Mitsubishi-Payen Pa.400 and Suzukaze 20

When Allied intelligence discovered an illus­tration of the Suzukaze 20 in a Japanese mag­azine, it was unlike anything so far seen in Japanese aviation design. Despite the radical appearance, it was felt the Suzukaze 20 was a bona fide aircraft and might be encountered in action. As it was, the plane was a work of fiction and so the Suzukaze 20 was later stricken from the publications on Japanese aircraft identification and coding. However, Allied intelligence may or may not have been aware of the very real inspiration for the artist of the Suzukaze 20.

At the time, because of the relative difficulty in obtaining information on Japanese military matters, intelligence services relied on vari­ous publications such as newspapers and magazines as a means to glean data on the Japanese military machine. In April 1941, the Japanese magazine Sora (translated as ‘Sky’) published a number of illustrations of various aircraft in a section entitled ‘Dreams of Future Designers’. Included in the selection of art­work was the rendition of the Suzukaze (‘Cool Breeze’) 20. The 25 December 1941 issue of the US magazine Flight would also feature the Suzukaze 20, along with three other aircraft: the Nakajima AT27 (codenamed Gus), the Mitsubishi T. K.4 Type 0 (codenamed Frank then Harry) and the T. K.19 (codenamed Joe). The Suzukaze 20 would receive the code – name Omar.

The illustration of the Suzukaze 20 depicted a single-seat fighter with the striking feature of having a cockpit blended into the vertical sta­biliser that was itself in the form of a half-delta. Another notable feature was the use of two radial engines, one mounted behind the other, driving two, contra-rotating propellers. Armament appeared to be heavy with four weapons fitted in each wing. Its speed was given as 769km/h (478mph), loaded weight 2,858kg (6,3001b), wing area 13.37m2 (144ft2) and wing loading 214.82kg/m2 (44 lb/ft2).

As the war dragged on it became evident that the Suzukaze 20, along with the other three aircraft illustrated with it, were works of fantasy and thus all four were removed from Japanese aircraft intelligence bulletins, the last of them disappearing by June 1943. Despite the Suzukaze 20 being a fictional air­craft, there was a kerne! of truth behind it that perhaps germinated in the mind of the artist that drew the Suzukaze 20. The kernel could have been the works of the French aircraft designer, Nicholas Roland Payen.

Payen was born in France in 1914 and became interested in aviation early in life. By the 1930s, he had begun to focus on the use of delta planforms as well as canards and ogival (bullet shaped) flight surfaces. Throughout his life, Payen would design a large number of air­craft in a wide array of configurations but, despite the prolific nature of his studies, only two were built before the end of World War 2. Both used Payen’s Flechair (an English con­traction of avion fleche or ‘arrow aircraft’) configuration that consisted of a trapezoidal fore-wing that housed the ailerons and a rear delta wing which contained the horizontal control surfaces. Payen had to rely on his salesmanship to gain access to material, wind tunnel time and other resources to build his aircraft as he had little money of his own to fund projects. Of course, the nature of his designs often made it a hard sell to the more conservative aviation industry. The Payen Pa. 100 Fleche Volante (‘Flying Arrow’) was his first aircraft to be built and was intended to be a racer to compete in the Coupe Deutsch de la Meurthe. Payen was able to borrow a 180hp Regnier R6 but the engine was later returned. He was then able to acquire a larger engine, a 380hp, 7-cylinder radial Gnome – Rhone 7KD Titan Major, but was too large for the Pa. 100. Payen had to seek donations (which he received) and rebuilt the Pa. 100 around the 7KD to create the Pa. 101. Unfortu­nately for Payen, the Pa. 101 failed to meet expectations. It finally took to the air on 17 April 1935, but on 27 April a hard landing broke the port landing gear and a fire broke out in the resulting crash gutting the Pa. 101. The accident saw Payen’s flight insurance revoked and so he went to work at the Bloch factory constructing a mock-up of the Pa. l 12 fighter that used two 150hp Salmson engines in tandem buried in the fuselage. The out­break of World War 2 saw the French military show no interest in this design.

