Is stall warning horn required equipment?

[robert38606]

The stall warning horn on my M20J is broken.  Something in the actuator broke.  Is that required equipment for flight?  I looked a the TCDS but I'm not sure I'm understanding it correctly.

If it is required equipment, then instead of spending a lot fixing it, can someone get an AOA indicator as a substitute?

Edited November 21, 2022 by robert38606

[Scottknoll]

Yes, the way I read the TCDS for the J, it states under “required equipment” 601 a+b or c.

So I think you need a and b. Or optionally, just c:
a: Gear warning indicator, Mallory, SC 628P
b: Stall warning indicator, Mallory, SC 628
or
c: Stall/Gear Warning indicator, IAI, 950D-0309-000

Edited November 21, 2022 by Scottknoll
Apparently it didn’t like my parenthesis around a/b/c

[carusoam]

Checking your POH is the easiest way to find the things required for flight… day,night,VFR,IFR…

Keep in mind…

The stall warning usually only gets heard in the last moments of landing…

Unless you are doing slow flight training…

It is a mistake warning… the kind you want to let you know you have made a mistake…

when important,

The stall warning comes on after a distraction… somewhat unexpectedly…

 

About the AOAi…

A great device to use, in real time, to know where you are, with respect to stalling… but doesn’t do the same thing…

 

You want both…

One to fly by…

the other to warn you of a mistake you are making… while you are probably not even watching the AOAi… 

 

Real Stalls happen with very little notice…

The surprise sound of the stall horn, triggers a quick reaction…. 

 

Flying without an operational stall warning is a bad idea…

You are unlikely to need it…

But, when you need it, and it doesn’t sound… the ground coming up at you would be an eye opening experience…

 

Have your mechanic try to revive your switch… it is an industrial BK switch that lasts nearly forever…

PP thoughts  only, not a mechanic…

Best regards,

-a-

 

[robert38606]

Thanks, y'all.  

[OR75]

it is an airworthiness item

 

[RobertGary1]

It’s listed on the type certificate so only if you can find a product with an stc that changes that would you be legal. 

[A64Pilot]

I’d definitely ground the wire at the switch to test if it’s the switch or horn.

Of course checking for continuity with the battery off will check the switch too.

I have not ever taken a Mooney stall switch out, but very often they are a mechanical mechanism connected to a common micro switch and just the micro switch can be changed, is a Mooney different?

Then there is the simple primitive move the vane slowly and listen for a click, no click and the switch hasn’t been made, I’ve seen a few where the vane had been bent slightly and it wouldn’t actuate the switch.

[N201MKTurbo]

1 minute ago, A64Pilot said:

I’d definitely ground the wire at the switch to test if it’s the switch or horn.

Of course checking for continuity with the battery off will check the switch too.

I have not ever taken a Mooney stall switch out, but very often they are a mechanical mechanism connected to a common micro switch and just the micro switch can be changed, is a Mooney different?

It’s an expensive micro switch.

[A64Pilot]

10 hours ago, MikeOH said:

Depends on if you want a legal replacement, I suppose.  To my knowledge the micro switch is not directly identifiable by a standard part number (like the Mallory SC628 is).  I believe you are forced, legally, to buy the stall warning switch assembly ... at something north of 1 AMU the last I heard

In my opinion a micro switch is a “standard part” even if you have no certs, if it fits, performs the same function and is the same form, your good.

Of course you would want a switch capable of handling the current the CB for that system is rated for, the system doesn’t pull that much but if your switch is rated at least as high as the CB then it can easily carry the load.

ALL Mooney’s as they are CAR 3 aircraft qualify as Vintage aircraft, I recommend everyone to become familiar with this AC as I believe it will become more important over time.

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_23-27.pdf

As an IA it’s also my opinion that an A&P can make this call, an IA would only need to become involved if there is a 337 involved, and I see no need for that.

Of course different people will have different opinions, any maintainer can’t go wrong by requiring a factory part, many default to that as it limits their liability.

[N201MKTurbo]

11 hours ago, MikeOH said:

Depends on if you want a legal replacement, I suppose.  To my knowledge the micro switch is not directly identifiable by a standard part number (like the Mallory SC628 is).  I believe you are forced, legally, to buy the stall warning switch assembly ... at something north of 1 AMU the last I heard

If you drill out the rivets and remove the microswitch, it has its part number on the side.

