ARPLAST PV-50, Manual

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Page 5 of 8 © Lyndhurst Touchdown Services Limited updated February 2007
Limiting Pitch Variation
The PV50 is equipped with two micro-switches which limit maximum and minimum pitch. Additionally the
hub is fitted a tube and two O rings which mechanically limit pitch. This mechanical limit is not an
operational limit. For additional safety set the mechanical stop 1° or 2° finer than the electrical fine limit.
For use in the UK the PFA may require blade pitches to be limited so that :
1. Maximum pitch will provide safe performance at low speed to enable a go around.
2. Minimum pitch will be sufficient to prevent the engine from over revving in the initial stage of climb.
Electrical Limits
The propeller hub contains two micro switches which limit the maximum and minimum pitches. The length
of the arms of the micro-switches determine the limits. A small amount of adjustment is now provided to
the limit switches.
Fly the aircraft and determine the maximum and minimum blade pitches that are required as given on the
LCD display. Record the blade pitch angles. With the aircraft on the ground and suitably tethered run the
engine and adjust the propeller to maximum coarse and maximum fine settings as given by the existing
limit switches. Mark or measure the position of the tube that runs outside the lead screw. Run the engine
and adjust propeller pitch to give the maximum desired fine and coarse settings as determined by flight
testing. Measure the difference between the actual tube positions and desired tube positions. Adjust the
switch arms by corresponding amounts to give correct minimum and maximum settings. Always stop the
engine when approaching propellers and take great care whilst working on propellers.
Mechanical Limits
The LCD display remains the pilots main reference for setting blade pitch. The electrical limit switches
must be set to limit fully course and fine operational limits. The mechanical fine limit should be adjusted
such that the mechanical fine pitch limit is slightly finer than the electrical fine pitch limit.
The propeller is normally supplied with a 20 mm long aluminium spacer tube which provides a mechanical
fine pitch limit of about 12 degrees (depending on blade type and diameter). Increase the length of this
tube to give a mechanical fine pitch limit just finer than the electrical limit. The mechanical course pitch
limit may be adjusted in a similar way adding a spacer to the front.
Spacer
O Ring
Normal Tractor
Fine Limit
Course Limit
Front Back
Front Back
Never operate without the rubber O ring.
Never set the mechanical fine limit equal to
or greater than the electrical limit.
O Ring
Special washers may be
used to provide correct
adjustment
Swash Plate