Newbie Qs: Engines and insurance

Dave S wrote:

(SNIP) The r.a.h. FAQ notes that certified engines need to be
equipped
and maintained just the
same as in a certified airplane, and says that any non-certified
engine is
subject to a 40 hour flight test program vs 25 hours.

If I'm not mistaken, for the 25 hr regimen, its a certified engine
and
PROPELLER combination. Some certified airframe somewhere has to have
been approved with that specific model of engine and prop together. I

want to say its partially a matter of "resonance" issues with certain

engine/prop assemblies at certain RPMs.

That brings up an interesting question. In the RV-6/7 arena, the
Sensenich 70CM series (fixed pitch) propellor is pretty popular. I've
looked around and it seems that they're only used on experimentals
(RVs, Thorpes, etc...), yet Sensenich claims the prop is "Type
Certified" and eligible for the 25 hr. fly off limit. I've seen a
number of RV-6s equipped with this prop and they did indeed get a 25
hr. test program when used on a certified engine. Anyone know how they
got this "type certification" if the prop isn't used on certified
airframes?

Just wondering,

John Galban=====N4BQ (PA28-180)