. I'm using the MAM pitot/static tube and it doesn't leak.
At 06:22 PM 13/12/2010 -0500, you wrote:
I have been doing flight tests on my airplane, followed
by calibration tests on my instruments. I get the following
stall speeds flying with a gross weight of 1550 lbs.
Reflex (6 degrees up) 58 mph
Neutral 55 mph
Flaps (6 degrees down) 54 mph
Flaps (12 degrees down) 53 mph
Flaps (18 degrees down) 51 mph
These are a bit higher than advertised in the Rebel literature
and I was wondering if others had experienced anything like
this. I calibrated the ASI with a water manometer so it should
be pretty accurate. No leaks in the system and one steam gauge
and one GRT EFIS which read 1 mph apart - steam lower.
Murphy advertises
Stall (No Flap) Power Off (mph) 44
Stall (FULL FLAP) Power On (mph) 40
The second thing that I would like a comment or two on as to
how much of a decrease in stall speed that one actually
experienced with vortex generators. Significant??
The third thing I was wondering if anyone out there is flying
with a Lift Reserve Indicator. What is your actual experience.
If anyone would like to read about LRI's, the following
web sites may be of interest.
Flying with a Lift Reserve Indicator
http://home.hiwaay.net/~sbuc/journal/li ... ve-pg2.htm
Place to buy an economical kit.
http://sites.google.com/site/lrikit/
Thanking you in advance for your responses. PS I like to
fly slow and sight see.
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