Re: Reflexor


jnmarstall <jnmarstall@...>
 

I have the MAC servor. I set it 1.5 bars up for takeoff and initial
climbout 85-90mph. cruise it is .5 bars up. Landing it is 3.5 bars up
(sorry about that D. Gall)
Jerry

----- Original Message -----
From: "Kelly Poor" <poorkelly@hotmail.com>
To: <Q-LIST@yahoogroups.com>
Sent: Thursday, May 22, 2003 9:37 AM
Subject: RE: [Q-LIST] Re: Reflexor


On my second take off in my Tri-Q I made the mistake of having the refexor
all the way down. The airplane would not lift off. I had to use alot of
back pressure on the stick to lift it off, which I should have not done.
After lift off while holding some serous back pressure to try to keep it
flying I cut the power and came back down with a few bounces. I learned a
lesson though. Part of the Pre takeoff check list is reflexor up. In my
plane the reflexor down is even with the wing, and deflects 3 or 4 degrees
when all the way up. Where the reflexor is set in cruise depends on how
heavy the plane is loaded. With a light load the refexor is set more in
the
upper half of the trave, the heavier it is loaded the more down I need to
set it. I would like to hear what some other Q's relexor travel is, and
where they set it for take off and in cruise conditons. Kelly


From: "David J. Gall" <David@Gall.com>
Reply-To: Q-LIST@yahoogroups.com
To: <Q-LIST@yahoogroups.com>
Subject: RE: [Q-LIST] Re: Reflexor
Date: Thu, 22 May 2003 00:45:26 -0400

Larry Koutz wrote:

Pulling the nose up before TO is what you do on all tricycle
airplanes. You
apply back pressure to the stick, the nose rises to a certain attitude
and
you hold it there with the stick. When the speed is right the
airplane lifts
off. Happens all the time. So does aero braking on planes.
Problem is in the Q-XX with down elevator there is an awful lot
of drag with
the elevator deflected. In addition to that, to actually get the nose
to
rise most pilots will pull in more back pressure than needed then
suddenly
the nose will rise and overshoot takeoff attitude and may lift off
early,
but anyway it IS the start of the COBRA maneuver and I know -that IS
certainly dangerous.
Well, the conventional airplane has the tail in back, so when it rotates
the
tail becomes less effective at pulling the tail down/nose up. This is a
natural limiting effect that is absent from the Tri-Q, and all those
other
tri-geared canard airplanes. Ask any Long-EZE flyer; you have to let off
on
the back pressure once you rotate. The only problem I'm concerned with in
this discussion is the fact that on SOME Tri-Qs, this can't happen until
the
airplane is well past what should have been liftoff speed. On these
planes,
someone has advocated using the reflexor to "help" get the nose up, and I
think that is a dangerous use of the reflexor and that there is a better
solution to be had in fixing the landing gear geometry.

With the elevator deflected the canard is trying to created MORE lift
than
it was designed to lift. With the ailerons reflexed UP the main
wing is less
likely to stall at the same angle of attack No matter what you
say the plane
will not lift off and actually fly unless each lifting surface
provides the
exact amount lift required and the plane doesn't care if the
elevator is up,
down or flushed in or the ailerons are both up, down or flushed in.
"Flaps," whether we call them aileron, elevator, reflexor, or flap, are
all
the same: trailing-edge devices that change the camber of the wing. Flaps
are most commonly known as "high-lift" devices. When you extend the
flaps,
you increase the maximum available coefficient of lift (Cl_max); when you
retract the flaps, you decrease the Cl_max; and when you "reflex" the
flaps,
you decrease the Cl_max even more. Look it up.

Therefore, when you take off with the reflexor TE-up, the Cl_max of the
main
wing is less than it was with the reflexor at neutral. Therefore, in
order
to make whatever Cl is needed to get the airplane off the ground at that
moment, you'll be lifting off with a smaller margin above the stall for
that
main wing. Additionally, since the elevator does not have to be extended
so
far now due to the reflexor "helping" to rotate the plane, you have more
additional elevator available with which to further rotate the airplane
than
if you were taking off with the reflexor neutral.

