Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Fri, 08 Aug 2003 21:19:46 -0400
Message-ID: <redirect-2515547@logan.com>
From: James Frantz <LFrantz@compuserve.com>
Subject: Rotation IAS and attitude
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>Some factory clarification here would be welcome.  =

Regards, Bill Hogarty<

Good request but regardless of the factory answer it is worth
understanding--

If you rotate to a pitch attitude and then wait till the aircraft flies o=
ff
you are asking for trouble.  Here's just one of many reasons why:

Let's assume you like to rotate to a pitch attitude of 8 degrees and wait=

till the aircraft flies off.  This may work nicely at low density altitud=
e
airports and results in the desired climb IAS.  However if you rotate to
the 8 degrees attitude at a high density altitude airport, your AOA may b=
e
so high (and close to the critical AOA -- stall-- ) that the aircraft wil=
l
take longer to accelerate and fly out of ground effect. In this scenario,=

even light turbulence or vortices could spell disaster!  This is called
taking off way behind the power curve, speed stability curve, reverse
command or as I like to call it "ON THE DARK SIDE."

When I taught mountain flying, it was an emphasis item to rotate to a low=
er
pitch attitude on T/O at high density altitude airports as compared to th=
e
lower density altitude airports we usually depart.  We always want to
rotate to the same AOA which does not equate to the same pitch attitude. =
 =


The folks like Bill, Brent and others, that think in terms of a Vr that
increases with increasing GWs and a rotation attitude that lowers with
increasing density altitudes are the safer flyers. Early rotations are a
high risk maneuver and are used on soft field T/Os only.  This issue is a=

technical one, but I do go over it briefly in our "Flying safe with AOA"
forums given at Oshkosh and Sun'n Fun.

There are as many T/O techniques as there are instructiors, but only a fe=
w
are based on sound aerodynamics. I'm very aware of the poor T/O technique=
s
taught by one former Lancair IV approved instructor.  If your technique
includes the early rotation, as fun as it is, keep in mind it is a higher=

risk maneuver with no advantages excepting soft field departures. =


James B. Frantz
Proprietary Software Systems, Inc.
www.angle-of-attack.com
LFrantz@compuserve.com
(952) 474-4154