The International Cessna 170 Association

Good morning, all,

My stall warning works fine....in fact too well. Adjusting it helped (great write up by GAHorn on this in 2011), but it still comes on no less than 10 mph above stall. I'm out of adjustment now. Comparing it to other 170Bs in the area, it would seem the vane attached to my switch is MUCH longer. There is an entry in the log where the switch was replaced, but there's also an odd reference to the vane attached to the switch in the logs that is not very clear.
I would like to replace the vane on the switch to see if that helps. Is there a source of where to purchase one, or a drawing of the vane's proper geometry?

Thanks in advance for any helpful information.

Best regards,
Rob

Im sure you know that the vane is (not easily) adjustable?

Good afternoon, Charlie,

Yessir...I was able to adjust it so that it wasn't coming on 20 mph before stall, but I've reached the physical limit of how far it can move. I believe the vane to be incorrect as it's quite a bit longer than all the others I've seen, not just bent differently.

All my best,
Rob

Can you post a picture?

Absolutely! I'll try and get out to the hangar in the next day or so and get a couple.

Thanks!

All my best,
Rob

I went out to the hangar this evening and got a picture of my 170B vane and one on an O-1A Birddog. No other 170s around tonight.
Here's another picture of just my airplane's vane looking outboard. I forgot my steel rule to get dimensions.
Thanks in advance to all.

All my best,
Rob

Rob,

If it ends up helping I have a vane/switch to spare.

Bob

Good evening, Bob,

Thanks so much! I just may take you up on that.

I ended up going back to the hangar and measuring my 170B vane and the O-1A Bird Dog vane. Here's the results:

170B = 1 inches long
O-1A = 0.25 inches long

Thanks again everyone!

All my best,
Rob

RobfromME wrote:Good morning, all,

My stall warning works fine....in fact too well. Adjusting it helped (great write up by GAHorn on this in 2011), but it still comes on no less than 10 mph above stall. I'm out of adjustment now. Comparing it to other 170Bs in the area, it would seem the vane attached to my switch is MUCH longer. There is an entry in the log where the switch was replaced, but there's also an odd reference to the vane attached to the switch in the logs that is not very clear.
I would like to replace the vane on the switch to see if that helps. Is there a source of where to purchase one, or a drawing of the vane's proper geometry?

Thanks in advance for any helpful information.

Best regards,
Rob

Well, Rob,…whatever that log entry says….(IE, whether it references a particular part number or other identifying features)…it is not the “correct” and “approved” item. 170-B models are Required Equipment (but not other 170 models) and therefore I’m afraid I have to advise you to remove it, obtain an airworthy correct Safe Flight detector, install it, and log it. The inspectors who have approved this previously should be advised of this, In my opinion.

I recommend you pursue Bob Nealons’ offer or an equivalent.

Allow me to tell about my own airplane and the Detector it had installed when I bought it:
The detector appeared correct in every way, and the restorer who did the near-perfect restoration may not have known it…but the installed unit was “bastardized”. It worked…on the ground during preflight and inspections… it appeared correct in every way. But it never…and I mean never…. activated during intentional stalls.
So I attempted to adjust it accordingly. It never activated in flight. Ever.

I disassembled it…and discovered the microswitch which the “vane” deployed appeared identical to other Safe-Flight Detectors…. and I also noted that it seemed identical to the “floppy disk” door-switches on early IBM style desktop computers. But that microswitch did not have imprinted upon it the identical “numbers” of the genuine article.

I contacted Safe Flight in White Plains, NY (yes, they are still in business, although their most popular current products are related to auto-throttle systems in jets)… and the person I met over the telephone actually owned a Cessna 172…was very familiar with the Detector.
He mentioned his suspicion that someone may have substituted an improper microswitch in my Detector using an incorrect part. He informed me that the vane should activate the switch at 5 grams of force…and suggested I use a postal-scale to test my swtich.
I did so and found it took MUCH more force to activate the installed microswitch.
The Safe Flight representative told me they are not able to supply a new detector except through proper channels (i.e., Cessna or other authorized distributors at the price of that time nearly $2400)…but that he could offer to “overhaul” my switch for about $350.
I asked if that “overhaul” was actually a complete replacement/substitution with a new switch …and without direct confirmation…he indicated that to be the case.

I thanked him.

I was unwilling to spend that kind of money so went shopping online for a salvage or used-part. I found a NOS Detector at an online auction and bought it for $20. (no one else was bidding …perhaps because it did not show-up in their search routines…as the seller mis-spelled/mis-identified it as a “Stall Warnor” ….I learned to check for mis-spellings when searching online for parts…. \

To my great surprise and pleasure…the new detector came in original 1950’s packaging complete with “Lifetime Warranty” certificate from Safe Flight.

Soo… your problem would be properly addressed by replacing that detector with a correct one….

Hope this helps.

I will get photos of the vane for you.

Bob

George, Bob...

Thanks so much!

All my best,
Rob

Do y’all clean/oil these switches? Mine feels a little tacky, but works fine. I haven’t done anything with it in the 3 yrs I’ve over the plane.

mmcmillan2 wrote:Do y’all clean/oil these switches? Mine feels a little tacky, but works fine. I haven’t done anything with it in the 3 yrs I’ve over the plane.

If anything, WD40. (Normally, nothing needed.)

GAHorn wrote:

mmcmillan2 wrote:Do y’all clean/oil these switches? Mine feels a little tacky, but works fine. I haven’t done anything with it in the 3 yrs I’ve over the plane.

If anything, WD40. (Normally, nothing needed.)

thanks!

You can use electrical contact cleaner and gently blow it dry with low pressure air.