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

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...:)

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

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....

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

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

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

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 .

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]

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.

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

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

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.....

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

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.

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.

Who carries a handkerchief now a days?

Corona face mask.

In 15 years of flying a C172, I have never heard the stall warner in flight, or during a landing. It works Ok when tested, but maybe my noise cancelling headset is reducing the volume from the reed situated 4 ft down the wing. When I flew an aerobatic Slingsby, the thing was going off at every updraft of wind, or tight turn that we did at cruise speed.
.

Scifi, You have a point with the noise cancelling headsets. I mostly don't hear my SkyDemon warnings from my (leg supported) cradle, and I have a normal set of good ol' DCs, not even noise cancelling ones!
We fly from a relative short and grass RWY with trees in front and we have to be careful with our approach speeds, we aim for 60KTS on short final and we make close to a full stall landing flare, which normally causes the horn to start moaning just before touching.

The reed in the stall warning horns of 150/152/172's is in the horn itself, which it just behind the plastic trim, right at the corner of the windshield. The noise cancelling headset will reduce, but not eliminate the sound of the horn (the headset people thought of that). In any case, when you're flying in a phase of flight where a stall is more likely, you should be aware, and attuned to the possibility of a stall warning. It's pretty common for a 172 to be flown around, and the stall horn never sounding, but it'll be a little better flying if for some landings it does. It you have the stall horn peep just before the mainwheels touch, it's set up to be a good landing, at the slowest practical speed. If you doubt the stall warning is working, at altitude, and clear of traffic, bring the plane to the approach to stall, and listen for it! The reed horns do need to be blown out (bugs) from time to time. If the plane has had major repair work, or a wing adjustment, the stall warning should have been checked, and adjusted if needed (my job, following STOL kit installations, in a former life). Recently, while test flying a Grand Caravan, I was getting the stall warning, just as the mainwheels touched, and they were satisfying landings....

Interesting you say that. It is also my belief that the aircraft should be held off until all possibility of flight is exhausted. In the UK, a light aeroplane was required (prior to EASA) to have a 'Star Annual' every three years. the aeroplane was also to be flight tested at this time. Specific in the flight test report form was the question "does the stall warner activate on landing?,' It was considered that it should not. The stall warner was required only to become active 7mph or 5 kts. before the stall (happy to be corrected on these numbers, I'm writing from memory).

For certified planes, it is required that the stall warning (if equipped) be sounding no more than 10 (MPH/Knots) before the stall, in that configuration, and must be sounding by 5 (MPH/Knots) before. It was my job, decades back to set this up on Cessnas upon which STOL kits had been installed, as the wing cuff installation requires entirely repositioning the stall warning sensor. When I was test flying the Caravan last December, doing stall testing in every configuration (for a modification approval) I found that the stall warning speed was too fast, indeed, sometimes I was getting a warning 19 knots before the stall break. The modification would not have been a factor in this, it was just the plane. I snagged it, and deferred it, as the Transport Canada test pilot was known to be coming to check a few of my test points, and I did not want to have adjusted the stall warning, and have to refly three hours of stalls to get new warning speeds for the report. I briefed the test pilot about this. He flew some stalls while I rode right seat, and got all the same results I had. so when the testing was done, I formally snagged it for adjustment. I offered to fly the adjusting testing the following day, but the weather was poor for the next few days, so I came home, and the company pilot did it. Every maintenance check flight I fly will include stalls to the break, both flaps up and down, to confirm handling, and stall warning operation.

Apropos Stall warners I've been hankering after one for my S6 Rans having previously 'enjoyed' the leading edge tab device on my 1963 Jodel.
Up to these revealing posts not only were kits a bit pricey, but entailied drilling into the leading edge, and more !
The rans Main Spar is an Ali tube leading edge and I've no wish to attack it, especially near the fuselage.

So thinking out loud !
Could a pipe, cunningly curved, be introduced externally to the wing - with an aperture forward facing and its tail end feeding a pitot type hose leading to a cabin reed horn near my head ?
I don't mind experimentind with pipe and sticky tape, but a heads up would be appreciated on the C150/172 system.dimensions i.e. How far out (%) along the wing is the hole, what area ? &,
Is it right on the wing nose centre or a little above or below ?
I know I can drive off to an airfield and seek permission to have a good look at an example but Covid restrictions frustrate that at present.

Regards, mikehallam. (England).

LAA Permit Annual Test Flight requires stall warning test if fitted. Full stall with speeds recorded at buffet, stall warner, and nose drop, with and without flaps or airbrakes.
The two I did in 2020 both needed adjustment. The Jodel DR1050 is much easier than the Bolkow Junior.

Yeah, don't cut that in any way, anywhere.

In my opinion, it could work, after a lot of experimentation, and next tries. Having done a lot of flight testing to locate/qualify new static ports on an aircraft, I would not attempt this. I'm not saying it can't be done, just that I would not invest my time in it. For the value of your time you'd get into it, buy an aftermarket AoA system, and devote good effort to setting it up accurately, you'll be happier in the end.

