600115-005 intake duct

[EricJ]

I'm all for OPP processes, improved parts, modernized parts, innovation, etc.   Intake ducting does require some extra-careful diligence for the obvious reasons.   That said, if sufficient diligence is applied here it could be a very good thing.   That's a fairly high bar, though.

[Shadrach]

On 11/10/2023 at 5:30 PM, EricJ said:

Automotive junkyards have a thing where you can check with nearly any other junkyard and find inventory of parts, and then they share in exchanges.   It's a brilliant program.    Maybe one day Mooney or MSCs will do this, too.   

This is mostly because LKQ swallowed up most of the small independent dismantlers.  Most of the Indies are now owned by “Big Junk“  

[Ragsf15e]

1 hour ago, Shadrach said:

Yes, but that was an OEM part that likely should have been replaced sometime during Clinton's second term...

I am intrigued at the prospect of a silicone duct as it is far more durable that rubber. To my understanding it is more flexible but less likely to permanently deform.  The failure mode for the OEM rubber piece begins with a localized crease. Once that happens, almost all of the stress from movement is transferred to the creased area with the weakened material. With time and vibration, said week spot slowly develops a small tear that propagates along the crease and compromises the structure.  Remember that under normal circumstances, the only suction to which this duct is exposed is the pressure drop aft of the air filter. Brackett recommends cartridge replacement at 5 in H2O which is just under .4 inHg (0.18psi).  It seems to me the risk of an engine out related to the duct is a complete structural failure of the duct that throttles the engine at which point the above suction numbers go out the window, engine performance is greatly degraded and things go pear shaped rapidly.  It looks to me like silicone might be the better choice. 

It very well could be that silicon is better, but I would think it might need some internal reinforcement similar to the oem part.  My point was that this part might be one that requires very careful design/testing as it can fail in such a way that is catastrophic.  Agree that the one on the crashed plane should have been fixed a long time before.

[MooneyJohn]

On 11/20/2023 at 11:23 PM, MikeOH said:

@MooneyJohn

That is great you are developing a replacement!

Not trying to be a wet blanket but if you are planning to mold this out of silicone will you be including an internal mesh like the original?

I can only speculate, but my concern is without the reinforcement when the material ages I can see bits and chunks breaking off and being ingested.  The originals tend to tear/rip but have to be really deteriorated before something big breaks off (it has happened and the engine stops!)

I take your concerns very seriously. The current duct being manufactured at best is 3/32 thick and only lasts two to three years before the part starts to degrade. There is not any approved instruction for repair or time change from the manufacturer. As for the reinforcement, I believe the material is there to only hold the poor quality of the manufactured part together. I have created over a dozen different prototypes to test fit and function. The current prototype is a 3D printed part with TPU material, also the thickness of the new design has been increased to 1/8. The final product will be made out of silicon for its durable, flexible, strength, and temperature control. 

[N201MKTurbo]

27 minutes ago, MooneyJohn said:

 

I take your concerns very seriously. The current duct being manufactured at best is 3/32 thick and only lasts two to three years before the part starts to degrade. There is not any approved instruction for repair or time change from the manufacturer. As for the reinforcement, I believe the material is there to only hold the poor quality of the manufactured part together. I have created over a dozen different prototypes to test fit and function. The current prototype is a 3D printed part with TPU material, also the thickness of the new design has been increased to 1/8. The final product will be made out of silicon for its durable, flexible, strength, and temperature control. 

I’m not sure what you are proposing would qualify as an Owner Produced Part. The intent of the OPP regulation is for the owner to produce an exact duplicate of the existing part. Using different material and different thickness seems to violate this. Although your design may be better, it seems like it would require an STC to be legal because it is a design change from the original part.

[1980Mooney]

3 hours ago, MooneyJohn said:

 

I take your concerns very seriously. The current duct being manufactured at best is 3/32 thick and only lasts two to three years before the part starts to degrade. There is not any approved instruction for repair or time change from the manufacturer. As for the reinforcement, I believe the material is there to only hold the poor quality of the manufactured part together. I have created over a dozen different prototypes to test fit and function. The current prototype is a 3D printed part with TPU material, also the thickness of the new design has been increased to 1/8. The final product will be made out of silicon for its durable, flexible, strength, and temperature control. 

 

3 hours ago, N201MKTurbo said:

I’m not sure what you are proposing would qualify as an Owner Produced Part. The intent of the OPP regulation is for the owner to produce an exact duplicate of the existing part. Using different material and different thickness seems to violate this. Although your design may be better, it seems like it would require an STC to be legal because it is a design change from the original part.

This raises a few issues.
 

Although well intentioned, would an IA ever sign off on it in an Annual?  

