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Droop Cam Shear Pin

The droop cam shear pin was put into the collective, droop cam, N2 governor linkage to separate the collective from the rest of the system. If anything after that point jammed the pin would shear and you would still have collective control, it is supposed to shear around 40 lbs.

You can find the shear pin by opening the forward left hand transmission inspection panel. There coming up from the collective bell-crank in the left hand rear of the hell-hole is the rod that connects to the upper bell-crank ( arm ) P/N 205-060-751-3.

That is connected to Fitting P/N 205-060-752-1 which is bolted to the jackshaft that goes through the fire wall by pin straight, headed P/N 204-060-752-5 ( shear pin ).

I have found on many aircraft the connection between the bell-crank arm and the fitting things go wrong. People will check for play between the arm and fitting and notice a little lateral movement. Then order a new arm and fitting.

The fitting does not come with the holes that connect it to the jackshaft. If the same angle between the arm and jackshaft is not maintained there will be rigging problems ( should be checked anyway ). Then they will find there is a pressed fit. They should be snug but free to move.

I have found some so tight they cannot be rotated even without the pin installed. So much for the shear connection. Make sure they can rotate freely, that way the pin is able to do its job.

Follow the instructions in the manual for installation and shimming. I recommend you replace the pin at an interval depending on your aircraft usage.

I have enclosed a photo of how not to install the pin. In this case the pin didn’t go through the hole in the fitting and they over torqued the nut and only friction kept it from moving.

Peter Frinchaboy

Helicopter Maintenance Manager

Sacramento Metro Fire District

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