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-   -   C172 stall warning test (https://www.pprune.org/private-flying/639331-c172-stall-warning-test.html)

Double Back 18th Mar 2021 09:34

C172 stall warning test
 
We recently "discovered" that there are bellows type of small bottles that can be used to test the C172 stall wrng horn. In stead of that dreadful.......Its looks easier as finding a step-up to get to the leading edge, and then forgetting about it. Plus in these corona days, kissing a leading edge can be dangerous :) Anybody experience with these thingies?
Or another solution?
Richard

Jhieminga 18th Mar 2021 10:00

Never kissed a Cessna leading edge myself.... but my students tended to use their ties as a 'barrier' so that they could apply some suction to the relevant location without direct contact. Only works with properly dressed students of course...:)

Double Back 18th Mar 2021 10:27

Yes, when I was a full time FI I let the students use a Kleenex. Who wants to have a mouthful of dead bugs :)

Less Hair 18th Mar 2021 10:35

Check stall warning unobstructed. No need to kiss it.

Pilot DAR 18th Mar 2021 11:55


Check stall warning unobstructed. No need to kiss it.
That's a part of it, and I agree that some Cessna POH's do say to "check for blockage". Although, the reed in the horn itself is also vulnerable to bug interference (I just cleaned out the one in my 150), and the hose connection to that horn has been known to work itself loose, again, resulting in no audible warning, when there should be one.

If I were responsible for a pneumatic stall warning Cessna, which was being flown by multiple pilots, I would: Have the "kiss" test done as a maintenance activity before the first flight of the day, and recorded for the day. The person performing this test, a maintenance person, or instructor, could clean the area to their personal satisfaction. Thereafter, for later flights in the day, I would encourage instructors to slow the plane to the point of stall warning at a suitable point in the flight if possible, to confirm the function of the system, and record that it was functioning, when this was confirmed.

A bellows type of device could be made to work, though could be a fussy nuisance, so maybe easier to do the "kiss" way which is familiar to everyone - just one person, once a day only....

ChickenHouse 18th Mar 2021 12:05

What's wrong with giving our beloved a SJ suckjob before flight?

Ex FSO GRIFFO 18th Mar 2021 13:33

I guess that you could try installing the 'flip-up-via-airflow' mechanical type stall warning horn switch.
You simply 'flick it' up with the 'master' on...and...voila.
I dunno what it would cost, but, have a look at a 'more modern' 172 and see the difference.

Other than that - 'suck it & see'........
Cheers

Double Back 18th Mar 2021 16:42

If I read the POH correctly, it should(or COULD) be tested, when in case You read the testing is an option/extension of the "check for stoppage". Working with those age-old POHs can be a challenge. Strange decision at that time, high wingers with those high placed, not so easy to reach openings, low wingers with lip-switches...

https://cimg4.ibsrv.net/gimg/pprune....4a1d10dd7c.png

fitliker 18th Mar 2021 17:01

When all else fails read the POH/ AFM :)

The fun way to check it is to get in slow flight and play a tune on it .
I flew with an inspector of twenty five years experience, who had never played a tune on the stall horn . We had some fun doing that . I can still see his face light up as he played a tune . I think the lesson was how to help someone having difficulty landing and I find that most students that have difficulty landing have not had enough practice or confidence in slow flight regime of flight .

Jan Olieslagers 18th Mar 2021 17:17

Two side-thoughts that might shock some people:

* I once saw a cartoon drawing of a Cessna undergoing this operation from a short-skirted lady student - and with a broad grin drawn on the engine cowling

* a properly trained pilot does not need this kind of gimmick at all. An approaching stall is felt in the seat of the pants (or skirt) and should trigger a warning automatically and instinctively.

[later addition, @below: admittedly, I can only speak for benign low-performance planes. Things may indeed be different on more demanding planes]

Balazs91 18th Mar 2021 17:43


Originally Posted by Jan Olieslagers (Post 11011527)
* a properly trained pilot does not need this kind of gimmick at all. An approaching stall is felt in the seat of the pants (or skirt) and should trigger a warning automatically and instinctively.

There are aircraft types where you would like to know that the stall approaches way before the shaking starts. Low wing symmetric wing profile during a turn won't give you too much time before a stall and a spin developed from it. An AOA indicator is the best for those cases in my opinion.

B2N2 18th Mar 2021 17:46

https://cimg4.ibsrv.net/gimg/pprune....33916d7c9f.jpg
$10 from Sportyís or Ebay.
Why test it? Because itís required equipment thatís why.
By certification requirements so the aircraft is not airworthy if itís found to be inoperative.

slacktide 18th Mar 2021 22:17


Originally Posted by Ex FSO GRIFFO (Post 11011385)
I guess that you could try installing the 'flip-up-via-airflow' mechanical type stall warning horn switch.
You simply 'flick it' up with the 'master' on...and...voila.
I dunno what it would cost, but, have a look at a 'more modern' 172 and see the difference.

