Smart Avionics PB-4, Руководство пользователя интерфейса

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vibration is out of phase with the propeller. Any of the following problems will
cause the position of the polar point to vary:
• The engine is not running smoothly or the engine mounts are in poor
condition.
• The RPM is not being reliably detected. Unless the RPM is correct, the IPS
and DEG and their associated standard deviations are meaningless.
• The wind is gusting. At low vibration levels, just a few knots of wind can
make it appreciably harder to obtain reliable data.
• You are using an RPM that is triggering an airframe resonance.
• The accelerometer is not securely mounted or the sensing axis is not
pointing at the propeller's axis of rotation or the sensing axis is parallel with
the direction of movement of the engine's pistons.
• You are using the wrong accelerometer axis.
• The spinner is wobbling.
• The engine cowling is not fitted to minimise the effects of turbulence.
7.8.3. Adding weight does not reduce the vibration level
If the balancer shows a significant level of vibration with a small standard
deviation and adding weight doesn't appear to reduce the level or substantially
change the angle, any of the following could be true:
• The amount of weight being added is too small to have an effect. The heavier
the propeller/spinner, the more weight has to be added to reduce a given
level of vibration.
• The propeller is suffering from pitch imbalance (the blades don't have equal
pitch). Pitch imbalance has to be corrected before the propeller can be
dynamically balanced.
• The weight is not being added at the correct position.
• You are using the wrong accelerometer axis.
49 www.smartavionics.com
Adding weight does not reduce the vibration
level