How do you set up an Aeromatic prop?
This answer explains what you would typically do assuming your prop has been set up for your specific airplane/engine combination.
Technicalities: The Aeromatic F200 has 4 angles to be set. These angles vary across the spectrum of airplanes.
These angles are; Phase angle, Counterweight arm angle, Low pitch angle and High pitch angle.
The high pitch angle is fixed and can't be changed because it is a function of design. These angles are set at the factory. In the field the installer may or may not have to change the low pitch angle.
There is another adjustment that may or may not need to be done by the installer in the field. That is the amount of counterweight needed. Theoretically everything should be perfect!
In other words, all of these angles and the amount of counterweights are set at the factory for KNOWN airplane applications. The history of the Aeromatic propeller shows that most of the time the factory settings are correct and the owner in the field needs only to make checks to verify the settings are correct.
The Aeromatic is designed so that at cruise the blade angle is at or close to the phase angle, in static full power it is at the low pitch angle, in a dive it will move toward the high pitch angle. These props have on average, about 18 to 20 degrees of blade angle change. However only about 4 to 7 degrees are used for all flight conditions. The extra high pitch angle is there to prevent over revving in a dive.
Note: I strongly recommend that you use a calibrated tachometer. Mechanical tachometers are notorious for being off calibration. Believe me, 200 rpm error is not at all uncommon. Also your propeller most likely will not perform correctly unless your tachometer is correct. Furthermore you can easily put your propeller into a dangerous vibration mode with a faulty tachometer. Calibrate your tach or buy that little hand held battery operated tachometer to do your rpm testing.
THE AEROMATIC F200 (for flange shaft engines up to 180 hp) A. Static full throttle regulation procedure. Assume a C-125* engine on a Swift with red line at 2500 RPM.
1. Remove all counterweights, bolts and nuts from the counterweight arms. Do not remove the counterweight arm clamp bolts.
Check static full throttle RPM. If it is not 2500, correction can be made by use of low pitch stop adjusting shims located under the synchronizer cover plate.
Remove the six screws and remove the cover plate. See note 1 below.
One shim of .016" will change RPM by about 50. Removing a shim will decrease RPM adding a shim will increase RPM. Do not add or remove more than one shim at a time.
If you can't get the right RPM by removing or adding a complete shim you can make finer adjustments by peeling the shims. See note2 below.
After reinstalling the counterweights in their original position you will see a slight decrease in full throttle static RPM. This is normal, DO NOT make any more adjustments on static RPM.
Note 1. You may loose some oil by removing the stop bolts. Catch the oil in a container and replace it after you finish with the static rpm adjustments. Doing the ground runs with less than full oil will not hurt the propeller.
Note 2. The shims are peel shims. The shim is made up of .002" laminations. Therefore you can make finer adjustments to RPM.
B. Flight RPM Correction and Altitude Adjustment for Original Regulation.
1. With the counterweights install and secured properly make a full throttle level flight as close to your airport altitude as safely possible. Engine speed at full throttle level flight should be 2500 RPM.
2. If you find that the RPM is 2600, add one -2 counterweight to each side. This will reduce the RPM by close to 100. A -1 counterweight will reduce RPM by close to 50. If your RPM is 2400 you must remove one -2 counterweight from each side. All flight adjustments are done by adding or removing counterweights. You do not readjust your static RPM.
3. Aeromatic propellers will decrease full throttle RPM by about 20 for each 1000' increase in altitude. If your home base is at 3000' you would adjust your full throttle level flight RPM to be 2440. This will give you the best all around performance.
Note 1: If you have your propeller set up for home airport of say 3000 or 4000' MSL and you decide to fly and land at an airport at sea level you should be careful on takeoff from that field that you do not over speed your engine. If you move your home base to a sea level airport after having adjusted RPM for a higher airport you should re-adjust RPM by adding or removing counterweights. The late Art Scholl, a renowned aerobatic pilot, used an Aeromatic prop on his 200 hp Ranger powered Chipmunk. I have heard that he would carry a small kit of extra counterweights so he could make adjustments for the altitude at which he was performing.
* An Aeromatic propeller that has been factory set up for a Swift with C-125 does not use the same angle settings as used on a PA-20 with a C-125. So, you can not just take a prop from a Swift and bolt it on a PA-20 just because it uses the same engine. The difference in the speed of the airplanes demands different angle settings.
THE AEROMATIC MODEL 220 (for spline shaft engines up to 260 hp perhaps more in experimental airplanes)
The setup and adjustment procedure for the model 220 is the same for the model F200. The only difference is in the way, mechanically, the pitch stops are designed. The 220 uses four pitch stop bolts, two for high pitch and two for low pitch. Each blade has it's own high pitch and low pitch stop bolt. There are peel shims under the head of each stop bolt. If you have to make static rpm adjustments follow these instructions.
1. Remove the counterweights, bolts, washers and cotter pins. DO NOT REMOVE THE COUNTERWEIGHT ARM CLAMP BOLT. Do a static full power run. It should be at red line rpm. If it is too high you remove shims under the low pitch stop bolt heads. (These bolts are marked 1L and 2L, the other two bolts are marked 1H and 2H.) You must do the same to the both blades. If the rpm is to low you add shims. After you get the static full power rpm correct, secure the bolts with safety wire and be sure that the seal is good. Permatex #2.
CAUTION: These stop bolts carry virtually no load. They merely provide a stop for the blade pitch. Even though they are 3/8" bolts do not torque them to the 3/8" torque specification. Just make sure they are tight enough to provide a good seal.
Note: 1. You may loose some oil by removing the stop bolts. Catch the oil in a container and replace it after you finish with the static rpm adjustments. Doing the ground runs with less than full oil will not hurt the propeller.
Note: 2. As on the F200 propeller you will not be adjusting the high pitch angle. Your propeller likely will never go to the high pitch stop position.
2. From here you will use the same procedure to adjust flight rpm as detailed above for the F200 propeller.