Sender: <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Wed, 28 Feb 2007 11:46:33 -0500
Message-ID: <redirect-1874113@logan.com>
Received-SPF: pass
 receiver=logan.com; client-ip=166.102.165.157; envelope-from=airmale@windstream.net
From: "JHWebb" <airmale@windstream.net>
References: <list-1873155@logan.com>
In-Reply-To: <list-1873155@logan.com>
Subject: RE: [LML] Re: stall strip survey (IVP)
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Thread-Index: AcdbA4uwCEgnNeEQRiyKZ3miqOFbWgARhqgA
Content-Language: en-us

?? 

  I have done thousands and thousands of stalls for a manufacturer to solve
handling problems as you mentioned. I have also solved similar handling
problems with the Lancair series. Stall strips, Aero engineers like to call
them flow strips, can be used to solve roll off problems at or slightly
before the stall. 
	Congratulations on improving the roll problem but you have not
solved the problem properly. Flow strips can improve, when properly
designed, handling problems at the stall. The goal is to improve the
handling qualities without significantly changing the stall speed. Your
change in stall speed is excessive. The increase should be on the order of
1-3 kts. 
	Normally the problems that one wants to solve are caused by non
symmetry from the left to right surfaces. This can be caused by an angle of
incidence problem or airfoil contour dissymmetrys from side to side. The
most common problem in the Lancair series is an angle of incidence problem.
This can be fixed by changing the angle of incidence or flow strips.
Changing the angle of incidence will improve the overall performance. Adding
flow strips will improve the stall handling problems but you still have
asymmetrical lift which impacts performance over the whole operating speed
range. This typically requires a larger aileron trim tab and more trimming
while flying the airplane.
	You don't have regulations to deal with that specify a maximum speed
for the stall so you are free to do as you please but remember that a lower
stall speed makes for shorter landings and safer emergency landings plus too
high a stall speed caused by improperly positioned flow strips leads to
earlier high speed stalls and requirements for higher approach speed. 
	The flow strip should add a prestall warning buffet and reduce the
rapidity of a rapid spanwise stall progression asymmetrically. So there two
design requirements at least. The principle items are length of the strip
and the positioning along the leading edge both vertically and spanwise. You
don't want the flow strip to be too large because you are in the case of the
Lancair trying to improve the stall progression. A 12.5 inch strip on both
sides is probably too long if your goal is to improve the symmetry of the
stall. In this arena tufting can tell you a lot. 
	Summarizing I would recommend that you address the problem to
determine if you have an AofI or contour problem. If it is AofI I recommend
that you fix that as this is most efficient. If your probem has its roots in
contour you are going to either rebuild the bad wing (big Job) or use flow
strips and live with it.

If you have specific questions don't hesitate to respond

Jack Webb
L360, LIV 
Aerospace Engineer BSAE 
FAA Designated Check airman for C421, C404 & C310
ATP, CFI Airplanes & Instruments, Multi, & Sea
Numerous Jet Type Ratings Both GA and Airlines
Experienced Experimental Test Pilot both multi and single engine aircraft
Former Chief Engineering Test Pilot for a Major Manufacturer
Ohio
                              BUFFET      STALL       COMMENTS
>             FLAPS FULL      NONE        61 KIAS     60 R
>
>
>
>   INDICATED STALL SPEED AT 2700 LBS (12.5" STRIPS 7/16" HI, ELEV 18 DEG):
>
>             FLAPS FULL      76 KIAS     75 KIAS     + - 5 DEG
>
>