Ralph Hooper: Harrier

Ralph Hooper on a walk around of the Harrier jump jet explaining how it works.

I’m Ralph Hooper and I was connected with its design from 1957 until I retired one way and another. Okay, well this is the two-seater version of the Harrier, so it’s got a longer nose, two cockpits in tandem. And because it’s got all this additional weight at this end it’s got a longer extension to the tail so there’s balance. But in all other respects, and when it operates, it’s the same as a standard Harrier. Now as we’re standing at the nose, we might begin with the pitch reaction controls. There’s a valve here and a corresponding one at the tail of the aeroplane, and as the pilot moves the stick fore or aft, so one or the valve will open and a blast of compressed air from the high pressure compressor of the engine issues forth. This produces a reaction on the aeroplane and pitches it either up or down as appropriate. Now there are corresponding valves in the wing tips which give you roll control, and there’s another pair of valves at the back of the aeroplane which would blow port or starboard so that you can yaw the aeroplane. Right, if we move down the aeroplane, we come to the intake, which is a very prominent feature, very large intake. It’s a high bypass fan engine, and therefore the intakes are large. And also we require the intake to work at the highest possible efficiency statically, when the air is approaching the intake from all directions, not just coming straight out of it. And that explains the size and the shape of the intake lips and also the blow in doors. Right, well to complete the intake problem, we have a series – a solution to the intake problem I should say, we have a series of blow in doors so called. They’re entirely free to operate as the air pressures the side, and when the engine is running statically then all these doors will be fully open. That one doesn’t want to, never mind. And there’s a continuous slot on the inside which feeds into the engine face. So that helps keep the static efficiency of the engine – of the intake up. Above it there’s a boundary layer bleed outlet, which I won't bother you with, that’s another feature of the operation of the intake. And above that again cabin conditioning inlet, since the chaps in the cockpit liked to be kept at a nice even temperature all the time and we like to spoil them. Right, moving down the aeroplane, you come to the front nozzles. Now this is a unique feature of course of the Harrier. These nozzles can be rotated from fully aft to fully down, these vanes deflecting the flow as appropriate. So if the aeroplane is hovering these would be going vertically, if it’s flying in conventional flight, they’re aft, and if it’s doing short take off, it might be operating at an intermediate angle. These are operated by air again bled from the engine operating an air motor and all four nozzles are connected together. When we started with the 1127 the usual proposal just had the cold nozzles deflecting and the back of the engine. Now it was up to anyone who was going to design an aeroplane round it to decide what to do there. But obviously with this in front of you it’s not going to take you very long to suggest that perhaps the same thing could be done with the hot end of the engine. And that was very much a job for Bristol’s, although originally there was the suggestion that we might do that at Hawker’s since it involved very hot flows and high temperature alloys, they had much more experience of this than we did. Okay, well we’ve moved back to the rear nozzle. Very similar in principle to the cold nozzles, so-called cold nozzles. They were really quite hot, they’re about 100 degrees centigrade with the engine running flat out. But this is 700 degrees, something like that. Don’t want to be standing where I am at the moment if it’s running. And we have to protect all the rest of the aeroplane of course from that heat, so this gas deflector here is quilted so that it expands smoothly and it’s hinged to move this way. And the whole side of the rear fuselage here is made of titanium because that resists heat very much better than the light alloys do. Right, well all good aeroplanes should have a tail plane and that’s what this is. It’s an all moving tail plane, and you have no separate elevations, normal fill in rudder. Right, this long extension at the back of the fuselage is peculiar to the two-seater to compensate for the additional weight at the front end. But the reaction control valves underneath here and on either side is exactly the same as the single-seater. These valves move in unison with the pilot’s rudder pedals and the rudder up on the fin there, and send a blast of air either to port or starboard to cause the aeroplane to change direction. And underneath here there’s a pitch valve which works in unison with the front pitch valve, and between them they will cause the aeroplane either to move nose up or nose down. We have one of these valves available here. This in fact is the front pitch valve, so it’s taking high pressure air from the engine and this is connected up simply to the pilot’s stick and the shutter either has it closed or can open it fully. Very simple. The intake valves are a little bit more complicated because when the pilot makes an extreme demand then the flow goes down to both wings, one blows up and the other blows down. Right, end of today’s lesson.

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