A mechanical power transmission apparatus, of the differential gear type, for actuating an airplane control surface requiring two independent actuator inputs to a single control surface. Predetermined, proportionately variable, asymmetric loads between the two actuators are accomodated by a load sensitive brake in conjunction with a fuse link which fails in the event of single actuator or drive means failure. The fuse link is provided by employing a shear pin to attach the pinion gear in the differential to the pinion shaft. The shear pin failure strength in conjunction with the load variable brake determines the allowable differential torque between the two driven bevel gears.