Folland Fo.117 (Unicraft Models, Resin)

TYPE: Fighter, Project

ACCOMMODATION: Pilot only

POWER PLANT: One Bristol Centaurus XII radial engine, rated at 2,500 hp

PERFORMANCE: 468 mph at 20,000 ft

COMMENT: In the middle war years it was realized that the current fighter like the Hawker Typhoon were in many respects a bit too large to meet the current requirement for single-seat fighters. Consequently, in September 1942 Specification F.6/42 was issued for a smaller and lighter fighter, the document stating an armament of four 20mm cannon and a speed of 450 mph at 20,000 ft, and this aircraft was to be superior in climb, speed and maneuverability to any fighter that might be developed out of Germany’s superb Focke-Wulf Fw 190. Proposals were forthcoming from Airspeed, Boulton Paul, Folland, Hawker, Supermarine, Vickers and Westland and those from Folland and Hawker were favored, the latter eventually being covered by the new Specification F.2/42 and flown as Hawker Fury.
Follands Fo.117 project generated some attention, particularly its contra-rotating airscrew which was then a new feature in fighter design. The Air Staff had assumed that the reason for having this smaller diameter propeller was to provide a smaller undercarriage and a more compact gun installation, but in fact Folland had used it to raise the wing in relation to the fuselage so that the exhaust and cooling air would be ejected above and below the wing roots, thereby reducing drag. The Fo.117 design was favored by RAE Farnborough but there were doubts about the firm having the ability to develop and manufacture such an advanced aircraft quickly enough.
Follands ability to carry through the project had been thoroughly assessed and it was clear that the company could not do the job by itself, but Folland was prepared to work with another firm. By 29 December several minor changes had been made to the design which had improved the Fo.117’s performance figures and altered the all-up weight to 4,160 kg.
Nevertheless, the Chief of the Air Staff (CAS) felt that the design had some particularly good qualities, especially in its potential maneuverability. Indeed the Folland and Hawker F.6/42 projects were discussed and compared very closely during January 1943. However, in March the Folland Fo.117 was abandoned, in part because the country’s design capacity was already overloaded and there were worries about squandering precious resources by giving a job like this to a company who would probably not have the aircraft ready in a sufficiently short period of time, Folland being relatively new and inexperienced in a job of fighter design. In addition, despite the Fo.117 offering a potentially better performance, Hawker’s own project would be ready much earlier.
However, later in 1943 the project was revived as Fo.117A, the revised design introducing a laminar flow wing while the 2,500 hp Centaurus XII still had the contra-rotating propeller. Plans were laid down for production aircraft to be produced by English Electric and six prototypes were actually ordered in September 1943 to an updated specification F19/43.However, in the end they were never built and there are no further details available to describe these airplanes and compare them with the original Folland Fo.117.

(Ref.:Tony Buttler: British Experimental Combat Aircraft of World War II, Prototypes, Research Aircraft and Failed Production Designs. Hikoki Publications, Manchester M22 5LH, 2012

Horten XIIIb (Ho X), (Sharkit Models, Resin)

TYPE: Supersonic fighter, project

ACCOMMODATION: Pilot and Navigator/radar-operator

POWER PLANT: One BMW 003R combined turbojet, rated at 1.000 kp thrust and one BMW 109-718 liquid fuel rocket, rated at 410 kp thrust

PERFORMANCE: 1.118 mph (estimated)

COMMENT: By 1943, the Hortens were discussing the possibility of supersonic flight. While this remained unchartered territory, the decided to experiment with a highly swept glider that would provide an understanding of slow speed handling with a highly swept configuration that might be capable of reaching or exceeding Mach 1.
The glider was designed as Horten Ho XIIIa and construction is believed to have begun in early 1944. The aircraft used wings from the Horten Ho III attached to a new central section which provided a span of 40 ft and a sweep of 60 degrees. The design was very clean with few protrusions apart from a dorsal spoiler and there were no vertical control surfaces. The pilot was housed in a gondola arrangement, mounted below the center section, with access via a tail cone cover. In an emergency, the pilot would jettison his cover and slide out the back of the unit.
The first test flight took place at Göttingen Airfield on 27 November 1944 and further 19 flights were conducted at Homberg by test pilot Hermann Strebel who reported that the glider handled well although he complained about poor roll control, limited forward visibility and landing problems caused by the extended skid.
Nevertheless, the Hortens were contemplating the construction of a more advanced prototype that would be powered by an Argus As10 piston engine in a pusher configuration. But this never came about ans at the end of the war a group of Russian soldiers who had just been liberated from a prison camp discovered the Ho XIIIa and destroyed it.  Furthermore, all the plans and research material for this project vanished without a trace. It now appears that the Ho XIIIb was the anticipated final development of this program and it was expected to have a supersonic performance under certain conditions. Looking very much like an advanced Lippisch design, this fighter would have been about the same size as the HoXIIIa with the same 60 degrees wing sweep. But unlike the glider there would have been a substantial upright fin containing the cockpit in very similar fashion to the proposed supersonic Lippisch P. 13a.
This similarity has often been remarked on although Reimar Horten denied any knowledge of Lippisch’s work during this time in post-war London. However, this seems highly unlikely and there was almost certainly wartime contact between the Hortens and Lippisch. The supersonic Ho XIIIb would have been powered by mixed propulsion system. This could have been either a BMW 003R combined turbojet linked to a BMW 718 rocket engine or a Heinkel/Hirth HeS 011 turbojet and a supplementary Walter rocket engine.
Presumably, a two seater version of the supersonic Horten Ho XIIIb was on the drawing board when in 1945 the “Third Reich” collapsed.

Bill Rose: Secret projects. Flying wings and Tailless Aircraft, Midland Press, Reprint of Ian Allan Publishing Ltd., Hersham, Surrey KTI24RG, 2010.