[Wing] Fw: Fw: Carb Heat

[Jim Oke]

Terry;

I have no engineering data on this assembly although such would be of
interest to me as I have the identical assembly on my RV-6A.

Some years ago I used to fly Beech Musketeers (Beech Model 23) for the Air
force and also taught aircraft systems for student pilots at PFS. To my
recollection, the Musketeers I flew had a very similar or identical carb
heat induction system. That is a piece of scat tube was held close to the
exhaust manifold and drew unfiltered air past the manifold into the carb
heat box. There was no form of muff that would circulate the air for an
extended distance past the manifold.

If you are able to examine the engine installation on a Musketeer and
determine the mechanics of the carb heat system were practically similar,
then approval by way of similar design and installation might be an
appropriate rationale.

Another approach would be to check the operational effectiveness of the carb
heat. If a similarly powered certified aircraft was run up and provided say
120 rpm drop when carb heat was selected under certain conditions and the
RV-4 was run-up and provided the same or greater rpm drop then this would
imply the RV-4 system was at least equally effective in providing heated air
to the engine regardless of the mechanics of how this was done. IOW, it was
the drop good enough for a certified aircraft then it ought to be OK for an
amateur.