BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

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AFMAN 11-217V1 3 JANUARY 2005
3.3.3. Power Control (Figure 3.2).
3.3.3.1. Proper power control. Proper power control results from the ability to
smoothly establish or maintain desired airspeeds and altitudes in coordination with
attitude changes. Power changes are made by collective pitch adjustments and
reference to the power indicator. Power indicators are not usually affected by such
factors as turbulence, improper trim, or inadvertent control pressures.
3.3.3.2. Collective Inputs. From experience in your aircraft, you know
approximately how far to move the collective to change the power a given amount.
Therefore, you can make power changes primarily by collective movement and then
crosscheck the indicator to establish a more precise setting. The key is to avoid over
fixation on the indicator while setting the power. A knowledge of power settings for
various flight conditions will help prevent over controlling power.
3.3.4. Trim Techniques. The inherent instability of helicopters requires the pilot to trim
the aircraft accurately in order to reduce the workload to an acceptable level.
3.3.4.1. Independent trim systems. For those helicopters equipped with independent
trim systems, trimming nose up/down, lateral right/left planes are relatively simple.
Small changes are made in the desired direction until the control pressures are
neutralized and the aircraft maintains a relatively stable flight path.
3.3.4.2. Force trim systems. For those helicopters equipped with a force trim system,
the ability to trim the aircraft accurately is somewhat difficult and comes only with
experience. Depressing the force trim button releases all trim axes simultaneously.
The pilot must ensure those in trim are maintained exactly, while the corrections to
the out of trim axes are made.
3.3.4.3. Yaw axis control. The key to smooth and accurate instrument flight in a
helicopter is the ability to maintain coordinated flight. This is because the yaw axis is
usually the most unstable axis in helicopters, particularly in those aircraft not
equipped with a Stability Augmentation System (SAS). The instability in the yaw
axis is compounded by power changes that cause a yawing moment and require an
immediate pedal correction. Induced vertigo is commonly the result of this moment.
Therefore power changes should be kept to a minimum and, when required, should be
applied slowly and smoothly. Pilot anticipation of pedal adjustments during power
changes will help to keep yaw moments to a minimum.