Jim, et al,
Yes, that would seem to be the next check since there are at least a few
small tail Lancairs with CG similarities but quite different elevator
effectiveness. I propose the following (and I will report on mine the next
chance I get).
1. Level the longerons in both the lateral and fore to aft directions
(even if you must jack up the aircraft).
2. Clamp the elevator horns to line up with the horizontal stab (neutral
position).
3. Place a strip of blue tape 12" inboard and parallel to the cutout
in the horzontal stab for the elevator horn (parallel to the aircraft center
line).
4. On the tape, mark the middle of the leading edge and the trailing
edge.
5. Construct a short (4 to 5 feet) water level tubing and measure the water
level difference between the middle of the leading edge and the middle of
the trailing edge at a chord line 12" in from the cutout in the horizontal stab
for the elevator horn. Call this A.
4. Measure the distance from the leading edge to the trailing edge (the
chord line defined in #3). Call this B.
5. Calculate and report the angle represented by the tangent of
(A/B). It should be a small negative angle (<1 degree) where the water
level showed that the leading edge was lower than the trailing edge.
When I installed the horizontal stab, there was a form placed on the
centerline in order to set the negative angle of incidence. Lancair
recommended that the angle was to be between -0.5 and -1.0 degrees. My AOI was
measured during building at -0.9 degrees. At cruise speeds my anecdotal
observation out the rear window is that the horn is virtually faired in with the
horizontal stab.
Maybe a difference in the angle of incidence can help explain the
difference in elevator effectiveness.
Scott Krueger
In a message dated 10/2/2008 8:13:08 P.M. Central Daylight Time,
panelmaker@earthlink.net writes:
Measure
the AOA of the horizontal stabilizer. Compare that to factory book
specs. A
high angle would serve to reduce elevator effectiveness on the
up
side.
Jim
-----Original Message-----
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Lorn
H Olsen
Sent:
Thursday, October 02, 2008 8:33 AM
To: lml@lancaironline.net
Subject:
[LML] Re: Small tail vs. large tail
Bill,
Elevator up and down
are to book specifications. Some time in the next
couple of months,
I will try to stop by when you are home and we can
do some
inspecting.
I would like to know why our planes fly so differently (if
they really
do).
Lorn