Questions & Answers


1) What can I expect for performance gains with the Constant Speed Propeller Conversion, and how does it change the weight and balance?

2) What is the thrust effect of the various propellers with relation to pitch, diameter, and RPM? What effect have you seen from the exhaust modification?

3) How can I tell if my engine can be modified to accept a constant speed propeller?

4) Have you compared the Hartzell constant speed to the MT constant speed, and what are the differences?

5) Have you compared a constant speed propeller to a fixed pitch propeller and what are the differences?

1. What can I expect for performance gains with the Constant Speed Propeller Conversion, and how does it change the weight and balance?

It is hard for us to give very exact performance figures because Super Cubs vary so tremendously and we definitely don’t want to mislead anyone. All we can do is provide how ours performed with the various propellers. We tested our Cub, which is 180 H.P., 29 in Tundra tires, and by no means built to go fast. With the McCauley pitched for “climb” performance, top speed was about 90-95 MPH. With a McCauley pitched for “cruise” performance it would max out at about 105 MPH. With our constant speed, the top end is now about 115 MPH. So we figure most Cubs should have about a 20% improvement in cruise speed if compared to a Borer “Climb” prop, and of course, something less if compared to a cruise prop. As far as the take-off performance goes, our prop will perform at least as well and probably better than even a “Climb” Borer prop. This is because the engine can produce its full rated power by going directly to 2700 RPM immediately upon throttle advancement. This is definitely a significant difference!! As far as the weight goes, it also varies with each aircraft. Ours had basically stock accessories, so it only gained about 10 pounds when installing the Hartzell Propeller, and only moved the empty weight CG forward about 7/16 of an inch. This was insignificant to us, but can be easily offset just by carrying a simple survival kit in the baggage compartment while flying around empty. If your Cub already has a light weight starter, or already has a lightweight rear mounted oil cooler, than obviously the weight change and CG effect will be greater. However, even if you already have these modifications, the CG should still not ever be any farther forward than mine. It just matters what you are comparing it too. There are also many other options we can do if desired. (i.e., Extended baggage, tundra tailwheel, battery location, ballast, etc.) However, generally the CG issue can be easily resolved just by paying attention to simple loading. Hopefully this answers your questions at least a little bit. We will be happy to work your weight and balance for you ahead of time, so we all know exactly what to expect. Please let us know if you have any other questions. We will be glad to help!

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2. What is the thrust effect of the various propellers with relation to pitch, diameter, and RPM? What effect have you seen from the exhaust modification?

Static Pull Test Results

August 21, 2003
82 deg F.
29.90
180 H.P. PA-18

Propeller Model Exhaust Pull RPM
Climb Prop McCauley 1A200FA/8240 Stock 825 lbs. 2450
Climb Prop McCauley 1A200FA/8240 Sutton 865 lbs. 2525
Climb Prop McCauley 1A200FA/8244 Stock 770 lbs. 2350
Climb Prop McCauley 1A200FA/8244 Sutton 815 lbs. 2430
Constant Speed Hartzell HC-C2YR-1BF/8477-4 Sutton 870 lbs. 2700

NOTE: These thrust tests were conducted for comparison sake only and should not be construed as being applicable to all other aircraft.

Thrust data provided by Hartzell

This data is being supplied to demonstrate the relationship between diameter and generated thrust at various airspeeds. From these tables it becomes obvious why we chose to STC the longest propellers available for these engines.

O-320-A series 150 H.P./2700 RPM, HC-C2YL-1BF hub with the following blades
Note: Measurement is represented in pounds of thrust.

Speed 80″ F8468-4 72″ F7663-4 78″ F8468-6Q
10 835 680 808
30 715 617 698
50 600 547 591
70 506 479 501
90 429 415 427
110 366 362 367

O-320-B series 160 H.P./2700 RPM, HC-C2YL-1BF hub with the following blades
Note: Measurement is represented in pounds of thrust.

Speed 80″ F8468-4 72″ F7663-4  78″ F8468-6Q
10 862 707 835
30 744 646 727
50 630 577 621
70 534 507 529
90 455 441 453
110 389 385 390

O-360-A series 180 H.P./2700 RPM, HC-C2YR-1BF hub with the following blades
Note: Measurement is represented in pounds of thrust.

