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Annual for an Experimental category plane.

Ed Dartford

Well-Known Member
Apr 25, 2010
Reaction score
Western Massachusetts
As Maintenance officer of a flying club I have been through many annuals. Often not a happy experience. My son Matt just had his "Conditional" (like an annual) on his RANS S21. His plane has the most hours for a S21 with the ROTAX engine, so it really is experimental. Over the last year RANS has made several S21 design changes based on things that came up with Matt's plane. Under Experimental rules Matt is authorized to make various repairs and do service jobs but he leaves more serious things to the experts at RANS who designed and built the plane. Here is what they did at the first annual.

Did my “conditional“ inspection which is the same as an annual, but only needed to be completed by an A&P. They redesigned the motor mount adding some bracing. My right lower dynafocal rubber was being stretched coming in close contact metal to metal. The new brace stiffened the motor mount up and all the dynafocals aligned perfectly in the center. It runs noticeably smoother now as well. They replaced the right landing gear cowl that cracked. Nothing was mentioned about my repair so they didn’t feel anything in addition was necessary. Replaced a brake pad that had cracked. Replaced both inner wheel bearings from both wheels. No idea why they’d be bad with such little use as compared to a land vehicle. They replaced one landing gear, mounting bolt that they thought was stretched but after they measured it, it was not. They needed to replace both fan motors and rheostat for my heating system which got burned out from too much draw, they suspect. They told me not to run it on full until they can do more testing. There was a threaded aluminum tube, holding both the radiator and oil cooler together that had stripped and was loose. They replaced it with a stronger, steel component and wire, tied all of the radiator and oil cooler mounting bolts. Paint matched the cooling mod components that they did in August but didn’t have time to paint then. Added a newly designed sealing trim gasket on top of the doors for drafts.

And after all that and a wonderfully smooth flight home. I decided to take the cowl off to inspect everything as they had to take all the components off and put back on for the motor mount swap. I simply just didn’t trust them fully. I found the outside edge of the air intake Plenum for the intercooler to be cracked. they said they had looked at that all week and it was fine so it cracked on the flight home. I suspect with a new motor mount a harmonic resonance was different, causing this piece to vibrate like a reed in the intake slipstream. They will redesign a component and implement that going forward. I did a doubler repair using the same techniques as before. They said it looked fine, and would suffice. Albeit a little over built… I teased Randy saying I’d rather over, build it, then under build it….

Anyways, Rans are great people they’re taking care of me, and I am reluctantly proud to be part of the research and development team…..

Matthew Dartford
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