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Thread: Rotor blade management

  1. #1

    Rotor blade management

    In my opinion some instructors are not giving enough blade management lessons.

    I feel that it takes over 100 take-offs and landings at different times in different winds and different airports to fully understand and practice blade management.

    Even though the machine has landed, the blades are still flying. The blades must be moved and kept in full consciousness and control with the wind until the rpm has bleed off substantially. In most cases less than 100 rpm. After 100 rpm, then blade flapping is more of an issue than rollover. There are way to many rollovers on landings. Some even on takeoff. In my opinion this happens when the pilot mind is on something else or lack of experience in winds.

    Some people spend way to much time glued to the rotor tach. I tell people that when you see a blade rpm that is critical to your design. Look at the tach then, look at the blades and make a mental note of how fast you think the blades are moving. Such as countable, blurry, etc.

    Remember the blades know what rpm is needed for takeoff. Don't rely on a rotor tach for this. Learn to get a feel for your machine. This takeoff rpm varies with weight and density altitude on the same machine. Don't try to takeoff by watching the runway and taking off at the same mark on the runway every time this will be disastrous, maybe not today or tomorrow but, it will happen.
    Last edited by BRENT DRAKE 38604; 01-15-2015 at 09:25 AM.

  2. #2
    Hi Brent. Do most roll overs happen when taking off or landing in cross winds. Also, can unbalanced blades contribute to roll overs.

  3. #3
    Tim,

    I have not analyzed the accident data. So I can not say for a certainty that there are more roll over accidents on departure.

    It would make sense that there would be more roll over accidents during take off. There are some contributing factors:

    1. Increasing throttle
    a. Torque this may be more than expected for a solo student as he gets excited and pushes the throttle faster than with the instructor.
    b. Drag increases quickly with speed. The larges drag producer is the rotor system. The rotor system drag pulls the nose of the gyro up.
    This can happen very quickly --- and may be quite a surprise. It may cause the tail wheel to be pushed hard onto the ground limiting the ability to steer. In the end this may cause an over steer when the tail leaves the ground.
    c. gyroscopic effect As the nose pitches up the force from the prop will favor a roll . The force will be applied 90 deg ahead in the direction of prop rotation.

    2. improper or insufficient rotor spin up.
    a. Excess blade flap -- this is cause by the slow speed of the rotor and fast forward speed of the gyro. Once sufficient forward speed has been reached blade flap can not compensate for the increasing lift on the advancing blade and the decreasing lift on the retreating blade. The blades hit the stop or limit of travel. This causes several bad things to happen. including pitch and roll motions that can not be overcome if allowed to develop.
    b. Speed on the ground. with slower blade speed there is less drag in the rotor and the gyro will gain speed quickly. Most gyros are not made for high ground speed. a turn at speed will be a problem for most gyros.

    There are more but I think you get the idea and I am too lazy to type them all.

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