stall warning horn

[bradbrady]

I've had my airplane almost 25 years and I can't recall ever looking to see if the light works (it's been over 6 years since my last night flight). The horn does work, and I usually warn new passengers not to worry about it when it goes off. I just tell them that is the airplane telling me it's ready to land.

Miles

Miles,
This is why I think you would make a good instructor. You Don't say when you hear the horn, were stalling, you say were ready to land! It's the little things
brad

[Metal Master]

My stall horn was under the upper instrument panel. It sounded when I stalled or when I flipped the switch on the wing. But until I just recently replaced the tach and had the T&B overhauled I didn’t know that the light worked. I had the upper cover off of the instruments and low & behold there was the stall light. I turned on the master flipped the switch. Lights & sound, amazing!. I put the cover back on and haven’t seen it since.

[N2255D]

TYPE CERTIFICATE DATA SHEET NO. A-799

Revision 54
CESSNA
170
170A
170B
November 5, 2004

III - Model 170B: 4 PCLM (Normal Category), 2 PCLM (Utility Category), Approved September 28, 1950; 4 PCSM (Normal Category), 2 PCSM (Utility Category), Approved October 29, 1951.

Required Equipment In addition to the pertinent required basic equipment specified in CAR 3, the following items of equipment must be installed:

Landplane: Items 1(a), 110, 201(a), 202(a), 204(a), 402(f) and 607

607. Stall warning kit in accordance with Cessna dwg. 0511062

[jrenwick]

It looks to me like it's legal not to have one, because the TCDS only mentions it once, in a list of miscellaneous equipment that includes lots of other things that are obviously optional.

Side question: if it isn't working, must it be removed, or is it sufficient to placard it "inop"?

John

[GAHorn]

The earlier airplane did not list the stall warning system as required equipment. The B-model lists it as required equipment. Unless "MEL'd" (inoperative per an approved Minimum Equipment LIst) the B-model's stall warning must be 1-operational, 2-installed per Cessna's dwgs (not out of sight under an instrument panel), 3-or in "other, approved status" (removed per STC, etc..)
I do not know of any other basis of approval for an inoperative stall warning system on a B-model. (The ragwing's square wing planform stall characteristics are such that significant, natural airframe buffet occurs prior to stall, thereby providing the pilot with ample warning of impending stall. The A-model's higher stall speed also has a well-defined buffet and "break", providing the pilot with defined stall warning and/or identification. The B-model's wing and flaps produced a slower stall that was judged less abrupt and therefore less identifiable. It was described as an "onset of high sink rate devoid of significant buffet or pitch-over tendancy" so that the CAA decided it needed a stall warning to warn the pilot of the event. (Translation: Due to increased dihedral, more effective flaps, and other minor wing improvements the onset of the B-model's stall is sufficiently masked (gentle) and warnings so insignificant a pilot might not recognize it in all configurations, therefore the mfr was req'd to give the pilot a completely seperate method of determining when a stall was imminent. This can be demonstrated with full flaps, when a B-model's wings can be held level with rudder alone, while the airplane demonstrates a high rate of sink without an obvious "break" and pitch-down.)

[jrenwick]

That's an expensive answer, George, but thanks. I didn't get that requirement from reading the TCDS. Where is it documented as required equipment?

John

[Bruce Fenstermacher]

John, scroll up to Walt's reply just above your first post about the TCDS for the wording in the TCDS which makes the stall warning kit a required system.

And here is another example of information I presume most of us don't have. What exactly is the warning kit in accordance with Cessna dwg. 0511062? Any one have that drawing?

I'll bet it consists of both a light AND a horn. And if you can't see the light because the circuit or bulb is broken OR the lens is so dark it masks the light well the "kit" is probably not working in accordance to the drawing.

Cessna dwg. 0511062 is another example of the type of fine detail of paper documentation we the association needs to be more proactive in obtaining to keep our aircraft airworthy in my opinion.

[jrenwick]

D'oh!! I see it now. Thanks, Bruce. My stall warning actuator is intermittent, so I guess I'm in the market for a replacement. Cessna part # 0511062-4. Does anybody have any suggestions?

John

[blueldr]

You better see if you can fix that stall warning system. They're expensive as hell!

