02/28/2014. Remarks by Johan Visschedijk: "After considerable experimentation with fixed and pilot-operated slots to smooth the airflow over the wing leading edge at low speeds and high angles of attack, Frederick Handley Page secured a master patent in October 1919, and immediately began to explore the possibilities thereby provided for STOL aircraft, especially those suited to carrierborne operation. This led to the type T Handley (retrospectively H.P.19) single-seat torpedo-bomber prototype that was then further developed to produce the two-seat type Ta Hendon (retrospectively H.P.25), designed by George Rudolph Volkert.

The Hendon Mk.I was in essence the Handley Mk.III with a longer fuselage. Power plant was a 450 hp Napier Lion IB twelve-cylinder liquid-cooled W-engine. Armament consisted of a trainable 0.303 in (7.7 mm) machine gun, and one torpedo or two 520 lb (236 kg) bombs.

Six aircraft (s/n N9724 to J9729) were ordered in November 1923 and the first of these flew on July 7, 1924. The type was not placed in service, but the aircraft went through a series of modifications that played a major part in the development of the fully automatic slot system. With an improved slot operating system the type was designated Hendon Mk.II, and with interlinked ailerons and slots it was designated Hendon Mk.III."

Span: 46 ft 0 in (14.02 m)
Length: 34 ft 6 in (10.52 m)
Wing area: 526.0 sq.ft (52.21 sq.m)
Max take off weight: 6,970 lb (3,160 kg)
Max speed: 110 mph (177 kmh)
Service ceiling: 9,500 ft (2,940 m)