Speed 80″ F8477-4 76″ F7666
10 924 838
30 810 754
50 693 664
70 590 573
90 504 497
110 432 432

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3. How can I tell if my engine can be modified to accept a constant speed propeller?

From what the Type Certificates for the O-320, and O-360 say, It looks like the only engine with a solid crankshaft would be the O-360-C4F. However, all the engines with a “4” in the middle refer to something like a “Heavy shaft”, so their eligibility is questionable. Most all others are capable of being modified to use a constant speed prop. Just for starters, this is what you can look for on your engine.

1) Look at the rear of the engine on the accessory case for a place to mount the governor. This will look like a square cover below the right magneto and vacuum drive area.

2) Look at the front right side of the engine case sort of near the top. This might be hard to see, but there should be a port with a pipe plug in it.

If you have these things, you are on the right track. Also, some engines will have the governor drive pad located on the front left side of the engine. This will require no plug like we discussed. To determine for sure what crankshaft you have, you will need to pull the spinner off and look directly at the end of the crankshaft. If there is a round steel plug filling the entire center of the shaft, your crank is definitely hollow. There are a couple of other things we will need to check, but we can generally figure those out from your maintenance records. I hope this helps out a little. Feel free to call me if you have any questions.

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4. Have you compared the Hartzell constant speed to the MT constant speed, and what are the differences.

On June 18, 2005 we conducted a comparison test between the Hartzell HC-C2YR-1BF/F8477-4 propeller and the MT-Propeller MTV-15-B/210-58. The Hartzell propeller was equipped with the C-3568-P spinner, and the MT-Propeller was equipped with the standard P-277-A spinner. Both were installed on Piper PA-18 aircraft with 180 H.P. Lycoming O-360 engines in accordance with Professional Pilots Inc. STC’s. The test began with aircraft “A” using the MT-Propeller, and aircraft “B” using the Hartzell Propeller. Both aircraft were loaded to gross weight (1750 lbs.) and performed three maximum performance take-off’s, which were measured from the beginning of the take off roll to the point at which the tires left the ground. The aircraft then performed a full power climb at approximately 2700 RPM to an altitude of 10,000 feet MSL. Time to climb, and all engine parameters were recorded at 1000 ft intervals. For comparison purposes, the pilots flew the aircraft at the published best rate of climb speed of 75 MPH, and a full rich mixture for the entire climb. Both aircraft performed this test within 30 minutes of each other with the same weather conditions. The aircraft then landed, and were attached to a hydraulic strain gauge for the purpose of thrust testing. The propellers were then removed, weighed, and switched to the opposite aircraft. Following the switch, the aircraft were re-fueled, thrust tested again, and test flown in the same manner as described above. The only parameter changed between the aircraft was the propeller. The following is a summary of the results recorded from these tests.

Weather:

Test #1 Test #2
Wind 010/12 020/12
Temp 19 C. 20 C
D.P. 15 C. 15 C.
Baro. 30.06 30.06

Departure runway 01 at Sutton’s Field, 0II8, Field Elevation 750 ft, Sod surface.

Propeller weights:

Hartzell HC-C2YR-1BF/F8477-4 with
C1576 dampener assembly and C3568P spinner assembly – 70 lbs

MT-Propeller MTV-15-B/210-58 with
P-277-A spinner assembly – 46 lbs

Thrust Testing:

Aircraft A Aircraft B Average
Hartzell Propeller 765 lbs. 748 lbs. 756 lbs.
MT- Propeller 781 lbs. 731 lbs. 756 lbs.

Take-off testing:

Aircraft A Aircraft B
Hartzell Propeller Attempt 1 287 ft. 291 ft.
Attempt 2 282 ft. 263 ft.
Attempt 3 275 ft. 288 ft.
Average 281 ft. 280 ft.
Average between both aircraft 280 ft.
Aircraft A Aircraft B
MT-Propeller Attempt 1 236 ft. 233 ft.
Attempt 2 271 ft. 301 ft.
Attempt 3 261 ft. 292 ft.
Average 256 ft. 275 ft.
Average between both aircraft 265 ft.

