To: Aladdinsane
My only experience with the NodaMatic suspension was on the Bell 214. Other Bell models had this system installed but I can’t say that the problems if any were the same.
As indicated in my post the transmission moves up and down in relation to the fuselage and by definition the engine. Connecting the engine to the transmission is a short shaft with couplings at either end. These couplings were filled with a viscous grease and the movement of the transmission relative to the engine caused the couplings to extend and retract turning them into grease pumps. The grease that was extruded from the couplings would be injected into the airflow going into the engine.
This grease would plate out on the engine inlet bell and it would attract sand and small debris. The engine was very sensitive to airflow distortion and would result in compressor stalls. The compressor stalls would generate a shock load into the drive line and rotor system resulting in frequent major inspections and resultant change out of dynamics and drive line components. More serious compressor stalls would result in airframe damage.
The problem was solved locally by frequent detergent washes of the engine, which ran up the maintenance rate, which was already over 70 MMH/FH
