Cost of Mooney Biscuit

[A64Pilot]

1 minute ago, Shadrach said:

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.   

Without getting Mooney’s drawing, I don’t think you possibly could.

And you have definitely modified the type design, because your biscuits are too soft or too hard etc, and it’s possible that the aircraft wouldn’t pass the drop test, and that of course changes max gross.

It’s actually a can of worms,one would think the best design would be one soft puck and others getting harder, so you initially have a soft compliment suspension, that stiffens up when needed, and as I interpret the reg, you could do that, but how well would it really work?

The whole owner produced parts is actually nuts, nothing stops you from building a crankshaft, or how about a high lift cam?

The HUGE overriding major big deal in manufacturing aircraft is conformity, everything to the last detail must meet the type design, the drawings.

‘Owner produced parts throws that out the window, I think it well intentioned, but expect it to change. I think it was meant as a way to keep old orphaned aircraft flying.

Neighbor has a Stinson Reliant, now where do you think he can get parts? I have a 46 C-140, it’s easy, but if you have an old Taylorcraft maybe not, with OPP you can keep the historic aircraft flying.

[PT20J]

30 minutes ago, Shadrach said:

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.   

Ross, I believe you have hit on a key point. Compared to a lot of countries (ask @M20Doc) the FAA is actually quite permissive. It's based on then idea that lesser government protection is required by those willing to accept greater risk. Experimental guys can do stuff we cannot do to certificated aircraft. Pilots flying under Part 91 have fewer regulations than  Part 135 operators, and Part 135 operators have a lot more leeway than Part 121 operators. So, the FAA allows owners to make parts for their airplanes that would require more stringent oversight if a non-owner produces parts. If the owner gets it wrong, then the owner is the one at risk (and of course any subsequent owners, but at least there is full disclosure if the log books are properly filled out).

Skip

[A64Pilot]

I’ll ask my Son to send a pic of a Thrush shock, it’s a stack of rubber biscuits, andI’ve heard some replace them with a Combine spring. Crop dusters will do anything.

‘I had one bring an aircraft into the repair station, I looked in the cockpit and saw he had replaced the torque meter, now it’s just an oil pressure gauge, but a very accurate one as the torque limit is 58.7 lbs at 2200 RPM or 64.5 lbs at 2000 RPM.

This guys torque meter said John Deere on it.  I tired my best to get him to understand that you can’t just do that.

Edited June 1, 2021 by A64Pilot

[Guest]

Just now, PT20J said:

Ross, I believe you have hit on a key point. Compared to a lot of countries (ask @M20Doc) the FAA is actually quite permissive. It's based on then idea that lesser government protection is required by those willing to accept greater risk. Experimental guys can do stuff we cannot do to certificated aircraft. Pilots flying under Part 91 have fewer regulations than  Part 135 operators, and Part 135 operators have a lot more leeway than Part 120 operators. So, the FAA allows owners to make parts for their airplanes that would require more stringent oversight if a non-owner produces parts. If the owner gets it wrong, then the owner is the one at risk (and of course any subsequent owners, but at least there is full disclosure if the log books are properly filled out).

Skip

The owner is the one at risk with his owner produced part until he sells the plane to someone else who doesn’t recognize it in the log book, if it’s there at all.

Clarence

[A64Pilot]

You know I believe even 121 guys can do the owner produced parts, need to look that up, because that’s tough to believe.

‘The Brits used to love to come as exchange Officers to the Army test activity, because we could do pretty much anything, but the brits had to get permission from the manufacturer to change brand of tires on their military aircraft.

on edit, sure looks like it, but i bet their approved maintenance program won’t let them

n. Owner/Operator Produced Part. Parts that were produced by an owner/operator for installation on their own aircraft (i.e., by a certificated air carrier). An owner/operator is considered a producer of a part, if the owner participated in controlling the design, manufacture, or quality of the part. Participating in the design of the part can include supervising the manufacture of the part or providing the manufacturer with the following: the design data, the materials with which to make the part, the fabrication processes, assembly methods, or the quality control (QC) procedures.

https://www.faa.gov/documentlibrary/media/advisory_circular/ac 20-62e.pdf

Edited June 1, 2021 by A64Pilot

[PT20J]

I've had a couple of instances where I had to make a OPP. One was a brake caliper for the Bearcat at the museum. They are unobtainium. We took the original to a machine shop and had them duplicate it. First try was obviously not airworthy. Took it to a second machine shop and they got it right. 

On my 1994 M20J, the fuel pressure transducer went bad. This model uses a fancy wheatstone bridge transducer made by Kulite to a Mooney drawing number. In other words it is not a COTS part. Factory was closed, but I doubt they would have given me the drawing anyway. Kulite wouldn't tell me what was different from their standard parts, but looking at several manufacturers specifications it appeared that there are quasi industry standard electrical/pressure specs for these things. I was pretty sure that the customization for Mooney was supplying it with a CPC connector. I found an obsolete drawing from Mooney specifying Omega as a replacement for Kulite transducers for oil pressure and manifold pressure (but no mention was made of fuel pressure). Omega being much easier to deal with than Kulite, I ordered a COTS Omega transducer with the proper pressure and electrical specs. It had an NPT fitting rather than a hose fitting, so I bought an adapter. I assembled the unit by installing a CPC connector and the hose adapter, and tested it and it worked fine. So, while I didn't have the original part specs, I convinced myself and my A&P that I had enough data to justify the substitution of the Omega part for the Kulite part and that my involvement in attaching the connector and fitting made it an OPP.

