One more view of the manufacturer’s model show plan view of the He 31. In the view it resembles a larger MiG-21 with more of a trapezoidal wing than the pronounced delta configuration of the Soviet fighter’s wing, although both incorporated a separate all-flying tailplane or “stabilator” for improved control at high speeds.

The side view emphasises the sleek lines of the design, interrupted on the underside of the fuselage only by the fairing for the de Havilland Spectre rocket motor. The latter was a bipropellant engine which used kerosene and hydrogen peroxide as fuel, and which could provide variable power from 10-100 per cent up to 8,000lb-thrust.

Although metal was never cut on a prototype, Heinkel did nevertheless build the Florett in three dimensions in model form, this example showing the prospective interceptor’s general arrangement, including the Hughes Falcon missiles attached to the wingtips. The AIM-4 Falcon was a first-generation air-to-air missile developed for the USAF in the late 1940s to counter slow bombers of limited manoeuvrability, and proved largely ineffective when used in the Vietnam conflict.

The head-on view shows the nose air-intake, within which sits the adjustable shockcone. The proposed single de Havilland (later Bristol Siddeley) Gyron Junior engine was to be a variant of the PS.50 (aka DGJ.10) version of the engine used on the Bristol 188, capable of 10,000Ib-thrust dry and 14,000lb-thrust with afterburner.

What might have been? This specially commissioned artwork by MARK HARRIS shows a pair of He 31 Floretts climbing to intercept high-flying enemy aircraft after its prospective entry into Luftwaffe service in 1962-63.

A two-seat trainer version of the He 31 was also proposed, and would have carried a reduced armament. Note that on retraction of the undercarriage the nosewheel would rotate through 90° to enable the wheel to lie flat beneath the second cockpit. The latter was raised slightly higher than the front cockpit, but would have offered somewhat limited visibility for the instructor

A detachable nose section was explored, the four-stage detachment sequence of which is seen here: 1: nose and cockpit in normal flight; 2 & 3: detachment of nose. The small print denotes, in descending order, the catapult cylinder, auxiliary piston, “handlebar” and ejected parachute pack. Number 4 shows the whole nose section descending by parachute with limiting detachment speed of Mach 1.1.

A technical drawing of Heinkel’s “Interceptor-Jagdflugzeug” (interceptor fighter) showing sections. The He 31 was designed by Siegfried Gunter after the prolific designer’s return to the company following his arrival in West Germany in 1956, having spent the immediate post-war period designing aircraft in the Soviet Union and living in East Germany during 1954-56.

This illustration of the proposed rocket-drum-machine for the He 31 appears to show a modified version, with three drums rather than two, the first having six rockets and the other two five, the latter each having one chamber empty to permit the exhaust gases to escape.

This contemporary three-view drawing of the He 31 illustrates the modular fuselage structure, armament installations and locations of the Gyron Junior turbojet engine and Spectre rocket motor. The side elevation bears a resemblance to the Soviet Union’s Sukhoi Su-17 Fitter - a generation beyond the He 31.

Apparently for internal (company) comparison purposes only, this “Florett B” design was examined in the autumn of 1957. It was to be powered by a Canadian-built Orenda Iroquois jet engine (BELOW, FAR LEFT) but was to retain the rocket motor. A somewhat larger aircraft, this had a span of 11.10m (36ft 5in), a length of 17m (55ft 9 1/4 in) and a height of 4.910 m (16ft 1 1/2 in). The plan view appears to show two different wing sizes (the starboard is larger), although this may be a distortion in the drawing. The fuselage also appears to be area-ruled.

This sketch dated February 12, 1957, shows the unusual delta+canard configuration of the Messerschmitt P.1211 and the “Fahrwerksseitige Einrichtung fur Senkrecht-Start und Landung” - Undercarriage Equipment for Vertical Take-off and Landing. The nose section appears to be articulated, perhaps for ease of entry and egress.

A contemporary inboard profile illustration of the P.1211 showing detail including the rocket projectiles stacked in a bay aft of the pilot and the Gyron Junior PS.50 afterburning turbojet. In the event, the Luftwaffe received more than 900 F-104G Starfighters, some 292 of which were lost, resulting in the deaths of 116 pilots