Mailing List lml@lancaironline.net Message #50464
From: Bill Hannahan <wfhannahan@yahoo.com>
Sender: <marv@lancaironline.net>
Subject: 360 in a small-tail LNC2?
Date: Sun, 22 Feb 2009 17:36:14 -0500
To: <lml@lancaironline.net>

At 200 kt indicated the angle of attack of the wing and stabilizer will be very small regardless of CG location.

 

Was the counterweight above or below the stabilizer? What was the flap setting?

 

It may indicate a discrepancy between the wing and stabilizer incidence angle.

 


Bill Hannahan


--- On Sat, 2/21/09, Sky2high@aol.com <Sky2high@aol.com> wrote:
From: Sky2high@aol.com <Sky2high@aol.com>
Subject: [LML] Re: 360 in a small-tail LNC2?
To: lml@lancaironline.net
Date: Saturday, February 21, 2009, 6:50 AM

Tom,
 
If, at cruise, you saw the elevator horn much above its faired-in position (down elevator, nose down trim, whatever) then the CG is too far back and the negative lift (downward balancing force) on the horizontal stab had to be reduced.  I.E. You may not have enough forward CG or the negative angle of incidence of the horizontal stab may not be enough. 
 
Remember, Lancair had a long engine mount to compensate for the rearward CG moment caused by adding the big tail.  If I remember correctly, that moved the empty weight CG 1.5 inches forward with no difficulty or even improved handling.
 
Rearward CG is bad even if it is within the design envelope.  Forward CG is bad if you can't flare the airplane when landing although raising the flaps will raise the nose. 
 
Your discomfort at slow flight should be a warning and, indeed, it may be exacerbated by having a rearward  CG.  You really need to know the CG values - such as when does the CG go out of the envelope with only fuel in the header tank and a too light pilot..........
 
Good Luck,
 
Scott Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

In a message dated 2/20/2009 12:51:25 P.M. Central Standard Time, dudewanarace@yahoo.com writes:

Works great.  I have a 400!  I'm sure the rest of small tail group would agree.  Might have to move your center of gravity back. (I need to)  Only thing I can say is that slow flight with full flaps isn't the most comfortable, but now that I am aware of how it handles, doesn't bother me a bit.  My CG is way to far forward I think, so that probably makes the slow flight a little different.

On a side note..   I turned around and looked at the tail the other day while indicating 200KTS.  I could see the elevator counter weight, or almost all of it.  I didn't expect to see that at 200.  Maybe 100..  haha  This leads me to believe that I have a forward center of gravity.  The big engine would explain that.  Once I get the plane on some scales, the only thing I can think of is to move the battery.  My battery is behind the passenger seat.

Has anyone mounted a battery behind the baggage compartment?  Advice?

Thanks
Tom
www.N54SG.com

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