600115-005 intake duct

[Shadrach]

2 hours ago, N201MKTurbo said:

The ones I have repaired didn't have any metal mesh. The tape they were laid up with appeared to be either cotton of fiberglass reinforced butyl rubber. 

I just looked at my spare today. Mine appears to have cotton cord embedded in the rubber. There is no metal.

[Shadrach]

9 hours ago, Allen_D said:

David,

I appreciate your contribution of the old duct for my project.

I've been conducting thorough analyses using Finite Element Analysis (FEA) to assess the performance of my version of the induction coupler under various loads. The primary goal is to ensure it won't collapse and adversely affect the engine. Considering the potential for backfire in its location, I've decided on using a flame-retardant material with high tear strength.

In examining worst-case scenarios, such as full RPM at 0 knots, I introduced a safety factor by increasing the maximum RPM by 20%. The latest test involved running the coupler at 3,240 RPM, utilizing a Shore 60A urethane. The results indicate minimal deflection, with approximately 2mm on the bottom surfaces and 1mm on the top.

Notably, I conducted a case at an exaggerated 2x the RPM, resulting in only 6mm of deflection. Responding proactively, I reinforced the design to ensure robustness under extreme conditions.

Moving forward, my next step involves creating the mold and experimenting with various urethanes to refine the manufacturing process. I plan to document these practices meticulously to verify and build upon my findings. If successful, I'll certainly send you a usable product.

I'll keep you informed of my progress.

- Allen

Allen,

I truly appreciate your efforts. I am ready to support this anyway I can, I also have a spar duct in my hangar. Happy to send it to you as pattern to produce a duct for me. My mechanic and I will conduct additional QC on our end.

[MikeOH]

5 hours ago, N201MKTurbo said:

The ones I have repaired didn't have any metal mesh. The tape they were laid up with appeared to be either cotton of fiberglass reinforced butyl rubber. 

Thanks for the correction.

My question is then altered to, "How is the lack of fiberglass or cotton mesh being addressed?"

[Allen_D]

14 hours ago, MikeOH said:

Thanks for the correction.

My question is then altered to, "How is the lack of fiberglass or cotton mesh being addressed?"

I appreciate your insightful question and would like to emphasize that my design choices take into account significant advancements in engineering tools and materials since the original part was conceived in the 1960s.

In the original design, a cloth mesh was integrated into the butyl rubber to augment tear resistance and enhance dimensional stability. However, with the evolution of materials, my revised approach opts for a urethane rubber without the cloth mesh. The advancements in materials and engineering tools have allowed for a more refined solution that doesn't require the additional reinforcement provided by the cloth mesh.

This decision is made with confidence in the improved properties of the selected urethane rubber. To address safety concerns, thorough ground tests at full RPM and regular inspections will be conducted if the induction coupler is installed on my plane.

Your keen interest and question are highly appreciated, and your feedback is invaluable to the continual improvement of the project.

Edited February 8, 2024 by Allen_D
I left out the purpose of the cloth mesh.

[cliffy]

Just a thought -

Has anyone assessed the deflection with impact ice on the inlet air filter thereby lowering the pressure inside the duct due to this ice restriction to air flow ahead of the duct? Both the C and E model ducts (they are different)  could/would be susceptible to this event.  

Failure analysis probably should include this possibility/probability.

As a long time A&P I would still have to fall back on "what is the approved data that was referenced to make this part", before I would consider installing same and signing it off. 

Don't take this wrong, no disrespect meant but-     How many here promoting the making of this part through OPP in a way that is "different " than the original (even if better than original)- How many of you actually hold an A&P and would sign your name to the log  book? That is a true test.

Also remember each owner who "designs" an OPP part shall sign HIS name to the log book signifying that he was the one who participated in the design.

BUT ultimately it comes down to an A&P being willing to put this part on the airplane; 

The question remains - How do you get around the "approved data" requirement in OPP?

A challenge-

Someone needs to go the their local FSDO and present this idea and ask about its legality rather than just guess as is being done here. That's what they are there for. 

Why waste your time if its not going to fly. 

 

 

[MikeOH]

3 hours ago, Allen_D said:

I appreciate your insightful question and would like to emphasize that my design choices take into account significant advancements in engineering tools and materials since the original part was conceived in the 1960s.

In the original design, a cloth mesh was integrated into the butyl rubber to augment tear resistance and enhance dimensional stability. However, with the evolution of materials, my revised approach opts for a urethane rubber without the cloth mesh. The advancements in materials and engineering tools have allowed for a more refined solution that doesn't require the additional reinforcement provided by the cloth mesh.

This decision is made with confidence in the improved properties of the selected urethane rubber. To address safety concerns, thorough ground tests at full RPM and regular inspections will be conducted if the induction coupler is installed on my plane.