That said, there are some important aspects of setting those up, and I've seen it done wrong. Indeed, I found an error to the unsafe side in one AoA manufacturer's instructions, so there are some things you have to know. But, correctly set up, they're a good system.

One of the problems with GA aircraft is the lack of a DDG: dispatch deficiency guide. At least the airline I flew with, called it like that. You could find the equipment that was mandatory to be operational or functional. There were options like needed to be repaired immediately, fly back to home base and repair, repair within 100 hrs or so. Many possibilities.
With GA aircraft You are left to swim.on Yr own. A technician might decide different than the pilot, and all pilots will have different views because of experience and kind of use with the A/C.
Like with this horn, I still don't know if its mandatory or not. The EASA minimum equipment list does not specify this.
I flew thousands of hours on a C172 and I could live w/o it, no problem. The Cessna warns more than enough for me to know I am dangling on the last kilos of lift. It hardly wingdips, IF any. Long time ago I did banner towing also and we used to put a rag in the hole of the stall warning opening inside the cockpit. Annoyed for the hours on end of blaring. IAS was something in the 40ties.

Small GA airplanes historically were not furnished with minimum equipment lists, which the pilot should take to mean that everything must work, or the plane is not airworthy. For an airplane with no MEL, the only "give" I've seen on flying with something not working was U/S nav lights for day only flying. Otherwise, it's gotta work. If a pilot determines something is not working, it's up to them to record it as a snag. Though difficult for pilots to access, the old way for the manufacturer/regulator to describe required equipment, when there was doubt, is in the notes of the type certificate data sheet. It's not easy to find, but it is the pilot's responsibility to fly in accordance with its terms.

Using the 172 as an example:

From TCDS 3A12, page 16:

And, in the POH for the 172S, page 6-20:

[As "required"]

So there is no provision for the pilot to choose to fly with it inoperative. I agree that generally, pilots are not taught where to find this information, but it's there, and the pilot's responsibility to know....

Do I LOVE PPRUNE!!!! and You Pilot DAR, tks a lot!!!

Never knew about these files, found several answers!
In order to help other people who like to look it up:
Go to:https://rgl.faa.gov/Regulatory_and_G...e?OpenFrameSet

In the left panel go to “revision history for TCDS” and click "by “number”, a long list opens. Go to number 3A12 and click on the triangle next to it. The whole list of TCDS regarding the C172 opens.
Btw the latest version (85) does not mention the stall wrng, however in earlier versions, as Pilot DAR gave, it does give it on page 16.

For slightly more modern Cessnas there is a Kinds of Operation List in the POH, a table listing the stuff required for day / night VFR / IFR.

Type Certificate Data Sheets, and STC's are the absolute foundation of how an aircraft (or engine or propeller) is approved. Unfortunately, they are rarely seen by pilots, and even maintainers don't read them as much as they should. I issue STC's for a living, and so regularly consider what's to be written on the STC certificate, what's to be written on a flight manual supplement, and what's to be presented to the pilot (or maintainer) as a placard. The regulators are getting a bit more risk adverse, and requiring that if a mod requires a serious placard (usually as a limitation) that it must be repeated in a flight manual supplement. Okay.... 'just more paper.

Sometimes for a changed aircraft supplement, I'll draft the required flight manual supplement with a comprehensive section 7, Systems Description, so that the pilots are provided the required understanding of differences. Some of these also come up in emergency and abnormal procedures too, and become if not "memory items" at least "stop and review the correct procedures, before you start flipping switches, 'cause it's different now.". I entertain (or alarm) myself when riding jump seat in the airplane, by casually asking the pilots if they'd read the flight manual supplement for the mod we're about to go and test fly. I often get a casual "nah....", to which my response is: "Well, I'd appreciate if you would, I wrote it, and I'd like to be sure you know what's in it! I'm along for this flight, so I can talk you through it, but if I'm not sitting back here, you'll have to get it right on your own, and it's different to the basic plane.". That always draws some consideration....

I know it's a lot of boring reading, but it's amazing the gems of information which can be found in the TCDS, TCDS Special Conditions, STC's, FMS, ICA's, and AD's. It's people like me (for better or for worse) who write them!

The weight and balance section of the POH/AFM lists all the installed equipment and required equipment .
One of the reasons why the POH is required on a flight as it has all the required equipment is listed in the weight and balance section of a newer approved POH . Older owner manuals are the reason and basis of most lawsuits against the manufacturers.
There is no need for a secret squirrel decoding ring while using the newer POH . If equipment is listed in the weight and balance and it is unserviceable it is a no go. The no go decision has already been made for you by the certification process . You may not fly it without a ferry permit .

That said I flew a 421 that did not have any weight and balance information in the owners manual . So we got an updated POH from Cessna and always carried the approved weight and balance sheet for quick reference . Nice airplane , but good luck finding an engine shop .