- Joined
- Oct 30, 2003
- Messages
- 18,363
- Location
- Santa Maria, California
- Aircraft
- Givens Predator
- Total Flight Time
- 2600+ in rotorcraft
A recent post referenced this presentation of ground effect so I felt a new thread was appropriate.
https://tinyurl.com/yxm2b66y
In my opinion things fly level when they displace air equal to the weight of the aircraft downward.
According to the Rotorcraft Flying handbook: https://www.ronsgyros.com/Gyro_Handbook.pdf
“ROTOR FORCE As with any heavier than air aircraft, the four forces acting on the gyroplane in flight are lift, weight, thrust and drag. The gyroplane derives lift from the rotor and thrust directly from the engine through a propeller. The force produced by the gyroplane rotor may be divided into two components; rotor lift and rotor drag. The component of rotor force perpendicular to the flight path is rotor lift, and the component of rotor force parallel to the flight path is rotor drag. To derive the total aircraft drag reaction, you must also add the drag of the fuselage to that of the rotor.”
“ROTOR LIFT Rotor lift can most easily be visualized as the lift required to support the weight of the aircraft. When an airfoil produces lift, induced drag is produced.”
I use the Rotorcraft Flying Handbook to teach rotor aerodynamics because that is what the FAA wants.
Yesterday in The Predator I flew half the length of the eight thousand foot runway at less than two feet above the ground at fifty knots. The power required for level flight at fifty knots was reduced from approximately 2,150 to 1,720. The density altitude was just under 2,000 feet. She has a digital tachometer and it jumps around. It is always wind at SMX so the rpm numbers are only an approximation.
This appears to me to be in conflict with the presentation.
I was not looking at the rotor tachometer so I don’t know how the apparent ground effect affected rotor rpm.
I do not recommend this as I feel flying that close to the ground at fifty knots increases risk.
I often fly low down the runway with clients at around 30kts with similar results to demonstrate ground effect.
The Rotor of the Predator is 115” (9’7”) high and 30 feet in diameter so at two feet above the ground the rotor is less than half the rotor diameter above the ground.
In my opinion the ground effect reduces the rotor tip vortices and increases the efficiency of the rotor.
I am not an expert and do not pretend to be one.
I have a call in to Raul Salazar and I am hoping he will get back to me. We have talked at length in the past. I will share what he shares with me.
The picture is not from yesterday and is closer to three feet above the ground.
https://tinyurl.com/yxm2b66y
In my opinion things fly level when they displace air equal to the weight of the aircraft downward.
According to the Rotorcraft Flying handbook: https://www.ronsgyros.com/Gyro_Handbook.pdf
“ROTOR FORCE As with any heavier than air aircraft, the four forces acting on the gyroplane in flight are lift, weight, thrust and drag. The gyroplane derives lift from the rotor and thrust directly from the engine through a propeller. The force produced by the gyroplane rotor may be divided into two components; rotor lift and rotor drag. The component of rotor force perpendicular to the flight path is rotor lift, and the component of rotor force parallel to the flight path is rotor drag. To derive the total aircraft drag reaction, you must also add the drag of the fuselage to that of the rotor.”
“ROTOR LIFT Rotor lift can most easily be visualized as the lift required to support the weight of the aircraft. When an airfoil produces lift, induced drag is produced.”
I use the Rotorcraft Flying Handbook to teach rotor aerodynamics because that is what the FAA wants.
Yesterday in The Predator I flew half the length of the eight thousand foot runway at less than two feet above the ground at fifty knots. The power required for level flight at fifty knots was reduced from approximately 2,150 to 1,720. The density altitude was just under 2,000 feet. She has a digital tachometer and it jumps around. It is always wind at SMX so the rpm numbers are only an approximation.
This appears to me to be in conflict with the presentation.
I was not looking at the rotor tachometer so I don’t know how the apparent ground effect affected rotor rpm.
I do not recommend this as I feel flying that close to the ground at fifty knots increases risk.
I often fly low down the runway with clients at around 30kts with similar results to demonstrate ground effect.
The Rotor of the Predator is 115” (9’7”) high and 30 feet in diameter so at two feet above the ground the rotor is less than half the rotor diameter above the ground.
In my opinion the ground effect reduces the rotor tip vortices and increases the efficiency of the rotor.
I am not an expert and do not pretend to be one.
I have a call in to Raul Salazar and I am hoping he will get back to me. We have talked at length in the past. I will share what he shares with me.
The picture is not from yesterday and is closer to three feet above the ground.