Pursuit Single Engine P-51B-1-NA, AAF No. 43-12093
May 18, 1943
| SUBJECT: Preliminary high speed and climb performance tests
BRANCH: Flight test SERIAL No. FS-M-19-1587-A A. Purpose 1. To report results of high speed and climb performance tests conducted at the manufacturer's factory on the P-51B-1-NA airplane, AAF No. 43-12093. B. Factual data. 1. Airplane was tested at a take-off gross weight of 8430 pounds, and was equipped as a standard production fighter with four .50 caliber guns with the gun openings taped but shell ejection chutes open, three antenna wires and a short radio mast aft of the cockpit. Finish was filled and sanded and was supposed to be the standard production finish. Airplane equipped with the Packpard Merlin V-1650-3 engine with 11.5 inch and 10.1 inch diameter blowers, and with a four-bladed Hamilton Standard propeller, blade design No. V-6487A-24. Power data obtained from Packard power curve P-18, No. 5 dated Nov. 21, 1942 for the V-1650-3 engine with 11.5 inch and 10.1 inch blowers. 2. High speeds obtained with the oil cooler flap and coolant flap set for automatic operation since there were no provisions on this airplane for selective operation and no time was available for a test installation of a selective control. |
| True Airspeed M.P.H. | R.P.M. | Man. Press. " Hg. | BHP From Power Chart | Altitude Ft. | Coolant Flap Position Inches open From Flush | Oil Flap Position Inches open From Flush |
| (a) Low blower Operation | ||||||
| 363 | 3,000 | 60.5 | 1,450 | 5,000 | 6.0 | W.O (5) |
| 394 | 3,000 | 60.5 | 1,485 | 10,000 | 5.0 | 3.5 |
| 425 | 3,000 | 60.5 | 1,530 | 16,800 | 1.5 | 1.0 |
| 422 | 3,000 | 49.0 | 1,270 | 23,200 | 1.0 | Flush |
| (b) High blower Operation | ||||||
| 422 | 3,000 | 60.5 | 1,270 | 23,200 | 1.0 | .5 |
| 441 | 3,000 | 60.5 | 1,275 | 29,800 | 1.0 | Flush |
| 421 | 3,000 | 48.0 | 985 | 35,000 | .5 | Flush |
| 403 | 3,000 | 40.7 | 815 | 38,000 | .5 | Flush |
| Opening coolant flap wide open from flush position slowed the airplane from 349 M.P.H. I.A.S. to 325 M.P.H. at 18,000 Ft.; opening the oil cooler flap decreased the speed an additional 10 M.P.H. I.A.S.
3. Climb Data, 3,000 R.P.M., Oil and Coolant flaps Wide Open. |
| Altitude Ft. | Man. Press. " Hg. | Rate of Climb Ft/min. | BHP from Chart |
| (a) Low blower Operation | |||
| S.L. | 60.5 | 3,600 | 1,500 |
| 5,000 | 60.5 | 3,570 | 1,510 |
| 10,000 | 60.5 | 3,540 | 1,525 |
| 13,000 | 60.5 | 3,520 | 1,510 |
| 17,400 | 52.3 | 2,965 | 1,320 |
| (b) High blower Operation | |||
| 17,400 | 60.5 | 2,965 | 1,320 |
| 20,000 | 60.5 | 2,915 | 1,310 |
| 26,000 | 60.5 | 2,780 | 1,260 |
| 30,000 | 51.6 | 2,125 | 1,075 |
| 35,000 | 41.8 | 1,280 | 850 |
| 40,000 | 32.8 | 450 | 630 |
| S/C 42,000 | 29.1 | 100 | 540 |
| A/C 42,600 | 28.2 | 0 | 515 |
| 4. Aftercooling for all level flight and climbs appeared to be adequate, however, the degree of aftercooling is dependent on the position of the coolant flap and some unexpected variations in true brake horsepower were obtained.
Oil and coolant temperatures are well under the maximum limit and remain almost constant for all conditions of flight if the cooler flaps are in the automatic position.
Engine power output is particularly dependent on changes in outside air temperatures due to the effective aftercooler and also to the high pressure ratio obtained through the scoop and blowers.
5. Determination of airspeed and altimeter errors with the standard North American pitot head (Kollsman D-2) location under the right wing with the staic holes approximately 34-3/4 inches aft of the leading edge and 14-1/2 inches below the lower surface and approximately one inch outboard from the outer edge of the flap. |
| True Indicated Air Speed M.P.H. | Calibrated Air Speed M.P.H. | Airspeed Installation error at Sea Level M.P.H. | Altimeter Error at Sea Level Ft. |
| 365 | 347 | +18 | +510 |
| 350 | 333 | +16.5 | +450 |
| 335 | 319 | +16 | +390 |
| 315 | 301 | +14 | +320 |
| 300 | 287 | +13 | +290 |
| 280 | 269 | +11 | +230 |
| 250 | 241 | +9 | +160 |
| 230 | 223 | +7 | +120 |
| This location of the pitot head results in a reverse static pressure change indication so that an increase in altitude is indicated when the plane is nosed down and a decrease in altitude indicated when the plane is climbed momentarily.
6. An additional airspeed and altimeter installation error was found to exist at altitude and was evidently dependent upon Mach's number. If this error in the airspeed and altimeter is neglected, an error in true speed of as great as 13 M.P.H. in level flight at 30,000 ft. may result. |
| I.A.S. M.P.H. | Additional Error in I.A.S. at 10,000 Ft. M.P.H. | Additional Error in I.A.S. at 21,000 Ft. M.P.H. | Additional Error in I.A.S. at 31,000 Ft. M.P.H. |
| 335 | +1.5 | +4.5 | - |
| 315 | +1.0 | +3.5 | - |
| 300 | +1.0 | +3.0 | +5.5 |
| 280 | +1.0 | +2.5 | +4.5 |
| 250 | + .5 | +2.0 | +3.5 |
| 230 | + .5 | +1.5 | +2.5 |
| In view of the substantial error introduced by locating the airspeed under the wing and the difficulty in determining the error, it is believed that,
in the future, all airplanes, on which performance tests are to be run, should be equipped with an airspeed head located on the wing at least one chord ahead of the leading edge.
7. This airplane was equipped with a pair of sealed balance ailerons which were very light at all speeds up to 400 M.P.H. Some 30° banks were made at 480 M.P.H. and the aileron forces were still consistent with the loads at low speeds. In general, the ailerons were considered very good, being effective at all speeds up to 500 M.P.H.; they are very light at stalling speeds but are still effective for any operation. The handling characteristics of this airplane have been improved by these ailerons which are the best yet fitted to the P-51 type airplane. |