[Bruce Fenstermacher]

I didn't want to bring that up but I remember George telling us about one he bought cheap at that online place we can't mention here.

If you find you really need the horn/light unit perhaps you could talk him out of that junk he got suckered in to buying.

[N2255D]

From CessnaParts.Com
=============================================
0511062-4 DETECTOR
Order part S1672-5 Call for Availability
==============================================
Order S1672-5 DETECTOR Stock Available $ 2,173.50 (EA)
Core/Deposit of $ 1,400.00 additional
EXACT SAME PART NUMBER MUST BE EXCHANGED FOR CREDIT
____________________________________________________________
From Iwantcessnaparts.com
===========================================
Part No. / Supersedes / Description
S1672-5 / 0511062-4 / Detector --- 2289.60 Each In Stock Info 1400.00 Core Chg.

Must be made of gold!!!

[cessna170bdriver]

...My stall warning actuator is intermittent, so I guess I'm in the market for a replacement. Cessna part # 0511062-4. Does anybody have any suggestions?

John

You will not like the co$t of a replacement $witch, or the horn/light a$$embly either, for that matter. I think Safe-Air is the only manufacturer of approved parts, and they are quite proud of their products.

Since the switch lives outside (more or less), dirt and/or corrosion on its contacts will be the likely culprit. If manually lifting the switch tab with the master on doesn't cause the horn to blow, remove the switch and short circuit the long wire to the airframe. If the horn beeps, you've confirmed the problem is in the switch. Spray the switch heavily with contact cleaner (aviation dept. at Shadio Rack ), and try the switch again. (Of course you should never allow an A&P to take his eyes off of you during this operation. . Also, Bruce's signature applies here.)

Miles

[cessna170bdriver]

From CessnaParts.Com
=============================================
0511062-4 DETECTOR
Order part S1672-5 Call for Availability
==============================================
Order S1672-5 DETECTOR Stock Available $ 2,173.50 (EA)
Core/Deposit of $ 1,400.00 additional
EXACT SAME PART NUMBER MUST BE EXCHANGED FOR CREDIT
____________________________________________________________
From Iwantcessnaparts.com
===========================================
Part No. / Supersedes / Description
S1672-5 / 0511062-4 / Detector --- 2289.60 Each In Stock Info 1400.00 Core Chg.

Must be made of gold!!!

At those prices, I'd be tempted to take my chances with a fine from the Friendlies.

Miles

[jrenwick]

...If manually lifting the switch tab with the master on doesn't cause the horn to blow, remove the switch and short circuit the long wire to the airframe. If the horn beeps, you've confirmed the problem is in the switch. Spray the switch heavily with contact cleaner (aviation dept. at Shadio Rack ), and try the switch again....

Thanks, Miles. That's exactly what I need to do. The horn sounds when I lift the switch vane on the ground, but only sometimes, and I never hear it when I'm landing or performing stalls.

The FAA has issued a notice to look out for these switches that have had their internals replaced with off-the-shelf parts. Now, why would anyone want to do that? The original part has a certain calibrated gram load to lift the vane, and the replacement parts require more force. Maybe they're using micro switches? You might end up with something that worked on the ground, but not in the air. I guess if that's what I wanted, I'm already there!

Thanks for the tip!

John

[cessna170bdriver]

The FAA has issued a notice to look out for these switches that have had their internals replaced with off-the-shelf parts. Now, why would anyone want to do that?

There are 2,173.50 reason$ one might want to give it a try.

It would be interesting to get a copy of that "notice" the FAA uses to sniff out modified switches. It would also be interesting to find out how many accidents, if any, have been traced to malfunctioning or modified switches.

The original part has a certain calibrated gram load to lift the vane, and the replacement parts require more force. Maybe they're using micro switches? You might end up with something that worked on the ground, but not in the air. ...
John

The actual switch is Microswitch brand if I recall correctly. My guess is that Safe-Air would have specified an off-the-shelf (way back when) switch, then designed the tab to operate that particular switch in a specific manner. It may be that they're paying Microswitch an arm and a leg to continue to manufacture a 50 to 60-year old design rather than go to the trouble of certifying a newer off-the-shelf design.

Miles