Hobbs Switch

Roger · #1 02-05-11, 05:22 PM

Under the right wing of my 337H in the location of the normal inspecion port/disc just outboard of the wing strut is (or was) a small wind activated tab attached to a micro switch, that is I assume attaches to my hobbs meter for inflight recording. The small aluminum tab is now missing, and the tny microswitch it attached to has a cracked housing, which allowed the pin holding the tab to "fly off into the sunset". So I need a repolacement micro-switch with it's integrated flight activated tab. The switch is about 1" long, and 3/8" wide. I can't find any reference to it in my manuals, and talking to an A&P today, he said that there are a lot of different switches that have been used over the years.

Does anyone have an idea on what this particlarl swith is (number, etc) and where I might locate a replacement?

tks/Roger

#2 02-05-11, 06:15 PM

I might have one. I took it off my skymaster, not sure if I threw it out though. I will check tomorrow. If I still have it, it yours. If you want a new one I'll get the part number off it for you, if I still have it.

#3 02-05-11, 06:25 PM

I found what I have. I've attached a pic.

Roger · #4 02-06-11, 09:51 AM

Thanks Tony

However that's not it. That pic looks more like a stall warning switch.

Roger · #5 02-06-11, 02:56 PM

my broken part

#6 02-07-11, 12:11 AM

Sorry I couldn't help. Good luck finding your part.

Ernie Martin · #7 02-07-11, 10:55 AM

Mine failed on my 337G and I replaced it with a HONEYWELL S&C - 311SM703-T - MICRO SWITCH, which can be bought for under $7 at:

http://www.newark.com/honeywell-s-c/...pdt/dp/78K5282

It required some -- but minimal -- adjustment (cutting part of the long lever, I think).

Ernie

Roger · #8 02-07-11, 04:39 PM

Thanks Ernie - I ordered one today

Ernie Martin · #9 02-08-11, 12:04 PM

Roger:

I looked today at the airplane and in my 337G the adjustment was to cut the lever to the proper size and then glue/solder near the cut end a dime-size disk we made from aluminum.

If you need to fly before you fix it, just connect the two leads together without the switch; in that configuration, the Hobbs runs anytime the master is on rather than at speeds over ~ 40 MPH (when the airflow pushes against the disk to close the switch circuit).

Ernie