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I have a tendency to give NASA reports more credibility . . . even if
they do not reflect EXACTLY some other implementation.
Adding flaps is little different from adding camber to a symmetrical wing.
It does increase the coefficient of lift . . . as much as a factor of two in
some cases.
. . . and when the added camber (too much flap) creates more turbulence
than redirected air flow, you get more drag vs. more lift . . . usually some
measure of both.
That's what sloted flaps are all about, to minimize the added
drag when extended.
But keep in mind that even if you do get a 2 times coefficient of lift with
flaps, your air speed can only be reduced to 0.7 (lift is proportional to
the square of speed)
Ref: Theory of Wing Sections gives good detail on many wing shapes and the
effect of flaps and pitching moments.
Wolfgang
----- Original Message -----
Sent: Monday, April 16, 2012 8:55
PM
Subject: Re: [LML] Fw: L320 flap
setting
Wolfgang,
Regardless of what the NASA report says, they never flew the wing as
implemented by Lancair. Extension of the flap more than a few degrees
beyond 0 does little for lift. The pitching moment does change the
attitude, but does not significantly change the stall speed (a few knots is
not significant). The drag addition is significant. The AOA is
another story. While the attitude changes with flap extension, the AOA
is still high and slower speeds just brings one closer to a stall, thus
reducing margins to take care of loss of pilot attention, wind shear,
distractions and anything that leads to mis-application of up elevator
with pitch sensitive controls. It is very easy to reach critical AOA at
slow speeds, with or without flaps..............
Scott Krueger
In a message dated 4/16/2012 7:20:08 A.M. Central Daylight Time,
Wolfgang@MiCom.net writes:
-7 to -10 isn't going to make much difference
in flight. If the latest manual says to use -7 then go for it.
The purpose of reflex flaps is to reduce drag
(lets you go faster) while giving up some lift coefficient. At higher speeds
you don't need that extra lift coefficient.
Reflex will also move the center of lift
forward causing a nose up force affecting the trim needs.
For landing, you give extra flap to increase
the lift coefficient (and the drag) so you can go slower without falling out
of the sky.
See attached file for more
details.
Wolfgang
----- Original Message -----
Sent: Saturday, April 14, 2012 12:01 AM
Subject: L320 flap setting
I have the exact concerns
reported by Rob Stevens in Australia. Since the manual is vague on
cruise flap settings, can some experienced L320-360 fliers help us with what
is the best cruise settings? Is it -7deg. , -10deg., or somewhere
else. Since construction variances can create different “faired-in
positions”, is there an angle which can be measured from the top or bottom
wing surface? Can anyone explain the aerodynamic reasons for reflexed
flaps? Rob and I need help!
Ed Gray Dallas L360
N77ZG XP360 Silver Hawk injection MT 3 blade prop Dual Dynon Skyview
SL30
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