The second aircraft was the Pa.22 which was the test bed for Payens proposed Pa. l 12 fighter. Originally to be powered by a ramjet, no such engine was available and a 180hp Regnier R6 engine was used instead. Payen constructed the Pa.22 in 1939 and the Ger­mans would later capture it after the invasion of France on 12 June 1940. The Germans, showing some interest in the design, test flew it on 18 October 1941 and found modifications were needed to correct poor longitudinal sta­bility. The aircraft was moved to Rechlin in Germany and after adjustments had been made to the cockpit position and the vertical stabiliser had been rebuilt the Pa.22 flew in the summer of 1942. After a number of short flights, the aircraft was wrecked in a crash landing. The Pa.22 was returned to France for repairs and was consequently abandoned by the Germans.

Prior to the outbreak of war, the Japanese had civilian and military personnel in France who studied and reviewed French aviation progress for possible use by Japan. This prac­tice went as far back as 1919 when Japan invited French military aviation instructors to teach the fledgling Japanese Army air force. The French also brought with them some of the latest aircraft that their country had avail­able. This training would forge a link between Japan and France that would last for many years, and it was by these means that the Japanese would learn of Payen’s work.

In 1938, Payen received a letter from Mit­subishi expressing an interest in his designs, notably the delta wing so often used in his air­craft concepts. A meeting was held between Payen, Commander Koshino and the captain of the UN corvette Sumikawa to talk about the Pa. l 12. During the discussions the UN inquired as to whether the Flechair design could be adapted to that of a two-seat, carrier borne, light bomber. The specifications required the aircraft to have the ability to take­off from and land on a deck space 80m (262ft) long, to have a range of at least 800km (497 miles), be capable of carrying a 800kg (1,7631b) torpedo or bomb and be Fitted with up to 180kg (396 lb) of armament.

Payen took the specifications and worked up a study to meet the UN requirements. The design was called the Payen-Mitsubishi Pa.400. This would have used two 670hp radial engines mounted one behind the other driving two, two-bladed, contra-rotating pro­pellers. For weapons, in addition to carrying the required torpedo or bomb, a nose mounted cannon (firing through the propeller hub), two machine guns per rear wing and a tail mounted machine gun were proposed. Endurance was to be 11-12 hours with a max­imum speed of 580km/h (360mph). Unlike his other Flechair designs, Pa.400 used staggered wings (his earlier offerings had the two wings level with each other). The study was reviewed and Payen was asked by Japanese representatives to obtain from the French gov­ernment the authorisation to export the tech­nical information for the Pa.400 study. This would have allowed the Japanese to further develop the Pa.400 in Japan. The authorisa­tion was granted on 28 September 1938, signed by the head of the cabinet of the Min­istry of Air. However, with the cloud of war on the horizon, Payen decided not to send the requested documents to Japan and it would appear the Japanese did not follow this up. To

DANIEL UHR

all intents and purposes, the Japanese seemed to have lost interest in the Pa.400.

Why would the Japanese show an interest in the Pa. l 12 and the Pa.400 only to abandon it on the brink of receiving the technical infor­mation? There were several factors which the Japanese may have become aware of upon further review of Payen’s initial Pa.400 study. The first was that Japanese radial engines of the time did not have sufficient horsepower and, more importantly, were not of the correct size to fit into the Pa.400’s fuselage. Thus, the Japanese would have had to either construct a new radial engine or adapt the Pa.400 to use a Japanese engine, radial or not. A more per­tinent problem was the use of tandem radial engines. To make such an arrangement work­able required a considerable feat of engineer­ing and such designs making it to prototype form were exceedingly rare. Another factor concerned the poor visibility afforded the pilot given that the cockpit was situated far back in the fuselage which made landing a challenge at the best of times, let alone landing on a moving and rolling aircraft carrier. The rear wings and the long nose blocked side and downward vision, a serious liability in aerial combat, and the relatively short wingspan of the Pa.400 would not have offered much agility, a trait favoured by Japanese pilots and designers. In addition, the Japanese may have learned that the Pa. 101 was a flawed design and since the French military paid Payen no attention may have concluded there was nothing worth pursuing where the Pa.400 was concerned. Finally, it may have been the rad-