And if an owner produces such a part, and it fails in the future for the next owner (causing a crash like that E in OK), won’t the current owner (or their heirs if there is a fatality) and insurance company come after the former owner who made the OPP?

[Shadrach]

4 hours ago, N201MKTurbo said:

I’m not sure what you are proposing would qualify as an Owner Produced Part. The intent of the OPP regulation is for the owner to produce an exact duplicate of the existing part. Using different material and different thickness seems to violate this. Although your design may be better, it seems like it would require an STC to be legal because it is a design change from the original part.

FAR 43.13 says “in such a manner and using materials of such a quality that the condition of the aircraft, airframe, aircraft engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deteriora- tion, and other qualities affecting airworthiness).”

Surprisingly, It looks like he FAA is fine with OPPs being as good as they can be as long as they are equally good or better than original.

[EricJ]

7 minutes ago, Shadrach said:

FAR 43.13 says “in such a manner and using materials of such a quality that the condition of the aircraft, airframe, aircraft engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deteriora- tion, and other qualities affecting airworthiness).”

Surprisingly, It looks like he FAA is fine with OPPs being as good as they can be as long as they are equally good or better than original.

Yes, it doesn't need to be an exact replica, but it must meet or exceed all of the requirements and performance of the original.   For something like an intake bellows, the ability to age and fail safe as well as the original may be difficult to demonstrate.

 

[Ragsf15e]

24 minutes ago, EricJ said:

Yes, it doesn't need to be an exact replica, but it must meet or exceed all of the requirements and performance of the original.   For something like an intake bellows, the ability to age and fail safe as well as the original may be difficult to demonstrate.

 

I also think you’re not supposed to use OPP if the approved part is “available”.  I wonder if the 6-12 months wait is considered available?

[Vance Harral]

34 minutes ago, Ragsf15e said:

I wonder if the 6-12 months wait is considered available?

This is of great interest to me as a Mooney owner, with regard to OPP and VARMA.  There is this reasonable-on-its-face idea that if the manufacturer is still in business and producing parts, the FAA isn't going to bless alternative sources.  But there can be a big difference between theoretical and practical ability to produce parts.  A manufacturer who still answers the phone, but only to tell you that they won't produce your part until they get a sufficiently large back order log that could take months/years, arguably isn't a manufacturer at all.

[Shadrach]

46 minutes ago, Ragsf15e said:

I also think you’re not supposed to use OPP if the approved part is “available”.  I wonder if the 6-12 months wait is considered available?

That may have been the intent of the reg, but “part availability” or lack-thereof is not codified in the regulation’s wording as I have read it. You are free to produce all of the parts your IA is willing to sign off as far as I can tell.

[1980Mooney]

1 hour ago, Shadrach said:

You are free to produce all of the parts your IA is willing to sign off as far as I can tell.

I am curious if you know - If an OPP part is "signed off" by the IA of the current (producing) owner,  can the IA for the next owner look at the same part and say that is not airworthy as built and should have never been approved?

We hear all the time (Mike Busch writes about it) that different IA's will have different opinions on condition, repairs, airworthiness, etc.  It comes up in pre-buys and the first Annual with "a new set of eyes" after a purchase by a new owner ("Pencil Annual's", "Annual from hell", "Catch-up Annual").  In this case you have a part made without engineering drawings, without performance or life/failure testing in operating conditions and are "assuming" it is adequate or better.  Two IA's can look at the same thing and form a different conclusion.

[Shadrach]

28 minutes ago, 1980Mooney said:

I am curious if you know - If an OPP part is "signed off" by the IA of the current (producing) owner,  can the IA for the next owner look at the same part and say that is not airworthy as built and should have never been approved?

We hear all the time (Mike Busch writes about it) that different IA's will have different opinions on condition, repairs, airworthiness, etc.  It comes up in pre-buys and the first Annual with "a new set of eyes" after a purchase by a new owner ("Pencil Annual's", "Annual from hell", "Catch-up Annual").  In this case you have a part made without engineering drawings, without performance or life/failure testing in operating conditions and are "assuming" it is adequate or better.  Two IA's can look at the same thing and form a different conclusion.

If a maintenance professional finds any substandard part/installation on an aircraft they’re inspecting, it’s incumbent upon them to notify the owner and recommend corrective action if possible. They are not obligated to perform corrective action nor return the aircraft to service. This gives both sides some leverage to prevent a pissing contest over something stupid. If the IA doesn’t like the previous work he can walk away from the airplane. If the Owner thinks the IA’s assessment is incorrect, he can walk away from the IA.  In my experience, if you surround yourself with smart, reasonable, professionals and communicate openly, this kind of thing does not happen very often.  I once removed my plane from a shop because I disagreed with their reasoning. They reinforced my decision by acting terribly unprofessional during the return of my aircraft. It was a poor business decision as I told the story for 10 years.

