Flight Test Engineering Branch
Memo Report No. Eng-47-1774-A
15 July 1944
P-47D AIRPLANE, AAF NO. 42-26167
USING 44-1 FUEL
Flight tests have been conducted at Wright Field on the P-47D airplane, AAF NO. 42-26167, at the request of the Power Plant Laboratory, Engineering Division. These tests were made to determine the increased performance of the airplane using the higher powers allowable by use of 44-1 fuel as compared with powers allowable with the standard fuel, grade 100/130, Spec. No. AN-F-28. From 15 April to 30 June 1944 approximately 30 hours were flown by Captain R. B. Johnston.
The P-47D is a single engine, high altitude fighter. It is equipped with a Pratt & Whitney R-2800-63 engine furnished with a water injection system and a four-bladed Curtiss Electric controllable propeller, blade design No. 836-2C2-18.
Preliminary tests were run to clear the airplane for performance with higher powers with and without water injection. Detonation equipment was installed to determine if any flight condition became marginal as to detonation, cooling or improper operation of auxiliary parts. No detonation was observed in level flight up to 65.0" Hg. without water and 70.0" with water. No detonation was observed in climb up to 65" Hg. without water. Detonation occurred at 65.0" with water in climb but was remedied by using a No. 18 water jet. Cylinder head and carburetor air temperatures remained below the limits in level flight. Excessive cylinder head and carburetor air temperatures were encountered in climbs, limiting the duration of any climb to a point where limits are reached.
The airplane and engine handled well at all altitudes at the higher powers. At 70.0" Hg., water injection, a maximum speed of 444 MPH was obtained at 23,200 feet. At 65.0" Hg., with water a high speed of 439 MPH at 25,200 feet and a maximum rate of climb of 3260 ft/min. at 10,000 feet were obtained. At 65.0" Hg., without water a high speed of 430 MPH at 25,400 feet and a maximum rate of climb of 2850 ft/min. at 12,000 feet were obtained. At 56.0" Hg. without water a high speed of 418 MPH at 29,600 feet and a maximum rate of climb of 2330 ft/min. at 12,000 feet were obtained. At 52.0" Hg. without water a high speed of 412 MPH at 31,400 feet and a maximum rate of climb of 2030 ft/min. at 12,000 feet were obtained.
III Condition of Aircraft Relative to Tests
A. Flight tests were conducted at a take-off gross weight of 13,230 lbs. with the c.g. at 29.9 MAC, wheels up. This weight corresponds to the full combat weight of the airplane and includes full internal fuel, 15 gallons of water and ballast for 300 rounds of ammunition per gun.
B. All tests were conducted with landing gear retracted and wing flaps neutral. In level flight the cowl flaps were closed and the oil and intercooler flaps neutral; in climb cowl flaps, oil intercooler flaps were wide open. Gun blast tubes and wing racks were installed and all antennae were in place.
C. The airplane was finished with standard, service camouflage finish.
IV Flight Characteristics
A. Taxiing and Ground Handling
This airplane is easy to taxi and handles well on the ground as compared to other fighter planes with conventional landing gear. The brakes are touchy for the first one or two times used but after this they are smooth and respond well without excessive pressure. The tail wheel is full swivel when unlocked and responds very easily. There is a handle on the right side of the cockpit to lock and unlock the tail wheel., When in the "lock" position the wheel locks when returned to the center for taxiing straight and for take-offs and landings. At times it is hard to unlock the tail wheel after landing but it unlocks if the cable leading back from the handle is "flipped".
Crosswind has very little effect on taxiing and ground handling. The tail wheel reacts well and the airplane handles well in rough ground landings.
Handling for take-off is good. With tail wheel in "lock" position, the airplane rolls straight and torque is very easily corrected for by using rudder and a few degrees right rudder trim. Aileron and elevator trim tabs are set in the neutral psoition for take-off. At lower power settings the take-off roll is very long but is greatly decreased by high power. Take-offs were not measured but they seem very short with War Emergency power and improve the pilot's confidence in the airplane. After the airplane is airborne, only a small change in rudder and elevator trim tabs is required to maintain climb.
