Andrzej Jeziorski/MUNICH

DAIMLER-BENZ Aerospace (DASA) has revealed details of a previously top-secret Stealth aircraft research programme conducted in Germany during the 1980s.

The programme, known as Lampyridae (Firefly), or Medium Range Missile Fighter (MRMF), was run from 1981 to 1987 by what was then Messerschmitt-Bolkow-Blohm (MBB), under a contract from the German air force.

The work led to the eventual development of a three-quarter scale piloted windtunnel model of a multi-faceted Stealth fighter. Former project leader Dr Gerhard Lobert claims that the design "very probably" had better radar characteristics than the Lockheed F-117 Nighthawk, despite the F-117 having more than twice the number of radar-scattering facets.

Windtunnel testing began on a 1:3.5-scale low-speed model and a 1:20-scale transonic model in 1985. According to Lobert, these tests demonstrated high-quality aerodynamic properties, despite the disadvantages of the polyhedral airframe design.

Following preparatory simulator work, the manned 3/4-scale model, 12m long, with a 6m wing span, was "flown" 15 times in 1987, in the German-Dutch windtunnel at Emmeloord. Complete flight cycles were simulated in the tunnel's 9.5m2 test section, with the aircraft flying at up to 120kt (220 km/h) and performing small-amplitude movements about all axes.

The project was driven by the idea that a future fighter could be lighter and cheaper if it were so superior at mid-range that it could avoid close-in dogfighting. The engineers' task was to develop a configuration with a forward radar cross-section in the X-band some 20-30dB below that of a conventional fighter. Like Lockheed in its development of the F-117, MBB used the principle of a polyhedral airframe, avoiding right angles and curved surfaces which produced lift by generating a system of vortices from its sharp leading edges.

In parallel to the design work, the company also developed a computational method of calculating radar cross-section, which has since been used to compare the Lampyridae design with available information about the F-117. The radar cross-section was also tested on a full-scale, 16m-long model.

Details of the radar-signature tests are classified, but radar cross-section targets "were met".

Source: Flight International