SUBJECT:     Comparitive Propeller Tests

SECTION:     Flight

SERIAL No.  FS-M-19-1533-A

A.    Purpose

        1.   To report results of flight tests of the P-47B airplane, AC No. 41-5942, conducted at the manufacturer's plant in order to obatin comparitive performance with a 13 feet 0 inch diameter, No. 826 Curtiss test propeller and with the standard production propeller, No. 714-102-12: cuffs were not installed on either propeller. Airplane equipped with Pratt and Whitney R-2800-21 engine with torque meter and with an exhaust driven turbo supercharger. Gross weight at take-off was 12,620 pounds at 28.3 percent m.a.c. wheels up. Radio mast and antenna in place, and eight .50 caliber guns installed. All tests with wheels and flaps up and with mixture auto-rich.

B.    Test results

        1.   High speed at 2700 RPM and 2000 b.h.p. at 5000 feet, 25,000, and critical altitude for 18,250 turbo RPM. Cowl flaps closed, intercooler and oil cooler flaps neutral.

	True Speed - MPH
Altitude Feet	Curtiss Prop. No. 826 13 ft. 0 in. Dia.	Curtiss Prop. No. 714-102-12 12 ft. 2 in. Dia.
5,000	342	350
25,000	408	414
Critical Altitude	415 at 27,000 ft.	421 at 27,300 ft.

        2.   Climb data obtained with throttle wide open and turbo on to give either 2000 torque b.h.p. or 18,250 turbo RPM. Cowl flaps, oil cooler flaps, and intercooler flaps wide open.

			Rate of Climb - ft/min.
Altitude Feet	I.A.S. MPH	Torque b.h.p.	Curtiss No. 826 13 ft. 0 in. Dia.	Curtiss No. 714-102-12 12 ft. 2 in. Dia.
10,000	185	2000	2720	2580
15,000	201	2000	2610	2440
20,000	218	2000	2440	2240
23,300*	231	2000	2295	2080
25,000	236	1900	2040	1850
30,000	252	1620	1345	1190
35,000	255	1350	700	550

               *Critical altitude for 2000 b.h.p. at 18,250 turbo RPM.
               Note: Above speeds are the same speeds as used for climbs in previous propeller tests on this airplane and are the minimum speeds at which the climbs can be made without overheating on a normal day.

               Best climbing speed was 15 MPH slower and the rate of climb 20 feet per minute higher for the Curtiss 12 feet 0 inch diameter propeller No. 826. Best speed for the Curtiss No. 714-1C2-12 propeller was 5 mph slower but there was no appreciable difference in rate of climb.

        3.   Distance required to take-off from a concrete runway and clear a fifty foot obstacle with engine operating at 2700 RPM and mixture auto-rich.

Propeller	13 ft. 0 in. Curtiss No. 826			12'2" Curtiss No. 714-1C2-12
Flap setting	1/2	1/2	Full	1/2	Full
RPM	2700	2700	2700	2640	2640
b.h.p.	1680	1760	1710	1600	1610
Man. Pr.-"Hg.	45	49	45.2	45.2	45.2
I.A.S. at T.O.	95	95	91	95	95
Ground Roll - Ft.	1190	1105	1115	1260	1210
Distance to clear 50 ft. obstacle - Ft.	1730	1655	1625	1755	1630
Gross weight - lbs.	12,150	12,450	12,250	12,450	12,250
Average of    No. of trials	4 trials	6 trials	4 trials	6 trials	5 trials

        4.   Determination of airspeed and altimeter error with a Kollsman type D-1 airspeed head located 43 inches in from the tip and with static holes 23-3/16 inches ahead of the leading edge and approximately 3/4 inch above the chord line.

Indicated Air speed MPH.	Water Column MPH	Calibrated Air speed MPH	Air speed Installation Error MPH
310	308	319.5	-11.0
280	279	289	-10.0
255	254.5	263.5	- 9.0
230	229.5	237.5	- 8.0
205	203	210.0	- 7.5
180	179.5	186.0	- 6.5