[N201MKTurbo]

42 minutes ago, MikeOH said:

Is it a Mooney, SafeFlight P/N, or the actual switch mfg’s P/N?  That is, will you be able to procure from a low cost source?

The microswitch has a microswitch part number on it. SafeFlight doesn't make microswitches, Honeywell does.

The last time I fixed one of these was about 25 years ago. The microswitch is hard to find and expensive. Not thousands expensive, but hundreds expensive.

[EricJ]

13 hours ago, MikeOH said:

Depends on if you want a legal replacement, I suppose.  To my knowledge the micro switch is not directly identifiable by a standard part number (like the Mallory SC628 is).  I believe you are forced, legally, to buy the stall warning switch assembly ... at something north of 1 AMU the last I heard

The Mallory (Sonalert) parts aren't standard, they're single-supplier.   Only one place makes them and they still make them with the same part numbers, so that's fortunate.    They are not, and have never been, FAA-PMA or TSO or anything like that.    

[EricJ]

Just now, MikeOH said:

I guess I wasn’t clear enough. The TCDS calls out a STANDARD Mallory part number. Therefore a perfectly legal option to buy that part number directly or through a distributor.

"Standard" means something that doesn't apply in this case.   It is a Mallory part number.   There is no standard that applies in this case, nor any cited.

[EricJ]

1 minute ago, MikeOH said:

I realize what STANDARD means with aviation parts. And, what building and certifying to a standard means.

You seem to be hell-bent on taking my post completely out of context. I never claimed it was a STANDARD aviation part, nor that it met a published standard; I said, and it is, a standard Mallory part and is legal only because it is called out in the TCDS.

You said twice in two separate posts that it was "standard".    "Standard part number" means it is a part number identified in a standard.

 

14 hours ago, MikeOH said:

To my knowledge the micro switch is not directly identifiable by a standard part number (like the Mallory SC628 is). 

 

19 minutes ago, MikeOH said:

The TCDS calls out a STANDARD Mallory part number.

I was just responding to those.

[JimB]

Or there is this https://lasar.com/switches/stall-switch-v3-2451-d8 

Or

https://lasar.com/switches/stall-switch-retrofit-kit-940065-505

Or

https://lasar.com/switches/stall-warning-switch-assy-800364-9509-800424-9015

[EricJ]

29 minutes ago, MikeOH said:

Fine, you can continue to ignore my point: the SC628 is a Mallory catalog standard part and insist on pointless pedantry.

Context matters. Continuing to insist I somehow was claiming this commercial buzzer met some MIL or aerospace standard simply because I used the word is ridiculous.

No worries.   Terms get misused all the time, and it can help reduce confusion, both present and future, to point out common misconceptions when terms are misused.   There's a difference between a manufacturer's part number and a standard part number, although they can sometimes be the same when a part does get standardized.   It can get even more confusing when third parties make replicate parts using the original manufacturer's part number or a similar part number even when there is not a standard for the part, and that has happened with this particular part.    And "standard" has generic meaning as well, like when marketing materials claim something is "an industry standard" in a generic sense and not any sort of actual standardization sense.    So there's plenty of room for confusion, which is why it can be useful to point out the difference when it is misused.

Doing so always runs the risk of hitting a nerve in somebody sensitive to such feedback, though, as the case in point.

For our airplanes it is an important distinction because the FAA allows repairs using "standard parts", i.e., parts that conform to a formal standard, as defined by the FAA (which is a reasonably practical definition of an industry standard).   Parts that do not conform to a formal industry standard as defined by the FAA are not standard parts and do not have standard part numbers and must have some other means of approval for use on an aircraft.   Mallory, as a manufacturer, is pretty clear that they generally don't deal with standards or environmental certifications and that it is up to the final equipment manufacturer to obtain whatever standardization or certification is needed.   They even state this specifically for FAA certifications, that they are not PMA but will provide supporting data to anybody who wants to use their parts in a higher-level assembly that seeks PMA or other FAA approval.

