U.S. Confidential - British Secret
Headquarters Allied Air Forces
Directorate of Intelligence
APO 925
Technical Intelligence Report
No. 163
Subject: Recovery and Reconstruction of
Type 0 Mk 2 SSF HAP
Air Technical Intelligence Unit
16 September, 1943
U.S. Confidential - British Secret
Reconstruction of Japanese Type 0 Mk 2 SSF
HAP
SUMMARY
This report is an attempt to give the complete story from the time of capture
to the actual flight tests of the Type 0 Mk. 2 SSF HAP which was reconstructed
by the Air Technical Intelligence Unit of Allied Air Forces.
As far as possible, all discussions are in chronological order.
A complete set of photographs from the time of capture accompany this report
and show in detail many operations which are difficult to describe by
narration.
CAPTURE AND SHIPMENT
The airplane to which this report refers was captured on Buna Air Strip Papua,
New Guinea, on December 27, 1942.
As soon as the strip became tenable, Technical Intelligence Inspectors made a
complete inspection, and removed instruments and small fittings, which
necessarily had to be protected from souvenir hunters. Immediately after,
a detachment of seven enlisted men from a U.S. Service Squadron, under the
direction of the Technical Inspectors, began the work of dismantling the airplane
preparatory to shipment.
Preliminary examination showed that a least two airplanes, all the engines
available and other small parts would have to be salvaged to assemble one
complete airplane. The party worked about twelve days inspecting the
airplane dismantling, preparing for shipment and removing it to Buna Beach,
approximately 1000 yards through coconut groves. Salvage work required
considerable ingenuity on the part of the personnel concerned as very few tools
and heavy equipment were available. An engine hoist and jeep trailer
together with a Japanese truck which was capture on the strip were sufficient
to complete the job. When extra personnel were needed for lifting and
loading, much valuable assistance was rendered by the Australian Troops
stationed at Buna at the time. A barge was secured and an attempt was
made to load the salvage at Buna Beach. After three engines had been
loaded, a storm came up and the barge sank before morning, dropping two of the
engines into the sea, and damaging the hoist beyond repair. The following
day, the submerged engines were salvaged and treated as well as could be with
available engine oil. A larger steel barge was then supplied and the
loading was continued without mishap. The larger barge proved to be
adequate to transport all of the salvage on one trip, and it was towed to Ono
Bay, eight miles distant, on 1 February, 1943.
The following day the equipment was transferred to a small freighter and sent
on to Milne Bay that afternoon. One officer and four enlisted men
accompanied the shipment as some little trouble was experienced with
soveniring. A policy of strict, *HANDS OFF* was then established, and no
parts were stolen.
After arriving at Milne Bay on the first of February, further transshipment was
necessary to a larger freighter, which was bound for the Australian
mainland. This freighter left Milne Bay on February 9, and arrived in
Brisbane, Australia, on the 19th of February. On this part of
the journey, the equipment was locked in the hold and a guard kept on the hatch
at all times. This was necessary due to the persistent efforts on the
part of personnel to inspect and souvenir the equipment. Upon arrival at
Brisbane, the equipment was immediately taken to the A.T.I.U Hanger on Eagle
Farm.
After complete examination and recommendations, the Command, Allied Air Forces,
decided to reconstruct one airplane and run test flights here rather than ship
immediately to Wright Field. This decision bore the condition that the
reconstruction of this airplane would not interfere with the repair and
assembly of operation airplanes. The reconstruction of this foreign type
airplane necessitated the assembling of sufficient tools, materials and
supplies, plus trained personnel to do the highly technical work
involved.
After a careful re-examination of all component parts of the airplane, it was
found that more damage than that which was first apparent had rendered the
airplane difficult to repair. This damage was caused chiefly by intensive
aerial strafing, bombing, small arms and medium caliber ground gun fire,
together with damage purposely inflicted by Japanese personnel and souvenir
hunters, both Japanese and American. IN addition, minor damage was
incurred by two of the engines as a result of having been submerged in salt
water.
