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Feature Article: Trim Exercises (Instructor Notes)
To teach the effectiveness of trim try the following exercise.
The instructor should demonstrate how to hold the nose in one
fixed position while the student varies the trim wheel for several
turns in each direction. From level cruise, have the student lock
his left elbow on the door. First the instructor varies the trim
up and down while the student holds the nose in a fixed position
against all pressure. Then let the student move the trim. This
clearly shows the control pressures as affected by trim. The function
of trim on control pressure should be shown on initial climb-out
on the very first lesson. Skill in moving the trim and keeping
track of these movements is an essential skill for what is to
An additional exercise, once some skill in leveling off is acquired,
is to have the student trim the plane for level flight. Then watch
the nose attitude change as the arms are held forward or back
over the head. Show the student that, in a correctly trimmed aircraft,
even head movement will have an effect. This is a good reason
not to keep sectionals where you must look down to read them.
Move the sectionals up to panel level. Further, if the plane is
placed into a 30 degree bank with about 2/3 if a trim down (direction
of wheel movement) the aircraft maintain both bank and altitude.
These are good confidence maneuvers and illustrations of the aircraft
stability and should be used to encourage the student to maintain
a light, trim sensitive, touch on the controls. The student should
be trained to keep track of trim turns, the indicator position,
and verbalize trim movements.
The next element in maintaining speed is knowing where the trim
is, in the first place, and knowing how much movement is required
for each power setting. From a hands-off trimmed climb at 60 knots,
the C-150 will be level with a full finger-tip trim turn of the
trim wheel bottom to top. The C-172 takes one and a third turns.
If you pinch the wheel you will always come up short. Some fine
adjustment may be needed for hands-off level flight but you will
be very close. To initiate the speed reduction required at the
numbers for landing, the trim is moved with full finger-tip turns
top to bottom three times while holding heading and altitude.
The C-150 is now hands off at 60 knots and the C-172 is hands
off at 70 knots.
Because of patent laws the nose gear geometry of different
manufacturers was forced to develop different mechanisms for flaps,
gear, and trim. Pipers trim differently, the addition of flaps
changes attitude and airspeed without requiring much trim change.
Cessnas require trim change for changes in airspeed and flaps.
The same factors exist in both cases.It is the interrelationships
between the factors that require pilots to adapt their skill to
the design requirements. The finger tip technique that works so
well on the Cessna must be changed to the pinch and flip, palm
roll, and electric assist of the Piper. In my mind, the greatest
skill difference in making manufacturer type transition lies in
the use of trim.
Last Modified May 27, ©2017 TAGE.COM