See under "Environmental Issues":

https://mspindy.com/faqs/transducers-external-drive-electromagnetic/

The Mallory Sonalert parts are not standardized and do not have standard part numbers, SC628 is a Mallory part number, although, sadly, other suppliers (usually offshore) have made replicate parts under the same part number.  I've got a bunch of different such parts in a box here.  Such replicate parts are not approved for use in our aircraft even if they use the same part number.

So the pedantry is not without point, especially when maintaining an aircraft where standardization and "standard part number" (or not) can make a difference as to whether a part is approved for use or not.   In this particular case there is no standard, so the source of the part matters, not just the part number.



 

[JimB]

16 minutes ago, EricJ said:

No worries.   Terms get misused all the time, and it can help reduce confusion, both present and future, to point out common misconceptions when terms are misused.   There's a difference between a manufacturer's part number and a standard part number, although they can sometimes be the same when a part does get standardized.   It can get even more confusing when third parties make replicate parts using the original manufacturer's part number or a similar part number even when there is not a standard for the part, and that has happened with this particular part.    And "standard" has generic meaning as well, like when marketing materials claim something is "an industry standard" in a generic sense and not any sort of actual standardization sense.    So there's plenty of room for confusion, which is why it can be useful to point out the difference when it is misused.

Doing so always runs the risk of hitting a nerve in somebody sensitive to such feedback, though, as the case in point.

For our airplanes it is an important distinction because the FAA allows repairs using "standard parts", i.e., parts that conform to a formal standard, as defined by the FAA (which is a reasonably practical definition of an industry standard).   Parts that do not conform to a formal industry standard as defined by the FAA are not standard parts and do not have standard part numbers and must have some other means of approval for use on an aircraft.   Mallory, as a manufacturer, is pretty clear that they generally don't deal with standards or environmental certifications and that it is up to the final equipment manufacturer to obtain whatever standardization or certification is needed.   They even state this specifically for FAA certifications, that they are not PMA but will provide supporting data to anybody who wants to use their parts in a higher-level assembly that seeks PMA or other FAA approval.

See under "Environmental Issues":

https://mspindy.com/faqs/transducers-external-drive-electromagnetic/

The Mallory Sonalert parts are not standardized and do not have standard part numbers, SC628 is a Mallory part number, although, sadly, other suppliers (usually offshore) have made replicate parts under the same part number.  I've got a bunch of different such parts in a box here.  Such replicate parts are not approved for use in our aircraft even if they use the same part number.

So the pedantry is not without point, especially when maintaining an aircraft where standardization and "standard part number" (or not) can make a difference as to whether a part is approved for use or not.   In this particular case there is no standard, so the source of the part matters, not just the part number.



 

And then there are all those "gray" areas in between that are subject to interpretation by the individual FAA inspector, A&P, IA, owner, manufacturer, repair station, etc. 

[A64Pilot]

I was the one that said in my opinion that a microswitch is a standard part.

Using the definition of the linked AC as to what is a standard part.

As a rated mechanic I would have no problem installing an off the shelf switch that would fit and function and could handle the electrical load.

This is no different than putting in a Sylvania bulb in you airplane when it came with a GE bulb, in my opinion

Think that stupid? Well back in the day when the drawings were created for Thrush in Engineering the draftsman in the bill of materials listed the GE bulb part number, which meant that only a GE bulb could be used, because he didn’t say “or equilivent ”  That kind of mistake was and is common.

 

[A64Pilot]

14 minutes ago, MikeOH said:

 

The odd thing here is that Mooney actually received TCDS approval for what amounts to an uncontrolled part!  Mallory is free to change design, materials, and manufacturing of the SC628 and it is still approved to use!  I.e., it is Malloy's standard part and they are free to change their standard any time they want

Done all the time, automotive parts were all over the aircraft I used to build, the engine and prop control cables were marine, made in Fl. Heck the brake master cylinders were from a Studerbaker truck, with different seals for aircraft hydraulic fluid. The trim lever was some kind of lawnmower part, as was the fresh air vent control cables. Maule starter solenoid is an outboard starter solenoid, OMC. What makes them legal aircraft parts is when they are inducted in the manufacturers quality control system, we bought the Master cylinders from NAPA, but you couldn’t legally, you had to buy from us as those weren’t standard parts.

But electrical parts are usually extremely common standard parts, relays, switches, other components, heck even butt splices and terminals are all not “aviation” ever seen aviation electronic components like transistors, diodes, resistors? There aren’t any they are all standard parts.

