Conference vmszoo::rc

1299.0. "Aircraft Flight Trim Chart" by SALEM::SAFFER () Thu Feb 28 1991 13:29

    
    The following trim chart was taken from the instruction manual for a
    Great Planes CAP 21 kit I just purchased.  Any feedback on the info, as
    far as accuracy, correction methods, etc.?
    
    
    {copied without permission...}
    
TRIM	   MANEUVER		OBSERVATION		CORRECTIONS
FEATURE
    -------------------------------------------------------------------------
CONTROL	   Fly general circles	 Try for hands		Readjust linkages so
CENTERING  and random maneuvers	 off straight		that Tx trims are
				 and level flight	centered

CONTROL	   Random maneuvers	 A. Too sensitive,	If A, change linkages
THROWS				    jerky		to reduce throws
				 B. Not sufficient	If B, increase throws

ENGINE	   From straight	 A. Aircraft continues	If A, trim is OK
THRUST	   flight, chop		    level path
ANGLE	   throttle quickly	 B. Plane pitches nose 	If B, decrease down-
*1				    up			thrust
				 C. Plane pitches nose	If C, increase down-
				    down		thrust

CENTER	   From level flight	 A. Continues in bank	If A, trim is good
OF	   roll to 45-degree	    moderate distance
GRAVITY	   bank and neutralize	 B. Nose pitches up	If B, add nose weight
	   controls		 C. Nose drops		If C, remove nose
							weight

SPLIT	   Into wind, pull open	 A. Wings are level	If A, trim is fine
ELEVATORS  loops, using only	 B. Plane tends towards	If B, add weight to
{also YAW  elevator.  Repeat	    outside when right	right wing, or add
 and CG}   with outside loops	    side up, and to	right rudder
	   to inverted entry	    inside when inverted
				 C. Plane goes in on	If C, add weight to
				    regular loops,	left wing, or add
				    out on inverted	left rudder
				 D. Plane goes out	If D, raise right half
				    on both types of	of elevator (or lower
				    loops		left)
				 E. Plane goes in on	If E, raise left half
				    both types of loops	of elevator (or lower
							right)

YAW	   Into wind, do open	 A. Wings are level	If A, trim is correct
*2	   loops, using only	    throughout
	   elevator.  Repeat	 B. Yaws to right in	If B, add left rudder
	   tests doing outside	    both in/out loops	trim
	   loops from inverted	 C. Yaws to left in 	If C, add right rudder
	   entry		    both in/out loops	trim
				 D. Yaws right on	If D, add left aileron
				    inside, left on	trim
				    outside loops
				 E. Yaws left on 	If E, add right aileron
				    inside, right on	trim
				    outside loops

LATERAL	   Into wind, do tight	 A. Wings are level	If A, trim is correct
BALANCE	   inside loops, or	    and plane falls to
	   make straight up	    either side		
	   climbs into Hammer-	    randomly in Hammer.
	   heads.  Do same from	 B. Falls off to left	If B, add weight to
	   inverted entry	    in both inside and	right wing tip
				    outside loops
				 C. Falls off to right	If C, add weight to
				    in both loops.  	left wing tip
				    Worsens as loops	
				    tighten
				 D. Falls off in	If D, change aileron
				    opposite directions	trim  *3
				    on inside and
				    outside loops

AILERON	   With wings level,	 A. Climb continues	If A, trim is correct
RIGGING	   pull to vertical	    along same path	
	   climb and neutralize	 B. Nose tends to go	If B, raise both
	   controls		    inside loop		ailerons slightly
				 C. Nose tends to go	If C, lower both
				    outside loop	ailerons slightly

WING	   Knife edge flight	 A. Plane tends to 	If A, reduce wing
INCIDENCE			    veer in nose up	incidence
				    direction
				 B. Plane tends to	If B, increase wing
				    veer in nose down	incidence
				    direction

*1: Engine thrust angle and C.G. interact; check both
*2: Yaw and lateral balance produce similar symptoms.  Note that fin may
    be crooked.  Right and left references are from the plane's vantage point
*3: Ailerons cannot always be trimmed without sealing the hinge gap