REFLECTOR: elevator range - increased drag

Mon Mar 20 13:27:14 CST 2006

John,

I saw the discussion on the Canard list.  I couldn't tell you what the CL 
max is for Velocities.  I'd guess it is dependent on the individual 
airframe, nose loading, etc.

I haven't run that test.  I was just trying to say, you'll need the down 
travel - but the listed up travel isn't as important.

Ron

----- Original Message ----- 
From: "John Tvedte" <JohnT at comp-sol.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Monday, March 20, 2006 1:07 PM
Subject: RE: REFLECTOR: elevator range - increased drag

> Ron,
>
> In our case with have 30 deg down - what we are wondering though is what 
> down elevator results in max. lift - CL max -
>
> In our case - mechanically we are limited to 30 deg down - so - will being 
> beyond 28 degs result in drag
>
> From Chapter 3 (XL) NOTE: wording - minimum acceptable
> The minimum acceptable deflection is as follows:
>
> • Up Elevator: 24 degrees min (preferably up to 26 degrees)
>
> • Down Elevator: 28 degrees (approximately 2-3/4” deflection from neutral)
>
> ------------------------
>
> From Chapter 10 (XL) NOTE: wording - least
>
> Full elevator deflection results in at least 26 degree trailing edge down 
> elevator travel
>
> and 23 degree trailing edge up elevator travel.
>
>
> John
>
> -----Original Message----- 
> From: reflector-bounces at tvbf.org on behalf of Ron Brown
> Sent: Mon 3/20/2006 11:56 AM
> To: Velocity Aircraft Owners and Builders list
> Cc:
> Subject: Re: REFLECTOR: elevator range - increased drag
>
>
>
> You'll need the recommended down travel.  Up is less important unless you
> are planning to fly upside down - not recommended.  Bottom line, make sure
> you have the down travel.
>
> Ronnie
>
> ----- Original Message -----
> From: "John Tvedte" <JohnT at comp-sol.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Monday, March 20, 2006 12:28 PM
> Subject: RE: REFLECTOR: elevator range - increased drag
>
>
> > Keith,
> >
> > Exactly -
> >
> > Here are some inconsistant #'s in the manuals (for XL).
> >
> > Chapter 3 - states 24-26 deg. up, and 28 deg. down. total - 52-54 deg.
> > http://www.velocityaircraft.com/manuals/03_XLG.PDF
> > <http://www.velocityaircraft.com/manuals/03_XLG.PDF>
> >
> > Chapter 10 - states 23 deg. up and at least 26 deg. down - so total of 
> > at
> > least 49 deg.
> > http://www.velocityaircraft.com/manuals/10_XLR.PDF
> > <http://www.velocityaircraft.com/manuals/10_XLR.PDF>
> >
> > John
> >
> > -----Original Message-----
> > From: reflector-bounces at tvbf.org on behalf of Keith Hallsten
> > Sent: Thu 3/16/2006 11:51 AM
> > To: 'Velocity Aircraft Owners and Builders list'
> > Cc:
> > Subject: RE: REFLECTOR: elevator range - increased drag
> >
> >
> >
> > John,
> >
> >
> >
> > Yes, this was jus discussed within the last few days on the Canard
> > Aviators list with respect to the Long-EZ.  Excess down elevator will 
> > act
> > as a spoiler.  The elevator should have a stop so that maximum down 
> > travel
> > gives the canard-elevator system the maximum lift coefficient.
> > Unfortunately, I don’t know exactly what elevator deflection gives CL 
> > max
> > with the Velocity canard airfoil.
> >
> >
> >
> > Here’s an except from the “Canard Pusher” newsletter for Rutan Aircraft
> > Factory planes:
> >
> >
> >
> > CAUTION  CP 48
> > ELEVATOR CONTROL STOP POSITION.  This applies to VariEzes as well as
> > Long-EZs using the original GU canard (Roncz 1145MS not affected).  The
> > design philosophy of the EZ canard type airplane calls for the canard
> > airfoil to develop maximum lift coefficient (CLmax) at full aft stick.
> > Thus the elevator trailing edge down (nose up command) stop must be set
> > correctly.  On an accurately built GU canard/elevator, this will
> > usually be at approximately 22 degrees (trailing edge down).
> >
> > Recently, we have heard from a few builders, both VariEze and Long-EZ,
> > who have noticed stall characteristics that were not "per the
> > handbook".  In all cases, the cause was the elevator nose up stop set
> > to allow too much elevator travel.  If you have noticed any of the
