OSCAR 2
A pilot's handbook for OSCAR 2 captured at Korako and translated by ATIS, provides interesting information. While the plane referred to is the long wing (37.6' span) OSCAR 2, its performance and characteristics are close enough to those of the current production short wing (35.6' span) OSCAR 2 to be considered identical. There are several obvious errors in the document and it is not known whether these existed in the original, an official JAAF publication, or resulted during translation and/or transcription. Pertinent data are as follows. (All data reduced to American units).
I. Airframe Specifications:
a. Span – 37.62 feet
b. Length – 28.98 feet
c. Height (3-point) - 10.12 feet
d. Wing Area – 236.0 sq. ft.
e. Aspect Ratio - 6
II. Engine and Propeller Specifications:
a. Engine - Type 2 1150 HP (Ha-115)
b. HP/AMP/RPM/Alt.
- 1104/41.7"/2800/S.L. (T.O.) (300 mm)
- 1104/37.8"/2700/9186' (Rated) (200 mm)
- 966/37.8"/2700/27887' (?) (Rated) (200 mm)
c. Fuel – 92 octane
d. Propeller – 3 blade hydraulic C.S.
1. Diameter – 9.2 feet
2. Blade Angle - 24°-44°
III. Weights:*
a. Empty – 3812 lb.
b. Normal Gross – 5320 lb.
c. Overload – 6069 lb.
IV. Flight Limitations
1. Diving Speed – Below 373 m.p.h. I.A.S.
2. Acceleration – Below 6 g.
3. RPM – Below 2600, 3000 in dive.
4. AMP – Below 37.8" Hg
5. Full Flaps (30°) – Below 155 m.p.h. I.A.S.
6. Combat Flaps (15°) – Below 249 m.p.h. I.A.S.
7. Retract Landing Gear – Between 99 -118 m.p.h. I.A.S.
8. Lower Landing Gear – Below 168 m.p.h. I.A.S.
*Japanese weight figures vary from U.S. practice. Empty weight rarely includes armament, radio, and miscellaneous equipment usually included in the basic weight of U.S. planes. Overload weight is very often exceeded in practice, normal gross [weight,] almost always.
V. Fuel Tank Selection and Time of Consumption
A. With Jettison Tanks
Fuel Tank/Capacity/Condition/Approx. time of Consumption
Jettison/52.8 gal./Cruise/l hr. 40 min
Jettison/52.8 gal./Cruise/1 hr. 40 min.
*No. 2 Tank/69.2 gal./Combat/20 min./cruise/ 1 hr. 5 min.
*No. 1 Tank/79.2 gal./Cruise/2 hr. 0 min.
Total - 254 gal./6 hr. 45 min.
Cruise Condition: 13,123', 1900 RPM, 37.8" Hg, 168-174 m.p.h. I.A.S.
Fuel Consumption - 31.7 g.p.h.
For take-offs and landings, subtract 30 min. fuel from No. 1 tank.
*The long wing OSCAR has four wing tanks. When there is a symmetrical wing tank arrangement, it is common Jap practice to connect the symmetrical tanks to a common fuel **** and designate them as one. Thus, "No. 2 tank" is evidently the two front wing tanks.
B. Standard Fuel
Fuel Tank/Capacity/Condition/Approx. time of Consumption
No. 2 Tank/68.6 gal./Cruise/1 hr. 30 min.
No. 1 Tank/79.2 [gal.]/Combat/20 min./Cruise/1 hr. 30 min.
Total - 148 [gal.]/3 Hr. 20 min.
Cruise Condition: 13,123, 1900 RPM, 37.8" hg, 180-186 m.p.h. I.A.S.
For take-off and landing, subtract 35 min. fuel from No. 2 tank.
VI. Fuel Consumption Data for Cruising:
A. Standard Load
Altitude(ft)/IAS(mph)/TAS(mph)/RPM/AMP(Hg)/SFC(gph)/Supercharger(Speed)
3281/177/192/1800/22.1/28.0/1
13123/181/228/1900/22.1/31.7/1
13123/187/235/2000/22.1/32.2/1
22966/173/257/2000/22.1/33.8/2
22966/167/249/2000/22.1/33.8/2
B. With Jettison Tanks
3281/168/183/1800/22.1/28.0/1
13123/170/214/1900/22.1/31.7/1
13123/175/220/2000/22.1/32.2/1
22966/160/238/2000/22.1/323.8/2
22966/153/228/2000/20.1/31.2/2
VII. Take-off Distance and Time (No Wind)
Flap[position]/RPM/AMP/Distance/Time/IAS/Load
0°/2700/37.8"/630'/118 sec/68.4/Normal
15°/2700/37.8"/564'/106 sec/65.2/Normal
0°/2700/37.8"/889'/151 sec/74.6/Overload
Note: 2500 RPM and 32.9" Hg (75 mm) are used for training and normal take-offs from good run-ways. 2600 RPM and 37.8" Hg (200 mm) are normally used for short run-ways or obstructions. Tabulated figures are for maximum power take-off under emergency conditions.
VIII. Climb
Normal climb is at 2500 RPM and 32.9" Hg (75 mm). Maximum climb, tabulated below, is for a steady climb under standard load conditions. Supercharger is shifted at 14,764 ft. Time of climb does not include take-off run. Cowl flaps are open two-thirds.
