An engine assembly includes a small air-cooled engine and a dry sump lubrication system including an external oil reservoir, wherein the dry sump lubrication system has an overall oil capacity that provides at least five hundred hours of engine oil life.

A hybrid propulsion system includes a heat engine configured to drive a heat engine shaft. An electric motor configured to drive a motor shaft. A transmission system is connected to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power. A first lubrication/coolant system is connected for circulating a first lubricant/coolant fluid through the heat engine. A second lubricant/coolant system in fluid isolation from the first lubrication/coolant system is connected for circulating a second lubricant/coolant fluid through the electric motor.

An engine assembly includes a small air-cooled engine and a dry sump lubrication system including an external oil reservoir, wherein the dry sump lubrication system has an overall oil capacity that provides at least five hundred hours of engine oil life.

A hybrid propulsion system includes a heat engine configured to drive a heat engine shaft. An electric motor configured to drive a motor shaft. A transmission system is connected to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power. A first lubrication/coolant system is connected for circulating a first lubricant/coolant fluid through the heat engine. A second lubricant/coolant system in fluid isolation from the first lubrication/coolant system is connected for circulating a second lubricant/coolant fluid through the electric motor.

An oil supply system for supplying oil to a lubricating cavity of a gas turbine engine, the oil supply system has: a de-oiler having a de-oiler air-oil inlet, a de-oiler oil outlet hydraulically connected to the lubricating cavity, and a de-oiler air outlet in fluid flow communication with an environment outside of the oil supply system; and a closed-loop oil circuit including a main pump having a main pump inlet and a main pump outlet, the main pump outlet hydraulically connected to the lubricating cavity, a de-aerator having a de-aerator inlet hydraulically connected to a scavenge outlet of the lubricating cavity, a de-aerator air-oil outlet in fluid flow communication with the de-oiler inlet, and a de-aerator oil outlet hydraulically connected to the main pump inlet.

An attachment and retaining mechanism is described for removably attaching a rotating filter element to a rotating shaft. The rotating filter element includes a filter media that is driven by a drive mechanism that rotates the rotating shaft. The filter element is removably attached to the rotating shaft such that the filter element and filtration system can be periodically replaced and/or serviced. In some arrangements, the drive shaft includes a D-shaped section that interacts with a mating section of the filter element sleeve of the rotating filter element. In other arrangements, the drive shaft includes at least one flat drive surface.

A filter system can include a replaceable filter cartridge having a spinner element structured to swirl a mixed flow of compressible fluid and oil, as well as an end cap used to enclose an open interior of a filter media of the filter cartridge. The filter cartridge can be configured to interface with and be supported by a mesh holder. A housing can be attached over the filter cartridge to enclose the system and create a flow path for a mixed flow of compressible fluid and oil. The replaceable filter cartridge can be constructed of materials suitable for disposal in a waste incineration process. The mesh holder can be inserted on a combo-block and secured in place by a compression fitting. A stand pipe can extend into the interior of the filter media and be coupled with a central passage of the mesh holder.

A hybrid propulsion system includes a heat engine configured to drive a heat engine shaft. An electric motor configured to drive a motor shaft. A transmission system is connected to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power. A first lubrication/coolant system is connected for circulating a first lubricant/coolant fluid through the heat engine. A second lubricant/coolant system in fluid isolation from the first lubrication/coolant system is connected for circulating a second lubricant/coolant fluid through the electric motor.

An attachment and retaining mechanism is described for removably attaching a rotating filter element to a rotating shaft. The rotating filter element includes a filter media that is driven by a drive mechanism that rotates the rotating shaft. The filter element is removably attached to the rotating shaft such that the filter element and filtration system can be periodically replaced and/or serviced. In some arrangements, the drive shaft includes a D-shaped section that interacts with a mating section of the filter element sleeve of the rotating filter element. In other arrangements, the drive shaft includes at least one flat drive surface.

An engine assembly includes an air-cooled engine and an external oil reservoir. The engine includes a vertically-oriented crankshaft a crankcase cover having a front portion and a rear portion, wherein the front portion of the crankcase cover and the cylinder head are located forward of a vertical plane that includes the crankshaft axis, a return pump housing formed in the exterior of the crankcase cover, a return pump positioned in the return pump housing, and a return pump inlet formed through the crankcase cover, wherein the return pump inlet is located in the front portion of the crankcase cover and the return pump inlet is located closer to the camshaft than to the crankshaft. The external oil reservoir includes an oil tank and an oil filter assembly.