I was wondering how the Harrier works in regard to the vectoring of the thrust to hold the stright and level hover. I had this idea for a unit to do this job with a single valve.I don't know if this is how they do it on a full size or not,but this valve has been stuck in my head for a year.Maybe it would work for models only. Maybe it would not work at all.A floating disk valve,controling four ducts,with gyros.Could some one look at this and blow it out of the water,so I can get it out of my head,and think about my prop-jets again.

Thanks BOB

Well it's amazing that the harrier can even be hovered. It basically stands on four legs. It's a balancing act it has 4 exhaust ports. 2 of which are more under the CG that the more rearward ones. These controll the main forward flight to hover, and vice versa. The other two help to keep it level, and pivot with rudder inputs I think to rotate the aircraft in a hover. Which is all done manually through controlls in the cockpit by the pilot. Basically if you look at a harrier it has two large extakes just forward of the CG, and two smaller ones further back. The mains provide the hovering force yet the airframe is slightly tail heavy in hover so thrust from the smaller rear extakes provide just enough thrust to keep it level. There's 2 on each side which keeps the lateral balance.
It's extremely inneficient, and not all too manuverable in a hover. The biggest problem is the huge amount of thrust you lose with the ducting. I belive you lose about 40% of the thrust.

Hi Bob, Sig

The Harrier uses two "systems" when in hover. The primary system is the four nozzles on the fuselage. Two "cold" nozzles just behind the intakes and two"hot" nozzles just before the trailing edge of the wing. These four combine to provide the thrust necessary to keep the harrier hovering in the air. When in hover, these nozzles are rotated down, and the thrust out of each one is constant.

There is a separate "puffer" system with ports on each wing tip, bottom of the nose, bottom of the tail and one lateral port in the tail linked to the rudder. These ports provide the manoverability and stability control in hover. Each of these ports is a valve in its' own right, and are directly connect to the appropriate flying control surfaces. The amount the valves open is proportional to the direction and amount of travel of the connected flying surface.

Although the Harrier doesn't move as quickly in hover as a helicopter, for a fixed wing aircraft standing still it does pretty well.

Ed

I was trying to post a picture of this valve but I did not know how to send it , when I tried to att. it said file too big.

Hey that harrier pilot lied to me at the airshow!
Maybe he thought I couldn't understand how it all worked so he gave me the psuedo-right-easy answer lol.

OK picture four duct holes in a square patern,with a disk of twice the dia. laying over the center of the holes,to partly cover all holes. Gyro driven servos would move the disk on two axies to divert the thrust side to side and for. and aft.

Bob

Hi Bob

I understand what your driving at. The problem with what your describing is losses at the valve because of the area required in front of it. The other issue would be is that you would require six holes; two for the wing tips, one for the nose, one for the tail, and two for the rudder.That would require a larger area and consequently more losses.

Not trying to shoot your idea down, just pointing out why it isn't used. The way the Harrier is setup, the different puffer jets are mechanically linked to the corresponding control surfaces and are controlled through the same stick that is used for forward flight. By directly linking them to the control surface and making their power proportional as well, it's easier for the pilot to control the aircraft because he's "flying" the plane while its in hover.

Hope this helps,
Ed

I see it a little better now...not to mention the vert.hold.Maybe my valve would be better, used in a hover-craft

Thanks for responding. Now I can get this idea out of my head and get back to my Prop-Jet.

Bob