 

[EricJ]

3 hours ago, 1980Mooney said:

I am curious if you know - If an OPP part is "signed off" by the IA of the current (producing) owner,  can the IA for the next owner look at the same part and say that is not airworthy as built and should have never been approved?

That happens all the time with approved, PMA, TSO'd, etc., parts, so I can't imagine it wouldn't happen with OPP parts.

At the last IA seminar an FAA rep told the story of a DAR approving a new airworthiness certificate on a Cessna being imported with an STC cowl on it.   The new airworthiness certificate was granted with the cowl in place.   The IA at the next annual wouldn't sign it off because he didn't think the cowl was approved.   We all know the stories of one FSDO signing off on something and the airplane getting tagged in some other district for being unapproved by them.

So, yeah, OPP is between you and your IA and all future bets are pending, just like any other part.

[EricJ]

6 hours ago, Ragsf15e said:

I also think you’re not supposed to use OPP if the approved part is “available”.  I wonder if the 6-12 months wait is considered available?

There's an oft-referenced presentation, that I've seen presented by FAA reps at least twice, that cites excessive cost or availability as justifications for OPP, and those are in the eye of the O.     Remember that OPP was invented for the airlines so that they could fabricate their own parts and avoid down time if a factory part wasn't "available", which probably meant by the next time the airplane was scheduled to fly.

[Pinecone]

22 hours ago, EricJ said:

and fail safe as well as the original may be difficult to demonstrate.

How does the current one "fail safe."  When failure has lead to the loss of aircraft???

[Andy95W]

1 hour ago, Pinecone said:

How does the current one "fail safe."  When failure has lead to the loss of aircraft???

I’m curious to see your data, at least regarding a properly installed and maintained component.

[N201MKTurbo]

I had an M20F with that boot for 19 years and 4000 hours. I replaced it once in the time I owned it. I found most of the wear and holes came from tools rubbing on it while undoing it to remove the lower cowl. I repaired the old one a number of times until it got pretty ratty. Even at that point, there was no way it was going to tear and get sucked in. The one that failed that way must have been in horrible shape. 
 

I bought the new one in the late 90s. I think I paid less than $200 for it.

I started undoing the boot from the cowl, but the tools and bolts were wearing holes in the boot, so I switched to removing the boot from the injector servo. It’s a little harder, but doesn’t wear out the boot.

[EricJ]

2 hours ago, Pinecone said:

How does the current one "fail safe."  When failure has lead to the loss of aircraft???

I think that one was a bit beyond maintenance spec, which allowed it to fail in an unsafe manner.   Anything can fail with enough determination.

[N201MKTurbo]

You could make a replacement like the original using the same techniques used to make fuel bladders. 
 

You could 3D print a negative mold of the inside of the duct which would part in two. Then make a paper mache plug of the inside of the boot. Then lay up uncurled, reinforced butyl rubber strips over the plug. Then cure it in an oven. When you are done, throw it in boiling water to remove the paper mache plug.

[Pinecone]

20 hours ago, Andy95W said:

I’m curious to see your data, at least regarding a properly installed and maintained component.

Properly maintained, they don't fail.

The problem comes when they are not replaced due to lack of availability.  So even if this OPP version needs to be replaced every 200 hours, that is better than what people are doing now.

 

[Pinecone]

20 hours ago, EricJ said:

I think that one was a bit beyond maintenance spec, which allowed it to fail in an unsafe manner.   Anything can fail with enough determination.

The point is, people want the new part to fail safe, but the original part did have non-safe failure mode.

[EricJ]

20 minutes ago, Pinecone said:

The point is, people want the new part to fail safe, but the original part did have non-safe failure mode.

Yes, when any system with fail-safe features isn't maintained to preserve the integrity of the system so that the fail-safe strategy works, you won't have a fail-safe system.   You can fly an engine with one mag, but you no longer have fail-safe redundancy in the ignition system.   It's not an excuse to make a new system without the same original fail-safe performance as the part it is replacing.   It doesn't meet the requirements of OPP if it doesn't.

[Pinecone]

5 hours ago, EricJ said:

Yes, when any system with fail-safe features isn't maintained to preserve the integrity of the system so that the fail-safe strategy works, you won't have a fail-safe system.   You can fly an engine with one mag, but you no longer have fail-safe redundancy in the ignition system.   It's not an excuse to make a new system without the same original fail-safe performance as the part it is replacing.   It doesn't meet the requirements of OPP if it doesn't.

How is the orginal intake boot in any way fail safe????

[N201MKTurbo]

1 hour ago, Pinecone said:

How is the orginal intake boot in any way fail safe????

I was wondering that myself.