Your keen interest and question are highly appreciated, and your feedback is invaluable to the continual improvement of the project.

@Allen_D

First I want to say thanks for trying to come up with an alternate for the intake boot. Potential good news for the Mooney community!

Selfishly, I am not personally concerned as I sprung the $600 for a new boot last annual; I felt lucky one was available and jumped on it. I don’t think I have to worry about it any longer.

So, my comments are more from the perspective of an interested engineer. Please take my criticisms in that context and as constructive.

While I get “ where you are coming from” in regards to newer materials I just don’t find your argument that because they are new materials the lack of secondary reinforcing mesh is no longer necessary; it seems to be a bit of an unsupported assertion.

You suggest frequent periodic inspection would be sufficient. Well, that’s already required/true for the existing design. Yet, it’s also true that those inspections are not being done!

Thus, we are back to if the new design will fail in at least as safe a manner as the old in at least as long a time. Not easy to prove.

The existing design seems to fail as the ‘rubber’ material deteriorates away in small pieces.  But, without a large ‘flap’ of material dislodging and blocking the intake. 

My concern is that any homogeneous material, regardless of how ‘modern’ may break off as a large ‘sheet’ or ‘flap’ and block the intake. IOW it is NOT a single fault tolerant design as is the original.

[EricJ]

7 minutes ago, MikeOH said:

My concern is that any homogeneous material, regardless of how ‘modern’ may break off as a large ‘sheet’ or ‘flap’ and block the intake. IOW it is NOT a single fault tolerant design as is the original.

That's the concern, that's there's a failure mode that isn't safe, i.e., it can collapse or block the intake in the event of a failure.   That's something that can be demonstrated by anticipating a number of possible failure modes and somehow demonstrating that it fails gracefully when a failure is induced.     A test fixture with a high pressure difference between in the inside and outside might not be too tough to make, and then induce the anticipated failure modes (e.g., tears, cuts, deformation, whatever), and show that it doesn't result in an intake obstruction.  We know that we have pressure differentials around 20 inHg or more during operation, so a fixture with that sort of pressure differential plus margin would be reasonable.

Anyway, that's one way to build confidence in potential users or to get somebody to sign it off.   Having some appropriate materials analysis showing that it doesn't catch fire or fail (e.g., melt, burst) during a backfire event would probably help, too.

 

[Shadrach]

49 minutes ago, MikeOH said:

@Allen_D

First I want to say thanks for trying to come up with an alternate for the intake boot. Potential good news for the Mooney community!

Selfishly, I am not personally concerned as I sprung the $600 for a new boot last annual; I felt lucky one was available and jumped on it. I don’t think I have to worry about it any longer.

You should be good then for about 300hrs or 6 years, which ever comes first.

[cliffy]

 

24 minutes ago, EricJ said:

Anyway, that's one way to build confidence in potential users or to get somebody to sign it off.   Having some appropriate materials analysis showing that it doesn't catch fire or fail (e.g., melt, burst) during a backfire event would probably help, too.

 

How is this "APPROVED" data?

 

 

[EricJ]

50 minutes ago, cliffy said:

How is this "APPROVED" data?

It's not.   Why would it be?   Approved data is not required for OPP.   That's kinda the point of OPP, also VARMA.

[Shadrach]

1 hour ago, cliffy said:

 

How is this "APPROVED" data?

 

 

According to Ass. Chief council Donald P Byrne’s memorandum, providing an existing part for duplication sufficiently meets the bar for conforming to approved data.

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

[Shadrach]

19 minutes ago, EricJ said:

It's not.   Why would it be?   Approved data is not required for OPP.   That's kinda the point of OPP, also VARMA.

You can forgive folks for being confused given the wording of AC20-62E, which clearly states that OPP must conform to approved data.

[EricJ]

Just now, Shadrach said:

You can forgive folks for being confused given the wording of AC20-62E, which clearly states that OPP must conform to approved data.

Yes.  Conformance to approved data and proper design are required but reverse engineering is allowed in order to determine that the new part conforms to the original design.   OPP covers cases where parts are orphaned and "approved data" isn't available.   It is the producer's responsibility that the produced part conforms to the original design and its characteristics are at least as good as the original.   OPP also requires documentation of the process, so this must be part of the development and should be available for review by the installer in order to establish suitability for installation.

My comments above regarding testing and analysis are in support of generating the sort of documentation that might be required to establish suitability and that the part is at least as good as the original in the absence of approved data.   This should be a normal part of an OPP process.

 

[Shadrach]

59 minutes ago, EricJ said:

Yes.  Conformance to approved data and proper design are required but reverse engineering is allowed in order to determine that the new part conforms to the original design.   OPP covers cases where parts are orphaned and "approved data" isn't available.   It is the producer's responsibility that the produced part conforms to the original design and its characteristics are at least as good as the original.   OPP also requires documentation of the process, so this must be part of the development and should be available for review by the installer in order to establish suitability for installation.