The following is a list of
parts shipped:
a) Four engines.
b) Five propeller
assemblies.
c) Two main fuselage and
wing sections, including ailerons and flap
d) Two rear fuselage
sections.
e) Two tail
assemblies.
f) Two landing gears and
two tail wheel assemblies, three tires.
g) One extra oil tank
and one extra fuel tank.
h) Two sets engine
cowling.
i) Two batteries
j) All instruments and
small control equipment available. (At least two of most items).
k) Available armament,
which included 20 mm. Cannon and 7.7mm. machine guns.
l) Miscellaneous small
items, such as fairing, wing tips and engine accessories.
DETAILED SUMMARY OF REPAIRS OF
COMPONENT PARTS
1. Engines.
Four engines were removed
from the airplane on the field and as before stated, two of these engines
received slight damage due to submerging in salt water. From parts
available that appeared to be fit for operational use, it was decided that only
one engine would be rebuilt. This was based on the fact that nose
sections, power sections and numerous cylinders had been pierced by
bullets. Carburetors, accessories and oil coolers had been extensively
damaged but one or more of all components parts were definitely available.
As repair facilities in the
Brisbane area were not available, all engine material and two mechanics were
sent to U.S. Air Corps Civilian contract shops in Melbourne. The main
factor encountered during overhaul was corrosion which made it necessary to
spend a great deal of time in cleaning parts for reassembly. The advanced
state of corrosion is explained by the fact that these engines had been immobilized
for at least six months, five of which had been spent on the Buna Strip and in
shipment from there to the repair facilities. The engines selected for
final repair came from the same main fuselage section as the airplane selected
for repair. The engine selected for final repair came from the same main
fuselage section as the airplane selected for repair.
Magnetos as well as the oil
cooler were taken from another airplane. Most of the time consuming
element other than the cleaning of parts was the making of piston rings,
gaskets and seals. Cylinders were ground out to depths ranging from .002
to .007 depending on the depth of corrosion. Attempts to manufacture the
top chrome plating ring were unsuccessful and the original top rings were used
and locally manufactured rings were used for the remainder.
Upon completion of repairs the engine
was given thorough block test and about twenty-three hours on a dynamometer
test stand. Results of the dynamometer test were published in Air
Technical Intelligence Report No. 159. At the conclusion of these tests,
the engine was dispatched by air transport and arrived in time to be installed
in the completed fuselage.
2. Propeller. Five completed propeller assemblies
were secured on the field and shipped. It was planned to assemble two
complete serviceable propellers from component parts available. Nearly
all of the blades and some other components were bent, holed by bullets, or
corroded. All parts which appeared to be repairable were then shipped to
the Airscrew Division of DeHavilland Aircraft, Pty. Ltd., Sydney, for major
overhaul.
Propeller No. 79776 was repaired to specification with the exception of No. 2
blade, Serial No. 55040, which is slightly thin on the trailing edge tip
station and has waves on the camber side, caused through numerous indentations
from the 42" station to tip. This propeller is qualified for full
flight test. Upon completion of repair this propeller was immediately
shipped to Eagle Farm, Brisbane, to await flight testing of the airplane.
It arrived in good condition.
Propeller No. 80560 was repaired for use as a secondary propeller as not enough
repairable parts were available to assemble a complete first class unit.
All parts were repaired to specification except blade Serial No. 55079 which
has pronounced indentations on the face on the 22”, 25=3/4” and 50” stations,
and blade Serial No. 55080 which has pronounced indentations on the 49"
and 53" stations. These blades were released for limited flying
only. Upon completion of repair this propeller was sent to Melbourne to
be used in conjunction with the testing of the HAP engine. It was later
shipped to Eagle Farm and arrived there in good condition on Jun 17, 1943.
Two constant speed governors have been repaired and tested and are ready for
use.
3. Main Fuselage and Wing
Sections.
Many sheet metal problems were encountered in the repair of the main fuselage
and wing section of the plane because of the extensive damage caused by the
aforementioned intensive aerial-strafing, bombing and ground fire. This
damage, coupled with the fact that the HAP type airplane is definitely not an
easily repairable type resulted in the consumption of excessive man hours of
skilled labor. Chief among the difficulties were the bullet holes which
ordinarily passed completely through the structure making numerous holds for
every individual bullet. A complete detailed description of these repairs
cannot be given but examples are described and shown in some of the
photographs.
