Hey guys I have searched but I was wondering and hoping that someone might have a 337 for using a whirlwind or sensenich ground adjustable prop on a certified plane that I can use as a template for my 150/160. Or if its even possible to achieve this.

Speaking generically, if the part is Experimental, then it remain that way until a regular type certificate has been issued. Engines, props and airframes have their own certification. So if you get a field approval, it would be akin to that FAA Inspector granting approval for certification to the prop model. Normally, Field Approvals are granted for certified equipment moved to a different platform. Such as a prop approved on one model of aircraft and a field approval may be granted, based on previously approved data, to another model aircraft.

FAA Inspectors do not stick their necks out. They need data from other approvals to do a field approval. They do not mess with certifying new stuff via Field Approval. It is hard enough to get them to do a Field Approval with certified things, like autopilots and transponders.

No harm in asking though, bring doughnuts, expect to be thrown out, then you will not be disappointed.

The FIRST thing you’ll need to find out is whether the prop you’re contemplating has completed a vibration survey on the engine model you want to attach it to.

If a vibration survey of the combination hasn’t been done, I doubt you’ll get approval, and in any case I wouldn’t fly it.

MTV

Dunno if "experimental" props have a TCDS,
but if they do, it should have a list of engines which are vibrationally compatible.

hotrod180 wrote:Dunno if "experimental" props have a TCDS,
but if they do, it should have a list of engines which are vibrationally compatible.

"Experimental" props don't have any certification basis. So, it's up to the installer to determine safety.

I've known of guys flying unapproved combinations of prop and engine. A mechanic was determined enough to get the manufacturer of the props to do a vibration survey (these were certified props) on that combination and found that there was a destructive harmonic just below takeoff RPM. You can have third and fourth order harmonics that you can't really feel, by the way. Till the prop and/or engine departs.

MTV

Several years ago we were involved in the R&D work and testing of a variable pitch experimental propeller.

Just after take off, about 50’ agl, in an RV4, both blades departed. The blade to hub retention system had failed completely. Unsure how many rotations from first blade departure to second, but it pulled one engine mount bolt completely through the firewall and bent the mount in 13 different places. Found one blade about 150’ into the trees, never did find the second one.

I was not driving, but witnessed. The driver was extremely experienced and managed to get it back onto what remained of the 2500’ x 50’ grass strip.

Built a test stand on an old pickup chassis, hung an 0-360 on it and pulled it around for the remainder of the testing. Unfortunately the product never got past the R&D stage before encountering financial challenges.

Be very cautious, especially if you were not directly involved with the engineering and construction of an unproven experimental propeller.

UpNorth

Its not just a vibration test but a noise test that is required now by the FAA.
Tried to get a different prop, certified McCauley from a Cessna 140 approved for our Tailwheel Cessna 150B.
Field Approvals are not allowed for Prop changes, at least according to the Los Angeles Aircraft Certification Office.
I was working with a propeller DER who thought it would be a simple approval.
I gave up on the project when the noise tests were found to cost $250K and that was back in 2006.

Scott & Kim, I like the paint job on your car!
Here's a couple similar ones.