A subsurface aircraft servicing pit is provided with a hold down assembly that secures a pit lid mounting frame in position on a bearing seat at the top of a prefabricated pit enclosure. A frame mount latch ring is suspended in spaced relation beneath the underside of the pit lid mounting frame and inwardly from the walls of the pit enclosure. At least a pair of frame mount latches are provided on opposite sides of the pit. The latches have bases secured to the pit walls and hooks that extend over the top of the frame mount latch ring. The frame mount latches are constructed so as to exert a downward force on the frame mount latch ring, thus holding the peripheral margin of the pit lid mounting frame tightly against a peripheral bearing seat surrounding the pit opening. The necessary force exerted by the frame mount latches may be provided by a coil spring located within the structure of each frame mount latch.

 
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> Design methods and configurations for supersonic aircraft

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