Airduct Question

SkyMac · #1 10-17-11, 06:53 AM

Hi
Need some help with my 74G model, whilst all the instruments are out I am replacing all the ducting, vacuum hoses etc. My need for assistance is on the ducting pipe connected to air intake scoop just above the static point of the right hand side.

This particular duct goes to where? in my airplane it ends behind what would have been the old avionics stack (which was hastily removed by the previous owner), it has a "Y" junction at this point, no more hose or fittings. I have a number of thoughts on it's use, but would appreciate some guidance.

I am able to locate the vent intake, but the actual duct itself, where or what it feeds air to or attaches to in the parts manual I cannot find.

Thanks everyone

cessnadriver · #2 10-17-11, 11:26 AM

Good day-Mate.
I just bought a 65 C337 but the air scoop your asking about (I think) is for cooling the avionics. I'm not sure but there is an AD for cooling the fuel gauges and the "Y" adapter maybe for that purpose? Hope this helps.
BILLS

hharney · #3 10-17-11, 02:10 PM

With the C model and others (but apparently it is not for the G model) there is an AD that the cooling duct had a connection to cool the fuel gauges. I don't see this for the G model (see link below for C model)

http://rgl.faa.gov/Regulatory_and_Gu...4?OpenDocument

Gord Tessier · #4 10-17-11, 02:20 PM

Hi, The purpose of the inlet is to cool the avionics stack. On mine, a 73 337G a male inlet fitting is at the top and back of the Garmin 430 stack looking in from above through the co-pilots access panel in front of the windshield.

SkyMac · #5 10-17-11, 05:04 PM

Hi Gord, Herb and Bills

Thanks for the replies, I will try to locate some photo's etc to see how it is situated on the stack, and then chase up what's missing.

Appreciate the help guys

Dave

edasmus · #6 10-17-11, 11:02 PM

On my 73 G model, a few years back, my avionics shop closed off that air inlet vent and installed an avionics cooling fan. Apparently the logic being that the air coming in from the outside contains moisture which is not too desirable back there. I'm not qualified to know if it is any better or not but it sounded logical and I do not recall it being overly expensive to install.

Ed

stackj · #7 11-05-11, 02:32 PM

It does sound to me that the hose you are talking about is for avionics cooling. As was stated in an earlier response, there is an AD to put a Y fitting in that line and run a piece of tubing to the engine gage cluster for cooling of the fuel gauges... (They had a tendancy to turn into smoke). A number of 337s have had a different gauge cluster installed which is manufactured by Mitchell Instruments. If your aircraft has the revides gauge cluster (each gauge an individual instrument which plugs into an installed rack), there was no need to keep the cooling tubing and nozzle in place. Most of the aircraft modified has the added cooling equipment removed when the modification was installed. There is no STC for the mod, but several have been installed via field approval.

hharney · #8 11-05-11, 06:18 PM

Jim

Skymac has a G model and these were not affected by the AD for the gauge cooling

Cheers

African 337 · #9 11-06-11, 01:31 PM

Interesting news about cooling the fuel guages. the plexiglass cover on my Left fuel guage started cracking and crazing and when I touched it it was really hot! I had someone do a rushed (not cheap though!) job on my avionics a short time before so expect they didn't replace the cooling pipe. Will investigate.