My comments above regarding testing and analysis are in support of generating the sort of documentation that might be required to establish suitability and that the part is at least as good as the original in the absence of approved data.   This should be a normal part of an OPP process.

 

I agree with everything you’ve said. However, every time OPP comes up, there are several folks that interpret the guidance in ways it was not written.    That tells me that it could be better codified.

[EricJ]

10 minutes ago, Shadrach said:

I agree with everything you’ve said. However, every time OPP comes up, there are several folks that interpret the guidance in ways it was not written.    That tells me that it could be better codified.

I was entertained to discover, in the words of the FAA guy making the presentation I attended, that the whole purpose of VARMA is to educate IAs that keep making people remove stuff from airplanes that is actually okay to be there.   VARMA is essentially just a mechanism by which the FAA can provide an official letter for an owner's records saying, "Yes, that starter relay that he bought at NAPA is perfectly legitimate to be installed on this particular aircraft", so that some future IA won't make them take it off.

[Allen_D]

3 hours ago, MikeOH said:

@Allen_D

First I want to say thanks for trying to come up with an alternate for the intake boot. Potential good news for the Mooney community!

Selfishly, I am not personally concerned as I sprung the $600 for a new boot last annual; I felt lucky one was available and jumped on it. I don’t think I have to worry about it any longer.

So, my comments are more from the perspective of an interested engineer. Please take my criticisms in that context and as constructive.

While I get “ where you are coming from” in regards to newer materials I just don’t find your argument that because they are new materials the lack of secondary reinforcing mesh is no longer necessary; it seems to be a bit of an unsupported assertion.

You suggest frequent periodic inspection would be sufficient. Well, that’s already required/true for the existing design. Yet, it’s also true that those inspections are not being done!

Thus, we are back to if the new design will fail in at least as safe a manner as the old in at least as long a time. Not easy to prove.

The existing design seems to fail as the ‘rubber’ material deteriorates away in small pieces.  But, without a large ‘flap’ of material dislodging and blocking the intake. 

My concern is that any homogeneous material, regardless of how ‘modern’ may break off as a large ‘sheet’ or ‘flap’ and block the intake. IOW it is NOT a single fault tolerant design as is the original.

@MikeOH

I've been searching for information on whether a cloth mesh has additional impacts beyond what I've mentioned, but unfortunately, I haven't found anything yet.

If you come across any sources that show it prevents fragmentation, I'd greatly appreciate it if you could share them with me. Your input is crucial, and I'm open to any ideas or questions you might have.

[EricJ]

2 minutes ago, Allen_D said:

@MikeOH

I've been searching for information on whether a cloth mesh has additional impacts beyond what I've mentioned, but unfortunately, I haven't found anything yet.

If you come across any sources that show it prevents fragmentation, I'd greatly appreciate it if you could share them with me. Your input is crucial, and I'm open to any ideas or questions you might have.

It may not be so much about preventing fragmentation as it is in maintaining structural integrity in the presence of fragmentation or other failures of the material.   If the reinforcement prevents a tear or a cut from spreading so that the material can't flop into the intake and obstruct it, that might be useful.   If those failure modes are naturally mitigated by the new material then it might not be needed, but an installer or inspector might want to see that demonstrated.

[Allen_D]

3 hours ago, EricJ said:

That's the concern, that's there's a failure mode that isn't safe, i.e., it can collapse or block the intake in the event of a failure.   That's something that can be demonstrated by anticipating a number of possible failure modes and somehow demonstrating that it fails gracefully when a failure is induced.     A test fixture with a high pressure difference between in the inside and outside might not be too tough to make, and then induce the anticipated failure modes (e.g., tears, cuts, deformation, whatever), and show that it doesn't result in an intake obstruction.  We know that we have pressure differentials around 20 inHg or more during operation, so a fixture with that sort of pressure differential plus margin would be reasonable.

Anyway, that's one way to build confidence in potential users or to get somebody to sign it off.   Having some appropriate materials analysis showing that it doesn't catch fire or fail (e.g., melt, burst) during a backfire event would probably help, too.

 

Thank you for sharing your concerns and suggesting a potential testing approach. I completely agree that demonstrating the safety and reliability of the design under various failure modes is crucial.

I'm considering the development of a test fixture with a significant pressure difference, as you've outlined. This fixture would simulate real-world conditions, inducing anticipated failure modes to ensure the induction coupler doesn't lead to an intake obstruction. Your suggestion aligns well with building confidence among potential users and obtaining necessary approvals.

Regarding the pressure difference, it's important to note that the maximum pressure differential pre-throttle body is about 5 inHg, and this occurs at an unreasonable 5400 rpm. 