[EricJ]

12 minutes ago, MikeOH said:

... The SC628 is a Mallory standard part number from their catalog; as opposed to a custom/special order part.  Again, I never claimed it met any FAA acceptable standard.  Simply because I used the word standard is not making such a claim.

So, yes, accusing me of something I did not do "hits a nerve."

But you keep doing it. 

12 minutes ago, MikeOH said:

Military and manned space flight programs commonly have a standard parts list.  That contextual usage of the term standard in that case does NOT refer to their meeting an accepted standard or not, merely that those parts listed are acceptable to use in a design.  Further, if a part not on that list is needed, then an NSPAR needs to be submitted with justification: NSPAR = NON-STANDARD Part Approval Request.  Pretty clear that doesn't mean approving a non-standard part by your definition is ok!  It just means approving it for use on that program.  Pretty rigid environment there, too.  Somehow, they manage to use the term standard in two different contexts without confusion.

Yes, and the distinction here is that most industries use the word "standard" specifically to indicate compliance to a formal standard, and there are millions of them, to distinguish parts or systems not complying to standards.   This has lots of implications for lots of things that are important to industries, like interoperability, substitution performance, traceability, interference with other systems, safety, etc., etc..    An organization can have its own standards and use the term that way, too, but that is fairly rare since it has the opportunity to add confusion within an organization and with vendors and other suppliers.   Usually when that's done it's done pretty carefully, or they're just comfortable overloading the term with the plebian use.   As I mentioned previously, these things all add up to create opportunities for confusion when using them in contexts where it should be more clear, like for aviation, where the term is actually defined by the regulating agency.    In this case, where it is defined with specific usage implications, when it is used improperly I don't see an issue in pointing it out in the hope to reduce the confusion in the affected context.  
 

12 minutes ago, MikeOH said:

The odd thing here is that Mooney actually received TCDS approval for what amounts to an uncontrolled part!  Mallory is free to change design, materials, and manufacturing of the SC628 and it is still approved to use!  I.e., it is Malloy's standard part and they are free to change their standard any time they want

There are tons and tons of aircraft parts done this way.    The sonalert is just one example.

I spent a fair amount of my career contributing to standards documents and the development of various standards and standard verification and management, compliance, developing systems to both define and comply to standards, etc., because it's a significant part of how technologies have to work.   From that perspective and in the aviation application there's not really a context where the Sonalerts are a standard part or have a standard part number.    They're a single-supplier manufacturer's part, which is essentially the opposite of a standard part.

[MikeOH]

17 minutes ago, EricJ said:

But you keep doing it. 

Yes, and the distinction here is that most industries use the word "standard" specifically to indicate compliance to a formal standard, and there are millions of them, to distinguish parts or systems not complying to standards.   This has lots of implications for lots of things that are important to industries, like interoperability, substitution performance, traceability, interference with other systems, safety, etc., etc..    An organization can have its own standards and use the term that way, too, but that is fairly rare since it has the opportunity to add confusion within an organization and with vendors and other suppliers.   Usually when that's done it's done pretty carefully, or they're just comfortable overloading the term with the plebian use.   As I mentioned previously, these things all add up to create opportunities for confusion when using them in contexts where it should be more clear, like for aviation, where the term is actually defined by the regulating agency.    In this case, where it is defined with specific usage implications, when it is used improperly I don't see an issue in pointing it out in the hope to reduce the confusion in the affected context.  
 

There are tons and tons of aircraft parts done this way.    The sonalert is just one example.

I spent a fair amount of my career contributing to standards documents and the development of various standards and standard verification and management, compliance, developing systems to both define and comply to standards, etc., because it's a significant part of how technologies have to work.   From that perspective and in the aviation application there's not really a context where the Sonalerts are a standard part or have a standard part number.    They're a single-supplier manufacturer's part, which is essentially the opposite of a standard part.

Oh, for chrissakes!

You win the internet.  If it wasn't for you, thousands of innocent readers would have been horribly misled by my terrible post; I've deleted it.  You should remove any quotes of mine so that there is no possibility of others being deleteriously affected.

I'm done trying to make helpful posts.  I'll leave that to the experts like you.

