Btw Nath, I was under the impression that although most Ki-84Ia's used an 1,800hp powerplant, some also used a 1,990hp unit.Is this correct?
Most Ki-84-Ia's used the Ha-45 and the model 11, which had a hp output of 1,800 hp at take-off and 1,650 hp at 6,560 ft. Early pre-production models also had individual ejector exhausts for a measure of thrust augmentation.
The aircraft that was tested at Wright Field, however, was powered by the Ha 45 type 21 (
1,990 hp at take-off and 1,850 hp at 5,740 ft), an engine that was installed in later version of the Ia in limited numbers. This engine, like its predecessors had a tendency to suddenly lose fuel pressure. The second to last version of the Ha 45 on the Ki-84 was the 23(
1,900 hp for take-off and 1,670 hp at 4,725 ft), which overcame the loss of fuel pressure by having a low-pressure fuel injection system but this powerplant had one flaw, it lost some of the previous Ha-45's hp. The availability of this type was very limited, however, due to the destruction of Nakajima's main production facility at Asakawa by bombers of the XX Bomber Command.
Below is the info on the Ki-84 tested at Wright Field:
and now...
Viewed from the cockpitThe following account of the characteristics of the Hayate was prepared by one of the USAAF test pilots responsible for evaluating a Ki.84-I-ko which had been recovered at Clark Field, Luzon, and transported to Wright Field, Dayton, Ohio, after preliminary testing by a Technical Air Intelligence Unit pilot in situ whose task it was to ready the fighter for the subsequent tactical trials in the USA. The evaluation at Wright Field comprised a total of 11 1/2 flying hours but the test programme was frequently interrupted by failure of exhhaust stacks as a result of the poor materials used in their manufacture coupled with inefficient welding. Problems were also experienced with the hydraulics.
THE COCKPIT of the Hayate was entered from the port wing root walkway and was facilitated by a retractable step and a push-in type handhold at the wing trailing edge, and a second retractable step just below the cockpit sill, these being extremely well located and making for easier access than offered by con-temporary AAF fighters. The stamped metal pilot's seat could be adjusted vertically by means of a handle on the left side, but the locking pin in this particular aircraft did not always engage, with the result that the seat had an annoying tendency to shift under g force changes. The AAF shoulder harness that had been fitted for the test programme was anything but satisfactory, affording no protection for the pilot whatsoever in the event of a crash landing as no stress member had been installed over which the straps could be passed and in the event of an accident involving longitudinal deceleration, the sheet metal seat back would undoubtedly have failed and the pilot would have struck his head on gunsight or instrument panel.
The layout of the cockpit itself was, in general, satisfactory, with the flight and engine instruments logically grouped, the former being arranged on the upper centre portion of the panel with the latter below. The flap and undercarriage controls were situated on the lefthand side of the floor, with the elevator trim wheel and engine control quadrant against the lefthand side wall. No fiight-adjustable aileron or rudder trim tabs were provided, preventing the aircraft being trimmed for hands-off flight. The auxiliary electrical panel and ignition boost control containing circuit breakers were below the instrument panel on the right; the internal and external fuel selector valves and fuel cooler and primer controls were on the righthand side of the floor, and the cowling and oil cooler flap controls were on the upper right cockpit side, together with the radio equipment. The auxiliary hydraulic pump was further aft on the righthand side and the mechanical up-lock release was on the left side of the cockpit floor.
The wobble pump, primer and starter button, all being on the right, kept one hand rather busy in starting, and it soon
became obvious that the Hayate handled rather poorly in taxying owing to inadequate braking action, a condition aggravated by the inefficient design of the rudder bar and toe brake assembly. Use of the brakes was mandatory for "S"ing in order to obtain a measure of forward vision. At the same time, braking had to be strictly limited in order to prevent overheating and locking as a consequence. It proved difficult to get the tailwheel to castor and vision for taxying was certainly not improved by the narrow cockpit and rearward position of the seat, but the actual take-off characteristics were good, with negligible torque effect if rated power was applied gradually. On the other hand, if power was piled on, full right rudder and some braking were necessary to counter the strong pull to port. Three-point take-offs could be safely executed at 95 mph (153 km/h) IAS with normal rated power or above, initial acceleration being normal with either 15 deg flap or no flap at all. At 150 mph (241 km/h) IAS only some four seconds were required for undercarriage retraction, this process producing no loss in altitude or sinking feeling and negligible trim change, and it was immediatcly obvious that initial climb rate wasextremely good, although no performance climbs could beattempted owing to flying time restrictions.
