Propeller gearbox oil cooler for a rotary wing aircract

A method of cooling a gearbox for a propeller of a rotor craft comprising:

• circulating a volume of lubricant through a propeller gearbox disposed at a tail section of the rotorcraft;
• flowing the lubricant into a propeller gearbox cooler;
• transferring thermal energy from the lubricant to a flow of air flowing across the propeller gearbox cooler;
• urging the flow of air across the propeller gearbox cooler via a fan disposed at the tail section and mounted coaxially with a drive shaft operably connected to the propeller to drive the propeller about a propeller axis;
• and
• venting the flow of air from the tail section of the rotorcraft.

A rotorcraft comprising:

• an airframe;
• a drive system disposed at the airframe, the drive system including a drive shaft rotating about a shaft axis;
• and
• a rotor assembly operably connected to the drive system;
• and
• a propeller system disposed at a tail section of the airframe including:
• a propeller disposed at the tail section;
• a propeller gearbox disposed at the tail section to connect the propeller to the drive shaft;
• a propeller gearbox lubricant cooler operably connected to the propeller gearbox and disposed circumferentially about the drive shaft, the propeller gearbox lubricant cooler transferring thermal energy from a flow of lubricant flowing there through to a flow of air flowing through the tail section across the propeller gearbox lubricant cooler;
• and
• a fan disposed in the tail section to urge the flow of air across the propeller gearbox lubricant cooler, the fan being arranged coaxial with the drive shaft.