How JAS 39 Gripen might have looked

In 1979 design studies for what was to become JAS 39 Gripen was started. By 1982 the basic configuration had been decided upon, before that several alternatives had been investigated.
In the end an unstable canard layout was adopted, as it would give the greatest benefits to performance, as it gives a high onset of pitch rate and low drag enabling the aircraft to be faster, have longer range and carry a larger useful payload.

Canard or aft tail configuration?


One of the two basic variants were 2102, which was a F-16 look-alike, but smaller and with side intakes.


The other basic variant was 2105 which was of delta canard configuration. It was also tested with a chin intake. 


2108 was an other canard layout.
For an instability of 5-10% at subsonic speeds, which was desired, Saab decided that a canard layout would entail a lower technical risk as the canard can be weathercocked turning the aircraft into a slightly stable one. This cannot be done with an unstable aft tail configuration.
Other advantages with a canard is more lift during take off and landing, 10% better supersonic turning performance and lower supersonic drag. Also envisioned was the possibility to point the nose off the direction of travel. The canard can also be used as an air brake after landing.  


The version most likely to compete with the canard layouts had a dorsal intake, which meant a short and straight duct. Wind tunnel tests showed that it would work well at high angles of attack and that 2107 had better turning performance than 2105. Saab judged the risks with the dorsal intake as too large.


2111 had a HIMAT-like, Rockwell designed wing. Subsonic turning performance was increased due to a lower induced drag and its aeroelastic properties, without performace reductions in other regimes. Note the leading edge flap on the canard, the double slotted leading edge flaps on the main wing and the small control surfaces near the engine nozzle.
Span was 9% greater than for 2105, sweepback 10% less, wing area 13% less but weight 3% greater. It was cancelled in 1982 as at that time it wasn't possible to manufacture it with the correct aeroelastic properties.

The final result


The image actually depicts JAS 39 Gripen, which is a slightly refined form of Saab 2110.

No comments:

Post a Comment