Excellent handling and control
Once the canopy was shut it became apparent that the cockpit left something to be desired from the viewpoint of comfort for a normal-sized pilot owing to the severely restricted head room, and the design of the seat coupled with lack of provision for rudder pedal adjustment would obviously have resulted in some discomfort during extended operations. However, body room was ample and heat level and ventilation volume were found to be good for warm weather operation at low and medium altitudes cold weather operation would have been another story owing to lack of cockpit heat. Despite a some- what narrow canopy, combat vision was excellent in climbing flight when gentle "S"turns were necessary. The cockpit noise level proved to be fairly normal for a radial-engined fighter without an exhaust collector ring, and the vibration level was definitely lower than that of the A6M5 Zero-Sen, especially at high speed, and comparing fairly closely with that of most contemporary US fighters.
It was quickly ascertained that, in general, the handling and control characteristics of the Hayate were superior to those of comparable US fighters and particularly in the low speed regime. The roll rate and turning radius were found to be slightly inferior to those of the A6M5, but control feel was very good; rudder and aileron forces were light, well correlated and produced quick, positive changes of attitude. Elevator forces, although heavier than those of the rudder and ailerons, were not objectionable and progressed with g forces with no apparent lightening. No flat spots or control reversal tendencies were encountered over an IAS range of 74 to 350 mph (119 to 563 km/h). There were little changes in directional trim between 150 and 350 mph (241 and 563 km/h), but the rudder control became extremely sensitive at 300 mph (483 km/h) lAS. sensitivity reducing somewhat at higher speeds.
As previously mentioned, flight adjustable trim was provided for the elevators only and the trim control worked easily, but excessive play at the cockpit end of the device resulted in some difficulties in the initial pre-setting of the tab, although very little trim change was necessary throughout the level flight speed of the aircraft. Only slight longitudinal trim changes occurred with opcration of the undcrcarriage and flaps. The lack of in-flight trimming for the ailerons or rudder did not seem serious, although a rudder trimmer would undoubtedly have improved the Hayate's capabilities as a gun platform. As flown, the Hayate had been rigged with too much right rudder trim and the attendant starboard wing heaviness proved something of a handicap in evaluating stall and handling characteristics accu- rately. However, the stability of the aircraft appeared to be very satisfactory. Yaw tests indicated some lateral oscillation, although not of a serious nature.
The stalling characteristics of the Hayate proved to be quite normal and stall warning occurred early enough to prevent a stall developing if recovery procedure was initiated promptly. In clean condition with power off at 8,000 ft (2440 m) the stall warning consisted of shudder and elevator buffet at 108 mph (174 km/h) IAS. The actual stall, which came at 102 mph ( 164 km/h), proved clean and the Hayate was stable with little tendency to drop off on a wing. and the ailerons and rudder remaining effective well below stalling speed. With the wheels and flaps down and the oil cooler shutters open, but the cowl flaps and canopy closed, the stall warning--occasionally accompanied by severe canopy buffet came at 92 mph ( 148 km/h) IAS and the actual stall occurred at 90 mph (145 km/h) with the nose dropping straight through. Again, there was no indication of instability.
With power on, undercarriage down and full flap, the Hayate did not stall. The rudder became inadequate below 81 mph(130 km/h) IAS and at this speed heading could be maintained
by use of full right rudder and right aileron. The ailerons became inadequate for maintaining altitude below 74 mph (119 km/h). the Hayate yawing left at this speed and then rolling with any further decrease in speed, but control was readily recovered by an increase in airspeed and a slight decrease in power.
