The South African
Military History Society

Die Suid-Afrikaanse Krygshistoriese Vereniging

Military History Journal
Vol 2 No 5 - June 1973

Koolhoven F.K. 46

The only Dutch built aircraft to serve with the SAAF

Arthur Blake

The activities of the Dutch aircraft manufacturer A. H. G. Fokker in Germany during the First World War are well known. Less famous is a Dutch aircraft designer who worked for the Allies during the same period. He was Frederick Koolhoven. After qualifying as a pilot as early as 1910, he worked in France for Dperdussin and in Britain for Sir W. G. Armstrong, Whitworth & Co. Ltd and the British Aerial Transport Co. Ltd.

Koolhoven's most successful wartime design was the Armstrong Whitworth F.K.8, an RFC/RAF two-seat reconnaissance bi-plane which could put up a stiff fight when intercepted. The Victoria Cross was awarded on two occasions to pilots flying the F.K. 8 who fought their way through attacking formations of German fighters, of which, ironically, some were Fokkers.

Koohoven, like Fokker, returned to the Netherlands after the war but he did not achieve the fame and fortune of his better-known compatriot. He established his factory at Waalhaven Aerodrome, Rotterdam and designed, in all, more than 50 types of aircraft. Some of these were built in small numbers.

The first Koolboven to reach South Africa was a F.K.41B imported in 1932 by the Air Taxi Co. (Pty) Ltd of Wingfield, Cape Town, as ZS-ADX. It was a high-wing cabin monoplane which featured prominently in the search for the missing Swiss pilot, Carl Nauer, along the West coast of Africa in 1933 (see 'Airman Lost in Africa', by Carel Birkby. Frederick Muller Ltd, London, 1938). It changed hands twice, the last owner being a Mr van der Merwe of Bethlehem in the Orange Free State. It was not pressed into service by the SAAF in 1939-1940 probably because it was no longer airworthy. The registration was finally cancelled after the 'aircraft census' of June 1947.

The SAAF did, however, use a licence-built version of the F.K.41 - the Desoutter 11. This type was built in Britain and the aircraft involved started its career in England as G-ABIG. It was exported to the Belgian Congo in 1933 as OO-CAB and was registered in South Africa in November 1936 as ZS-AHR. By 1940 it must have been in a comparatively poor state as the SAAF paid the Rand Flying Club only 150 UK Pounds (R300) for it. Its subsequent career is unknown.

The F.K.46 bi-plane trainer was a product of the early 'thirties. Dutch pilots nicknamed it 'De Koe' (The Cow) because it was a docile aircraft with few vices. In 1933, it was selected as the standard trainer for the Nationale Luchtvaart School, an organisation established two years previously to provide subsidised flying training on a national scale. At least one - '76' - served with the Luchtvaartafdeling (Army air component ) while others went to private owners.

Production of the type continued over the years at a leisurely pace. The thirteenth aircraft - construction number 4613 - was only completed in February 1939 and registered to the Koolhoven concern as PH-ATR. In comparison with earlier F.K.46s, it embodied modifications to the fin, elevator and rudder, incorporated to make the type more manoeuvrable and thus more attractive to the private owner interested in aerobatics.

According to the records in the Netherlands, PH-ATR was struck from the register in June 1940, a month after the German invasion of the country. So much was destroyed or plundered at the time that enquiries as to the fate of the aircraft are met with a philosophical shrug of the shoulders and 'of in de oorlogshandelingen vernield of met de noorderzon vertrokken'. There were rumours that it had been impressed into the Dutch forces and had carried an orange triangle and the serial number '1003'.

What happened was that PH-ATR was sent to South Africa before the outbreak of war. A Johannesburg firm, Visser & Co., had been appointed agents for Koolhoven to try to break into the local light aircraft market. The F.K.46 arrived by ship and was forwarded to the Witwatersrand by train. It was assembled at Rand Airport where it also completed its test flights. Meanwhile, Visser & Co. launched a publicity campaign to sell the type in the face of stiff competition from established British, German and American aircraft. Looking back, it seems as if the interest in the Dutch bi-plane was very limited. No less than UK Pounds 374-1 3-2 was spent on the publicity side of the campaign while the flying side consumed fuel worth only UK pounds 8-8-9. The outbreak of hostilities in September 1939 probably cut short the apparently futile campaign. From then on there was only one customer for aircraft in South Africa - the SAAF.

