Cost of Mooney Biscuit

**bradp** · June 1, 2021

@A64Pilot the availability of alternative sources for a part (ie factory, used), does not impact whether an owner can choose to go down the OPP route. Cost is definitely a factor that can be used to justify going down the OPP route.

The SA outfit does appear to be adhering to the OPP rules if a design drawing is provided and the lead time of 14-20 days implies that these are not “off the shelf” stocked inventory.

Implying for sale is not the same as advertising a service with a price - as McFarlane provides, and as this outfit in SA appears to do.

So if they can produce a part is safe and cost effective- go for it

Mark89114 · June 1, 2021

I really doubt if a mechanic is going back and look at pucks and verify they are the correct part, as long as they look close I suspect you are fine. Do they go back and look at all of the other parts installed and make sure they are correct? Maybe technically they are supposed to but realistically there are too many parts to verify.

And the PMA/TSO certifications are all nonsense, look how poorly built and generally crap quality some of these components are, here is the short list I can think of, speed brakes, backspring, fuel pumps, champion spark plugs, stall warning switches, Sandia KI-300 product line, etc. and so on. Feel free to add your own.

My opinion is use the rubber disks, make them out of old tires, probably not going to be worse than the overpriced, under engineered crap we are buying now.

A64Pilot · June 1, 2021

I don’t know what it’s called but you guys are trying to convince yourselves of something that isn’t true.

‘You have to provide the design, the producer sending you a design for you to send back to them where you fill in your tail number is not providing a design, plus the part is made AFTER the design is received, and to the drawing, not before.

This producer is clearly manufacturing batches of parts that are stocked and ready to be shipped, or they certainly are holding themselves out to be.

‘I gave you guys a way out, it’s in the link I posted. Basically someone is going to have to clam it’s an owner produced part and put that in the logbook, which you are allowed to do, and in fact are probably required to do.

You make that entry that’s in the article, that was written by a FSDO inspector, and that relieves an A&P from having to determine the source of the part, from that point on his liability is determining the airworthiness of the part and installing them correctly. But that would be true for any part, the biscuits from Spruce too.

‘If you want to use these parts, follow the instructions in that article. I wouldn't save any drawings either as I don’t see where that’s required and it would tough for me to try to prove that I produced that drawing, if some of you have the software and computer skills, then maybe copy it. But I woudn’t use the one sent by the producer, odds are pretty good if the FAA were ever to ask questions that they have seen it before, 99 times out of 100 they are responding to some kind of complaint, it’s very rare that they go looking, someone almost always tips them off.

Often it’s the manufacturer of a PMA part, so the guy who makes the $100+ ones that Spruce sells sees a drop in shipments, hears about this guy i’m South Africa and reports him via the FAA’s Suspected Unapproved Parts program,if they make enough noise the FAA has to investigate, often an AD is eventually issued, maybe.

‘The Powerplant DER we used to use compared the FAA to a bear in the woods, you walk by the woods day after day all the time knowing there is a bear in the woods, but nothing happens. Then one day for seemingly no apparent reason the bear comes charging out of the woods and your running for your life, wondering why?

https://www.faa.gov/aircraft/safety/programs/sups/

A64Pilot · June 1, 2021

17 minutes ago, Mark89114 said:

I really doubt if a mechanic is going back and look at pucks and verify they are the correct part, as long as they look close I suspect you are fine. Do they go back and look at all of the other parts installed and make sure they are correct? Maybe technically they are supposed to but realistically there are too many parts to verify.

And the PMA/TSO certifications are all nonsense, look how poorly built and generally crap quality some of these components are, here is the short list I can think of, speed brakes, backspring, fuel pumps, champion spark plugs, stall warning switches, Sandia KI-300 product line, etc. and so on. Feel free to add your own.

My opinion is use the rubber disks, make them out of old tires, probably not going to be worse than the overpriced, under engineered crap we are buying now.

Any good mechanic is going to want to see “certs”, you know something like a yellow tag, especially for a part a owner supplies, and even then the logbook entry will usually state, “installed owner supplied xxx” The yellow tag ensures the airworthiness of a part, that’s why most of us have a folder full of them or a bunch of them stapled in the logbook.

‘At the repair station I kept a file for each aircraft, and copied logbook entries work orders and yellow tags etc, made the FAA inspector happy, and covered the Companies behind.

By making that entry, you supply the “certs”

Why don’t you want to make the entry?

