Another way to measure fine speed changes is to set your WAAS GPS to set
your distance units to Km and, whilst under AP altitude hold control
in level flight, make the flap change with any trim adjustment as required and
wait the 3 minutes to record the new speed. KM/hr is more than twice
as fine as Kts.
Grayhawk
Steve,
For small deflections you can use: sin(3 deg) * (flap
chord)
My flap chord at the root is 10.75", so 0.56" -
Another option is a digital level.
The faired-in position is pretty accurate at -7 degrees. When
I calibrated my flap position transducer, I had to make a full size template
to locate 0 degrees. The fuselage fairing ended up right at -7.0, so it
is a good reference.
When measuring speeds greater that 120 KIAS, I recorded each point
for at least three minutes. I found that it took about 2 minutes to reach
a truly stabilized speed after a power or flap setting change. The
speed decay is so slow it isn't really detectable by starring at
the airspeed indicator. Imagine trying to see average needle
movement of 1kt/min. Fortunately the two minute settling time is very
consistent.
I think it would be quite valuable and educational to repeat
the same series to of tests on a small tail 320/360. I would be
more than happy to go over all the details with anyone interested in
volunteering. I think the biggest hurdle is mounting the alpha/beta
probe. I was able to grab onto the mounting provisions for my wingtip
lens with a fiberglass 'lens' to mount the probe. The internal transducers are relatively
simple.
Chris Zavatson
N91CZ
360std
Chris, I'm going to re-just my flaps to -10 reflex and see
what happens. What would you guess the measurement is up from the trailing
edge of the faired in position?
Thanks
for all your work. Do you need a small tail 360 for more testing?
Steve Alderman N25SA
-----Original
Message-----
From: Chris Zavatson <
chris_zavatson@yahoo.com>
To:
lml <
lml@lancaironline.net>
Sent: Sun, Sep 29, 2013 8:54
pm
Subject: [LML] Re: Lancair 320/360 performance and stability
So I happened to be looking for something unrelated in the FB manual and
came across this on page 10-24:
"Lancair flaps are full electric actuated. They are designed to run
from +45 down to -10 up (reflex). Note that the 'faired in position' for
flaps is actually a -7 deg reflex position. ....."
My standard build manual is in storage so I could not compare. It
would appear the intent was to be able to go to -10 degrees after all.
Chris Zavatson
N91CZ
360std
Chris,
today I made a picture during Cruise with Autopilot at 7500ft with
following configuration:
770 kg 40l in header, 20l in each wing (80l total), 75kg and 83kg
for pilot and co.
Flap was on 7° reflex CG 26,20"
My design CG is 22,8 - 30,3 from firewall back,
horizontal was installed - 0.6°
So it looks like if I would add more reflex than 7°, I would need more
down elevator.
So the gain with the higher reflex would be lost with the down
elevator....
Christian
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