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Old 5th September 2003 | 03:19
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Nozzles
 
Joined: Dec 2000
Posts: 102
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From: The edge
My immediate observation is that pilots are gradually being further and further removed from the physics of what happens to the aircraft when the pilot demands something of it. In flight control systems, for example, we progressed from mechanical linkages, where all the feedback you felt was real, through hydraulic systems where artificial feel was added. Then came aerodynamically stable (just) airframes that were fly-by-wire controlled. The current situation in the fighter world is that the latest machines are naturally unstable and human pilots are unable to control them in simple level flight. Thus, the pilot puts in a familiar control input to achieve a certain manoeuvre, but has no idea what the flight control surfaces are doing to achieve that manoeuvre. It makes emergency failure diagnosis more difficult because there is no logical link between input and effect. Additionally, as designers are finding new and unconventional ways of manoeuvering aircraft (e.g. 3-D engine exhaust nozzles, flexing wings etc.) the water will become even more muddied. However, I think that the whole concept is something we simply need to get used to. It is the future, but people (especially as they get older) are less inclined to embrace new concepts. As an ex-Harrier pilot I once flew a simulator that was a development platform for future VSTOL concepts. They wanted to take the nozzle lever out of the cockpit, and make the aircraft controllable with only two 'inceptors'. In a Harrier, if you want to do a vertical take-off, you move the nozzle lever so the nozzles point vertically down, select full power with the throttle then control pitch, roll and yaw with the stick and rudder. In the two inceptor concept, you pulled back on the right-hand inceptor (where the stick normally lives) whilst on the ground with the engine idling. The system said "he must want to go up", so it rotated the nozzles to the vertical and spooled up the engine. Once in the hover, letting go of the stick meant the thing would hold altitute. You could not pitch the aircraft-pushing the RHI forward would simply spool the engine down because the system thought you wanted to go down. If you pushed the left-hand inceptor (where the throttle normally lives) forward, the system realised you wanted forward speed, so it would power up the engine slightly and slowly rotate the nozzles aft. Once the wings were developing enough lift in forward flight, the system would rapidly pull back the power on the engine-extremely disconcerting as your 'throttle' was still parked at max! We figured that a kid who was good with video games but had never flown a flight simulator would pick it up quicker than us, as he/she would lack the preconceptions that we had about what should be happening. And I think that's the answer-the new generation will have a lot less problems accepting these systems than those of us discussing the issue!
Hope this helps with the assignment-if you need more, let me know.
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