Robert Fulton
Out of sheer curiosity and stock prices going up , I’m TRYING to track
down any information on a STC or field-approvable air-conditioning rig to
my C23 Sundowner. Is there ANYTHING available that will allow some type of
temperature reduction through air-conditioning available for our wonderful
aircraft? I just saw a STC for a Bonanza (par for the course…). Any
thoughts or brainstorming on how one could do it?
Bob Steward, A&P-IA:
Never seen one done for any Mouse based plane. Piper had it for the
Cherokee series back in early 70’s and of course the big guys have got it,
but most of the other small GA planes just have to climb to altitude for
their A/C.
As to field approval, sure, anything’s possible, but just HOW HIGH is that
stock going to go?
I’d say that first order of business would be to locate an older Piper with
airconditioning. Get a copy of the POH and then a copy of the parts
catalog. Scour the junkyards for the belly mounted condensor assembly (it
was retractable to reduce drag when not used) and get part numbers of the
flywheel/ring gear for the engine. It has a separate sheave for the A/C
drive as I recall. Although you COULD use the antique York compressor that
Piper used, I’d suggest that a newer style “round” compressor off some
Asian car would be a better bet (less weight, less cost, and it is more
efficient, not to mention SMALLER).
After you have a line on all of this, inquire at the local FSDO how they
FEEL about this project. If they are not supportive, probably better to
sell the Beech and buy the Piper. All you want now is that they are not
openly hostile to the idea. If they shrug their shoulders and say, “Hmmm,
that would be an interesting project”, then you have found that they will
not FIGHT you on the deal.
The next phase is to engineer all the big items without permanantly
altering your plane. You need to find a way to mount the compressor using
bolt holes on the engine that already exist. You will have to design
lightweight brackets that the FSDO inspector will be convinced won’t fall
off and cause the plane to crash. You’ll need to make measurements under
the instrument panel to assure that the evaporator will fit, and that the
fan can be mounted such that it will clear the controls in all extremes by
at least 3/8″. Remember that they’ll be keen to see designs that will not
fail with up to 9Gs (ultimate), so be prepared to take pictures of your
brackets with stacks of bricks on them and a weight in pounds written on a
card large enough to easily read.
Getting a copy of AC 43.13 2A from the GPO (Will come with AC 43.13 1A/or
B) would be a god thing to do, because you are going to have to meet the
requirements, and how will you know what they are unless you have a copy?
So have I scared you off yet? If not, then you can get an experimenntal
airworthiness certificate and install all your goodies. Run it , tune it,
make sure it works just like you want (no changes later) and then write the
flight manual supplement. This is going to instruct an unfamiliar pilot
with every possible situation that could occur with this installation. Be
sure to address all the caveats about not taking off with the A/C
compressor engaged (or calculate new operating limitations and T/O and
climb charts to show the effects). Mention belts breaking, Freon leaking
into the PAX compartment (you ARE going to use the R134A, not R-12 right?)
the procedures for FIRE in the engine compartment and in the PAX
compartment, etc. Be sure that you write the “ICA” (Instructions for
Continued Airworthiness) which tell how to maintain and troubleshoot your
new system.
FLY FLY FLY until you have everything tested and documennted, and then go
back to the FSDO with pictures and drawings and a box of doughnuts and ask when they can come inspect your plane. If you start now, they should be able to approve it by the time it gets warm NEXT summer.