Manoeuvrability was good; rolls, loops, Immelmanns and turns being executed with ease at normal speed, although well
co-ordinated manoeuvres proved somewhat difficult owing to the lack of in-flight aileron and rudder trimming. Handling on the approach and during landing was very good, with no undesirable characteristics or ground looping tendencies manifesting themselves, and vision, too, was good during the approach, although less than adequate after the flare was made. After extension of the undercarriage below 160 mph (257 km/h)and the application offull flap at 130 mph (209 kmh), a three-point landing could be satisfactorily executed (with elevator trim set for zero stick force) using speeds of 120 mph ( 193 km/h) over the fence and 110 mph (177 km/h) just off the runway, the actual touch-down being made at 92 mph ( 148 km/h). The Hayate landed easily. with all oleos soft, and was stable during the landing run which was pleasantly short. Crosswind landings could be made comfortably, but the brakes were relatively poor, although rather better than those encountered on the Ki.43-II Hayabusa.
General functioning
The Japanese instruments functioned well and appeared reliable with one or two noteworthy exceptions. The gyro turn indicator appeared to be binding inasmuch as only one-third needle width right or left was the maximum indication obtainable under any attitude or rate of turn; the caging knob was missing (or had been omitted) from the artificial horizon, making it impossible to cage the instrument for aerobatics or to erect the gyro after it had been upset--no gyro erection tendency was apparent in five minutes of level flight after up-setting, and the left fuel gauge consistently read lower than the right hand gauge although the fuel tanks theoretically fed evenly. Control friction was nominal on the ground, with no binding or roughness present, but interference between the auto mixture control and the stick became evident when an attempt was made to apply full left aileron when the mixture control was set normal.
The operation of the Nakajima Ha-45 18-cylinder radial was generally satisfactory throughout the series of flight tests, but while easy to start cold proved somewhat difficult when hot, the externally energized starter apparently having an insufficient torque rating. The engine ran somewhat roughly between 1,400 and 1,600 rpm and between 1,900 and 2,100 rpm, but the engine controls were smooth in operation with positive response. The engine control quadrant friction locks were unreliable, however, and rarely held the controls in fixed position, the auto mixture and supercharger controls creeping and the propeller control tending to vibrate at low rpm positions. Operation of the four-bladed electrically-controlled constant speed Pe-32 propeller was good, although it displayed a tendency to overspeed excessively unless extreme care was taken when power was being applied after a prolonged dive.
The hydraulic system usually worked smoothly but some difficulty was experienced with the hydraulically-operated undercarriage. On one flight, the mainwheels retracted only partway and on another retraction was completed but the up-locks would not engage. On both occasions repeating the cycle of operations appeared to clear the trouble. Prior to the delivery of this particular Hayate to Wright Field, the hydraulic pump had failed completely on one flight with the result that the wheels crept down. The auxiliary hand pump, which was connected to the reserve portion of the main hydraulic tank, worked well and its capacity was such that approximately 100 strokes were required to retract or extend the flaps, but its efficacy in so far as the undercarriage was concerned was not checked. In the event of a complete hydraulic fluid failure, the undercarriage could be unlocked manually and allowed to fall into place, the process being aided by yawing the aircraft until the indicator lights showed that the down-locks had engaged. One poor feature of the hydraulic system was the need to open and shut the by-pass. This had to be opened below 1,200 rpm to prevent the pump from overheating. The electrical system functioned well, with the exception of one instance of generator failure prior to take-off, but the location of the generator switch in the baggage compartment (which could not be reached by the pilot) was poor.
It was concluded from the test programme carried out at Wright Field that Hayate was essentially a good fighter which compared favourably with the P-sIH Mustang and the P-47N Thunderbolt. It could out-climb and out-mananuvre both USAAF fighters, turning inside them with ease, but both P-51H and P-47N enjoyed higher diving speeds and marginally higher top speeds. The light power loading and control forces of the Japanese fighter were to be admired, but it was not so well constructed as its US contemporaries, perhaps reflecting the slipping Japanese production standards at that stage of the war; it was obviously incapable of standing up so well as US fighters under continual usage and it was more demanding on maintenance. It revealed little effort on the part of its manufacturer to render its pilot's task easier or safer--it lacked fire extinguishers and means of emergency escape--but it was a sturdy little warplane and a very dangerous antagonist in fighter-versus-fighter high-g mananuvring combat when flown by a reasonably experienced pilot.
**Test info and data received from magazine AIR INTERNATIONAL, VOLUME 10, NUMBER 1, JANUARY 1976.
[This message has been edited by Nath-BDP (edited 02-14-2001).]
