AIRCRAFT POWERPLANT GEARBOX WITH SELECTABLE POWER COUPLER

An aircraft powerplant (20) assembly includes a gearbox (88) and a power coupler (90). The gearbox (88) includes a first engine power transfer apparatus (120), a second engine power transfer apparatus (122) and an accessory power transfer apparatus (124). The power coupler (90) is mounted to the gearbox (88). During a first operating mode, the power coupler (90) is configured to operatively couple the first engine power transfer apparatus (120) to the accessory power transfer apparatus (124) and operatively decouple the second engine power transfer apparatus (122) from the accessory power transfer apparatus (124). During a second operating mode, the power coupler (90) is configured to operatively couple the second engine power transfer apparatus (122) to the accessory power transfer apparatus (124) and operatively decouple the first engine power transfer apparatus (120) from the accessory power transfer apparatus (122).