Edited June 1, 2021 by A64Pilot

**EricJ** · June 1, 2021

13 hours ago, takair said:

Here is a link to the FAA interpretation. There are a couple of areas that may touch on this situation. From my own previous discussions with the FAA, one of the questions with regards to “sale” is really “intent to sell to the certified world”. One question with owner produced parts might be....were they manufactured before the order was placed or only subsequent to the order being placed under the conditions within the letter of interpretation? It seems, if they are stocked...it might be pushing the spirit of the law. Link below from a Cardinal group....

http://www.velocolutions.com/FAA-owner-manufactured-part.pdf

Thanks for posting this link to the Byrne memo. I had a transcribed copy, but this is much more traceable so that's better.

The examples cited in this memo help clarify a lot of questions many have about Owner Produced Parts. Many seem to want to make it a lot harder than it needs to be, and some of the examples included in this document are useful.

**Shadrach** · June 1, 2021

1 hour ago, A64Pilot said:

I don’t know what it’s called but you guys are trying to convince yourselves of something that isn’t true.

‘You have to provide the design, the producer sending you a design for you to send back to them where you fill in your tail number is not providing a design, plus the part is made AFTER the design is received, and to the drawing, not before.

This producer is clearly manufacturing batches of parts that are stocked and ready to be shipped, or they certainly are holding themselves out to be.

‘I gave you guys a way out, it’s in the link I posted. Basically someone is going to have to clam it’s an owner produced part and put that in the logbook, which you are allowed to do, and in fact are probably required to do.

You make that entry that’s in the article, that was written by a FSDO inspector, and that relieves an A&P from having to determine the source of the part, from that point on his liability is determining the airworthiness of the part and installing them correctly. But that would be true for any part, the biscuits from Spruce too.

‘If you want to use these parts, follow the instructions in that article. I wouldn't save any drawings either as I don’t see where that’s required and it would tough for me to try to prove that I produced that drawing, if some of you have the software and computer skills, then maybe copy it. But I woudn’t use the one sent by the producer, odds are pretty good if the FAA were ever to ask questions that they have seen it before, 99 times out of 100 they are responding to some kind of complaint, it’s very rare that they go looking, someone almost always tips them off.

Often it’s the manufacturer of a PMA part, so the guy who makes the $100+ ones that Spruce sells sees a drop in shipments, hears about this guy i’m South Africa and reports him via the FAA’s Suspected Unapproved Parts program,if they make enough noise the FAA has to investigate, often an AD is eventually issued, maybe.

‘The Powerplant DER we used to use compared the FAA to a bear in the woods, you walk by the woods day after day all the time knowing there is a bear in the woods, but nothing happens. Then one day for seemingly no apparent reason the bear comes charging out of the woods and your running for your life, wondering why?

https://www.faa.gov/aircraft/safety/programs/sups/

If the drawing matches the part, the drawings match the part. If a template is reviewed and and executed (signed) by the owner and then submitted.

It seems that you’re suggesting that if the owner puts in the additional effort to make a drawing that looks like the fabricator’s template, that would be legal, but using the fabricator’s template based of the fabricator’s previous fabrications makes it illegal.

So it’s not the quality of the guidance used but more the semantics behind whether or not the owner was adequately involved in the creation of the document? What standard are you using to determine the owners involvement? I’ve had my attorney fabricate several vendor supply agreement for me. I tell him what I want and he papers it up. When I submit that document to the supplier it has my signature on it… It’s my submission.

What if I requested specs from a fellow Mooney M20F owner who recently had McFarland make a RAM AIR cable for them?Would using his data as a template disqualify it as an OPP. What if I called McFarland and asked them if they’d made any in the past (surly they’ve made dozens of them) and could share the documents. I’m not in the would, but if they did, would that make it illegal to use? Would it increase safety and quality if I rejected using verified and useable data as a starting point and instead did all of my own measurements with no assistance from others owners or professional?

It would seem to me that the accuracy of the documented specifications and the owner’s understanding, verification and signature on the final submission would satisfy the regulations as being owner supplied.

Any lawyers on the board care to ring in?

**Will.iam** · June 1, 2021

2 hours ago, A64Pilot said:

I don’t know what it’s called but you guys are trying to convince yourselves of something that isn’t true.

‘You have to provide the design, the producer sending you a design for you to send back to them where you fill in your tail number is not providing a design, plus the part is made AFTER the design is received, and to the drawing, not before.

This producer is clearly manufacturing batches of parts that are stocked and ready to be shipped, or they certainly are holding themselves out to be.

