421C R/STOL Maintenance manual and replacement flap tracks

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    Does anyone know if a maintenance manual for the Robertson STOL system on a 421C can be downloaded online, or does anyone have a soft copy they could post via this forum? I have just bought a 421C which did not come with the R/STOL manual.

    Also my mechanic tells me there is some corrosion in the flap tracks, some of which will need replacing. I have contacted Sierra via email but does anyone know how readily available these parts are and at what cost?




    Hi Ryan,

    There is an AFM Supplement for the R/STOL if that is what you are talking about. It is mostly procedural and airspeed changes. I would think Sierra would be able to provide you with this. I would try giving them a call with your A/C serial number. I do have one that I can copy, but I am not 100% sure if there were any differences in kits for the 421C. The maintenance manual for inspection and repair purposes is something your mechanic should be able to get. The AFM Supp. is about 25 pages and required to be onboard the aircraft.

    The last time I spoke to Sierra about 3-4 months ago, the gentleman I spoke with told me there were still new parts available for the older kits EXCEPT for the jack screws. Those would have to repaired or found in salvage yards if they break.



    Thanks very much for your reply. Sierra have replied to me and sent me the maintenance/inspection manual PDF.

    I have not seen the AFM as yet and so do not know if it has the R/STOL supplement but I would assume so, if not I will contact Sierra for this too.

    Yes it seems replacement flap tracks are available but some are made to order and that takes 1 month.

    Do you know if corrosion is a common problem in these flap tracks?





    I just recently purchased my airplane, so I am far from an expert on the R/STOL. But, the previous owner’s pilot told me to make sure I keep the tracks greased up well, so maybe this is an issue.

    Maybe some anti-corrosion spray along with grease in the track would be the way to go.

    Tony Saxton (TAS) would probably be the best guy to talk to about this.

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