> > following symptoms, check that you have no more than 22 degrees to 22-
> > 1/2 degrees trailing edge down travel on your elevator.
> >
> > 1)  Perform a 1-'g', wings level, straight ahead stall with sufficient
> > power to maintain level flight.  Slowly pull the control stick back to
> > full aft stick.  This should result in a nose high attitude with a
> > "pitch bucking" that can vary from hardly noticeable to quite vigorous,
> > perhaps "one buck" per second, with a deck angle change of several
> > degrees per "buck".  This is normal and will vary depending on the cg.
> > If, however, you notice a strong stall break (canard stalls) and the
> > nose comes down through the horizon until you are in a stable shallow
> > dive, even though you are still holding full aft stick, the speed may
> > build up to over 100 KIAS before the EZ begins to climb again.  This
> > very long period pitch "bucking" can be as long as 30 seconds per cycle
> > and is indicative of too much elevator trailing edge down travel.  You
> > can verify this by releasing back pressure on the stick during the nose
> > down phase of the cycle and gently raising the elevator trailing edge
> > perhaps 1/8" at a time.
> >
> > This should allow the canard to develop more lift and pitch the nose
> > up.  Try to determine by experimenting with elevator position, where
> > CLmax is, then set your elevator stop at that position.
> >
> > 2)  Another classic symptom may be noticed during a take off.  At full
> > aft stick, it may take a longer take-off roll to lift off that it does
> > at, say, slightly forward with the stick.  If you have ever noticed
> > this, it should be corrected.  Under certain circumstances, this could
> > become a serious problem.  A Long-EZ builder/flyer in Alaska,
> > attempting to take off on a rather short runway, discovered that he was
> > rapidly approaching the end of the runway and, even though he was
> > holding the stick all the way back, was not rotating.  Realizing he was
> > not going to make it, he backed off from the full aft stick stop and,
> > to his surprise, the airplane literally jumped into the air!  Again,
> > his trailing edge down elevator stop was set for too much travel.  This
> > same scenario has also been reported to us by a San Diego VariEze
> > pilot.
> >
> > What causes this?  If the elevator stop is set so that at full aft
> > stick your canard can develop its maximum possible lift, this will
> > result in the lowest possible rotation speed for take-off and a good,
> > clean canard stall (limiting the main wing angle of attack) or classic
> > "per the book" stall at full aft stick in flight.  If, however, you
> > have set your elevator stop for too much travel (perhaps you thought
> > you could lower your rotation speed?!!) what happens is that you are
> > now on the "back side" of the lift curve, lift is less than maximum,
> > and the elevator is creating lots of drag.  The result may be running
> > off the end of the runway.  Keep in mind that this condition could be
> > aggravated even further if it were raining.
> >
> >
> >
> > Keith Hallsten
> >
> >
> >
> >
> >
> >
> >  _____
> >
> >
> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> > Behalf Of John Tvedte
> > Sent: Thursday, March 16, 2006 8:37 AM
> > To: Velocity Aircraft Owners and Builders list
> > Subject: REFLECTOR: elevator range - increased drag
> >
> >
> >
> > All,
> >
> >
> >
> > Factory Spec (minimum) is for 26 degrees down and 23 degrees up or 49
> > degrees total.
> >
> >
> >
> > Our Elevator has 30 degrees down and 28 degrees up or 58 degrees total.
> >
> >
> >
> > I am wondering if anyone knows if having too much elevator range can
> > result in getting the canard in the "back side" of the lift curve, lift 
> > is
> > less than maximum and the elevator is creating lots of drag?
> >
> >
> >
> > Wondering if I can get a survey of what people are getting for their 
> > down
> > and up elevator travel - flying airplanes greatly appreciated?
> >
> >
> >
> > Thanks,
> >
> >
> >
> > John
> >
> >
>
>
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>
>
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