A.Weyl Fokker: The Creative Years (Putnam)
Platz thought that a modern two-seater specifically designed as a trainer might be a selling proposition. During the war no special training aeroplanes had been designed in Germany; all trainers were merely obsolete operational types converted for instructional purposes. A few aircraft, such as the L.V.G. B.III, were simplified and redesigned for cheaper materials for production as trainers.
For his training two-seater Platz chose side-by-side seating. He thought this would be better for demonstrating control movements than the conventional tandem arrangement. Because the parasol wing arrangement combined stability with an unobstructed field of downward vision he chose this configuration.
The only available engine of less than 100 h.p. was an old 75-h.p. Mercedes, a six-cylinder engine of 1913 vintage with a dry weight of 146 kg. (322 lb.). It had a flat, square nose radiator.
The prototype was test-flown by Parge at Schwerin early in 1919. It was later taken to Amsterdam, where it was painted green. It was flown a good deal at Schiphol until it was crashed by Meinecke in October 1921 while attempting an emergency landing.
The V.43 was resuscitated as the Fokker S.I with modern water-cooled engines of 80 to 90 h.p. In 1922 Fokker took to the U.S.A, an S.I with a Curtiss OX-5 engine. The U.S. Army Air Service bought it and gave it the designation TW-4.
In certain aspects the Fokker S.I resembled the Fokker F.VI; in particular, its upper longerons were cranked upwards behind the cockpit. The nose radiator was 76 cm. (30 in.) high and 54 cm. (24 in.) wide; its total cooling surface was 8-9 sq. m. (96 sq. ft.). Shutters were fitted behind the radiator to regulate the engine temperature. The petrol tank was installed between the engine and the cockpit, and fuel feed was by pressure.
With the official Project No. P245, the Fokker TW-4 was tested by the McCook Field Engineering Division of the United States Army Air Service. The report was critical of the aircraft’s taxying characteristics: the rudder was too small for adequate ground control. Take-off was easy, but the run was rather long; landing was also easy, but the TW-4 floated a long way after the round-out and would need an experienced pilot to get it into a small field or aerodrome. Laterally and longitudinally the aircraft was stable; it was slightly tail-heavy at full throttle, slightly nose- heavy in the glide. The field of view was excellent downwards and sideways, but extremely poor upwards and sideways. Accessibility for maintenance was good.
In his summing-up, the test pilot stated that the lack of upward visibility was a serious drawback in a military trainer, which would have to be used at aerodromes where numbers of aircraft would be in the air at the same time.