The last single-seat fighter of Koolhoven design built by the British Aerial Transport Company, the F.K.25 Basilisk was designed around the 350hp A.B.C. Dragonfly I nine-cylinder radial engine and carried the usual armament of twin synchronised 7.7mm Vickers guns. Of wooden construction with a monocoque fuselage, the Basilisk featured a hood-like fairing, ahead of the cockpit, which enclosed the guns and shielded the pilot. Three prototypes were ordered, the first of these flying during the summer of 1918. The second prototype, completed in 1919, differed from its predecessor primarily in having a deeper fairing ahead of the cockpit. Further work on the Basilisk was abandoned at the end of 1919.

Engine: 350hp A.B.C. Dragonfly I nine-cylinder radial
Take-off weight: 990 kg / 2183 lb
Empty weight: 659 kg / 1453 lb
Wingspan: 7.72 m / 25 ft 4 in
Length: 6.22 m / 20 ft 5 in
Height: 2.49 m / 8 ft 2 in
Wing area: 19.69 sq.m / 211.94 sq ft
Max. speed: 228 km/h / 142 mph
Armament: 2 x 7.7mm Vickers

The British Aerial Transport Company Limited F.K.24 Baboon was a two-seat training biplane produced during World War I. Using experience gained designing the Bantam, aircraft designer Frederick Koolhoven (assisted by Robert Noorduyn) designed the two-bay biplane elementary trainer.

The aircraft had a flat-sided fuselage and an uncowled 170 hp (127 kW) ABC Wasp engine simply bolted to the firewall. Maintenance and repair costs have been kept to a minimum through the use of interchangeable upper and lower wing panels, ailerons, elevators and rudders.

Six aircraft were planned but only one was built in July 1918 as a consequence of the end of the First World War and the subsequent sharp reduction in orders for military aircraft.

The Baboon was registered with British Aerial Transport Co. Ltd in May 1919. The only notable act was when it won the Hendon Trophy Race over a 20-mile (32-km) circuit in July 1919 flown by Major Christopher Draper. The Baboon was scrapped at Hendon in 1920.

Powerplant: 1 × ABC Wasp I, 170 hp (130 kW)
Propellers 2-bladed BAT tractor, 5 ft (1.52 m), 7 ft 10 in (2.39 m) diameter
Wingspan: 25 ft (7.6 m)
Wing area: 259 sq ft (24.1 m2)
Length: 22 ft 8 in (6.91 m)
Height: 8 ft 10 in (2.69 m)
Empty weight: 950 lb (431 kg)
Gross weight: 1,350 lb (612 kg)
Fuel capacity: 12 imp gal (54.55 l; 14.41 US gal)
Maximum speed: 90 mph (140 km/h, 78 kn)
Landing speed: 40 mph (64 km/h; 35 kn)
Endurance: 2 hours
Rate of climb: 833.33 ft/min (4.2333 m/s)
Time to altitude: 10,000 ft (3,048.0 m) in 12 minutes
Wing loading: 5.2 lb/sq ft (25 kg/m2)
Power/mass: 0.126 hp/lb (0.206 kW/kg)
Crew: 2
Capacity: 400 lb (181.44 kg) disposable load

The first prototype F.K.23 was originally ordered as the fourth of a batch of six development F.K.22s, and while retaining the wooden structure with monocoque fuselage, it embodied extensive redesign. Overall span and wing area were reduced to 6.09m and 14.86sq.m respectively, and the tail surfaces were redesigned. Armament comprised two synchronised 7.7mm Vickers guns and power was provided by a 170hp A.B.C. Wasp I, flight testing being initiated in May 1918. Two further prototypes (originally ordered as the fifth and sixth F.K.22s) were similarly powered, but dimensionally larger, and after further redesign resulting from initial flight trials, a batch of 12 F.K.23 Bantam Is was ordered, the first of these being delivered to the RAE at Farnborough on 26 July 1918. At least nine Bantam Is were completed, one of these being sent to France and evaluated at Villacoublay in the late summer of 1918. One example was sent to the USA for evaluation at Wright Field, but this fighter’s principal shortcoming was the poor reliability of its Wasp I engine.

Engine: 170hp A.B.C. Wasp I
Wingspan: 6.09m
Wing area: 14.86 sq.m

The first design by Frederick (Frits) Koolhoven after joining the British Aerial Transport Company (B.A.T.), the private-venture F.K.22 single-seat fighter flown in September 1917 was of wooden construction with a monocoque fuselage. Powered by a 120hp A.B.C. Mosquito six-cylinder radial engine, it displayed sufficient promise to win an official contract for a batch of six development aircraft. The first and third of these were powered by the 170hp A.B.C. Wasp seven-cylinder radial (F.K.22/1) and the second by a 100hp Gnome Monosoupape nine-cylinder rotary (F.K.22/2), the remaining three eventually being completed as prototypes for the F.K.23. The F.K.22/2, retroactively named Bantam II, was the first to fly, commencing its trials in December 1917 and being delivered to Martlesham for official trials on 19 January 1918. Armament comprised two synchronised 7.7mm Vickers guns, and this prototype, later re-engined with a 110hp Le Rhone 9J nine-cylinder rotary, was eventually assigned to the Central Flying School at Upavon.

F.K22
Engine: 120hp A.B.C. Mosquito six-cylinder radial

F.K.22/1
Engine: 170hp A.B.C. Wasp seven-cylinder radial

F.K.22/2
Engine: 100hp Gnome Monosoupape nine-cylinder rotary
Take-off weight: 571 kg / 1259 lb
Empty weight: 393 kg / 866 lb
Wingspan: 7.52 m / 24 ft 8 in
Length: 6.30 m / 20 ft 8 in
Height: 2.26 m / 7 ft 5 in
Wing area: 21.37 sq.m / 230.02 sq ft
Max. speed: 161 km/h / 100 mph

The Bristol TB.8 two-seat trainer of 1914-15 was powered by 80 hp rotary engines. Various makes were used including Gnome, Le Rhone and Clerget. Later models were powered by a 100 hp Gnome Monosoupape engine.

About 36 were built, of which some were supplied to the RNAS and six went to Roumania.

Wingspan: 37 ft 8 in
Length: 29 ft 3 in
Max speed: 73 mph

Intended as a successor to the F.2B two-seat fighter-reconnaissance aircraft, the F.2C Badger was designed for the 320hp ABC Dragonfly I nine-cylinder radial. Three prototypes were ordered. Armament comprised two fixed 7.7mm Vickers machine guns and a 7.7mm Lewis gun mounted on a Scarff ring in the rear cockpit.
The first prototype suffered a crash landing because of an engine failure during its first take-off on 4 February 1919, but was rebuilt and flown. The second prototype was completed with a nine-cylinder Cosmos Jupiter of 450hp and flew on 24 May 1919, but later had a Dragonfly substituted for the Jupiter. A third aircraft was completed as the Badger II with a Cosmos Jupiter engine and redesigned wings, this being re-engined in 1921 with a 385hp Jupiter II (this power plant having meanwhile been taken over by Bristol) and subsequently being used primarily for engine development purposes.

F.2C Badger
Engine: 320hp ABC Dragonfly I nine-cylinder radial
Take-off weight: 1430 kg / 3153 lb
Empty weight: 884 kg / 1949 lb
Wingspan: 11.20 m / 36 ft 9 in
Length: 7.21 m / 23 ft 8 in
Height: 2.76 m / 9 ft 1 in
Wing area: 33.18 sq.m / 357.15 sq ft
Max. speed: 217 km/h / 135 mph