Altitude(ft)/ Time(min/sec)/Rate(fpm) / IAS(mph) / RPM / AMP("Hg)
3,281 / 1.13 / 2730 / 146 / 2700 / 37.8
6,562 / 2.25 / 2898 / 146 / 2700 / 37.8
9,843 / 3.30 / 3070 / 143 / 2700 / 36.2
13,123 / 4.35 / 2893 / 140 / 2700 / 31.9
16,404 / 5.49 / 2320 / 137 / 2700 / 37.8
19,685 / 7.24 / 1949 / 130 / 2700 / 34.3
22,966 / 9.12 / 1791 / 127 / 2700 / 30.7
26,247 / 11.09 / 1535 / 112 / 2700 / 26.77
29,528 / 13.36 / 1142 / 115 / 2700 / 23.2
32,810 / 17.20 / 687 / 109 / 2700 / 19.3
36,794 – Ceiling
IX. Level Flight
Condition /Altitude / RPM / AMP /IAS /TAS/ SFC/Impeller
Cruise /13,123 / 1900 / 20.1" /177/ 224/ 29.1/1 Speed
Cruise /19,685 / 2000 / 22.1 /174/ 249/ 26.4/2
Combat /13,123 / 2600 / 35.8 /*242/ *224/ 95.1/1
Combat /19,685 / 2600 / 35.8 /*240/ *249/ 106.0/2
Full Speed /9,843 / 2700 / 34.8 /252/ 313/ nil/1
Full Speed /19,685 / 2700 / 37.8 /221/ 320/ nil/2
*Error, possibly in original, probably in either translation or transcription. Neither IAS nor TAS appear to be reasonable.
X. Indicated Stalling Airspeed at 6562 Feet
Condition/Flap Opening/Indicated Stalling Speed
Cruising/0°/74.6 m.p.h.
Landing/30°/65.2 m.p.h.
Landing Gear Down/0°/78.9 m.p.h.
With jettison tanks, indicated stalling speed is approximately 6.2 m.p.h. less. (?) Landing descent is at 93-106 m.p.h, contact at 78 m.p.h. Landing roll on grass is about 1840 feet without brakes, 1500 with.
XI. Turning Performance:
Altitude/Direction/IAS/Radius/Time/RPM/AMP
1969'/Left/205 m.p.h./307.4'/10.8/2700/37.8
1969'/Right/205 m.p.h./301.5'/11.0/2700/37.8
Note: Turns are executed without difficulty but the ailerons get heavy with increased speed.
XII. Handling Characteristics and Aerobatics:
a. Airplane is normal in every respect. Take-off is simple, turns are easy, landings are normal 3 point with practically no instability after contact.
b. In tropical conditions, vapor lock occurs during climb and at high altitude. It can be reduced by installation of a main and auxiliary [sic] tank pressure system (No. 1 and No. 2 tanks are provided) and a fuel cooler. It can be combated [sic] by operating the hand fuel pump 2 or 3 times. To minimize vapor lack, [sic] reduce the ground test run as much as possible, operate throttle slowly on take-off, take measures to keep fuel temperature low during refueling.
c. Although various types of acrobatics are possible, avoid half rolls, snap rolls, spins, inverted climbs, and steep pull-ups at high speed.
d. Enter loops at 2300 RPM and 199 m.p.h. IAS. The speed at top is about 81 m.p.h.
e. Loop rolls (Immelmans?) entered at 2300 RPM and 217 m.p.h. IAS. Altitude gain is about 1600 feet.
f. Climbing Rolls can be executed at 2300 RPM and an initial speed of 186 m.p.h. 106 m.p.h is the proper speed for Rolls.
g. Slow Rolls can be executed from level flight by gradually increasing the boost. To prevent the nose from dropping during inverted flight, adjust the trim tab to "down elevator"
h. Slow turns are made in level flight with the throttle cut at an indicated air-speed of 143 m.p.h. Loss of altitude will be about 2000 feet.
i. Steep climbs are made at 2600 RPM and 37.8"Hg. A 3281 foot climb can be gained at 50°. The Initial air-speed will be 217 m.p.h. and the final speed, 112 m.p.h.
j. Steep dives are made by setting the propeller at maximum pitch to avoid excessive RPM. The RPM will then be around 2000.
k. Supercharger change-over at 2700 RPM should be at about 13,800 feet. At 2600 RPM, 13,400 feet. The operation should be performed at 2200 RPM and below 29.92"Hg. During combat the change-over can be effected [sic]at rated horsepower without ill effects.
l. Descend at an IAS of from 186-220 m.p.h. in flat turns with the throttle open slightly.
Comment [by intelligence analyst]
This document shows OSCAR to be a ship of fair performance, good climb, and excellent maneuverability. There is no evidence that OSCAR pilots take the restrictions seriously and they seem to get away with it. The engine limitations appear to be too stringent and the performance in ATAD #T1 is based on power ratings slightly higher than those presented here. There have been reports of OSCAR showing high "flash" performance and it is possible that some sort of power-boost may now be incorporated. There is reason to believe that Jap pilots prefer OSCAR to the higher performing TOJO and TONY.