The Koolboven concern placed the value of PH-ATR at 19,000 Guilders (approximately R3,800) or a thousand rand more than a brand new de Havilland D.H.82A Tiger Moth. The very expensive aircraft was duly examined by the SAAF during the process of impressing the country's civilian air fleet for the duration. Koolhoven's position in the deal was that of a company in a neutral state negotiating through its agents, Visser & Co., to sell an aircraft to South Africa, a country at war with the Netherlands' powerful neighbour. Under these circumstances, the aircraft was valued at UK Pounds 1,750 (R3 500) or R300 less than the original claim. Soon Frederick Koolboven was to lose much more.

Waalhaven Aerodrome, the site of his works, was selected by the Germans as one of their landing zones in the airborne offensive against Vesting Holland in May 1940. German and British bombs dropped on Waalhaven flattened the Koolhoven plant and it was never rebuilt. Before the war, Koolhoven had been accused of being a member of the N.S.B. - the Dutch Nazi Party - but during the occupation of his country by the Germans he never lifted a finger to help them. He died in 1946.

As a result of the events in Europe, a new party entered the negotiations to buy PH-ATR. He was the Custodian of Enemy Property, an official appointed in terms of the Government's wartime economic measures to watch over the frozen assets of parties in enemy countries. He became involved as Rotterdam was now in enemy occupied territory. When the SAAF finally impressed the aircraft, they paid only 1 000 UK Pounds (R2 000) for it. The money went to the Custodian who in turn paid Visser & Co. the UK Pounds 374-13-2 spent on publicity, but strangely enough not the UK Pounds 8-8-9 spent on fuel. The liquidators of the Koolhoven Company received the balance after the war.

Only scant details are known of the Koolhoven's service with the SAAF. It received the serial number '1598' but there is some doubt whether it ever carried it. There is mention of the aircraft being used for 'light communications and technical training' and of a Board of Survey held at No.31 Group, Voortrekkerhoogte, in June 1944 to decide whether the aircraft should be scrapped or not. By that time it had been given the instructional airframe serial number 'I.S.108'. The aircraft was evidently not struck off charge until August 1948.

A photograph taken during the war shows PH-ATR/1598/I.S.108 on the ground probably at Zwartkop Air Station. Judging from the photograph the F.K.46 could have done very little flying in SAAF service. It shows the aircraft fitted with a stub propeller and being used for ground training. A typical Koolhoven civilian colour scheme and the Dutch civil registration have been retained although SAAF roundels have been applied to the top wings. The rudder striping is almost certainly red, white and blue rather than the local orange, white and blue combination. It is unlikely that the SAAF would have permitted an aircraft with such an exotic colour scheme to be used for regular flying.

So it would appear that the SAAF's only Dutch-built aircraft spent its entire military career on the ground in use as a hack for training purposes. If any reader knows of anyone with the unique serial number '1598' in his log book, the author would be delighted to have his name and, if possible, his present address.

Manufacturer: N. V. Koolhoven Vliegtuigen, Waalhaven Aerodrome, Rotterdam.
Type: Two-seat training bi-plane.
Power plant: One 130 h.p. de Havilland D.H. Gipsy-Major four-cylinder in-line inverted air-cooled engine on a wooden mounting. Engine no.8680 is on record as being fitted to the aircraft. Fuel in centre section of wing with gravity feed to engine.
Wings: Single-bay staggered bi-plane of equal span and chord. Top plane in two halves and mounted on an inverted Vee cabane above the fuselage. Structure of two spruce spars, plywood ribs, covered with three-ply. Ailerons on lower wings only.
Fuselage: Rectangular welded steel tube structure covered with fabric.
Tail Unit: Fin and tailplane of wood braced with tie-rods. Rudder and elevators of welded steel tube and steel sheet ribs covered with fabric.
Undercarriage: Divided type with bent axles hinged to the middle of the bottom of the fuselage and braced by radius rods to the rear spar of the wing. Oleo compression legs attached to the sides of the fuselage.
Accommodation: Two open cockpits with dual controls.
Dimensions: Span 8 m. Length 7,1 m. Height 2,8 m.
Weights and Loadings: Weight empty, 550 kg. Weight loaded, 850 kg.
Performance: Speed at sea level 175 kmh. Cruising speed 155 kmh. Landing speed 64 kmh. Climb to 2000 in 10,3 minutes. Absolute ceiling 4750 m. Cruising range 590 km.

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