Ground effect in a gyro ????

[t-bird]

I am always saying that I keep my gyro into the ground effect after takeoff till 65 mph and then climb out.

But is this statement correct ?

Wind is moving up through the rotors and not down like a helicopter. Thus not pushing against the ground creating a cushion of air.

If you fly really low over a dam with no wind ,no disturbance to the water surface can be detected as in a helicopter.

You don’t have any significant ground effect in a high wing plane because the wing is too far from the ground. The gyro’s rotor is even further from the ground than a high wing plane.

Would like to hear what the experts are saying.

[Learjet]

me no expert... but you're definitely enjoying ground effect in a gyro in the following ways:

1. Your gyros forward airspeed pushes / rams air against the rotors creating an air cushion build up. Within a height equal to approx that of the rotors wingspan, the proximity of the air cushion to the ground increases the air pressure beneath the rotor which increases lift.
2. Rotor wingtip vortices are a major contributor to induced drag. Rotor-wing close proximity to the ground obstructs the formation of wingtip vortices, thus reducing the rotor drag and bringing about an increase in lift.

So in a nutshell, ground effect is not simply brought about by helicopter rotor downwash, but by a ram / air cushion effect (think of a boats' bow wave) and increased air pressure on the rotor/wing underside when in close proximity to the ground, together with the retarding of wingtip vortex formation (which reduces drag) and further increases lift. Which is why gyros and fixed wing aeries also experience notable ground effect.

[t-bird]

Thanks for the explanation.

How much of the ground effect are attributable to the wing tip vortex and how much to the Ram air.

Would adding “swept wings” to the wing tip reduce drag and perform better ?
Have a look at these wing tips http://www.cartercopters.com/

[Gyronaut]

LearJet, very Succinctly put. (Look it up Johnny Bravo)

Try it, fly two rotor lengths above the runway at a given speed (slower the better) and check your Manifold Air Pressure or required RPM to maintain level flight.

Then fly the same pattern at 3ft above the runway at the same speed and check your MAP/RPM. Ground effect is real.
As for rotor design, I feel it is a vastly under-researched subject. We are still using the same basic rotor design and pitch settings as Jean De La Cierva did in 1920.

I know Johan von Ludwig has been doing some excellent work here in SA but wonder if SAGPA shouldn't fund some research in different blade profiles etc so that Johan comes up with a better mousetrap? We have the technical ability and enough brilliant enthusiasts in SA to show 'em. For Example: Magnifan (on this forum) is a real rocket scientist and specialises in flow-dynamics; Strue I bet there are many more engineers and scientists that would be keen to get involved in a project like this?

What say you?