Abstract: An extendable infra-red antenna is carried in a bay portion of the aircraft ormally closed by laterally-swinging, clam-shell doors. Separate, unconnected linkage assemblies driven by a common crank extend and retract both the doors and the antenna. When retracted, the antenna linkage is driven into an overcenter disposition but the door linkage is not. As a result, the doors begin to open before the antenna begins to deploy. Conversely, when the antenna is fully extended, its linkage is not overcenter but the door linkage is. The antenna then begins to retract before the doors begin to close. The overcenter relationships cause one member to first move in a direction opposite to that of the other so as to insure against any interference between the moving members. Stop means are provided to permit the antenna to be firmly secured in both its extended and retracted disposition.