The Pa.400 depicted here is in the colours and markings as used on a Nakajima B5N2 torpedo bomber (known as Kate to the Allies) flown by Petty Officer First Class Toshio Takahashi from the carrier Hiryti during the attack on Pearl Harbor.

ical design of the Pa.400 that saw more con­servative UN officials directing Mitsubishi to focus their efforts on more conventional air­craft projects.

Enter the Suzukaze 20. A photograph of what was likely the Pa. 101 appeared in Japan in a printed document in the late 1930s. The caption for the photograph read ‘French Brand New Model Pey-yan 266th. Airplane No – mu 400 Horse Power’. The ‘Pey-yan’ was the phonetic spelling in Japanese of Payen while ‘No-mu’ was the phonetic spelling for Gnome. How it got to Japan is open to speculation but the two prevailing theories are that Payen, in trying to drum up funds for his work, made it available to a French diplomat to take to Japan to shop around to Japanese industry. Alternatively, the photograph was given to the UN by Payen during the discussions over the Pa.400.

The photograph – and perhaps other sources because Payen’s aircraft were shown in publications such as Bill Barnes: Air Adven­turer (from April 1935) – likely played a part in the rendering of the Suzukaze 20. The similar­ities to Payen’s designs cannot be ignored. For one, the Suzukaze 20 utilised two radial engines in tandem driving two, contra-rotat­ing propellers. Also, the Suzukaze 20’s cockpit was blended into the large, half delta-shaped vertical stabiliser, another Payen trait seen in the Pa. IOO/Pa. IOl and Pa.22. The artist likely removed the rear delta wing and slid the for­ward wings back and enlarged them since their shape is reminiscent of the Pa.400. With the exception of the nose, the fuselage shape of the Suzukaze 20 was similar to that of the Pa.400. Even the horizontal stabilisers of the Suzukaze 20 had a delta shape, perhaps a nod to the Pa. 101. However, whether or not the artist based the Suzukaze 20 on Payen’s designs may never be known for certain.

Contemporaries

Horton HoX (Germany), Messerschmitt P. l 106 (Germany), Lippisch PI3a (Germany), BMW 803 engine (Germany), Wright R-2160 Tornado engine (US), Pratt & Whitney R-4360 Wasp Major engine (US), Butler – Edwards ‘Steam Dart’ (UK), Scroggs ‘Dart’ (US)

For the Mitsubishi-Payen Pa.400, based on the design study conducted by Payen.

Type Light Carrier Bomber

Crew Two

Powerpiant Two Gnome-Rhone 14 M4/5 radial engines, each developing 670*680hp maximum, driving two contra-rotating, two-bladed propellers Dimensions Span Length Height Wing area 6.58m 10.00m 2.68m 25.00m2 21.6ft 32.8ft 8.8ft 269ft! Weights Empty 2,179kg 4,7841b Loaded 5,860kg 12,9191b Speed Max speed 570km/h 360mph at 4,950m at 16,240ft Max speed (one engine) 447km/h 278mph at 4,950m at 16,240 Landing speed 89km/h 55mph Endurance 12-14 hours Ceiling 4,950m 16,240ft Armament Five machine guns, two in each wing and one in the tail; one cannon firing through the propeller hub; one 800kg (1,764 lb) torpedo or bomb

Deployment

None. The Suzukaze 20 was a fictional aircraft while the Pa.400 remained a design only.