‘I gave you guys a way out, it’s in the link I posted. Basically someone is going to have to clam it’s an owner produced part and put that in the logbook, which you are allowed to do, and in fact are probably required to do.

You make that entry that’s in the article, that was written by a FSDO inspector, and that relieves an A&P from having to determine the source of the part, from that point on his liability is determining the airworthiness of the part and installing them correctly. But that would be true for any part, the biscuits from Spruce too.

‘If you want to use these parts, follow the instructions in that article. I wouldn't save any drawings either as I don’t see where that’s required and it would tough for me to try to prove that I produced that drawing, if some of you have the software and computer skills, then maybe copy it. But I woudn’t use the one sent by the producer, odds are pretty good if the FAA were ever to ask questions that they have seen it before, 99 times out of 100 they are responding to some kind of complaint, it’s very rare that they go looking, someone almost always tips them off.

Often it’s the manufacturer of a PMA part, so the guy who makes the $100+ ones that Spruce sells sees a drop in shipments, hears about this guy i’m South Africa and reports him via the FAA’s Suspected Unapproved Parts program,if they make enough noise the FAA has to investigate, often an AD is eventually issued, maybe.

‘The Powerplant DER we used to use compared the FAA to a bear in the woods, you walk by the woods day after day all the time knowing there is a bear in the woods, but nothing happens. Then one day for seemingly no apparent reason the bear comes charging out of the woods and your running for your life, wondering why?

https://www.faa.gov/aircraft/safety/programs/sups/

I think it's called confirmation bias.

**EricJ** · June 1, 2021

9 minutes ago, Shadrach said:

It would seem to me that the accuracy of the documented specifications and the owner’s understanding, verification and signature on the final submission would satisfy the regulations as being owner supplied.

And provided data could just be providing an existing part and asking somebody to duplicate it. (This is clarified in the Byrne letter.) McFarlane provides a drawing from a part you ship to them, which is nice if you're not confident in determining the measurements accurately to fill in their template yourself.

And providing data or a part to duplicate is only one of 5 possible ways to sufficiently participate to produce an Owner Produced Part. Supervising the manufacture of the part is completely sufficient, and "supervision" isn't defined in FAR 14 CFR Part 1. In industry supervising manufacture is sometimes just inspection of a completed part for pass or fail, but checking in along the way for a few steps during production is usually pretty easy to do and all the better. Or one can just provide the materials for production, which also fully satisfies the participation requirement and doesn't seem to me to be too difficult in many cases.

9 minutes ago, Shadrach said:

Any lawyers on the board care to ring in?

I ain't one of those, but one of the FAA's attorneys (Byrne) wrote a helpful guideline with examples that takair provided a link to.

This doesn't seem difficult or complicated to me, and we're actually given multiple, practical and not all that difficult (by my estimation) means to accomplish having an Owner Produced Part made. The Byrne letter, AC 20-62E, and Far 21.9(a)5 are the main guidance from the FAA on the topic. The articles by Don Dodge and Mike Busch have already been cited, and are pretty consistent with the official guidance. By my reading none of those documents make it as hard as some would like to suggest. An awful lot of additional hurdles seem to get read into them that just aren't there. Our local IA seminars usually have an FAA person speaking on this topic, and I've not come away from those thinking this should be all that difficult, either.

**Shadrach** · June 1, 2021

6 minutes ago, EricJ said:

And provided data could just be providing an existing part and asking somebody to duplicate it. (This is clarified in the Byrne letter.) McFarlane provides a drawing from a part you ship to them, which is nice if you're not confident in determining the measurements accurately to fill in their template yourself.

And providing data or a part to duplicate is only one of 5 possible ways to sufficiently participate to produce an Owner Produced Part. Supervising the manufacture of the part is completely sufficient, and "supervision" isn't defined in FAR 14 CFR Part 1. In industry supervising manufacture is sometimes just inspection of a completed part for pass or fail, but checking in along the way for a few steps during production is usually pretty easy to do and all the better. Or one can just provide the materials for production, which also fully satisfies the participation requirement and doesn't seem to me to be too difficult in many cases.

I ain't one of those, but one of the FAA's attorneys (Byrne) wrote a helpful guideline with examples that takair provided a link to.

This doesn't seem difficult or complicated to me, and we're actually given multiple, practical and not all that difficult (by my estimation) means to accomplish having an Owner Produced Part made. The Byrne letter, AC 20-62E, and Far 21.9(a)5 are the main guidance from the FAA on the topic. The articles by Don Dodge and Mike Busch have already been cited, and are pretty consistent with the official guidance. By my reading none of those documents make it as hard as some would like to suggest. An awful lot of additional hurdles seem to get read into them that just aren't there. Our local IA seminars usually have an FAA person speaking on this topic, and I've not come away from those thinking this should be all that difficult, either.