Skip

[PT20J]

7 minutes ago, A64Pilot said:

You know I believe even 121 guys can do the owner produced parts, need to look that up, because that’s tough to believe.

I believe you are correct. But, they have liability and other regulatory constraints that pretty much guarantee that the parts are as good or better than the originals. Just read the NTSB report on Alaska Airlines 261 to see what Alaska Airlines went through just to change the grease used on trim jackscrews (and no, the type of grease didn't cause the stabilizer to jam and the plane to crash. It was total lack of any grease.)

Skip

[EricJ]

1 hour ago, A64Pilot said:

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.

You are misunderstanding the requirement.   You are not doing the quality control, you are specifying a quality control procedure for the manufacturer.    From the Byrne letter:

"4. The person provided the manufacturer with quality control procedures to be used in the manufacture of the part."

or from AC 20-62E:

"Participating in the design of the part can include supervising the manufacture of the part or providing the manufacturer with the following: the design data, the materials with which to make the part, the fabrication processes, assembly methods, or the quality control (QC) procedures."

Quality control procedures usually aren't just inspection, they're process control as well, which can have a lot of implications that may touch on material temperatures, tempering, equipment, handling, documentation, etc., to make sure the part comes out in an acceptable state.   From my perspective (informed by several decades of engineering), this may be the most difficult of the five possible paths to participation for OPP in many cases.   It's also probably the least relevant in obtaining a proper part for most of our applications, but I understand why it is included for the cases where it would make sense.

[EricJ]

21 minutes ago, A64Pilot said:

You know I believe even 121 guys can do the owner produced parts, need to look that up, because that’s tough to believe.

My understanding, from the old grizzled instructors at our A&P school, was that OPP was originally developed for the airlines.   

 

[A64Pilot]

12 minutes ago, EricJ said:

You are misunderstanding the requirement.   You are not doing the quality control, you are specifying a quality control procedure for the manufacturer.    From the Byrne letter:

"4. The person provided the manufacturer with quality control procedures to be used in the manufacture of the part."

or from AC 20-62E:

"Participating in the design of the part can include supervising the manufacture of the part or providing the manufacturer with the following: the design data, the materials with which to make the part, the fabrication processes, assembly methods, or the quality control (QC) procedures."

Quality control procedures usually aren't just inspection, they're process control as well, which can have a lot of implications that may touch on material temperatures, tempering, equipment, handling, documentation, etc., to make sure the part comes out in an acceptable state.   From my perspective (informed by several decades of engineering), this may be the most difficult of the five possible paths to participation for OPP in many cases.   It's also probably the least relevant in obtaining a proper part for most of our applications, but I understand why it is included for the cases where it would make sense.

OK you convinced me

[A64Pilot]

31 minutes ago, EricJ said:

My understanding, from the old grizzled instructors at our A&P school, was that OPP was originally developed for the airlines.   

 

That would make sense as their maintenance procedures guide or whatever it’s called is extensive, and I bet expands greatly on it. I’d guess galley parts for say the coffee maker would be treated differently than some flight control hydraulic valve.

I’ve never worked 121 or even 135 for that matter but it’s my understanding that the 121’s guys books cover in great detail. far more than the FAR’s

Anyone way more curious than I am, here is a link

https://www.faa.gov/documenTLibrary/media/Advisory_Circular/AC 120-16F.pdf

Edited June 1, 2021 by A64Pilot

[thinwing]

On 6/1/2021 at 1:24 PM, hammdo said:

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

funny...

-Don

do they leave the string?

[hammdo]

How else do you 'uninstall' it?

-Don

[thinwing]

small ,regular or extra large size?

 

[Shadrach]

Again, Gert replied in short order to my question about the rubber material. Full response below:

Hi Ross

The discs are made from a compounded mix of natural rubber and Styrene Butadiene Rubber with a shoring of 70 deg with excellent weathering and Ozone cracking resistance. The original specifications were provided by a retired Lord Engineer( J Dawson) who was in charge of manufacturing of the discs. Without boring you too much with technical detail the material specification for the Mooney discs are exactly the same as the Beechcraft Retractable Sierra. The same molds were used but Mooney discs are approx. 2mm thicker. The Lord product was made by injecting the molten rubber mix into the mold via multiple ports, which led to surface cooling and sometimes splitting of the material at the joints. The modern method of pressurising the material in the mold cavity itself largely erased that sort of problem issues.

I have been manufacturing these discs for Beechcraft owners for a while now and have hopefully prolonged the life of many of these wonderfull little aircraft. I am hoping to do the same for Mooney owners too. I am manufacturing at almost cost and derive great pleasure out of providing an affordable alternative to the shark attitude of some manufacturers. It is a way for me to give back to the industry that has given me so much joy in my lifetime.

Blue skies,

Gert

 

 

Edited June 4, 2021 by Shadrach

[MikeOH]

2 hours ago, thinwing said:

small ,regular or extra large size?

 

Well, depends on if you have a large flow pump

[hammdo]

Also depends on the 'room size' is in question...

-Don