The International Cessna 170 Association

My stall warning horn works great when I move the stall warning vane on the ground during preflight. However, the stall warning system will not operate airborne during stalls. Has anyone seen this problem? Is there a way to adjust any of the system components.

I just had the same problem in my 172D. Moving the vane on the ground made the AI happy when doing the annual but it would not work in the air. I tried spraying the vane with LPS2 and that took care of the problem.

IF and it is a BIG if, I was to squirt a lubricant in the SafeAir tab style switch found on a 170, I would not use LPS2. This is way to thick. An electronics cleaner/lubricant would be more appropriate.

There is nothing to adjust inside the switch which BTW is a special switch purpose made and only available from SafeAir. It does look like a common electronic switch one might have found at Radio Shack in the day, but it is not. The contact pressure of the switch is specially calibrated.

Cessna wants an arm and a leg for a new SafeAir switch and they are the only people who will sell you one under agreement with SafeAir as I understand it. However, a switch returned to SafeAir for service will be returned to you, likely with a new switch installed and at about 10% of the price Cessna wants.

Note: SafeAir should have been SafeFlight,

Bruce, I couldn't find anything on SafeAir. Did you perhaps mean SafeFlight?

If it were me, I would do some checking with salvage yards and see what price they are asking. Of course those might be about to go bad, but most places like Air Salvage Dallas (Lancaster, TX) will ck them out before selling them. Give Lucky a call.

cessna170bdriver wrote:Bruce, I couldn't find anything on SafeAir. Did you perhaps mean SafeFlight?

Yes Miles, SafeFlight. I forgot and relied on memory again.

Thank you gentlemen. In work.

I wrote about this circa 2000 when I bought N146YS. It had exactly the same problem....worked on the ground only.

I contacted SafeFlight in WhitePlains, NY and talked to their representatvive (who happened to own a 172) and he explained they would not sell directly but only thru an authorized distributor such as Cessna, Spruce, etc..... but they would “overhaul” an existing unit sent in to them. In further discussion I was able to determine they simply sent out a new replacement unit for around $350 “overhauled” (year 2000 price.)

He also pointed out that the Lift Detector should operate at .5-grams of weight/pressure. (That is POINT-five... one-HALF gram) I used a postal scale and determined my Lift Detector required 3 OUNCES of pressure to operate.

I took it apart and discovered that someone had “restored” it previously using what appeared to be an identical micro-switch from a desktop computer. The difference was the spring inside that switch, which was clearly too much spring.

I solved my problem very luckily.... I MIS-typed the spelling on Ebarf (a common method I discovered to win hard-to-find parts on-line) by using the term “Stall warner” instead of “lift detector” (I’ve also successfully used terms like “generater” instead of “generator”, etc etc. to find parts online).

My lucky find found a NOS Safe Flight Lift Vane which I won for $20 (yes... twenty dollars).

Even better... it came in original packaging which INCLUDED the Safe Flight LIFETIME warranty-card in the box. ( I think I posted a copy of that card in my original post..... you’ll have to search for it... good luck getting them to honor it.). To top that off, it also included NOS horn/light assembly.

(Don’t bother to ask me about it.... When our fellow Member Kevin West’s horn died... I gave him my working horn/light out of my panel and installed the NOS one in N146YS. He still owes me a beer.).

Soooo.... here’s what I suggest to you Nodakflyer... Use a postal scale to measure the amount of force it takes to lift that vane-switch. I’ll bet you’ll find some similar situation exists in your airplane. You now know several ways to take care of this problem:

1-Leave well-enough alone, saying nothing to your IA and don’t inadvertently stall your airplane. (If you don’t have a B-model it’s not required-equipment anyway.)

2-Buy a unit from a salvage-yard or “authorized distributor” and pay their ridiculous price (salvage is usually one-half retail.)

3-Find some way to reduce the spring-pressure of your existing switch in a repair-scheme, or locate some such micro-switch you can use in an “owner produced parts) scheme.

4-Get lucky with some auction site or another helpful Member here. Sorry I don’t have another to donate.

Thanks very much for the great advice.