I’m familiar with Byrne’s 1993 clarification (I referenced it a few post ago). That is likely why you and I are on the same page. Both of us reading the clarification and not reading into anything beyond. I’m amazed by the pretzels some people are willing to tie themselves into in order to see a potential gotcha. On the other hand, I’ve had experience with some weenies within the administration. (none of which were on the maintenance side). Just one lousy experience with a weenie is enough to make you want to minimize further interactions with them. I can see how someone who feels like they need to appease a weenie would naturally start to think like one. I think the FAA’s reputation was earned years ago and there’s little they can do to change it. I know two people that have gone to the “Dark side” (FAA); both are exceptionally practical and pragmatic individuals when it comes to GA...in most cases more so than many mechanics who fear interacting with the FAA.

A64Pilot · June 1, 2021

1 hour ago, Shadrach said:

If the drawing matches the part, the drawings match the part. If a template is reviewed and and executed (signed) by the owner and then submitted.

It seems that you’re suggesting that if the owner puts in the additional effort to make a drawing that looks like the fabricator’s template, that would be legal, but using the fabricator’s template based of the fabricator’s previous fabrications makes it illegal.

So it’s not the quality of the guidance used but more the semantics behind whether or not the owner was adequately involved in the creation of the document? What standard are you using to determine the owners involvement? I’ve had my attorney fabricate several vendor supply agreement for me. I tell him what I want and he papers it up. When I submit that document to the supplier it has my signature on it… It’s my submission.

Two things, OK maybe three

Your first sentence the drawing has to be owner produced and the drawing has to precede the part, in other words the part has to be made to the drawings specs, not the other way around, and by the producer sending you a drawing that’s complete clearly is not an owner designed or produced part, you signing it doesn’t make it your design

Your second sentence, your absolutely correct, you just stated why this is not an owner produced part, no I’m not saying it would be legal, I’m saying if you choose to go ahead and purchase these parts and claim that you designed the part, at least have an original drawing.

‘None of you is pretending to actually participate in the manufacture of this part, yet you choose to act as though it’s an owner produced part.

Your third statement having a lawyer draft a letter that you sign doesn’t make it an owner produced part either.

‘There are five ways it can be a owner produced part and none of them are sign a form letter or a supplied drawing.

You guys are wanting your cake and eating it too, none of you have answered why your won’t make the logbook entry that you produced the part

I’m not going to convince any of you. that’s obvious, but I do believe many who are not responding may be giving it consideration.

‘All of our insurence policies I’m sure require that the aircraft be maintained in an airworthy standard, it may behoove you to ensure that they are.

For those that consider PMA and TSO etc to be nonsense, there is a category of aircraft just for you, and many of them are actually pretty good aircraft, you should should sell your Certified Aircraft and build one of them, then you don’t have to worry about picky IA’s and A&P’s anymore and you can choose the parts you like

**Shadrach** · June 1, 2021

4 minutes ago, A64Pilot said:

Two things, OK maybe three

Your first sentence the drawing has to be owner produced and the drawing has to precede the part, in other words the part has to be made to the drawings specs, not the other way around, and by the producer sending you a drawing that’s complete clearly is not an owner designed or produced part, you signing it doesn’t make it your design

Your second sentence, your absolutely correct, you just stated why this is not an owner produced part, no I’m not saying it would be legal, I’m saying if you choose to go ahead and purchase these parts and claim that you designed the part, at least have an original drawing.

‘None of you is pretending to actually participate in the manufacture of this part, yet you choose to act as though it’s an owner produced part.

Your third statement having a lawyer draft a letter that you sign doesn’t make it an owner produced part either.

‘There are five ways it can be a owner produced part and none of them are sign a form letter or a supplied drawing.

You guys are wanting your cake and eating it too, none of you have answered why your won’t make the logbook entry that you produced the part

I’m not going to convince any of you. that’s obvious, but I do believe many who are not responding may be giving it consideration.

‘All of our insurence policies I’m sure require that the aircraft be maintained in an airworthy standard, it may behoove you to ensure that they are.

For those that consider PMA and TSO etc to be nonsense, there is a category of aircraft just for you, and many of them are actually pretty good aircraft, you should should sell your Certified Aircraft and build one of them, then you don’t have to worry about picky IA’s and A&P’s anymore and you can choose the parts you like

1) I would happily sign a logbook entry stating that I submitted the diagram with specifications to the manufacturer and had the items manufactured to those specifications.