Of the two main fuselage and wing sections the one which appeared to be the
most structurally complete was chosen for repair. This was airplane No.
3030. No. 3032 possibly had less bullet holes but its repair was
precluded by the fact that approximately six foot of the right wing was torn
off apparently as a result of a bad landing. Some parts were used from
No. 3032 to replace damaged ones on No. 3030, but in general new ones had to be
fashioned to insure a proper fit.
A. Fuselage
- Left Side.
The left side of the fuselage
was damaged comparatively little, and required only a few flush patches to
complete the repair.
B. Fuselage
- Right Side.
Right side of the fuselage
required about ten flush patches on the front half and complete new skin on the
rear half.
C. Fuselage
- Internal.
Repairs to the interior of the fuselage were
extensive. They included the replacement and repair of a number of
stringers, formers and backers. Most of the control cables, electrical
wiring and lines were destroyed or damaged severely in this section
necessitating replacement.
D. Wing
- Left.
Both wings were damaged severely and required
extensive and painstaking repair. As noted above the accessibility of nearly
all parts of the wing was very poor. The left wing was holed through in
many places by bullets and shrapnel and many parts of the ribs, stringers and
spars required replacement or repair. Repairs to the small parts were
accomplished by installing new ones. Skin repair was kept flush either by
using flush patching or installing new skin of comparable thickness to
the original. The greatest single difficulty came in the strengthening of
extruded T sections which comprise the flange members of the spars, and which
were shot through by projectiles. Dural angels were machined carefully to
fit the T section and were either bolted or riveted in place, depending upon
the pace available and the amount of shear the splice was required to
withstand. Now pitot lines and electrical connections were installed as
the repair was completed.
E. Wing
- Right.
The right wing presented the same difficulties
as the left, but in a much more intensified form. Damage was very
extensive near the wing root and flap section as a result of the explosion of a
"daisy cutter" bomb nearby. The entire section from the rear
spar to the trailing edge for a distance approximating the flap length was
rebuilt completely. The spar was repaired by the use of the specially
machined dural angles as in the left wing. As the old structure of the
wing would not fit after allowing space for the spar repairs, the adjoining
parts were of necessity, redesigned. Spar splices were checked for
adequacy of reinforcement necessary and aircraft bolts used when any doubt of
the available space for rivets was evident. Some flush patching was used
on this wing but much of it was recovered with new skin.
F. Flaps.
As noted above the flap in the right wing was
nearly destroyed by the explosion of the anti-personnel bomb near by.
This required its complete repair or replacement together with the lines and
actuating mechanism. Sufficient parts were procured from Aircraft No.
3032 to make a complete operating unit. The left flap presented less trouble
and was completed in good time. The interconnecting cable for the flaps
on both ships tested was rigged to an extremely high tension and was
definitely over three hundred pounds. This was thought to be in error and
appeared much too high as the supporting brackets were failing on both
ships. The cable on final repair was rigged to approximately two hundred
pounds of tension. Flaps worked well with this set-up.
G. Wing
Tips.
The wing tips were fitted from available ones
and then repaired. Some work was required on the plexi-glass wing tip
lamp covers which were reformed from new material.
H. Canopy.
Neither the canopy from No. 3030 or No. 3032
were repairable, but one from a previously captures Zeke was fitted.
4. Rear Fuselage Section.
A. Fuselage.
It was decided to use the rear fuselage section
from Airplane No. 3032 as it appeared to present the least problems for
satisfactory repair. It was damaged very severely as the result of
shell-fire and souvenir hunting. No. 3030 was rejected because it had
been blasted out of shape by bomb concussion. Numerous small parts were
secured from it, however, to assist the restoration of No. 3032.
As most of the skin covering was so badly holed
nearly the entire section was recovered with skin of comparable thickness to
the original. Stringers, formers, brackets and other small parts were
either replaced by parts from the other fuselage or they were fashioned
new. Nearly all control cables and electrical wiring were replaced as the
original was all practically destroyed.
