Heinkel He 231

Heinkel He 231
Type:	VTOL fighter aircraft project
Design country:	BR Germany
Manufacturer:	Ernst Heinkel Flugzeugwerke
First flight:	-
Commissioning:	-
Production time:	-
Number of pieces:	not built

The Heinkel He 231 was the name given to the design of a tail-sitter - VTOL -Jagdflugzeugs the West German manufacturer Heinkel in the 1950s.

history

On December 2, 1957, the Federal Ministry of Defense issued an invitation to tender in which the requirements for a VTOL all-weather fighter were recorded. The first concept of the development team at Heinkel around Siegfried Günter was in the direction of a tail starter ( tailsitter ).

Concept of a rear starter

Among other reasons, the significant weight advantage was decisive for the inclusion of the rear starter concept with jet propulsion and afterburner. The engine with the best thrust / weight ratio and the smallest installation dimensions at that time was the General Electric J79 . But even with this engine, the aircraft would have been too long to take off from the rear because the center of gravity would have been too high above the ground. The design was then revised and received four significantly shorter General Electric J85 engines and delta wings.

The disadvantages of the rear seater turned out to be:

• Danger of pushing in cross winds during landing. In addition, the poor visibility and the extreme angle of attack during the transition made landing difficult.
• Overload starts were not possible without additional missiles , which would have particularly limited the tactical application possibilities.
• Poor mobility on the floor.
• Difficult loading and maintenance.

In the mid-1950s, some models ( Ryan X-13 Vertijet, Lockheed XFV-1 , Convair XFY-1 Pogo and SNECMA Coléoptère ) were developed based on this concept, but not least because of the disadvantages described, they did not get beyond the prototype stage.

First flat starter concept

Three-sided view of the second concept stage

In the further course of development, only drafts of aircraft taking off in a horizontal position were examined. If the entire thrust was to be available for both vertical and horizontal flight, one had to rely on the most space-saving engines possible. The Rolls-Royce RB.108, which was actually designed for vertical take -off , was unsuitable because it did not have an afterburner and was not designed for higher dynamic pressures.

So you came back to the J85. The resulting design provided for two engines in the front and rear sections with a takeoff weight of 4950 kg. Each engine should have a jet deflection with a cross-section that remains constant during the transition. The control around the transverse axis should be carried out in hover by the thrust control. For the control around the other two axes, bleed air of the compressor stages was provided, which should be blown out at the surface ends.

The problems to be expected in connection with the thrust vector control in an afterburner engine would have required extensive basic studies. In addition, it was concluded that the additional weight of the jet deflector together with the complicated fuselage structure would be at least as great as the additional weight of an overall swiveling engine system in nacelles and the necessary higher landing gear.

Duck wing concept

In the third development phase, different designs with a total of pivoting engines were examined. After extensive wind tunnel investigations, it was concluded that the tender requirements could best be met with a four-engine duck -type aircraft . The control around the longitudinal and transverse axis in slow flight could be done by the thrust control. At a height of 20,000 m, the four intended J85 engines and a total thrust of 77.7 kN should achieve twice the speed of sound.

During the take-off transition, with the engines pivoted vertically, a height of 15 m should be reached within 5.6 s. It was then planned to achieve a speed of 345 km / h after a total of 20 s in aerodynamically supported level flight. The reverse landing transition should take a total of 39 s.

construction

The fuselage of the duck-designed aircraft was structurally simple and had a largely circular cross-section with a maximum diameter of 1.10 m. Payload, fuel and landing gear should be housed in the fuselage. The use of a 25-mm automatic cannon 251RK from Oerlikon with 150 rounds and four Sidewinder air-to-air missiles at fuselage stations was planned as standard armament.

A special feature is the intended increase in surface strength against the noise of the jet engine. A sandwich honeycomb core construction with a steel outer skin was also considered, and ultimately a conventional light metal construction was chosen for financial reasons.

After a fundamental revision of the design in the second half of 1958, plans were made to expand the rear engine nacelles by adding a second engine each. Instead of the J85, the RB.153 from Rolls-Royce should now be used.

After the development ring south was founded in February 1959, this design was called EWR VJ 101 A and was further developed until autumn 1959, before it was merged with the VJ 101B presented by Messerschmitt to form the VJ 101C.

Technical specifications

Parameter	He 231 tail sitter	first flat starter concept
crew	1
length	approx. 10 m	approx. 10.30 m
span	approx. 6 m	approx. 6.40 m
height	4.10 m
payload	450 kg
Empty mass	4600 kg	4950 kg
Max. VTOL takeoff mass	7460 kg
Engines	four General Electric J85

See also

• List of aircraft types

literature

• Hans Redemann: V / STOL weapon system VJ-101, part 1: He 231. Flight Revue, November 1971, pp. 18-22.

Web links

• Data and drawings

Individual evidence

1. ↑ Photo of the rear seat design ( memento of the original from October 27, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
2. ↑ ^{a b} aiaa.org ( Memento from July 7, 2010 in the Internet Archive )