Abstract: A system for starting a gas turbine engine includes a rotor drive system and a hydraulic motor system operatively connected to the rotor drive system. A gas turbine engine is operatively connected to the hydraulic motor system for starting the gas turbine engine. A method for starting an engine includes initiating single-engine-operation on a multi-engine aircraft. Single-engine operation includes operating a first engine and powering down a second engine. The method includes running a hydraulic motor system. The hydraulic motor system is driven by the rotor drive system and is operatively connected to the second engine. The method includes identifying a need to start the second engine and starting the second engine using the hydraulic motor system.

Abstract: A rotorcraft includes at least one first engine operatively connected to a first rotor, and a second engine operatively connected to at least one of a second rotor or an electrical generator for driving an electrical system, wherein the second engine is a different size than the first engine. The second engine can be smaller than the at least one first engine, for example.

Abstract: An aircraft including a fuselage having one or more surfaces. At least one engine is mounted in the fuselage. The at least one engine includes an exhaust outlet. A high velocity jet is arranged at the fuselage forward of the exhaust outlet. The high velocity jet is positioned to direct a stream of high velocity gases toward the exhaust outlet redirecting exhaust gases from the one or more surfaces.

Abstract: A rotorcraft includes at least one first engine operatively connected to a first rotor, and a second engine operatively connected to at least one of a second rotor or an electrical generator for driving an electrical system, wherein the second engine is a different size than the first engine. The second engine can be smaller than the at least one first engine, for example.

Abstract: A system for starting a gas turbine engine includes a rotor drive system and a hydraulic motor system operatively connected to the rotor drive system. A gas turbine engine is operatively connected to the hydraulic motor system for starting the gas turbine engine. A method for starting an engine includes initiating single-engine-operation on a multi-engine aircraft. Single-engine operation includes operating a first engine and powering down a second engine. The method includes running a hydraulic motor system. The hydraulic motor system is driven by the rotor drive system and is operatively connected to the second engine. The method includes identifying a need to start the second engine and starting the second engine using the hydraulic motor system.

Abstract: A helicopter includes a tail rotor, a primary drive system operatively connected to the tail rotor, and a secondary drive system operative connected to the tail rotor. The secondary drive system is configured to supplement torque provided to the tail rotor by the primary drive system. Related tail rotor drive systems and methods of applying torque to tail rotors are also described.

Abstract: An APU compartment drain system is provided that ensures thorough draining of fluids from the compartment that may otherwise accumulate therein. Such drainage is achieved despite the presence of a predetermined range of negative pressure differentials across the compartment. In accordance with one embodiment of the invention, a floor disposed along the tailcone lower skin is configured to collect any and all liquids that may leak or otherwise drop from the APU. A drain tube is in fluid communication at its upper end to the floor and at its lower end to a check valve selectively open and placed as closely as possible to the aircraft overboard drain port. Liquids collected by the floor are gravitationally directed into the drain tube upper end. The check valve is configured to be open to fluid drainage from the tube out of the drain port when the pressure head of fluid upstream of the check valve exceeds fluid pressure at the drain port due to aircraft or APU operating conditions.