Kawanishi HI IK Soku – data

Contemporaries

Blohm und Voss BV 222 Wiking (Germany), Blohm und Voss BV 238 (Germany), Domier Do214 (Germany), Boeing C-98/B-134 (US), Consolidated PB2Y-3R Coronado (US), Martin JRM-1 Mars (US), Martin PBM-3R Mariner (US), Sikorsky VS-44 Excalibur (US), Convair R3Y Tradewind (US), Short Sandringham (UK), Short Solent (UK)

Because the HI 1K1 was not built, the specifications given are estimates made by Kawanishi.

Type Transport Flying Boat

Crew Five

Powerplant

Four Mitsubishi MK4Q Kasei 22 (Ha-32-22) 14-cylinder, air-cooled radial engines developing l,850hp for take-off, l,680hp at 6,886ft and l,550hp at 5,500m/l 8,044ft; each engine drove a 4.3m (14.1ft) diameter, four – bladed, alternating stroke propeller

Dimensions Span Length Height Wing area Wing loading Power loading	47.97m 37.70m 12.55m 289.95m! 156.72kg/m2 6.12kg/hp	157.4ft 123.7ft 41.2ft 3,121ft2 32.1 lb/ft2 13.5lb/hp
Weights
Empty	26,405kg	58,2131b
Loaded	45,550kg	100,4201b
Useful load	19,095kg	42,0971b
Performance
Max speed	470km/h	292mph
	at 5,000m	at 16,404ft
Cmise speed	369km/h	229mph
Landing speed	144km/h	89mph
Range	3,890km	2,417 miles
Climb	11 min 30 sec to 3,000m (9,842ft)
Ceiling	N/A

Armament

Three 13mm Type 2 machine guns with 200 rounds of ammunition per gun

Deployment

None. The HI 1K1 Soku did not advance past the mock-up stage.

There are a few Japanese wartime aircraft such as the Kugisho Tenga jet bomber that remain shrouded in mystery to this day. The Kawanishi K-200 most certainly falls into this category, a design that had it proceeded would have resulted in the first turbojet pow­ered flying boat.

Very little is known of the genesis of the K-200. Kawanishi may have been approached by the UN to initiate the project or Kawanishi may have undertaken the design themselves to see if a flying boat could be constructed using the new jet engines being designed following the success of the Ne20 turbojet. Towards the close of the war, Kawanishi was developing two other large flying boats: the Kawanishi K-60 and the Kawanishi HI IK Soku. Both of these were at the behest of the UN so it may not be unrea­sonable to assume that the UN also asked Kawanishi if they could add a jet powered fly­ing boat to the mix. Exactly when Kawanishi began to study the prospect of the K-200 is not known though 1945 is the likely year.

Depending on the source, the K-200 was either to be the replacement for all UN flying boats in service or the K-200 was to be a car­rier for a Japanese atomic weapon. The for­mer assumption would likely have depended on the performance of the K-200 had it been built. Certainly the prospect of the K-200 did not deter other flying boat projects such as the K-60 nor improvements of the H8K already in use. If the K-200 was to be such a replacement for operational flying boats and proved superior to them, it most likely would not have entered widespread service until 1946. As far as the latter, the K-200 would have needed capabilities that exceeded flying boat designs then in service in order to serve as a means to drop an atomic weapon on the US. It has been suggested that the Nakajima Fugaku was also devised to carry an atomic weapon but there is no support for this notion. The same may be said for the K-200. One can speculate as to whether the K-200 would have been any more successful in pen­etrating US coastal defences than a high flying bomber. As we shall see, the K-200 may have had a flaw that would have made any such use all but impossible.

What the definitive shape of the K-200 was to be is open to conjecture. Certainly Kawan­ishi would have utilised their successes with the H8K and to a lesser degree with the Kawanishi H6K (codenamed Mavis) as a foundation for the K-200. As such, it is likely that the hull design would have followed a similar pattern. One speculative illustration of the K-200 shows a hull not unlike the H6K but deeper, though not to the extent of the H8K. A conventional tail akin to the H8K was used but the horizontal stabilisers were mounted halfway up the vertical stabiliser. The wings appeared very similar to the H8K and were fit­ted to the hull in a like position, this being on the top of the hull and, at least for the K-200, nearly central mounted on the hull. Interest­ingly, the K-200 was illustrated with fixed wing floats, which contrasted with the retractable floats used by the H8K3 as a means to increase speed. Perhaps such a modification would have been considered for the K-200 as well.

The K-200 is shown as having an armament layout similar to the H8K1. If this was the case, a Type 99 20mm cannon was fitted in a tail turret and in the top mounted turret forward of the wings. On either side of the forward bow was a blister that would have been armed either with the Type 99 cannon or a Type 92 7.7mm machine gun. Finally, a Type 99 cannon would have been fitted in the bow. The K-200 was also probably able to carry a payload of bombs, depth charges or torpe­does.

As far as propulsion, the K-200 was to use six turbojets. They were to be mounted on top of the wings with each turbojet housed in a separate nacelle. Grouped in sets of three, the engines were fitted to each side of the hull on top of the wings. The reason for this was to minimise the amount of sea spray ingested by the engines during use. If the K-200 was of similar dimensions to the H8K, then the tur­bojet engines would have to move something in the region of 24,948kg/55,000 lb of weight when the K-200 was fully loaded. If the Ne 330 turbojet was the engine of choice, all six would produce a combined thrust of 7,800kg/l 7,196 lb. This may have been suffi­cient to give the K-200 a speed superior to the H8K2, which topped out at 467km/h (290mph).

Where the K-200 may have come up short is in terms of its range. Six turbojets would have required a significant amount of fuel in order to give the flying boat a useful opera­tional radius. As an example, the Ne 20 turbo­jet consumed around 740kg (1,6301b) of fuel per hour. The Nakajima Kitsuka, which used two Ne20 engines, carried a maximum of 1,447kg (3,1901b) of fuel (and without drop tanks only 723.5kg/l,595 lb) and therefore, at its cruise speed, could muster a 824km (512 mile) operational range. If the Ne330 con­sumed approximately 2,535kg (5,5881b) of fuel per hour at full thrust, then six would require at least 15,028kg (33,528 lb) of fuel for approximately one hour of operation at max­imum speed. Flying at a cruise speed would, of course, extend the operating range. Options to attempt to save weight may have included removing any armour, stripping the defensive armament and/or constructing the aircraft from wood as was the plan for the HI IK Soku. Even with such measures the K-200 would have been hard pressed to match, let alone exceed, the range of the H8K or more conventional piston engine flying boats.

It is not known how far Kawanishi studied the feasibility of the K-200, if at all. With resources allocated to the H8K, the HI IK Soku and the K-60 among other projects, Kawanishi designers may have put the K-200 to one side pending availability of turbojets sufficient to warrant the effort in developing the flying boat. Aside from anything else, even a reliable turbojet such as the Ne20 could only muster four to five hours of operation before it would suffer from problems. It may have been seen that preliminary perfor­mance estimates fell short of expectations and offered no significant advantage over designs currently in use or projected to enter service. Finally, a lack of materials necessary to construct the K-200 may have played a role in sidelining the design; the engine and con­struction material issue saw the K-60 ground to a halt and this may very well have extended to the K-200. Regardless of the reasons, the K-200 would never be anything more than a concept.

As a side note, following the war it was planned to construct a civilian version for use by Japan Airlines.

Kawanishi K-200 – data

Contemporaries

Beriev R-l (Russia), Martin P6M Seamaster (US)

Specifications

There is no exact information available on the Kawanishi K-200.

Deployment

None. The K-200 existed only as a concept or paper design.