PPRuNe Forums - View Single Post - Trim only sets AoA
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Old 18th Feb 2020, 03:26
  #13 (permalink)  
gums
 
Join Date: Jun 2009
Location: florida
Age: 81
Posts: 1,610
Received 55 Likes on 16 Posts
Salute!

@TCASBLUE , sorry we all got away from the basic trim question. But a lotta things have changed since those days of yore when I and many others here flew simple planes with simple control surfaces connected to simple cockpit control doofers - sticks, wheels, levers, yokes, etc.

Your basic answer is YES !!! Pitch trim results in an AoA, and that determines the induced drag component of the equation. And thousands of nasal radiators flew millions of landings aboard moving runways using power to control rate of descent, unlike most Air Force folks that "pointed" and used throttle to control speed. In some planes as I flew in mid seventies like the A-7, the thing was very stable with AoA, and tho I landed on concrete it was easy to trim for a speed/AoA, and use throttle to nail the descent rate on approach. The Viper control law with gear down was heavily biased for AoA, but still had the gee command base law. Nevertheless, I could use the trim for AoA and power for descent rate.

In all fairness for the non-FBW folks, and remember that all FBW planes have variations of the control laws. The Viper pitch trim was purely gee unless gear was down, and even then it was gee cmd with heavy AoA and pitch rate bias. The 'bus pitch laws have more stuff cranked into it, but the folks I have talked with say that moving from the Viper to the 'bus was real easy.

Great thread, folks.

Gums ends...

Last edited by gums; 18th Feb 2020 at 03:32. Reason: added verbiage
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