Rate of climb: (In Feet Per Minute, F.P.M) (Calculated from time measurements to avoid instrument error)

Aircraft A Aircraft B Average
Hartzell Propeller 2000 ft.  760  750  755
  3000 ft.  741 759 750
  4000 ft. 690 652 671
  5000 ft.  690  631  660
  6000 ft.  526  504  515
  7000 ft.  444  377  410
  8000 ft.  366  294  330
  9000 ft.  345  267  306
  10000 ft.  242  179  210
   
    Aircraft A Aircraft B Average
Hartzell Propeller 2000 ft.  698  650  674
  3000 ft.  698  612  655
  4000 ft.  659  545  602
  5000 ft.  545  432  488
  6000 ft.  476  432  454
  7000 ft.  403  368  385
  8000 ft.  243  299  271
  9000 ft.  194  264  229
  10000 ft.  180  156  168

Please note that the performance numbers in this table by no means represent the full capability of the 180 H.P. Super Cub due to the fact that neither aircraft were allowed to lean their engines or deviate from the 75 MPH climb speed. These two factors were kept constant to increase the accuracy of the comparisons between the two propellers and help eliminate the effects of pilot technique. Also please note that propeller efficiency can vary tremendously depending on various airspeeds. This test was meant to give a base line understanding of the characteristics of each propeller and should not be construed as being capable of determining the overall effect on each individual aircraft.

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5. Have you compared a constant speed propeller to a fixed pitch propeller and what are the differences?

MT-Propeller MTV-15-C/200-50 Comparison with McCauley 1A175 propeller Installed on Lycoming O-320 engine

On July 7, 2005 we conducted a comparison between the constant speed MT-Propeller installed on a PA-18 in accordance with Professional Pilots Inc. STC SA02087CH, and the McCauley 1A175/8242 (Borer) propeller. Both propellers were installed on PA-18 aircraft utilizing Lycoming O-320 engines rated at 160 H.P. The test was conducted at Baker, Montana with several witnesses present. The test began by thrust testing both aircraft using a hydraulic strain gauge. The aircraft were then loaded equally, and to near gross weight. The aircraft then conducted several maximum performance take-offs, and also performed a climb to 10,000 ft. MSL. The tests were conducted with a full rich mixture, and half flap configuration to minimize the effects of various pilot techniques. The following is a summary of the results recorded from these tests.

Weather:

Wind 310/13
Temp 30 C.
D.P. 18 C.
Baro. 29.84
Density Altitude 5500 ft.

Departing runway 31 at Baker, Montana. Field Elevation 2960. Paved Surface. Aircraft take-off weight 1600 lbs. for attempts 1 and 2, and 1750 lbs. on attempt 3.

Propeller Weights:

MTV-15-C/200-50
Including spinner assembly
43 lbs.
McCauley 1A175/8242
Including spinner assembly
36 lbs.

Thrust testing (Static):

MT-Propeller (2680 RPM) 649 lbs.
McCauley (2400 RPM) 528 lbs.

Take-Off distance:

MT-Propeller McCauley Propeller
Attempt #1  230 ft. 285 ft.
Attempt #2 200 ft. 240 ft.
Attempt #3 315 ft. 365 ft.
Average 248 ft. 297 ft.

Rate of Climb to 10,000 ft.:
(Adjusted for equal speed/distance)

MT-Propeller 477 fpm
McCauley 451 fpm

Cruise speed:
(Approximately 65% power at 10,000 ft.)

MT-Propeller 112 mph
McCauley 92 mph

Summary: 

During these tests, the constant speed MT-Propeller had a static thrust 23% higher than that of the fixed pitch McCauley. The aircraft with the MT-Propeller demonstrated an advantage of approximately 19% during the take-off phase, and approximately 6% during the climb phase. The cruise speed of the MT-Propeller equipped aircraft was approximately 22% faster than the McCauley equipped aircraft. This test was conducted to obtain a base line understanding of the performance differences between the two types of propellers. The McCauley 1A175 82/42 (Borer) propeller was chosen for the comparison because we believe it provides the greatest performance of any fixed pitch propeller currently on the market. Individual aircraft may vary considerably due to other modifications that may be installed, but the capability of allowing maximum engine efficiency through the use of the constant speed propeller should always be present.

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