On Sun, 14 Sep 2003 23:53:18 +0000, Dave Hyde wrote:

Kevin Horton wrote:

Just another example of the errors in indicated airspeeds at high
angles of attack.

You're more generous than I. Performance numbers, particularly at low
speed/high AOA, presented in terms of *indicated* airspeed are useless.

Dave 'position error' Hyde


Yeah, it is amazing how many people don't understand that. Up here in
Canada we have a class of aircraft called Advanced-Ultralights. Sort of a
Piper Cub class of aircraft. The responsibility for the design standards
was handed to the Transport Canada Maintenance and Manufacturing folks
(i.e. A&Ps). I think the powers that be figured the folks who are
responsible for all the Type Certificated aircraft design standards (i.e.
Aircraft Certification) were philisophically incapable of writing a
"simple" design standard. Anyway, the Advanced-Ultralight design
standards require a stall speed of 39 kt Indicated Airspeed or less.
Indicated Airspeed. Amazing.

I betcha I could get a 747 to stall at 39 KIAS if you let me mess around
with the location of the static ports and the locatation and orientation
of the pitot tube.

When I was working on the Diamond DA-20-C1 program, Diamond spent a long
time trying to fine tune the pitot-static system. They had a good system
on the DV-20, but they had made a change in the spar design which forced
them to move the pitot-static tube. They decided on a location and then
messed around with the angle on the bottom of the Piper type pitot-static
tube. One of the variations they tested indicated about 10 kt low at the
stall and about 20 kt high in cruise. We joked about selling that
pitot-static tube as a high-performance option.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/