B. Fin.
The vertical fin was damaged to the extent that
it involved removal of the skin covering to repair the internal members.
These were all strengthened to at least initial strength. Fairing was
fitted from the best available.
C. Horizontal
Stabilizers.
These presented no unique problems for repair
but some time was consumed, as the flush patching necessary was difficult to
rivet in the small spaces. Bother were fitted up well to the fuselage.
5. Flight Control System.
A. Ailerons.
Numerous dents, bends and bullet holes rendered
the ailerons inoperative without considerable repair. Trailing edges had
to be entirely replaced as well as a number of the ribs. Covering and doping
was done according to U.S. Specifications.
B. Elevators
and Rudder.
These occasioned less repair than the aileron
after the best units of the lot had been selected. Nevertheless,
considerable time was necessary to put them in first class condition.
Covering and doping was done to U.S. Specification.
6. Landing Gear.
A. Main
Gear.
Both main landing gear legs were completely
removed, inspected and repaired where necessary. The left leg of No. 3030
was shot through with a heavy caliber bullet necessitating its replacement from
other parts available. Parts were not interchangeable to a high degree,
so much hand fitting was required. Several tests of the fluid contained
in the oleo leg and retraction mechanism and of the hydraulic system fittings
showed the fluid contained in the oleo leg and retraction mechanism and of the
hydraulic system fittings shoed the fluid be a mineral base type. It was
therefore decided to use U.S. Air Corps Specification 35800 Grade M Medium
fluid in place of the original.
B. Tail
wheel.
The tail wheel was completely disassembled,
inspected and repaired where needed. No particular trouble was
experienced in obtaining a complete operating unit.
C.
Arrestor Hook.
Arrestor hook was not damaged,
so needed very little attention.
D. Tires.
Three main wheel tires and tubes were selected
from those available and sent to and airplane tire manufacturing firm for
complete reconditioning. Upon receipt of the tires from the repair shop
they didn’t appear to be entirely first class condition so investigation was
begun to find one of our own tires that would fit. This turned out to be
the general 22 x 6.50 x 10 4-ply, and appeared to be entirely satisfactory.
7. Tanks.
A.
Fuel Tanks
Both wing tanks and the fuselage tank required
considerable repair as they had been holed in numerous places. As the
tanks were not of the self-sealing variety and repairs were accomplished by
welding. All tanks were then subjected to fluid and pressure tests as
specified in technical orders for U.S. airplanes. Test pressure was
limited to that specified by the Japanese. Now chafing strips were
installed.
B. Oil.
The fuselage oil tank was repaired in the same
manner as the fuel tanks and tested for leakage. Now chafing strips were
installed and tank was re-varnished.
C. Hydraulic.
A new plug
was the major repair on the hydraulic reservoir tank. This was machined
and metric threads cut on it.
8. Cowling and Fairing.
In general
cowling and fairing was not difficult to replace as there were a number of
spares available.
A. Engine cowling was fitted and needed very
little repair except the oil cooler scoop which was completely rebuilt.
Shutters were in good condition.
B. Propeller spindles were in general, badly
damaged, but one was available which appeared to be serviceable with a small
number of patches. This was repaired and was suitable
C. Formation and navigation light covers including
those on the wing tips and tail cone were either badly damaged or missing
completely. These were remolded from plexi-glass by a commercial firm.
9. Instruments.
Two complete sets of instruments and some spares were shipped from the field,
and from these, two sets were repaired and calibrated. The main
difficulties encountered were corrosion, the effects of shell fire on delicate
parts, and the method in which the instruments had been removed from the
ship. Much time was spent in cleaning and fitting of small parts, and
refinishing. Tracing and replacing various connections presented some
difficulty as no information of their original position was available.
Japanese instruments were used throughout excepting the free air temperature
gauge.
10. Gun Sight.
Three reflector gun sights damaged to varying degrees were on hand and from
these, one was placed in serviceable condition. Repair consisted mostly
of cleaning, repairing and replacing damaged parts. Two glass reflector
plates were manufactured locally. The lens assemblies were in
particularly bad condition, and it was necessary to use lenses from all three
units in order to get a serviceable set. As the original light was
missing, an American bulb was substituted, necessitating some adjustment in the
lens assembly to obtain the proper image.