So, you're right, the airplane will not lift off and actually fly unless
each lifting surface provides the exact amount of lift required, and the
plane doesn't care about the control surface positions. BUT, you'll be
operating with the main wing closer to stall AOA and you'll have a VERY
effective elevator control available to help you accidentally over-rotate
and put you into a main wing stall. Or maybe just a little gust will come
along and start that main wing stall for you. Once the back end drops
out,
look out, buddy!!

I'm not saying that WILL happen, I am saying it MIGHT happen, because we
don't know what the margin is, and because not everybody has the same
reflexor position stops, and on and on. I'm only advocating CAUTION in
using
TE-up reflexor, and I AM saying that there's a better solution than using
the reflexor to address the problem of airplanes that won't rotate for
takeoff in a timely manner.

I know of only one person that had this happen and his ailerons were
reflexed DOWN and he was correcting for a roll on final. He put in
aileron
to correct and the plane rolled the opposite way!
Well, a documented aileron stall! Now we know why the reflexor should not
be
allowed to go TE-down...! That's also a good indication of how heavily
loaded the main wing is at low airspeeds, as per our analysis the other
day.
If it can do this with MORE margin above stall AOA (due to TE-down
reflexor)
then think how close to stall that main wing might be when you use TE-up
reflexor.

People are using it for this purpose -successfully. I recommend it for
landing, trimming, cruise control.
All good uses for a reflexor. Just please don't use it to "help" rotate
for
takeoff.

for takeoff, set it like a trim setting in any other airplane, that is,
set
it for the approximate trim setting that you will need on initial
climb-out
after liftoff. In other words, don't use "extra" nose-up reflexor to
"help"
get the nose up.

If you find yourself needing to do something to get the airplane to
rotate
for liftoff, don't succumb to the temptation to use excess reflexor but
adjust your static ground attitude, instead.

That is RIGHT. I have experience and I know reflexors are effective.
And
they also CORRECTED a badly built airplane and made it flyable.
The ultimate
solution was to CORRECT the flying surface angle of incidence.
They didn't "correct" that badly-built plane, they only made it possible
to
fly it so that you could sort out the real problem of incorrect flying
surface angles of incidence. You said it yourself: "The ultimate solution
was to CORRECT the flying surface angle of incidence;" likewise, the
ultimate solution to fixing the late-rotation problem is to adjust the
landing gear to give a better ground attitude.

Sure, you can get the airplane to fly using the reflexor to make it
rotate,
but I say that this is not to be construed as a desirable standard
operation, only a useful tool to help you diagnose the airplane's
deficiencies during its flight test period. Tho objective of the flight
test
period, of course, is to correct such deficiencies, as you finally got
around to correcting your flying surface incidence angle deficiencies and
stopped flying around with the reflexor up -- what -- 45 degrees? All I'm
saying is that taking off with the "trim" (reflexor ) set to full "up" in
order to get the nosewheel off the ground and then having to re-trim for
climb is unnatural and potentially unsafe, and that there is an "ultimate
solution" in establishing a correct static ground attitude.


I do NOT know that the stall speed is effected at ALL by the
reflexors, only
the attitude of the plane. I have tested this in flight in my
airplane and I
find no significant stall speed change, just attitude. Near the
ground this
may be different but I don't have a long stretch of the Great Salt
Lake
to
test the effects down low.
I wouldn't expect the stall speed to be significantly changed unless the
reflexor were significantly deflected, but I thought I recalled you
saying
at one time that you had observed something. My bad. Apparently I'm
wrong.
However, I can think of several reasons to expect the stall speed to
change
with different positions of the reflexor, not the least being that TE-up
reflexor allows the elevator to be "retracted" like a retracted flap
instead
of extended (deflected TE-down) like an extended flap. And we all know
that
wings with extended flaps (TE-down elevator) have lower stalling speeds
than
wings with their flaps retracted (elevator more "neutral") as would be
observed with the reflexor TE-up. I don't suppose that ground effect
would
make much difference.

I have never had an aft wing stall, that I know of.
I'm just trying to keep it that way. Say, you're not driving a Tri-Q on a
regular basis, anyway! Your plane is a taildragger, and I don't expect
that
you make a habit of taking off with the reflexor "trim" set anywhere
other
than approximately right for climbout, do you?

