How is this helicopter flying if the blades aren't spinning?

[Butuz]

You don't need negative pitch and in fact, thinking about it, neg pitch on the blades in an auto-rotation scenario would be disastrous, you want the blades to spin as fast as possible in the direction they're meant to spin, which, if using the upward flow of air, is only possible with positive pitch.

No mate you've got that the wrong way round - if you give positive pitch whilst falling through the air like a brick it will stall the blades. You can give 0 pitch and minimise the loss of RPM, or you can give negative pitch and it is actually possible to speed the blades up (not up to your normal rotor RPM, but up enough so that you can hopefully land).

Most heli's cant give large amounts of negative pitch though so by the time you come to land your blades will have slowed down significantly which is why autorotation is rather hard to master without er... dying.

Andrew

[iranu]

Vectored thrust on a turboshaft engine? Roflmfao.

Max Vertical take off weight of a Harrier GR7 is roughly 8,600kg (18,950lb) and requires 21,750lb of thrust from one Pegasus 105 (soon to be 107) vectored turbofan.

Max take off weight for a MIL 24 is roughly 12,000kg so there is absolutely noway that the hind's engines are going to hold it up so it can manouever like that.

I'm gonna pop along to project hall 3 and speak to a mate who works on RTM322 for teh lowdown this afternoon when I get into work.

"The 11th August marks the 20th anniversary of the Westland Lynx helicopter setting a new world helicopter speed record of 249.1 mph (400.87 kph). Although other attempts have been made, 20 years on Lynx retains the title as the world's fastest helicopter.

The Lynx helicopter, registered G-LYNX, flew a 15km course across the Somerset Levels at 500 ft on a calm hazy evening back in 1986 with Westland Chief Test Pilot Trevor Eggington at the controls and Derek Clews, Flight Test Engineer alongside. The average speed achieved over two runs was 249.1 mph (400.87 kph), beating the record held by a modified Mil “Hind” helicopter by over 20 mph (32 kph)." Westland Helicopters.

The Hinds wing has nothing to do with speed. Max speed is defined by the blade characteristics of the helicopter. It is unlikely that the lynx record will ever be broken.

"As the forward speed of the helicopter increases, a region near the blade roots on the retreating side actually experiences a reversed flow. Combined with the large blade incidence on the retreating side, as forward speed increases, the blades approach a stalled condition. At the same time, regions near the tips on the advancing side experience a very high velocity flow, approaching the point where shock waves form, leading to shock induced flow separation. Due to these limiting factors, the maximum forward speed of a helicopter is limited to about 250 mph (402 km/h)."

[MadduckUK]

bla bla bla

your wrong. Airwolf had a max speed of Mach 2 with its turbo thrusters

zoooooooooooooooooooom

[TeePee]

I understand that, iranu, but I want to know why, aerodynamically, shifting some of the life burden to stub wings wouldn't allow it to go faster. With lift from wings the blades don't need to produce so much and so the differential pitch would be reduced. The drag from the wings would be far less than the rotor drag, especially if the retreating blade is so close to the critical angle of attack.

[iranu]

your wrong. Airwolf had a max speed of Mach 2 with its turbo thrusters

zoooooooooooooooooooom

now nowalanow, nowalanow, nowalanow, now na now now now now now, do do do do do do.

Gotta a love that bit o' tv. Each week the same helicopter/Mig gets shot down with some impossible missile shot with the pilot(what was his name) using the force and no instruments to do the shooting after he has been jumped by 3 Migs/Helis and turned the tables on them.

On a more serious note. As far as a speed is concerned a small wing would not make any difference as it doesn't do anything to increase speed only a small amount of lift and requires forward momentum to generate that lift. The chopper's blades must be relied on to lift the heli otherwise it can't get airborne. It would be a bit of a weird design if the heli needed the wings to get it off the ground, it would have to do a kind of STO manouver!

Max speed is contained by max rotor speed which is aroundabout where the blade tips enter mach 1, hence the new design of scoops at the blades tips.

[TeePee]

My question is more that the blades can rotate slower if they aren't required to produce as much lift, if some lift is produced by the wings.

Max speed is more centered around the difference in speed between the forward moving part of the rotor arc and the rearward part of the rotor arc. Both halves have to produce the same amount of lift, and so they move to a different angle of attack. At higher speeds, they are at the limits of where they can move to.

I think.

[yamangman]

Having worked for a company that produces helicopter main rotor and tail rotor gear boxes, there is absolutely no way that a tail rotor would continue to spin normally whilst the main rotor remained stationary.

That's a tell-tale give away that, that and it's flying of course, but still, I don't work for a company that produces helicopter rotor gear boxes, so what do I know