Apart from the
Heidevogel of 1911, Koolhoven designed 59 aircraft, which he consecutively numbered FK-1 to FK-59. About half of these were design studies that were never built. Koolhoven designed projects FK-1 to FK-28 in England for
Armstrong Whitworth and
BAT, projects FK-29 to FK-34 for
N.V.I. and projects FK-35 to FK-59 for his own company. The first 'true' Koolhoven airplane therefore would have been the FK-35. However, on formation of the N.V. Koolhoven, Frits Koolhoven took with him the design of the
FK-30 "Toerist" light sportsplane originally designed for NVI, but not built. Several "Toerists" built by the new FK Koolhoven therefore constitute the earliest airplanes of that company, if not by production date, then at least by numbering. The website of the Koolhoven foundation lists 26 Koolhoven designs, starting with the
F.K.30 and then going from
F.K.35 to
F.K.59. It however also notes that the designs F.K.37, 38, 39 and 59 were never built, while only giving pictures of wooden models for the designs
F.K.35 and
F.K.36. Jane's Encyclopedia of Aviation only lists the Koolhoven designs
F.K.40,
41,
42,
43,
46,
48,
49,
51,
52,
53 and
58 but mentions a
F.K.50-b bomber project, which the Koolhoven foundation site doesn't. The best-known of those designs are the F.K.41 high-wing monoplane, which was built under licence as the
Desoutter Mk.II and the
F.K.50 twin engine transport monoplane, two of which were used by the Swiss aircraft company . Amongst the military designs, the most successful were the
Koolhoven F.K.51 biplane reconnaissance aircraft, which saw service in extensive numbers in the Dutch air force from the mid-1930s until the
Second World War, the
Koolhoven F.K.52 biplane which was used by the
Finnish Air Force and the
Koolhoven F.K.58 single-seat monoplane fighter. The latter was the plane ordered by
France and flew in the
Armée de l'Air during the
Battle of France A complete list of the Koolhoven aircraft and projects is given below: •
Koolhoven Heidevogel early experimental aircraft, one built, 1911 •
Koolhoven F.K.30 "Toerist" (Tourist) Light high-wing sports monoplane, 1927 •
Koolhoven F.K.35 Seaplane scout and fighter, available as low-wing monoplane or biplane, 1926 •
Koolhoven F.K.36 Larger biplane version of the F.K.35, 1926 •
Koolhoven F.K.37 Design for a 3-engined airliner for the
KLM (not built) •
Koolhoven F.K.39 Various design studies for a monoplane two-seat fighter (not built) •
Koolhoven F.K.40 Airliner for 4 or 5 passengers, 1928 •
Koolhoven F.K.41, High-wing monoplane cabin "
sport coupe", built under licence by
Desoutter in England •
Koolhoven F.K.42 High-wing open cockpit Private plane, 1929 •
Koolhoven F.K.43 Three passenger cabin sportsplane/air taxi resemblant of the F.K.41, 1930 •
Koolhoven F.K.44 "Koolmees" (Great Tit) Private plane resemblant of the F.K.41/F.K.43 •
Koolhoven F.K.45 Biplane aerobatic plane, 1931 •
Koolhoven F.K.46 Biplane trainer, 1930 •
Koolhoven F.K.47 Biplane private plane/trainer, 1933 •
Koolhoven F.K.48 Six passenger twin-engined airliner used by the
KLM, 1934 •
Koolhoven F.K.49 Twin-engine photo- and cartography aircraft, purpose built for the Dutch air force 1935 •
Koolhoven F.K.49A Multi purpose aircraft, 1937 •
Koolhoven F.K.50 Eight passenger twin-engined airliner, a more powerful F.K.48, used by
Alpair 1935 •
Koolhoven F.K.51 Military biplane trainer with open seating, 1935 •
Koolhoven F.K.52 Two-seat biplane scout and fighter with enclosed cabin, 1936 •
Koolhoven F.K.53 "Junior" low/mid wing light touring plane, 1936 •
Koolhoven F.K.54 High-wing monoplane cabin "
Executive plane" with retractable gear, 1937 •
Koolhoven F.K.55 Experimental high performance fighter with contra-rotating propellers, 1936 •
Koolhoven F.K.56 Low-wing monoplane two-seat advanced trainer and scout, 1937 •
Koolhoven F.K.57 Twin-engined low-wing executive plane, 1938 •
Koolhoven F.K.58 Modern monoplane high performance fighter, 1938 •
Koolhoven F.K.59 Multi-purpose development of the F.K.52, no information available whether built, last Koolhoven design, 1940 •
NVI F.K.29 Two-passenger, single-engine biplane, one built, 1923 •
NVI F.K.31 Two-seat reconnaissance-fighter aircraft, 17 built, 1923 •
NVI F.K.32 two-seat training biplane, 1925 •
NVI F.K.33 Ten passenger, three-engined airliner, one built for KLM, 1925 •
NVI F.K.34 Three-seat reconnaissance seaplane, 1925 ==References==