Private Pilot Flight Training and Instruction
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Trimming Cessnas (instructor notes)
Cessna has engineered its trim so that certain changes in trim
can be anticipated to correspond to flight path changes in different
models. For example, in the C-150 from level cruise abeam the
numbers, a power reduction to 1500 can be trimmed off by holding
heading and altitude to 60 knots. It will take three full top-button
to the full travel bottom to do this. Pinching between the buttons
will leave you short. 10 degrees of flaps while holding sixty
with the yoke can be re-trimmed to a 60 knot descent by undoing
one of the previous three turns. Bottom button all the way to
the top. Let go and if the nose begins to change pitch make the
slight trim adjustment required. 10 more degrees of flap while
holding 60 knots can be locked there by taking off another full
turn of trim. Full flaps while holding sixty can be set by taking
off the last turn. You, every student and pilot, should learn
a count or feel system for applying and removing flaps. Learn
to use the flaps without looking at the indicator during application.
A four count works well for 10 degrees on a Cessna. Flaps that
have indent settings will work only if calibrated for trim movement.
Cessna ruined a terrific engineering design when they build
the C-152. The trim/flap ratios of the C-152 are there but not
at 1 to 1. You can work out the procedure for stabilized airspeeds
by using the suggested procedure of the C-150 and keeping track
of the amount of trim required for each ten degrees of flap. It
can be done but the neat engineering isn't there. Abeam the numbers
the C-152's power should be set at 1600. By the 'key' position
it will be at 1500.
Written by Gene Whitt
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