The reflexor is NOT a band-aid for nosedraggers, it never was. It
WAS
a
band-aid for squirreley taildraggers, that proved to be useful for
inflight
trimming, too.
I don't know that many Tri-qers would support that assertion. I would
certainly want a reflexor if I had a Tri-Q.
Hmmmm, I didn't say the reflexor was not appropriate for Tri-Qs, but
apparently you and Lynn French both took it that way. Sorry, that's not
what
I meant. What I meant was that the reflexor was initially developed for
the
taildragger (Tri-Qs hadn't been invented at that point), and that the
development of the reflexor was initially in response to the
taildragger's
perceived lack of tailwheel authority. It has since proved useful in more
ways and is now widely regarded as a necessity for all Q-2xx's, for which
I
agree! That doesn't negate its potential for harm if used incorrectly,
either.

Now it seems that some advocate its use as everything, to the
point of suggesting that it be geared into the control stick or used
in
place of the front-wing elevators. ARRGH!
Who has said this- might be worth a try!
Hey, Rutan effectively did it on the Ams/Oil racer when he geared the
T-tail
to the control stick. It worked for them, but we don't have the benefit
of
their expertise. Anyhow, I bet they had a separate trim system and that
they
didn't take off with the trim set to full up with the intention of
suddenly
re-trimming as soon as they broke ground.

The current discussion centers around the suggestion to use the
reflexor
to
"fix" a tri-Q that won't rotate for takeoff.
This is not a "fix", just a technique I used to get a "new 70
something
pilot wanta be" to see that his plane (a Tri-DFly) needs to be
rotated to a
certain attitude and held there until the plane is ready to fly off.
He
couldn't handle the quick nose rotation at about takeoff speed. I also
showed him the effectiveness of the reflexor.
Okay, apples and oranges? I'm trying to discuss apples (Tri-Qs that won't
rotate for takeoff) and you're talking oranges (a teaching demonstration
in
an airplane that presumably did not "need" extra help rotating for
liftoff).

I stand on my conviction that the CORRECT solution to this problem is
to
either lengthen the nose gear or
shorten the main gear (or both) and, maybe, move the main gear
forward.

How come regular tri geared plane designers don't use this design
technique.
They don't have to! They generally aren't elevator limited like canards
are.
The conventional airplane's stabilizer/elevator is most effective at
lifting
the nose when it is at its most negative angle (nose down), and it loses
authority as the airplane rotates nose up. The canard's
stabilizer/elevator
(canard) is at its LEAST effective for lifting the nose when the airplane
is
nose down, and it becomes MORE effective as the airplane rotates nose up.
Hence my assertion from the get-go of this whole discussion that the
correct
fix for an airplane that rotates late is to make the airplane sit more
nose-up by altering the landing gear. A more nose-up stance will make the
canard/elevator initially more effective at lifting the nose and allow
the
nose to be lifted at a lower speed/sooner during the takeoff roll.

That is why we are supposed to test each new airplane, because
each plane IS
unique, even though they are similar.
Yessir!

I believe that a properly set up Tri-Q should be able to high-speed
taxi
on
the main gear using elevator alone. It will probably not be able to
initiate
nose-wheel liftoff as early in the takeoff run as a
conventional airplane,
but a positive rotation to takeoff attitude should be available
well below
actual liftoff speed. This is a simple result of the fact that the
main
gear
is ahead of the main wing.
That IS my point exactly! A "properly set up" Tri-Q may not need
a reflexor,
but a "new plane" certainly might and they aren't that hard to put in.
I
think flyers of these planes would put them in again- you might
consider
a
reflexor too!
Ummm, I am not advocating getting rid of reflexors or not having them,
just
not over-USING them for stuff that is better addressed in other ways.
Sure,
in a new plane you can take the test-pilot risk (if you know what you're
looking for) and use the reflexor to make up for a deficiency long enough
to
diagnose and correct that deficiency. Just let's not make the temporary
use
into a standard operating procedure and ignore the opportunity to
actually
correct the inadequacy.


David J. Gall
I'm tired, so I'm not proof-reading tonight. Any errors are the fault of
my
computer not being smart enough to know what I'm trying to say wighout me
acutally hvaing to yas ti. :-)
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