Mailing List lml@lancaironline.net Message #40329
From: <PTACKABURY@aol.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] stall strip survey (IVP)
Date: Wed, 28 Feb 2007 00:23:56 -0500
To: <lml@lancaironline.net>
I too am just finishing my 40 hours of phase 1 on Lancair IV N94PT (no pressure, TSIO-550).  I started with 10 inch long stall strips (triangles of plastic about 3/8 inch on a side taped to the leading edge) mounted 15 inches outboard of the wing/fuse joint.  They were mounted at the leading edge stagnation point (as best as Charlie Kohler could eyeball it), eg at the tangent point of a vertical line with the plane level.  I took some stall data in this config and then removed the strips and repeated.  With the strips I had about 5 KIAS of warning and never actually experienced a developed stall as I initiated recovery at the buffet.  Without the strips I experienced an abrupt right bank of about 45 to 60 degrees.  Forward stick, a little aileron against the bank and the recovery was positive and immediate with a few hundred feet of altitude loss.  There was no aerodynamic warning prior to the stall, at least none that was useful.  Power was idle, ball centered, CG forward for all stall tests.  I did both 1 G and accelerated stalls, clean and configured, light (~2600#) and moderate (~2850#) weight.  The speeds varied some but the characteristics were consistent.
First indication of buffet, 1 G:
without strips, light:
    Vs: 73 KIAS, Vso: 68 KIAS
without strips, moderate:
    Vs: 77 KIAS, Vso: 72 KIAS
with strips, light:
    Vs: 78 KIAS, Vso: 70 KIAS
I have set my Chelton warning (Vs) at 80 KIAS so it doesn't always come on at touch down but does provide a reasonable comfort zone prior to stall.  I have not decided whether I am going to reinstall the strips prior to paint.
regards, paul




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