Replace stall warn unit?

[DaveF]

Is it allowable to replace the panel-mounted stall warn unit with a horn mounted behind the panel, as was done in later Cessnas? Or just move the light/horn unit from the panel to under the panel?

I'd like to take the 2-1/4" hole currently used by the stall warn unit and use it for something else. In its default mounting location the dim red light is blocked by the yoke shaft and useless. And the TCDS doesn't say WHERE the stall unit must be mounted.

Has anyone done this?

[bagarre]

You could move it to the other side of the panel. There are two 2 1/4 holes over there as well.

[minton]

Isn't the original unit a "Dual indication" unit, red light and buzzer?

[KS170A]

Which model are you inquiring about? The B models require it, the 170 and 170A do not. I relocated mine (in an A model) under the panel so I can hear it but do not see the dim light (that I would not see anyway if I happened into an inadvertent stall).

[Ryan Smith]

Interested to know the resolution to this as well. Does the TCDS for the B model state that the SWH must provide visual and audio notification? It states that Cessna drawing 0511062 has the technical information regarding the SWH. I can't find that drawing in the MX Library, and would be interested to see it. It's also curious that it's not required equipment for seaplane operations.

Safe Flight manufactures/ed a horn similar to what I'm familiar with from my family's 170 without the center light that presumably mounts behind the panel. I wonder if this is an acceptable substitute, or if the version with integrated light is specifically required? I'm also curious if a more modern solution is applicable. A quick search of Safe Flight's website yields their listing of various lift detection and AOA detection vanes, but nothing about horns or other devices. To recall, the Maule I've flown some doesn't have a horn mounted on the outside of the panel, rather a beeping tone is audible through one's headset/cabin speaker. I believe there is a panel annunciation as well.

Does anybody have access to the Cessna drawing referenced in the TCDS? Does the Association have this on file somewhere?

[minton]

[Bruce Fenstermacher]

If you can't find the drawing chances are we don't have it. There is a drawing of course for every Cessna part. Many many of them never make it to the public.

You couldn't actually rely on the Cessna drawing to tell you what the minimum standard was as it is likely the system and placement exceeded the minimum requirement.

As for what would be required in the B model, you would probably have to research CAR 3 to see what was required then and match that as a minimum. Of course you could always comply with the current part 23.

[DaveF]

I have a B, so the stall warning unit is required. I also have a field-fabricated replacement instrument panel, which was designed without a single thought for future changes. I have no spare holes to work with. The fact that I'm looking at the hole under the yoke shows how desperate I am for options.

I'm not sure when Cessna changed to audio-only stall warning, but it was sometime in the '60s. I learned to fly in a '61 150 which was sound only. My '73 182 had a buzzer under the panel and my '76 210 buzzed through the overhead speaker. I think the answer to this question is to write up a 337 to "upgrade" the stall warning to a later model design, then see if the FSDO will approve it.

[Ryan Smith]

I'm not sure when Cessna changed to audio-only stall warning, but it was sometime in the '60s. I learned to fly in a '61 150 which was sound only. My '73 182 had a buzzer under the panel and my '76 210 buzzed through the overhead speaker. I think the answer to this question is to write up a 337 to "upgrade" the stall warning to a later model design, then see if the FSDO will approve it.

If there is no equipment spec as to what is approved for notification device (specific component), then is it really an "upgrade"? Another search of the site last night yielded a result regarding the drawing. Apparently Cessna will charge you an astronomical fee ($>$250) to LOOK at the drawing; not copy, not take notes, but burn it to memory. Thus, the Association does not have a copy of the drawing. If it's that damn important, you'd think they'd let you know the specifics about it. It's on the same level of idiocy of "We have to pass it to see what's in it!"

It would be nice if somehow type clubs could collectively lobby Cessna for copies of this information as they have no desire to continue support of products this old. I kind of wonder what Cessna thought the fleet lifespan of these airplanes would be back in the 1950s. Agree to release themselves of all liability of the information, enforce some sort of non-compete that would prevent people from building new 170s from scratch and calling them certified, and everyone can be happy. I think that a reasonably competent L2 law student could draft a good enough proposal to keep Textron happy. Perhaps I'm overstating things...

[KS170A]

... keep Textron happy. Perhaps I'm overstating things...