[Shadrach]

26 minutes ago, EricJ said:

It may not be so much about preventing fragmentation as it is in maintaining structural integrity in the presence of fragmentation or other failures of the material.   If the reinforcement prevents a tear or a cut from spreading so that the material can't flop into the intake and obstruct it, that might be useful.   If those failure modes are naturally mitigated by the new material then it might not be needed, but an installer or inspector might want to see that demonstrated.

In my experience it just frays where the duct is compromised so instead of being torn, it’s just torn and fuzzy…

[PT20J]

Why not team up with McFarlane? They seem keen on increasing their PMA parts business. 

[Shadrach]

3 hours ago, PT20J said:

Why not team up with McFarlane? They seem keen on increasing their PMA parts business. 

This would be great. This part could really benefit from design/materials improvements. Plus the price has become so ridiculous that to OPP would be the same or less costly than a factory part. When that happens, it’s time for a an alternate vendor to get involved.

[EricJ]

22 minutes ago, Allen_D said:

Thank you for sharing your concerns and suggesting a potential testing approach. I completely agree that demonstrating the safety and reliability of the design under various failure modes is crucial.

I'm considering the development of a test fixture with a significant pressure difference, as you've outlined. This fixture would simulate real-world conditions, inducing anticipated failure modes to ensure the induction coupler doesn't lead to an intake obstruction. Your suggestion aligns well with building confidence among potential users and obtaining necessary approvals.

Regarding the pressure difference, it's important to note that the maximum pressure differential pre-throttle body is about 5 inHg, and this occurs at an unreasonable 5400 rpm. 

That's a good point.   I was thinking post-throttle body, which wouldn't apply to this.    The abrupt increase in pressure due to a backfire might be the more difficult test condition.

 

[Allen_D]

2 hours ago, EricJ said:

That's a good point.   I was thinking post-throttle body, which wouldn't apply to this.    The abrupt increase in pressure due to a backfire might be the more difficult test condition.

 

@EricJ

If we can establish that the new part is at least as strong as the original – and even stronger – it should inherently be capable of withstanding conditions such as a backfire. The aim is to not just meet but surpass the standards set by the original design.

[Allen_D]

On 2/7/2024 at 6:02 PM, Shadrach said:

Allen,

I truly appreciate your efforts. I am ready to support this anyway I can, I also have a spar duct in my hangar. Happy to send it to you as pattern to produce a duct for me. My mechanic and I will conduct additional QC on our end.

@Shadrach

Let me finish this before I start something else.

[Allen_D]

8 hours ago, cliffy said:

Just a thought -

Has anyone assessed the deflection with impact ice on the inlet air filter thereby lowering the pressure inside the duct due to this ice restriction to air flow ahead of the duct? Both the C and E model ducts (they are different)  could/would be susceptible to this event.  

Failure analysis probably should include this possibility/probability.

As a long time A&P I would still have to fall back on "what is the approved data that was referenced to make this part", before I would consider installing same and signing it off. 

Don't take this wrong, no disrespect meant but-     How many here promoting the making of this part through OPP in a way that is "different " than the original (even if better than original)- How many of you actually hold an A&P and would sign your name to the log  book? That is a true test.

Also remember each owner who "designs" an OPP part shall sign HIS name to the log book signifying that he was the one who participated in the design.

BUT ultimately it comes down to an A&P being willing to put this part on the airplane; 

The question remains - How do you get around the "approved data" requirement in OPP?

A challenge-

Someone needs to go the their local FSDO and present this idea and ask about its legality rather than just guess as is being done here. That's what they are there for. 

Why waste your time if its not going to fly. 

 

 

@cliffy

The flow rate employed for the CFD analysis mirrors that of our IO-360s at 5400 RPM. This intentional setup is designed to generate loads higher than actual, incorporating a safety factor into the analysis. This safety factor proves crucial in scenarios involving a restricted air filter, as the air filter bypass door activates, preventing pressure from dropping to levels that could cause the induction coupler to collapse.

Ensuring that the new part matches the strength of the original is pivotal for meeting the requirements of the type certificate.

On the topic of "approved data," it's worth noting that attempts were made to obtain the engineering drawing from Mooney, but unfortunately, they declined to share this information, rendering "approved data" unavailable.

Recognizing the legitimate concern surrounding A&P sign-off, the local FSDO is conveniently located less than a quarter mile from my hangar. I plan to seek their advice once I have a tangible prototype. Their endorsement could prove influential in persuading any hesitant A&P.

I want to emphasize that I welcome and take no offense to any comments. The purpose of my post is to gather feedback comprehensively, ensuring a safe and well-considered solution. I share the belief that taking no action could lead to more accidents. The unavailability and exorbitant cost of the part contribute to individuals using aging induction couplers beyond their safe operational lifespan. We all have a stake in this matter.

I appreciate everyone's engagement in this discussion.