2) these are not off-the-shelf items. Per Gurt’s email, production will take place within 14 to 21 days of receiving the signed and verified document with the specifications.

Let me ask you this. What if I took the so called “form letter” and re-drafted it with my own graphics, colors and carefully used my own words in the text?

Edited June 1, 2021 by Shadrach

JimB · June 1, 2021

I just changed my 20 year old pucks with new ones from Spruce. They were not cheap but I don't ever expect I will have to replace them again as long as I own the aircraft.

Actually that is sort of my plan at the moment. I really want to keep this aircraft when I retire so I am trying replace or upgrade everything that I can anticipate needing changed over the next 20 years now. Then hopefully I won't have any big ticket expenses later. So if I kick the bucket in the next few years and you see that my widow puts my aircraft out there for sale, you should buy it!!

A64Pilot · June 1, 2021

1 hour ago, Shadrach said:

1) I would happily sign a logbook entry stating that I submitted the diagram with specifications to the manufacturer and had the items manufactured to those specifications.

2) these are not off-the-shelf items. Per Gurt’s email, production will take place within 14 to 21 days of receiving the signed and verified document with the specifications.

Let me ask you this. What if I took the so called “form letter” and re-drafted it with my own graphics, colors and carefully used my own words in the text?

If your really asking for advice or what would I do if I wanted to use these parts, I’d take his drawing and add some tolerances to it maybe + or - .020 or something, because the way it is now the parts can’t vary even .001 because he specs to the third decimal, likely because a calculator derived that from a metric equal. But if a part is only .001 out they way the drawing is now, it doesn’t meet spec and isn’t usable, and I’m sure these things don’t have to be that precise.

‘But by adding in some tolerance I have changed the drawing specifications, and I would provide quality control for the parts and “buy” them in when I received them, by measuring them and ensuring they meet tolerances, I am providing quality control, which is one of the five things you can provide and make it an owner produced part.

‘Then I would make the logbook entry exactly like in that link I provided

But in all honestly as having had a lot to do with an aircraft with elastomer landing gear biscuits, my concern is that there is no durometer spec for the parts on the drawing, so they could be marshmallow soft or rock hard. I’m certain Mooney’s parts spec a durometer, or I’d bet lunch they do anyway.

With Thrush part of the landing gear drop test required the biscuits to be tested and within the drawings specs for hardness, just as the tires had to be inflated to spec pressure. How hard or how soft the biscuits were mattered greatly to when something broke.

According to my logbook. my 41 yr old airplane had its biscuits replaced for the first time three or four years ago, and they appear to be in new condition now, so if they only last say ten years, and if they cost $150 ea and there are 11 of them, then that’s $1650 or $165 a year, I can handle that.

what bothers me is $1,000 for an off the shelf relay, or $500 for an off the shelf switch

Edited June 1, 2021 by A64Pilot

**Shadrach** · June 1, 2021

Just now, A64Pilot said:

But in all honestly as having had a lot to do with an aircraft with elastomer landing gear biscuits, my concern is that there is no durometer spec for the parts on the drawing, so they could be marshmallow soft or rock hard. I’m certain Mooney’s parts spec a durometer, or I’d bet lunch they do anyway.

The above is absolutely a legitimate concern. I will email Gurt for an answer.

You did not answer my question. It's a simple yes or no. Would a rewrite in my own language and format be adequate to meet your definition of owner provided data?

A64Pilot · June 1, 2021

Just now, Shadrach said:

The above is absolutely a legitimate concern. I will email Gurt for an answer.

You did not answer my question. It's a simple yes or no. Would a rewrite in my own language and format be adequate to meet your definition of owner provided data?

If I understand the question and I may not, but in my opinion no

Its not a matter of getting the language right, thats what a lawyer does, and we are talking about mechanics here.

‘It’s a matter of participating in the production of the part, so you need to be involved in its design, supervising its production or maybe quality control.

‘Well design is tough as it’s already designed, and I doubt your traveling to S Africa to watch it be molded and cooked, but quality control is easy, a quick visual to ensure it’s bonded, not cracked, get the calipers out and measure it and ideally he supplies a statement of its durometer. Then there is no question that you have been involved with the production of this part, and it took you maybe a minute of your time, and your probably going to give them a good look over anyway.

‘I’d make a quick list of my inspection points and keep that along with the part drawing in the aircraft maintenance records.

