lml@lancaironline.net Mailing List Archive

Bill,

Having spent years working with low speed aerodynamics and flow strips (Stall strips), I must add that the installation of those strips are very critical and Certificated manufacturers use very precise template's to be sure that they are properly positioned. Otherwise it takes several test flights to get the strips positioned properly. Properly installed the stall speed increase should be only about 1 to 2 knots. What you are doing is tripping the stall inboard just a little early. Ideally you want to trip the stall 1 knot early.

The second positioning problem is to adjust the left and right strip to achieve symmetrical stall progression. You want no tendency to roll left or right. If the wing has bad problems this may take more that 1 knot increase to repair. Usually in the flight test phase it is best to tape the strips on, due to the need to move them to achieve a satisfactory stall with minimum impact on the stall speed. Frequently movement of 1/16 of a inch up or down will make a very noticeable change.

They will only improve the characteristics if the problem is flow addressable. For example, an asymmetrical stall progression Most problems on the LIV can be improved with proper application of strips.

Jack Webb

BSAE

Years of Experimental flight test In GA.

----- Original Message ----
From: Bill Harrelson <5zq@cox.net>
To: lml@lancaironline.net
Sent: Monday, August 25, 2008 6:14:41 PM
Subject: [LML] Re: some MORE thoughts on accidents

Paul,

Thanks for sharing your stall experience with us. In the IVs that I have flown I have found very similar numbers and exactly the same stalling characteristics that you describe. I think that it is important for folks to understand that stall strips increase stall WARNING, but don't necessarily improve stall characteristics.

I do have a question on one statement that you made. You say "Remember your stall margin is increased base to final to touchdown because you are descending and are therefore at less than 1 G." Perhaps I am misunderstanding what you are trying to say here but I believe that you are less than 1 G during the TRANSITION from level to descending flight but that once established in a constant rate descent (or climb for that matter) you remain at 1 G and therefore, your stall margin would be the same. Is there something I'm missing here? Thanks.

Bill Harrelson

N5ZQ 320 1,550 hrs

N6ZQ IV under construction