All take-offs were made without flaps.
When trimmed in level flight for rated or normal power, the airplane is statically and dynamically stable directionally and longitudinally. Laterally, it has neutral stability. Also, when trimmed for 180 MPH glide, the stability is the same as with power.
D. Trim and Balance
Trim is easily maintained by using the aileron, elevator and rudder trim tab controls which are conveniently located on the left side of the cockpit. The trim tab controls work easily and are very sensitive. It takes considerable practice to trim the airplane and keep it trimmed because as one trim control is changed it requires changing others. At all altitudes and speeds the airplane can be trimmed to fly hands off. The auxiliary fuselage tank causes little extra trim when the gasoline from it is used first. If it is not used first, the airplane becomes slightly tail heavy. When opening shutters or putting down wheels and flaps, a medium amount of trim is needed.
Control can be maintained in all attitudes and speeds up to the diving limits. Changes in speed require change in trim and if trim is not made or controls held, the airplane yaws violently. Thus, it requires quite a bit of practice for the pilot to maintain perfect control. For this reason, this airplane is not good on instruments. When the airplane gets out of trim it is very hard to retrim it on instruments.
No acrobatics were tried but rolling into turns and changing directions is very easily accomplished because of very light aileron forces. Rudder and elevator have somewhat heavier forces but not objectionably so. The radius of turn is large and the stick forces become very heavy in a turn requiring both hands on the stick.
The water control switch is objectionable because it must be held "on" by the pilot. This occupies the pilot's left hand and he cannot trim the plane or use both hands on the stick which is necessary to make a tight turn.
G. Stalling Characteristics
There is sufficient warning to the pilot of a stall. Slight buffeting of elevators can be felt in the stick, especially with cowl flaps open. Landing is not recommended with cowl flaps open because of false warning of stall and buffeting of elevator. Another warning of a stall is a jerking of the stick to the left. It will snatch the stick from the pilot's hand if he is holding it losely. The stall is normal and the nose falls straight forward and normal recovery is easy.
H. Spinning Characteristics
No spins were attempted.
I. Diving Characteristics
Acceleration in a dive is fast with control forces building up and becoming high above 350 MPH indicated. There is little vibration except as the speed approaches compressibility. A normal amount of trim is required but the forces on stick and rudder could be held by the pilot. However, the trim tab controls are easily accessible and the airplane can be trimmed easily for a dive.
In a pull out from a trimmed dive of approximately 450 MPH indicated the stick forces increase with the number of "g's" applied during pull out. At approximately 5 "g's" the forces are very heavy. There is no tendency toward stick reversals.
J. Operation on reduced Number of Engines
K. High Altitude Trials
Several flights were made over 30,000 ft. and no objectionable characteristics were noticed. The airplane performs and handles very similar to the way it does at lower altitudes. Sufficient heat from the engine and heater keep the pilot comfortable.
L. Approaches and Landings
There is good visibility to the sides and front for approaches though the nose partially blocks view ahead and below. Three point landings are very easily made in this airplane with full flaps and elevator trim well back. It will flare out nicely or can be forced on the ground by pulling the stick back abruptly and it will stay on the ground. Ground roll is straight wth very little tendecny for the nose to swing. Brakes can be applied with safety either to stop the roll or the keep the roll straight though the rudder is effective down to a very slow speed. Ground roll is fairly long though brakes can be safely used and greatly shortens this distance.
M. Night Flying
No night flying was done
N. Noise and Vibration Level tests at Crew Stations
O. Pilot's Report on Vision and Cockpit Layout
Vision is generally good from the cockpit. In level flight vision over the nose is good though this decreases with speed. For take-off with cowl flaps open and tail down the pilot can only see out the sides. The canopy is clear and there is no distortion. The struts are placed so that the pilot can look around them as necessary. The only blind spot is a cone af about 15° around the tail. A rear view mirror is installed but is very little help.