‘I stay away from the word manufacturing because for some reason the FAA does, they keep calling it producing, and the person making it the producer, there must be a reason why. If you build an experiment airplane, your the manufacturer, not the producer?

**EricJ** · June 1, 2021

36 minutes ago, A64Pilot said:

If your really asking for advice or what would I do if I wanted to use these parts, I’d take his drawing and add some tolerances to it maybe + or - .020 or something, because the way it is now the parts can’t vary even .001 because he specs to the third decimal, likely because a calculator derived that from a metric equal. But if a part is only .001 out they way the drawing is now, it doesn’t meet spec and isn’t usable, and I’m sure these things don’t have to be that precise.

Having a drawing with nominal dimensions is not unusual, even if there are a few digits past the decimal point. McFarlane's drawings for cables don't specify tolerances, either. What would be concerning would be if there was a tolerance specified that isn't realistic or is incorrect or creates problems. If you arbitrarily put a tolerance on a drawing, you should have some good justification of where that tolerance came from, what justifies it, what determines the limits, and assurance that articles on the outside edges of those tolerances with stackups don't create problems in the intended installation.

In other words, I think you're adding a lot of unnecessary and potentially dangerous difficulty and complication by including an arbitrary tolerance than in just leaving a drawing with nominal dimensions and no tolerance claimed. Unless you can provide backup for a specified tolerance, there shouldn't be one.

For example, how do you set ignition timing on an airplane? How close is good enough? There is seldom a tolerance specified, just, for example, 25 degrees or 20 degrees. Does this mean there can be no error at all since there is no tolerance specified? There must be acceptable error, because nobody can set timing perfectly with no error. Why isn't there a tolerance specified if there can be an error?

The only place I've seen tolerance specified for ignition timing is in the MM for the Grumman Yankee, which says +/- 2 degrees. I've not personally seen it anywhere else, and certainly not for Mooneys. I don't think that means that Mooneys have to have perfectly set timing, because none do.

Quote

‘But by adding in some tolerance I have changed the drawing specifications, and I would provide quality control for the parts and “buy” them in when I received them, by measuring them and ensuring they meet tolerances, I am providing quality control, which is one of the five things you can provide and make it an owner produced part.

Actually the Byrne letter says the owner provides the quality control procedure to the manufacturer, so doing it after the fact on your own would likely not meet that requirement.

You clearly have your own interpretations of the requirements, but much of what you say isn't actually part of any of the guidance or instructions from the FAA.

Edited June 1, 2021 by EricJ

**Shadrach** · June 1, 2021

1 minute ago, A64Pilot said:

If I understand the question and I may not, but in my opinion no

Its not a matter of getting the language right, thats what a lawyer does, and we are talking about mechanics here.

‘It’s a matter of participating in the production of the part, so you need to be involved in its design, supervising its production or maybe quality control.

‘Well design is tough as it’s already designed, and I doubt your traveling to S Africa to watch it be molded and cooked, but quality control is easy, a quick visual to ensure it’s bonded, not cracked, get the calipers out and measure it and ideally he supplies a statement of its durometer. Then there is no question that you have been involved with the production of this part, and it took you maybe a minute of your time, and your probably going to give them a good look over anyway.

‘I’d make a quick list of my inspection points and keep that along with the part drawing in the aircraft maintenance records.

‘I stay away from the word manufacturing because for some reason the FAA does, they keep calling it producing, and the person making it the producer, there must be a reason why. If you build an experiment airplane, your the manufacturer, not the producer?

Thanks for the clarification on your position. I'd like to touch on something you said earlier. I do not think anyone here thinks PMA/TSO is nonsense in general. However, when one has been keeping a 30+ year old vintage bird airworthy for years on end, there are certain parts that may give you pause. The $4 Fram G2 fuel filter with an FAA/PMA 123-002-002 sticker over the Fram logo and charge $15 is a funny one. Or say spending $400 to have a Delco Remy Generator Overhauled. The cost is trivial over the long haul but one of the best ways to increase the cost and availability of a standard off the shelf part is to slap a PMA/TSO sticker on it.

**EricJ** · June 1, 2021

Just now, Shadrach said:

Thanks for the clarification on your position. I'd like to touch on something you said earlier. I do not think anyone here thinks PMA/TSO is nonsense in general. However, when one has been keeping a 30+ year old vintage bird airworthy for years on end, there are certain parts that may give you pause. The $4 Fram G2 fuel filter with an FAA/PMA 123-002-002 sticker over the Fram logo and charge $15 is a funny one. Or say spending $400 to have a Delco Remy Generator Overhauled. The cost is trivial over the long haul but one of the best ways to increase the cost and availability of a standard off the shelf part is to slap a PMA/TSO sticker on it.

