SUBJECT: Comparative Propeller Tests

SECTION: Flight

SERIAL No. Eng-47-1714-A

A.    Purpose

        To report results of comparative propeller flight tests run at manufacturer's plant, Farmingdale, Long Island, New York.

B.    Factual data

        1.   Airplane equipped with Pratt & Whitney R-2800-63 engine with water injection equipmentl A-17 turbo regulator installed for 2300 horsepower test, A-13 turbo regulator for 2600 horsepower tests.

        2.   All performance is given at the same horsepower as that obtained on similar tests on the same airplane with the Standard Curtiss 714-1C2-12 propeller installed. Results of this test were reported in Memorandum Report No. Eng-47-1652-A.

        3.   All level flight tests were run with cowl flaps closed, intercooler and oil cooler flaps neutral, throttle wide open, engine RPM 2700, and mixture auto-rich. All climb tests run with cowl flaps wide open, engine RPM 2700, and mixture auto-rich.

        4.   Airplane was ballasted to simulate the following conditions: Six .50 caliber guns; 300 rounds of ammunition per gun; 305 gallons of gasoline; 15 gallons of water; 14 pounds pyrotechnics. In this condition the weight was 13,260 lbs. with the Curtis 836-2C2-18 propeller, and 13,365 lbs. with the Hamilton standard 6507A-2 propeller. C. G. location at 13,260 lbs. was 29.63 percent M.A.C.

        5.   The following propeller configurations and type of tests were run:

               A.   Curtiss 836-2C2-18 propeller with standard cuffs and finish, no vent holes: High Speed vs altitude is given in Fig. 4 and Rate of Climb vs altitude curve in Fig. 7.

               B.   Hamilton standard 6507A-2, regular production type propeller: High speed vs altitude is given in Fig. 3 and Rate of Climb vs altitude is given in Fig. 6.

               C.   Curtiss 836-2C2-18 propeller with standard cuffs and tip vent holes: 24,000 foot speed vs power data given in Fig. 5. Climbs from 13,000 ft. to 31,000 ft. given in Fig. 7.

               D.   Curtiss 836-2C2-18 propeller with standard cuffs and tip vent holes: 5,200 ft. and 24,000 ft. speed vs power data given on the faired curves in Fig. 5. These speed power curves were run as a base for cuff comparison tests.

               E.   Curtiss 836-2C2-18 with Curtiss "C" type cuffs, pentrate finish, and vent holes: 5200 ft. and 24,000 ft. speed vs power data given in Fig. 5.

               F.   Curtiss 836-2C2-18 with Curtiss "D" type cuffs, flattened blade shank, pentrate finish, and vent holes: 24,000 ft. speed vs power data given in Fig. 5.

        6.   The location of the airspeed head and the position correction is given in Fig. 1.

C.    Conclusion

        Climb performance of Curtiss 836-2C2-18 propeller and Hamilton Standard 6507A-2 propeller was nearly identical, the difference between the two being within the limits of experimental accuracy. A definite difference of performance in level flight high speeds was found, with the Hamilton Standard propeller giving from five to eight miles per hour faster speeds throughout the altitude tested.

        Results of tests on Curtis 836-2C2-18 with standard cuffs and tip vent holes showed no increase in speed at 24,000 ft., and a slightly higher rate of climb than that obtained on the 836-2C2-18 without vents. This increase in rate of climb was within the limits of experimental accuracy. Also, since no increase in speed was obtained by adding the vent holes on the blade tips, no increase in rate of climb would be expected.

        Level flight high speed tests run on the Curtiss 836-2C2-18 propeller with tip vent holes, pentrate finish and experimental "C" type Curtiss cuffs showed a small trend toward improvement over the Curtiss 836-2C2-18 with standard cuffs, and tip vent holes at horsepowers above 2000. This is shown in Fig. 5.

        Level flight high speed tests run on the Curtiss 836-2C2-18 propeller with a flattened blade shank, tip vent holes, pentrate, and experimental "D" type cuffs also showed a small trend toward improvement over the 836-2C2-18 wth standard cuffs, and tip vent holes at horsepowers above 2000 as shown in Fig. 5.

        A comparison of climb and level flight performance is given in Fig. 2.

D.    Recommendations

        None