They are ASTOUNDINGLY expensive, considering how simple they are. It's just a Honeywell microswitch with some formed sheet metal. Most likely due to liability insurance expenses.

https://www.safeflight.com/products/...lift-detector/

https://www.aircraftspruce.com/catal...s/prestall.php




Pilot DAR 19th Mar 2021 02:50


I guess that you could try installing the 'flip-up-via-airflow' mechanical type stall warning horn switch.
No, you really couldn't practically do that, it'd be an STC, and an expensive one at that. I find the pneumatic stall warning systems (in Cessnas) to be superior to the switch type systems anyway - I speak owning one of each. If I were to ever consider changing, I would go away from the switch, not toward it! If I thought that my flight safety actually depended upon a working stall warning system, I would rather one which is not affected by a small amount of wing ice (when you'd need it even more), and worked even with the master off - like when you're tucking the plane into a tight spot forced landing, after turning the master off in your pre forced landing checklist...

It is permissible to approve a certified plane with "buffet" being the only stall warning - no stall warning system. I have flown a certified single engine turbine plane which had no stall warning system, just buffet, as well as various "Cubs", Tiger Moths, and other vintage planes. But, I agree, if equipped, it should work- If it doesn't work, the plane is not "airworthy", and should not be flown.

Yes, the switches are astoundingly expensive, but they're not a regular microswitch, they are specially made for that application, yes, I'm sure, with high product liability costs.....

Big Pistons Forever 19th Mar 2021 03:21

A friend had to replace his heated stall warning vane on a deiced twin Cessna. It was 7000 USD :ouch: :ugh:

Yes the heating pad added a bit to the cost but they are still stupid expensive

The reed system works fine and a first flight of the day check is plenty

chevvron 19th Mar 2021 10:08


Originally Posted by Double Back (Post 11011496)
If I read the POH correctly, it should(or COULD) be tested, when in case You read the testing is an option/extension of the "check for stoppage". Working with those age-old POHs can be a challenge. Strange decision at that time, high wingers with those high placed, not so easy to reach openings, low wingers with lip-switches...

https://cimg4.ibsrv.net/gimg/pprune....4a1d10dd7c.png

I did that check on all the C150s I flew; did it at Denham once and on that occasion, I couldn't get a peep, so when airborne I carried out a stall just to check and still didn't get a peep.
Entered the snag in the tech log and of course, pointed it out to the person on the desk; 2 weeks later, that same aircraft spun in with 2 fatalities.
Interviewed by AAIB, they told me there was no record of the snag being rectified even though it was clearly in the tech log.
Next time I flew at Denham, the club owner interviewed me and bollocked me for carrying out a stall without an instructor on board.

what next 19th Mar 2021 10:44


Originally Posted by Pilot DAR (Post 11011786)
Yes, the switches are astoundingly expensive, but they're not a regular microswitch, they are specially made for that application, yes, I'm sure, with high product liability costs.....

The high price must be mainly due to liability issues and paperwork because these things cost around 150$/Euros/GBP for homebuilt aircraft. Which is still 100 times the cost of the parts... But otherwise I fully agree with you, keep it as simple as possible. The pneumatic stall warner of the Cessnas is very realiable - in my experience a lot more than the electric ones in Pipers for example. And really, whats the big deal in putting a piece of cloth over it and just testing it?

Balazs91 19th Mar 2021 11:50


Originally Posted by what next (Post 11011980)
The high price must be mainly due to liability issues and paperwork because these things cost around 150$/Euros/GBP for homebuilt aircraft. Which is still 100 times the cost of the parts... But otherwise I fully agree with you, keep it as simple as possible. The pneumatic stall warner of the Cessnas is very realiable - in my experience a lot more than the electric ones in Pipers for example. And really, whats the big deal in putting a piece of cloth over it and just testing it?

And the quality is exactly the same, no matter if it's a certified part or not. The certified one just have a very expensive paper next to it.

jmmoric 19th Mar 2021 12:05


Originally Posted by Double Back (Post 11011496)
If I read the POH correctly, it should(or COULD) be tested, when in case You read the testing is an option/extension of the "check for stoppage". Working with those age-old POHs can be a challenge. Strange decision at that time, high wingers with those high placed, not so easy to reach openings, low wingers with lip-switches...

https://cimg4.ibsrv.net/gimg/pprune....4a1d10dd7c.png

Who carries a handkerchief now a days?

Less Hair 19th Mar 2021 12:28

Corona face mask.


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