My fave is the Piper instrument air filter (Piper pn 460-990) that is just a Tampax tampon.

https://shop.boeing.com/aviation-supply/p/754-817=PI

**hammdo** · June 1, 2021

And they didn't remove Tampax's name either...

funny...

-Don

A64Pilot · June 1, 2021

1 hour ago, EricJ said:

Having a drawing with nominal dimensions is not unusual, even if there are a few digits past the decimal point. McFarlane's drawings for cables don't specify tolerances, either. What would be concerning would be if there was a tolerance specified that isn't realistic or is incorrect or creates problems. If you arbitrarily put a tolerance on a drawing, you should have some good justification of where that tolerance came from, what justifies it, what determines the limits, and assurance that articles on the outside edges of those tolerances with stackups don't create problems in the intended installation.

In other words, I think you're adding a lot of unnecessary and potentially dangerous difficulty and complication by including an arbitrary tolerance than in just leaving a drawing with nominal dimensions and no tolerance claimed. Unless you can provide backup for a specified tolerance, there shouldn't be one.

For example, how do you set ignition timing on an airplane? How close is good enough? There is seldom a tolerance specified, just, for example, 25 degrees or 20 degrees. Does this mean there can be no error at all since there is no tolerance specified? There must be acceptable error, because nobody can set timing perfectly with no error. Why isn't there a tolerance specified if there can be an error?

The only place I've seen tolerance specified for ignition timing is in the MM for the Grumman Yankee, which says +/- 2 degrees. I've not personally seen it anywhere else, and certainly not for Mooneys. I don't think that means that Mooneys have to have perfectly set timing, because none do.

Actually the Byrne letter says the owner provides the quality control procedure to the manufacturer, so doing it after the fact on your own would likely not meet that requirement.

You clearly have your own interpretations of the requirements, but much of what you say isn't actually part of any of the guidance or instructions from the FAA.

You see, I have been an Aircraft manufacturer for 15 years so I understand what the FAA is saying, you provide QC by inspecting the part AFTER manufacture, you can’t inspect something that doesn’t exist yet.

But you have to have something to inspect to. The drawing provides that as well as the tolerances the part is required to meet, as is, I doubt any of his parts can meet drawing specs because he states no tolerance, and when no tolerance is stated, none exists and holding .001 with an elastomer is tough and surely unnecessary

Everything in an aircraft manufacturing facility is “bought in” nuts, bolts, cotter pins, everything. often it’s just checking “certs” which provide traceability of the parts, but anything made for us meant the drawings came out and each part was inspected IAW the drawings.

Many, many parts were supplied. the throttle and prop cables were supplied by a boat parts supplier in Fl, the brake master cylinders came from NAPA, they were I believe Studerbaker truck master cylinders that we modified slightly and installed rubber bits thst were compatible with 5606.

But all of it was QC’d or inspected when it arrived at the plant.

Pic of my Son, by his hand you will see four Master cylinders, those are the Studabaker truck parts. I never knew Studabaker built a truck, and astonishingly they are widely available through NAPA.

Edited June 1, 2021 by A64Pilot

A64Pilot · June 1, 2021

40 minutes ago, Shadrach said:

Thanks for the clarification on your position. I'd like to touch on something you said earlier. I do not think anyone here thinks PMA/TSO is nonsense in general. However, when one has been keeping a 30+ year old vintage bird airworthy for years on end, there are certain parts that may give you pause. The $4 Fram G2 fuel filter with an FAA/PMA 123-002-002 sticker over the Fram logo and charge $15 is a funny one. Or say spending $400 to have a Delco Remy Generator Overhauled. The cost is trivial over the long haul but one of the best ways to increase the cost and availability of a standard off the shelf part is to slap a PMA/TSO sticker on it.

It’s always been that way. Maule uses an OMC relay for their starter relay, but they don’t jack the price up as much.

‘Beechcraft door locks I’ve been told cost hundreds and come from Home Depot, they are cheap desk locks.

‘In the example of these off the shelf purchased parts what makes them aircraft parts is that they have been indoctrinated into the manufacturers quality control system.

You hear all the time what makes an aircraft alternator an aircraft part is that in manufacturing every single piece part is inspected and the auto ones it’s every now and again, but airplane parts get special treatment. Well that’s not really true. Auto parts are purchased and QC logs the certs, the box or maybe the part gets a QC stamp and its an aircraft part.

