McCauley 3 blade propeller report for N6019P.

The propeller was ordered from Ottosen Propeller and drop-shipped directly to my local FBO GPI Aviation at ANQ. The Hartzell prop was removed with little difficulty as was the governor. The installation was a little more involved but was accomplished in 7 hours by two people. The governor position required elongation of the RPM control cable hole per the STC. Other configurations may or may not require this elongation.

Initial flight testing of the propeller was conducted in smooth air. Initial reaction was WOW! Takeoff was much shorter and with an increased climb rate. The governor rpm was set correctly from the factory and no adjustments were made. At a altitude of 4500 msl a 2 knot speed increase in speed was observed ( 152 Knots). However, a vibration peaking at 2300 RPM was noted. This vibration was in the lower frequency range but increased (and decreased ) with rpm and in amplitude between 2200 and 2500 rpm. At rpm’s outside of this range there was no vibrations. The initial flight test was concluded and the tests documented by the installing A&P who was co-pilot.

Subsequent flights confirmed the previous paragraphs findings. Since this was objectionable I contacted Maurice Taylor, McCauley, and others. Maurice supplied the names of several factory recommended dealers in my area. McCauley was very responsive and positive and asked me to take it to one of these recommended dealers. I chose Tiffin Propeller at 16G and arranged a time for them to check the set up. They checked blade angle and tracking and then dynamically balanced the propeller to 0.15 IPS ( the limit is 0.2). This did not cure the problem and over a period of 2 days of time we experimented with several configurations. The original , recommended configuration was the best but I was still not satisfied.

The next and only remaining possibility was to replace the propeller. McCauley sent a new propeller and this was installed and balanced to 0.19 IPS. The flight test showed much less vibration at 2300 rpm and none outside the range of 2225 to 2500. The low frequency vibration problem was reduced to acceptable levels!

The conclusion, is that there is a difference in the “feel” of the propeller and it takes some getting used to – like a new pair of shoes. I have become totally accustomed to this new feel over a period of 5 hours flight time. I believe the following data represents the two 3 blade propeller’s performance as installed on my aircraft. I have several “go fast” modifications installed on the aircraft.

1. Speed: 152 Knots @ aprox. 75% power – 2 knot increase @ 4500 msl, 2300 rpm, 24.1 inches

2. Acceleration: Noticeably stronger

3. Takeoff: Much Improved Short field – 20 to 25% reduction

4. Climb Rate: Full Fuel, 1 person (too heavy), 120 mph equals 1500+ fpm @ 2000 msl

5. Noise level: est. 8 dB or more reduction

6. Worst case vibration 3 blade Vs 2: Same @ 2300 rpm/ nill @ 2200 & 2500 rpm

McCauley and Tiffin Propeller have the right idea of customer service and both were very responsive to my complaints. McCauley supplied a new propeller without complaint and within 2 weeks of the original service call. The Tiffin Aire propeller people are great and run a first class operation (1-800-458-2487). These people know Comanches too. My final recommendation would be to purchase your propeller from a dealer that is close to where you live as you will almost certainly need to dynamically balance it.

They will add that little bit of extra enthusiasm to the project if they have made some money (I think all pricing will be within $100-200 anyway). I would insist on a balance level of 0.10 as it is achievable in 3 or 4 iterations by a good shop. I would be happy to discuss specifics with any ICS member that cares to contact me. The best initial contact method is email (csjmoore@gte.net) but if no email is available try my pager 800-796-7363 PIN 1041149. I will make a reasonable effort to return your queries.