Every RPM reduction gearbox I look at seems to have more parts in it than a Swiss watch. Great for keeping time but many parts to wear and breakdown.
What seems especially worrisome is the direct coupling of the engine drive shaft, through the gear, to the prop. This seems fine when the engine is turning the prop, but potentially damaging if the prop starts turning the engine.
The torque converter, with it hydraulic coupling, seems to offer a safer approach because the prop is not directly connected to the engine power output shaft.
Hydraulic torque converters are commonly used with automobile automatic transmissions. Are any aircraft using them?
As smaller, higher RPM engines become more common, is there a chance they will be a market for them in aviation?