11. Electrical
Two main junction box and switch panel had been left intact in airplane No.
3030, and only a few repairs were necessary on this part of the system.
However, the lines in both wings and the tail had all been damaged by gunfire
and for the most part were completely replaced. All cockpit lights and
fixtures had been removed and were replaced with like kind in so far as
possible. American bulbs were substituted throughout the airplane.
12. Pneumatic System.
This system was particularly difficult to replace because of the fact that all
component parts and connecting line had been removed, and no previous
information on the system was at hand. Parts of this system had
previously been connected with the oxygen system, adding some difficulty in
their straightening out. After completing the oxygen system, and
eliminating the pneumatic system parts which had been connected to it, the
system took definite shape and was completed after expending much work in the
repair of the units and replacement of connecting lines. No air
compressors were sent from the field with the shipment of HAPS.
13. Oxygen Equipment
An attempt was made to install the original Japanese Oxygen system complete,
but while the parts were in storage, the only good oxygen regulator on hand was
taken from ATIU and never returned. Consequently, an American type
regulator was installed in the airplane and adaptation made to the original
system.
A high pressure system was retained because the Japanese oxygen bottles were
fitted in particular place and no American bottles were found that would fit.
14. CO2
This system was complete, and the only work necessary was refilling the supply
bottle.
15. Radio
No radio equipment was captured with the airplane, excepting the radio compass
installation, which was very similar to Fairchild installation. This was
replaced and installed in the airplane. For added communication, a search
was made for a small set which would not be heavy in weight and occupy very
much space. The U.S. SCR-183 radio set was selected and installed in the
airplane. Much trouble was encountered in perfecting satisfactory setup,
but it was finally accomplished and was proved quite successful.
16. Brakes.
As the project neared completion and the airplane was ready to fly, it was
found that the brake system in the airplane was very poor. This was
probably due to the rather weak landing gear installed on the airplane.
An attempt was made to strengthen the brakes but this was finally abandoned
when it became apparent that no repairs other than a major modification would
give satisfactory braking. It was decided that the brakes should never be
used except in extreme emergency.
17. Finish.
The outside appearance of the aircraft upon completion was very poor and a new
finish was applied. A study was made of the original finish as to weight
color and texture, and comparable paint of a lacquer type was selected and
applied. A dove gray color was used for the fuselage, blue for engine
cowling and red for trimmings. The U.S. AAF "Star" was painted
on the airplane except for photographic purposes when the original Japanese
markings were applied.
18. Armament
Sufficient armament was recovered to insure a complete set of 2x20mm cannon and
2 x 7.7 mm. Mgs. For the HAP.
Flight Tests
The initial flight test of HAP was performed on 20 July, 1943, at Eagle
Farm. This flight was for 25 minutes duration to test the trim of the
airplane. No trouble was encountered and no adjustments were necessary
except trimming. Succeeding flights were made on 21 July, the second of
which resulted in some damage to the airplane from ground looping after a dead
stick landing. The engine cut out on a slow roll and never recovered due
to carburetor trouble. The right landing gear was damaged sufficiently to
require replacement.
It is believed that a grabbing brake probably caused the ground loop as no
tendency was noted for ground looping on the first two flights. After the
right landing gear was repaired, the airplane still had a tendency to ground
loop the opposite way so a tail wheel lock was secured and installed.
Since that time, no further mishaps of this nature have occurred. At no
time have brakes been good even after much time and effort had been expanded in
relining, adjustment and checking of the system. Consequently, all pilots
have been ordered not to use brakes except in extreme emergency.
Since beginning flight, some U.S. instruments have been installed including an
altimeter, rate of climb, airspeed indicator, and free air temperature gauge.
In general, mechanical operation of the airplane has been good except for minor
items.
Numerous flights have been accomplished to the present time including altitude tests,
speed runs, rates of climb, simulated combat against other fighter planes and
for photographic purposes. As noted above, full armament has been
installed to duplicate original weights in order to give a true test of
performance.
Complete flight test results will be released as quickly as data becomes available.