ONE OF THE loudest noises at the Farnborough air show has been from the chorus of detractors who criticise the more extravagant manoeuvres used by manufacturers in demonstrating their products. What relevance, they have asked, is there in demonstrating steep take-offs and low-speed, high-alpha passes with a large commercial airliner? Where is the combat application, they have queried, to a manoeuvre which effectively stops a large fighter in mid-air on its way to completely reversing its direction of flight? The answer to both questions is that, while the manoeuvres themselves may not ever figure in the operations manuals, the use of the technologies, which have enabled them, will certainly cause those manuals to be rewritten.
Back when the technology of vectored thrust for vertical take-off and landing was in its infancy, the thought of using that vectored thrust for enhancing the combat manoeuvrability of the British Aerospace Harrier was probably far from the designer's mind. "Viffing", as the concept of suddenly stopping or deflecting the aircraft from its previous track was later christened, was generally disregarded even later on, and only when it was demonstrated successfully in real combat during the Falklands war of 1982 did it acquire general acceptance. That it allowed pilots of the relatively slow Harrier to outwit their opponents in faster, dedicated fighters was a lesson, which should not be ignored.
The detractors of the performance of the Sukhoi Su-37 might consider that lesson before dismissing its vectored-thrust demonstrations.
The real significance of these various manoeuvres lies in the indications, which they give of the general performance and abilities of the aircraft. An airliner, which can take off at a steep angle, is one whose abilities can be exploited to overcome the ever more demanding (perhaps even more ridiculous) regulations being proposed by national or local governments. To execute a steep take-off followed by a power-reduction and a bunt (as insisted on at airports like California's John Wayne) might not make any sense in direct operating economics, but if it saves its operator a substantial noise-limit-infringement fine, then it makes a great deal of commercial sense.
There are probably fewer real-world applications for the high-alpha, low-speed demonstration pass of an airliner - except, perhaps, the simple one of demonstrating to the assembled gathering that a modern airliner is both quiet and stable at low speeds. That is a reinforcement of two messages of increasing importance to the world at large - those of environmental acceptability and safety.
It may equally be, of course, that Sukhoi's "Kulbit" (somersault) manoeuvre does end up to be one of great combat significance, even should a squadron-level pilot never use it in combat.
In a dogfight, "super manoeuvrability" confers on the pilot the ability to easily turn inside a conventional aerodynamic platform, allowing for early missile lock-on. On the down side, using thrust-vectoring in a dogfight to obtain rapid changes in the aircraft attitude results in a rapid bleed-off of energy. If the pilot does not kill the opposition with his first shot, then his own aircraft's lack of energy will means he could present an attractive target.
The real challenge in developing the systems now being seen on the Su-37 (and those seen previously on the Rockwell-DASA X-31) must lie in maximising the ability of the aircraft to undertake those manoeuvres while minimising the energy lost in doing so. What also needs to be noted from the apparent success of the Su-37 (much closer to a production aircraft than was the X-31) is its significance for weapons designers. The basic assumptions of how a target may try to evade an incoming missile in a close engagement will also need to be reconsidered, if thrust vectoring becomes the norm. If it does, however, it will be the mind of the air-show critic, which first has to perform a somersault.
Source: Flight International