‘Unfortunately it’s become pretty common to jack parts prices through the roof in order to make the plant profitable, but very often they are actually losing business

I never could get the idiot that owned the plant I worked at to understand that if you jack the prices up high enough, you don’t make any money, because you don’t sell any parts. People learn the sources of supply and buy direct and or if the price is high enough just about anything becomes repairable, and people would specialize in “repairing” flight controls etc when there wasn’t an original part left. You see that in Ga with exhaust systems and engine baffling and a few others, engine mounts, welded landing gear assemblies and well bunches of things are “repaired” but try to find any of the original part.

‘Oh, we got skads of parts quotes, for insurence, but never sold any parts, or usually didn’t anyway.

jaylw314 · June 1, 2021

1 hour ago, EricJ said:

My fave is the Piper instrument air filter (Piper pn 460-990) that is just a Tampax tampon.

https://shop.boeing.com/aviation-supply/p/754-817=PI

No way!

**PT20J** · June 1, 2021

Everyone likes to complain about the FAA, but I think it is pretty amazing that they allow owners to produce parts for our airplanes. That's quite a privilege -- A&Ps can only repair and alter stuff -- they can't make parts. The intent seems obvious: You can make a part for your airplane. Your are not supposed to be changing the type design, so the part is supposed to be equivalent to the original. If you don't have the skills and/or equipment, you can pay someone else to make it to your specifications. If you don't have a specification you can hire someone to reverse engineer the original to create a specification for you. Now suppose the place you hire to make a part decides to use your specs and make parts and sell them. They can't do that because that's manufacturing airplane parts which requires FAA approvals. OK, suppose they keep your drawing and provide it to other owners to approve and then make the parts for other owners. Hmmmm. Sounds a little sketchy. What if your specs were incorrect? Now other owners would have bad parts. The FAA wants to allow you to keep your bird flying. But the FAA is also very concerned about bogus parts. Google "counterfeit aircraft parts."

I believe Mike Bush agrees that there should be two logbook entries: One by the owner that made or had the part made and one by the A&P that installed it. The owner's entry is the basis for the A&P to determine that the part is airworthy.

So, if you get a part made, and you are confident that it is equivalent to the original, you should have no qualms about making the logbook entry. And, if the part matches your description, the A&P should have no problem installing it and making the second logbook entry.

Skip

**carusoam** · June 1, 2021

20 hours ago, M20Doc said:

How does McFarlane Aviation call an engine control cable “owner produced” when they clearly stock them for ready sale?

Clarence

The manufacturing process has many steps...

The final step of some manufacturing processes is QC...

The final step of QC may occur after the product ships to the customer...

Example one: Ordering an engine from TCM... it is 90% built as a standard, gets completed via my order... and available to ship in only two weeks...

Example two: nothing more important than QC for pharma products... their finished products sit in controlled warehouses while the final QC documents go through an extensive review process... that can take months...

Example three: (Probably) For Macfarlane...

They produce the engine control (at risk*) based on the drawings they have in house... Stock them on a shelf... await the final detail...

The final detail arrives... when the customer supplies his old control hardware...

The final manufacturing step is in place to control the quality of the owner produced part...

Macfarlane has a part they can use to verify... the drawing of their new new part is the proper one, to match the user requirements...

*At risk manufacturing... producing something following all the guidance required, but one or two or a few.... some part of the QC can’t be done until, in our case, the user supplies the final detail...

Why is it at risk..?
If no user comes forth... the parts have been made, and nobody buys them....

or... the customer’s parts look nothing like the ones that were sitting on the shelf...

or... the customer’s part looks a lot like the ones on the shelf, but the material is incorrect...

PP thoughts only, not a Quality Engineer...

Best regards,

-a-

**Shadrach** · June 1, 2021

Just now, PT20J said:

OK, suppose they keep your drawing and provide it to other owners to approve and then make the parts for other owners. Hmmmm. Sounds a little sketchy. What if your specs were incorrect?

We should mention both sides of the risk here. Yes the drawings could be wrong. On the other hand, my drawings might be wrong. I see a set of documents that has produced a part that is installed and functioning properly as an asset to be utilized, not a dangerous method of cheating. How would one get the proper specs for Gear pucks if all they had was a 30 year old puck that was compressed beyond serviceability? I suppose you could fully extend the trailing link and measure the max distance and then divide that by the number of pucks and spacers. I would much prefer to have a fabricator give me the specs from a successful installation for verification rather than start from scratch.

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