Typical Jump-Takeoff Position - All Systems Go
(this image has been enhanced to remove nose rod & extended fins)
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The forward angle of the craft is needed because of the way Gyro rotors are built even if this particular craft lifts off like a helicopter. Gyro rotors are built so they won't tilt forward any lower than 90 degrees to the mast as in normal flight the rotor relies on air passing up through the rotor at all times to maintain its autorotation. It is a problem for a Gyroplane to have the leading edge of its rotor tilt below the effective wind whereas helicopters normally require the effective wind to pass down through their rotors and so they can, and need to, tilt forward lower than 90 degrees to their rotor shaft in order to fly forward. A Gyro relies on the Prop thrust for forward flight and the rotor autorotation to provide lift. To have the CC gain required forward speed during a jump takeoff, and do so with the rotor tilted forward for a helicopter style lift-off, the CC itself has to be tilted forward as the rotor can't be.
1st Picture in Sequence - 04:23:20 PM
The Cartercopter angled forward on the runway at the start of the sequence. The 6 photos were taken over a 5 second period. In this first picture, the pre-rotator has just been released after spinning up the rotor. The weight of the craft is still being fully supported on the landing gear wheels. The blade pitch is still at zero degrees. The Engine is also running up as a result of the pre-rotator load being released. (Normal jump-takeoff rotor speed is planned to be around 525 rpm).
2nd Picture in Sequence - 04:23:21 PM
In this picture the pilot has begun to pull collective and the rotor is starting to take the weight of the craft. Although the body has begun to lift, the main wheels remain on the runway (the landing gear uses a compressed air over oil configuration). The rotor disk is also just starting to cone-up as it takes up the load. The Prop is applying full forward thrust.
3rd Picture in Sequence - 04:23:22 PM
In this picture the nose wheel has begun to lift off as the rotor takes even more load. The rotor disk coning is also increasing. Air is being pulled down through the rotor as happens with a helicopter taking off. In this take-off, the pilot has also adjusted the rotor disk angle slightly forward to keep it parallel to the fuselage.
4th Picture in Sequence - 04:23:23 PM
At this point the rotor has almost fully assumed the load of the craft. Also, due to the way these test were conducted the craft has also rolled forward several feet. As the controls of the engine are refined it is expected that the craft will be airborne as any forward movement of the craft takes place. (in a normal jump-takeoff collective is expected to go from 0 degrees to a max of 10 degrees in 4 seconds)
5th Picture in Sequence - 04:23:24 PM
The craft has now lifted off the runway and all weight has been transferred to the rotor. The pitch of the craft is now almost parallel to the runway. As the craft builds up forward speed the effective wind will stop flowing down through the rotor and will start flowing up through the rotor and will cause it to 'windmill'. The rotor disk angle is tilted slightly rearwards as speed builds up.
6th Picture in Sequence - 04:23:25 PM
The pusher Prop is thrusting the craft forward through the air (down the runway). The forward roll that has occured in these tests is due to a delay in when collective is being pulled after releasing the pre-rotator clutch. In future tests, once the Prop-pitch control computer is adjusted, the collective will be applied much sooner and zero-roll take-offs will be done. The current tests are not intended to push the craft to maximum performance but to gather information that is expected to boost power output and harness a better portion of the engines power curve. Based on work done since the above tests we are all very optomistic that the next tests will produce dramatic improvements all round. (above text info prepared by Joe Churchman of CarterCopters LLC and Doug Marker) |