Setting the Warp Drive Propeller Blade Pitch

The propeller blades driving your aircraft must all have the same pitch or angle setting. If they do not have the same pitch setting, they will each have a different angle of attack when passing through the air. If they have different angles of attack, they will be producing different amounts of thrust. This uneven thrust will cause a great deal of vibration that will be passed on to the engine mounts and the airframe. In time this vibration will wear out the motor mounts and damage the re-drive tower bearings. Therefore, proper propeller pitch setting is a necessity.

The pitch of the 3 propeller blades is measured using the Warp Drive Propeller Angle Setting Tool. The individual propeller pitch is adjusted using rubber strap wrench to twist the propeller in the hub. You will have to back off the tension of the 12 bolts on the propeller hub holding the base of each of the propellers in order to do this. You may also have to back off the tension on the 6 bolts holding the propeller hub to the re-drive tower as these also exert a clamping force on the base of the propellers.

For all intents and purposes the face of the propeller hub is at a right angle (90 degrees) to the horizontal thrust line of the aircraft in flight. Therefore, we want to set the propeller angle of attack against this reference line given by the face of the propeller hub.

Ensure that the propeller blades are all mounted with the round leading edge of the blades pointing in the same direction. The propellers on Challenger using the Rotax engines rotate counter clockwise when looking forward at the propeller hub from the rear of the aircraft.

First set the Pitch Tool against the flat face of the propeller hub. Adjust the inner wheel so that the bubble is in the exact center of the level. Now adjust the center wheel to the desired pitch angle of the propeller. This is usually about 12.5 degrees for most Challenger aircraft using the Rotax 582 engine. Lock this setting with the friction knob.

Set the Propeller Pitch Setting Tool to zero degrees against the face of the propeller hub. Then set the wheel to the desired pitch angle.

Rotate the first propeller blade until it is parallel to the floor. Now slide the Pitch Setting Tool over the very tip of the this propeller blade. The large rigid side of the Pitch Setting Tool will lie flush against the flat bottom of the propeller air foil. The thin more flexible movable side of the Pitch Setting Tool will clamp on to the rounded top surface of the propeller airfoil. Tighten the tool onto tip of the prop so that it is held snugly in place. The propeller pitch angle is set here at the very tip of the propeller blade.

Adjust the angle of attack of the propeller using a rubber strap wrench to rotate the propeller hub until the bubble in the Pitch Setting Tool is exactly centered. If the propeller will not rotate, you will have to loosen the propeller hub bolts some more to reduce the clamping force on the propeller blades.

Do this procedure on each of the three propeller blades. They must each have the exact same pitch angle. Double check that none of the propeller angles have changed position.

Once you have the desired angle on all three propeller blades, gradually tighten the bolts holding the propeller blades in the hub. Tighten these bolts gradually a turn at a time other wise the tightening process will change the angle of your propellers. Keep checking the propeller angles as you do this. They must stay at the same angle on all three blades.

Now re tighten the 6 bolts that hold the propeller hub to the re-drive tower. Tighten them progressively in a 1,4,2,5,3,6 pattern. Make sure that when you tighten the hub, that this does not change the pitch of the propeller blades. You may have to tighten the hub gradually repeating the tightening pattern many times to avoid making the propeller blades move in pitch. Keep checking the propeller pitches as you tighten the hub.

Now safety wire the propeller hub bolt heads. The safety wire must pass through the head of the first bolt, then be twisted until it reaches the second bolt. It then must pass through that bolt and be twisted again. The wiring should be done in a way that if one of the bolts begins to back out, the rotation will actually act to tighten the adjoining bolt.

When you next start the engine, check the maximum rpm at full throttle. This max throttle setting should not exceed the maximum rpm of the engine (6800 rpm for the Rotax 582). If the maximum engine speed goes past 6800 rpm, the propeller pitch is set too fine. You will have to increase the pitch angle of the blades. If the max rpm is below 6200 rpm, the pitch setting is too coarse, you will have to reduce the blade pitch angle to get the most power from the engine.