 

[MikeOH]

1 hour ago, A64Pilot said:

Done all the time, automotive parts were all over the aircraft I used to build, the engine and prop control cables were marine, made in Fl. Heck the brake master cylinders were from a Studerbaker truck, with different seals for aircraft hydraulic fluid. The trim lever was some kind of lawnmower part, as was the fresh air vent control cables. Maule starter solenoid is an outboard starter solenoid, OMC. What makes them legal aircraft parts is when they are inducted in the manufacturers quality control system, we bought the Master cylinders from NAPA, but you couldn’t legally, you had to buy from us as those weren’t standard parts.

But electrical parts are usually extremely common standard parts, relays, switches, other components, heck even butt splices and terminals are all not “aviation” ever seen aviation electronic components like transistors, diodes, resistors? There aren’t any they are all standard parts.

True.  But, as you point out you can't just go buy the NAPA part; you need to buy the 'marked up price' part from the aircraft manufacturer for the QC aspect.

And, agree about all the 'standard' electrical parts.

But, none of those electrical examples are called out by the TCDS directly like this SC628 Sonalert.  Wouldn't you find it odd if the TCDS directly called out that NAPA master cylinder part number?

I would have expected Mooney to have purchased the SC628, applied their QC, assigned a Mooney part number, and called that part number out in their IPC just like your master cylinder example.

[KB4]

This should help 

On 11/21/2022 at 10:11 AM, robert38606 said:

The stall warning horn on my M20J is broken.  Something in the actuator broke.  Is that required equipment for flight?  I looked a the TCDS but I'm not sure I'm understanding it correctly.

If it is required equipment, then instead of spending a lot fixing it, can someone get an AOA indicator as a substitute?

This should help. 
 

 

[A64Pilot]

8 hours ago, MikeOH said:

True.  But, as you point out you can't just go buy the NAPA part; you need to buy the 'marked up price' part from the aircraft manufacturer for the QC aspect.

And, agree about all the 'standard' electrical parts.

But, none of those electrical examples are called out by the TCDS directly like this SC628 Sonalert.  Wouldn't you find it odd if the TCDS directly called out that NAPA master cylinder part number?

I would have expected Mooney to have purchased the SC628, applied their QC, assigned a Mooney part number, and called that part number out in their IPC just like your master cylinder example.

Possibly it was a system as opposed to single parts, if you add a system say to your TCDS it’s often done by listing it in the TCDS.

For example we inducted an STC’d smoker into our aircraft as I’m sure it was easiest, we did the same for an airconditioner / heater. The smoker wasn’t anything but an RV water pump and a lawnmower gas tank, so I built our own smoker from then on. I didn’t tackle the airconditioner, the Zee was pretty good.

However in my opinion that doesn’t stop you from repairing the thing as opposed to replacing the module.

‘It’s my opinion and a whole lot of this stuff is the responsibility of the owner and or repair to make a judgement call, but using the linked to AC for guidance to find a suitable replacement part and repair the module, just like I’d expect an Avionics tech to open up my radio and replace a diode as opposed to me buying a new radio.

Like for example me not paying $800 ea for landing gear solenoids that weren’t available and getting on a months long wait list for Mooney to buy some and resell.

However Months ago I did pay $1,000 and am on a list waiting for a no-back spring, because I don’t think it’s likely I could source that spring as a standard part, I assume it is a special order and hopefully has QC controls that normal low price springs don’t. So it’s not applicable for everything, this is where the opinion of the owner / repairer comes in. That decision is my responsibility and of course I’m liable for my decision.

Don't you think if you made an OPP and later that part failed and caused an accident that you may likely find yourself in court? Same possibility exists for standard parts, but much lower. The OPP YOU are the manufacturer, standard part your not.

This is why many A&P’s insist on only OEM parts, it limits their liability to the installation of the part

[Hank]

10 hours ago, MikeOH said:

Oh, for chrissakes!

You win the internet.  If it wasn't for you, thousands of innocent readers would have been horribly misled by my terrible post; I've deleted it.  You should remove any quotes of mine so that there is no possibility of others being deleteriously affected.

I'm done trying to make helpful posts.  I'll leave that to the experts like you.

Pedantry Gone Wild!! Sorry, @MikeOH!