P. Ponk Aviation
Propeller STC's and Performance Information
P. Ponk currently offers installation of McCauley 3 blade D3A34C401/90DFA4 and 6 (84" and 86") BLACKMAC propellers on Cessna models A185E and A185F under STC #SA00640SE
This propeller is also approved for installation in all Cessna 180 and 182 models equipped with the P.Ponk 047050 engine.
Please give us a call or
send us an email for our current price.
NEW Hartzell Blended Airfoil Propeller
Propeller Certification Info:
During the course of our certification, 7 different propellers were tested on the same day using the same airplane.
The airplane was attached to a load cell that would measure static thrust to an accuracy of + or  1 pound.
All props were adjusted to take full power at 2600 rpm. We found most of the propellers produced the best static thrust between 2600 and 2670 rpm. Higher rpm produced less static thrust due to the blade angle changes required to run the higher rpm.
PROPELLER MODEL

BLADE
LENGTH

POUNDS PULLED
STATIC THRUST

At 2600 rpm and full power....

McCauley 2 blade D2A34C58 
82"

pulled 940 pounds 
McCauley 2 blade D2A34C58 
86"

pulled 1016 pounds 
McCauley 2 blade 2A34C66 
88"

pulled 1019 pounds * 
McCauley 3 blade D3A34C403 
80"

pulled 970 pounds 
McCauley 3 blade D3A34C401 
80"

pulled 1015 pounds 
McCauley 3 blade D3A34C401 
86"

pulled 1183 pounds 
McCauley 3 blade D3A34C401 
88"

pulled 1183 pounds 
* Note: The D2A34C58 88" and 2A34C66 88" propellers use the same blades, and would pull the same. 
Remember....same airplane, same day, same engine, same power settings. Quite a difference in the thrust.
We could have certified the C401 up to 88" length, however, in testing we found no significant difference between the 86" and 88" other than increased noise. We did find that maximum static thrust on most propellers was reached between 88% and 92% of the speed of sound measured at the propeller tip. Above 92%, the propeller produced more noise, but no more thrust. Conclusion: You are using energy to produce noise instead of thrust because of the sound barrier. Some pilots believe the longer the propeller, the better the performance. However, beyond a point, additional propeller length will actually result in a decrease in performance. Longer and faster is not always better!
Click on the button below to check your propeller's efficiency.
Note: Some browsers may not properly execute the Java applet that performs the tip speed calculations. In that case, the following formulas can be used to make the calculations.
To determine propeller tip speed:
Prop Diameter X Pi / 12 X RPM X 60 / 5280 = Tip Speed in MPH
Example: 86" prop turning at 2800 RPM
86 X 3.1416 / 12 X 2800 X 60 / 5280 = 716.4 MPH
To determine the speed of sound:
Square Root (absolute temp + ambient temp) X 33.4 = Speed of Sound
Example: 59 degree F. day
Square root (460+59) X 33.4 = 760.9 MPH (speed of sound)
To determine propeller tip mach speed:
Tip Speed / Speed of Sound = Tip Mach Speed
716.4 / 760.9 = .942 MACH (to fast)
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