Cockpit layout is very good with conventional controls in convenient places and plenty of room for the pilot's comfort. There are no projections which catch clothing. Adjustable seat, rudder pedals, safety belt and harness can be easilty adjusted on the ground or in the air. The cockpit is easily accessable with sliding canopy and sufficient hand holds and steps for the pilot. The emergency exit is satisfactory with a handle that releases the canopy which slides back out of the way. Also, the panels on each side can be released in case of nosing over on its back.
The instruments are very well grouped and are easy to see with the flight instruments in the center and engine instruments grouped around them. The electrical panel is on the lower left side of the cockpit and is easily accessable.
P. Crew Report on Layout of Indivdual Stations
V Performance Data
A. Airspeed Calibration
1. The location of the airspeed position correction are given in Fig. 1.
B. Speed in Level Flight
1. The maximum speed at 2700 RPM. 70.0" Hg. (water injection) was 444 MPH at 23,200 ft.
2. At 65.0" Hg., 2700 RPM, water injection, a high speed of 439 MPH was obtained at 25,200 ft. With the water off at 65.0" Hg., 2700 RPM, 430 MPH was obtained at 25,400 feet.
3. The high speed at 56.0" Hg., 2700 RPM, was 418 MPH at 29,600 feet. The high speed at 52.0" Hg., 2700 RPM was 412 MPH at 31,900 feet.
4. Curves of Speed vs Altitude are given in Fig. 2 for a take-off gross weight of 13,230 lbs.
5. Power data for level flight is given in Fig 3, 4, 5.
1. The service ceiling for 2700 RPM was 38,000 feet. The maximum rate of climb for 2700 RPM, 65.0" Hg., water injection was 3260 ft/min. at 10,000 feet. Without water at 65.0" Hg. the maximum rate of climb was 420 ft/min. less.
2. The rate of climb at 56.0" Hg., 2700 RPM, was 2330 ft/min. at 12,000 ft. and at 52.0" Hg., 2700 RPM, 2030 ft/min. at 12,000 ft.
4. Power data for climb is given in Fig. 8, 9, 10.
D. Stalling Speeds
Stalling speeds are given in the following table.
|Up||Down||Open||35" Hg. 2200 RPM||107|
|Up||Up||Open||45" Hg. 2550 RPM||103|
|Up||Up||Open||35" Hg. 2200 RPM||106|
|Up||Down||Open||45" Hg. 2550 RPM||104|
|Up||Down||Open||35" Hg. 2200 RPM||107|
| *This speed is the ship's uncorrected indicator speed, and is effected by attitude of airplane and balance of airspeed lines.
All data given in the following curves has been reduced to NACA Standard Atmospheric Conditions.
A. The R-2800-63 can be operated at 65.0" Hg., 2700 RPM, in level flight and climb without water injection when using 44-1 fuel. It can be operated at 70.0" Hg., 2700 RPM with water injection with 44-1 fuel. Climbs at high power must be limited because of high cylinder head temperatures and carburetor air temperatures. Short climbs can be made without difficulty.
B. A gain of 19 MPH can be realized by using 65.0" Hg., 2700 RPM over 56" Hg., 2700 RPM. 8 MPH can be gained at 65.0" Hg. by using water injection. With water injection at 70.0" Hg., 2700 RPM, 7 MPH can be gained over 65.0" Hg., 2700, water injection.
C. In climb operation a gain of 510 ft/min. by using 65.0" Hg., 2700 RPM over 56.0" Hg., 2700 RPM can be realized. 410 ft/min can be gained at 65.0" Hg., 2700 RPM using wate injection. No 70.0" Hg. climbs were made.
1. It is recommended the Pratt & Whitney R-2800-63 engines be rated at 65.0" Hg. with and without water injection when using 44-1 fuel or its equivalent.
2. It is recommended that the use of 70.0" Hg. be further investigated.
3. It is recommended that pilots using these higher powers be cautioned concerning the high cylinder head temperatures and carburetor air temperatures which may be encountered in extended climbs or level flight.
IX General Dimensions and Photographs
A. General Dimensions
1. Span 41 ft.