Tuesday, 3 May 2016
The First Jets - Huckebein
After the failure of the Flitzer Project, Focke Wulf turned back to the 183. This was a true swept wing design. Swept wings reduce drag and the formation of shock waves as a plane approaches the speed of sound, i.e. transonic speeds.
The 183 had the usual problem of the poor quality early jet engines being unable to cope with long air intakes, hence the short body. So the tail had to be thrown back leading to doubts about flutter. The 183 prototype was still under construction when British troops captured the factory in April, 1945.
German designers knew more about swept wing designs than anybody else but a true understanding of the maths didn't come until later. Swept wings are fast but they introduce a whole new set of problems. Firstly landing speeds go up and the 183 would have had a narrow track landing configuration as there was no room in the thin wings for the wheels. Couple this to makeshift airfields and you have potential issues.
IAe 33 Pulqui II
The 183 would have had a 600mph top speed and a 47K' ceiling but would it have worked? The omens are not good.
After the war, Tank moved to Argentina and designed the IAe 33 Pulqui II as a successor to the pedestrian but functional Meteor. The plane is a reworked 183, with a British engine allowing a longer body.
And it was a dog with awful stability and wing-tip stall issues.
As a swept wing plane approaches stall speed, it loses lift from the wing tips, changing the centre of gravity and pushing the nose up, increasing the stall in a vicious positive feedback.
The landing behaviour of the Sabre gave rise to an all new problem for pilots - the Sabre Dance. Apparently watching novices porpoise towards the runway on landing approach became quite a spectator sport.
The British-engined MIG 15, probably the best of the early swept wing fighters, used a wonderfully Slavic crude but effective way to control the Sabre Dance: runners on the wings that stopped the air sliding down and off the wing tip.
The next generation of western transonic fighters had 'notches' in the wing leading edge which had much the same effect as the MIG's runners.
As far as I know, neither of these fixes were known to German jet designers in the 1940s.
The Germans did experiment with forward-swept wings which avoid the wingtip stall issue all together by stalling first at the wing roots. So why has no one ever built a forward-swept wing fighter?
Well, in a sharp climb the wings warp and the nose lifts, tending to push the plane into a stall.
At least one American transonic fighter made the wing tips wider than the wing root, which also helped to prevent wing tip stall.
And so it goes.
Designers did eventually get it right. The Lightning was the ultimate supersonic swept wing but it wasn't really a fighter. It was a point-defence interceptor where speed and rate of climb trumped all other factors. It had the same function as the Me 163 rocket plane.
Along with the Bloodhound rocket/jet powered missile the Lightning was the last ditch defence of the dispersed British V Bomber airfields. It's job was to keep away Soviet nuclear bombers just long enough for the V Bombers to get airborne and clear.
The Lightning had to use braking parachutes to land and we lost one a month to crashes in the 60s but it climbed at a near vertical inclination straight off the runway. And by God it was fast.
So would the FW 183 been part of the Wonderwaffe? Only if they had ten more years to get it right.