I will try to stay off a soapbox, but I can tell you there is only ONE thing that keeps Textron happy: Money, and LOTS of it (hence the outrageous fee to look at a drawing). Unfortunately the new Cessna/Textron does not like airplanes, as evidenced by top management's attitude and the people he is putting in charge of things.

MHO, for what it's worth, the Type Clubs and entrepreneurial/imaginitive members are the best hope for the 170. Hell, if Cessna's CEO says a current-production airplane with all the bells and whistles "...has no future..." (ala his comments about the C-162 at NBAA last year), just think what he'd say about the 170!

[GAHorn]

Here's what I think is true about this subject.

The 170-B requires a stall warning per CAR. The particular one selected and certified by Cessna was the Safe Flight make/model which was identified by part number*. Any substitution of any other type, or relocation to an area not in the primary view of the pilot will require aother basis of approval, either a Field Approval, STC, or other basis.

It makes no difference what Cessna got approved on other models aircraft for the owner/pilot except as a basis to apply for approval. IMO. One would think it'd be like an altimeter, one TSO'd could be replaced with any other meeting the same TSO. Unfortunately, the combination horn/light was not TSO'd. (And that should help explain the advantage of items meeting TSO.)

*edit for accuracy, thx gary

[bagarre]

What exactly does CAR3 say about requiring a stall warning device to be installed? I can't find it off hand and don't have much time to dig. (I always though it was required because Cessna didn't make it an option 1952 and beyond. Didn't realize they didn't make it optional because the FAA mandated all aircraft to have one)

It would seem odd that they'd require a visual indication such as a light when aircraft aren't even required to have an electrical system.


If the regs don't require a visual indicator that is panel mounted in plain sight of the pilot, I don't see why the original horn couldn't be relocated and still satisfy the requirement of having a stall horn so long as you can still hear the thing.

[Bruce Fenstermacher]

I think the point George makes would be the one most FAA inspectors would take. That being since the stall/warning with a audio and visual indication was the one used by Cessna to satisfy the requirement of the time, that that is the one you need to use.

Of course to gain a different view from these inspectors you would have to show the visual indication was not required of the CAR and that is why you are removing the visual indication from the system you are installing.

CAR3 is not readily available though it can be found. I've also found it nearly impossible to figure if what you are looking at is current and correct for the time. I have a copy somewhere. Perhaps if I have time to kill in the next few days I'll find and look at it for insight.

[bagarre]

Given that we're talking about still using the original stall horn and not replacing it with some other design that needs further approval.

Stall warning.
(a) There must be a clear and distinctive stall warning, with the flaps and landing gear in any normal position, in straight and turning flight.
(b) The stall warning may be furnished either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself.
[(c) During the stall tests required by Sec. 23.201(b) and Sec. 23.203(a)(1), the stall warning must begin at a speed exceeding the stalling speed by a margin of not less than 5 knots and must continue until the stall occurs.
(d) When following procedures furnished in accordance with Sec. 23.1585, the stall warning must not occur during a takeoff with all engines operating, a takeoff continued with one engine inoperative, or during an approach to landing.
(e) During the stall tests required by Sec. 23.203(a)(2), the stall warning must begin sufficiently in advance of the stall for the stall to be averted by pilot action taken after the stall warning first occurs.
(f) For acrobatic category airplanes, an artificial stall warning may be mutable, provided that it is armed automatically during takeoff and rearmed automatically in the approach configuration.]

So, that's CFR14 and not CAR3 but doesn't require a visual indication. Only that the warning be clear and distinctive.

Which would be a good first step in justifying the relocation of the device if it still satisfies the above.

[Ryan Smith]

I think I'll channel my inner blueldr and say, "Who's going to know the difference?"

You get ramp checked by the fuzz, are they going to have the information readily available regarding the SWH cockpit notification device to be able to ground your airplane right there? These airplanes have all been so heavily modified over the years that unless they are as in tuned with the airplanes as we as a group are, there are things that could very well slide. If your airplane is spotless (like many on here are), I don't think there will be enough suspicion raised to warrant further investigation. Rather simplistic, I know, and I have seen what can get an airplane grounded and in many cases, it's ridiculous.

Does anybody care to tackle the question as to why the SWH is not required equipment for seaplane?