| 摘要 |
A helicopter (10) incorporates apparatus (15) for mounting a device such as an aerial or a sight (14) above a main sustaining rotor (13). The apparatus comprises first and second ring gears (16, 20) located respectively below and above the rotor, the first gear (16) being supported from helicopter structure (17) concentrically of an axis of rotation (11) of the sustaining rotor, support means (37) supporting the second gear and the device above the rotor in a manner permitting relative rotation of the rotor hub, and synchronizing means (25) rotationally fixed to the rotor hub and meshing with the first and second gears to retain the device stationary during rotation of the rotor system. In a preferred embodiment, positioning means are provided to rotate the first gear in either direction of rotation whereby the device can be rotated and selectively positioned independently of the rotation of the rotor.
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