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Don't Do This..

I had to replace this exact hose and purchased a shorter hose that connects from the top of the fuel servo assembly. The fue hose that came with the FWF kit is just too long and I know on a few RV8, it rubs on the inside of the bottom fairing. By using the top side outlet, the fuel hose stays away from all the exhaust.



20210226_120053.jpg
 
I just replaced all my hoses. I tag them until I can torque the fittings, then mark the fittings that they were torqued. EVERY time I go past the engine compartment, I can't help but look at EVERYthing to make sure I have things where they belong, and things look GOOD. Now, after 50 or so looks, I think everything is OK. But I'll be checking things out again next time I go by.....🤣😂🤣😂
 
One thing about seeing something like this is that now you've got to check the rest of the plane so very carefully. Because there's certainly something equally dumb but much more subtle hidden away.

Dave
 
Yep, that’s pretty scary if this got by any accepted standard of pre first flight inspection, but let’s take a closer look before calling somebody stupid. Is this her/his first build? Did he/she have access to an EAA Technical Counselor? At my airport we have about 30 expert RV builders that are frequently called on to inspect our members airplanes prior to first flight, along with our expert EAA tech counselor , with a big focus on FWF - and many of us are RV builders. Did this builder have the same pre-flight scrutiny available to him/her? Maybe not, but this is obviously a miss by someone. The builder, especially if he/she is a first time builder, is not an expert - yet. We all need help. Builders, especially new ones, need to be aware of the benefits available to them, at no cost, when involved in a local EAA chapter. If they don’t have that access, then they need to be educated on the need for that level of oversight.
When I built my first airplane you had to have an inspection prior to close out of any major airplane component - tail, wings, fuselage, engine - and that inspection had to be be documented. On my first airplane it was documented by my EAA technical counselor, but those documented inspections had to be on final paperwork for my FAA AW inspection. The first question my FAA inspector asked me was “who did your inspections”. We aren’t REQUIRED to do that anymore, but it is implied. Somebody needs to inspect every portion of the build. If that person is the first time builder, they need to be made aware of the gravity of the importance of that inspection.
In my opinion, eliminating the requirement for phase inspections (documented) by an EAA tech counselor, or other qualified person (A&P), is a mistake. Bolting a fuel line to an exhaust pipe (heat shield not withstanding) couldn’t pass anyone’s level of scrutiny if they had any level of experience in this area. We need to fix this. If Dan/Vic/or any inspector is seeing something like this more than once, it is too much.
The safety record for EAB aircraft is improving, and in fact for Vans aircraft it is approaching the safety record of the certified world, but we are not there yet. Why?? It’s not because of the Vans aircraft design. It’s because of the experimental nature of what we do - like bolting a fuel line to a shaking exhaust pipe. I’m sorry if it sounds like I’m blaming the builder - I’m not. We need to get better at these kinds of things. this airplane could possibly win awards for its attention to detail and beauty of its construction, but there is one serious miss that could be corrected by better scrutiny/QC. Making airplanes easier to build is fine, but let’s not make them easier to certify with relaxed periodic safety inspections.
 
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So I'm going to betray my own ignorance here. The shield is attached to the exhaust and the fuel line runs through an adel clamp attached to the same shield? I don't doubt that this is terrible idea, but what is the proper way to use a heat shield to protect a fuel line that runs in past the exhaust? It the shield is attached to just the fuel line (curve on the fuel line side) and is adequately secured to never contact the exhaust, is that okay?
 
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Scott Hersha said:
Yep, that’s pretty scary if this got by any accepted standard of pre first flight inspection, but let’s take a closer look before calling somebody stupid. Is this her/his first build? Did he/she have access to an EAA Technical Counselor? At my airport we have about 30 expert RV builders that are frequently called on to inspect our members airplanes prior to first flight, along with our expert EAA tech counselor , with a big focus on FWF - and many of us are RV builders. Did this builder have the same pre-flight scrutiny available to him/her? Maybe not, but this is obviously a miss by someone. The builder, especially if he/she is a first time builder, is not an expert - yet. We all need help. Builders, especially new ones, need to be aware of the benefits available to them, at no cost, when involved in a local EAA chapter. If they don’t have that access, then they need to be educated on the need for that level of oversight.
When I built my first airplane you had to have an inspection prior to close out of any major airplane component - tail, wings, fuselage, engine - and that inspection had to be be documented. On my first airplane it was documented by my EAA technical counselor, but those documented inspections had to be on final paperwork for my FAA AW inspection. The first question my FAA inspector asked me was “who did your inspections”. We aren’t REQUIRED to do that anymore, but it is implied. Somebody needs to inspect every portion of the build. If that person is the first time builder, they need to be made aware of the gravity of the importance of that inspection.
In my opinion, eliminating the requirement for phase inspections (documented) by an EAA tech counselor, or other qualified person (A&P), is a mistake. Bolting a fuel line to an exhaust pipe (heat shield not withstanding) couldn’t pass anyone’s level of scrutiny if they had any level of experience in this area. We need to fix this. If Dan/Vic/or any inspector is seeing something like this more than once, it is too much.
The safety record for EAB aircraft is improving, and in fact for Vans aircraft it is approaching the safety record of the certified world, but we are not there yet. Why?? It’s not because of the Vans aircraft design. It’s because of the experimental nature of what we do - like bolting a fuel line to a shaking exhaust pipe. I’m sorry if it sounds like I’m blaming the builder - I’m not. We need to get better at these kinds of things. this airplane could possibly win awards for its attention to detail and beauty of its construction, but there is one serious miss that could be corrected by better scrutiny/QC. Making airplanes easier to build is fine, but let’s not make them easier to certify with relaxed periodic safety inspections.
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Scott, I agree completely. What DanH has done by posting this is to help nudge (or push) the community into being more engaged with our fellow builders, even if there is not a regulation that requires it. Those of you who are seeing lots of aircraft are most certainly seeing this kind of thing more than the rest of us, and while it's not always comfortable to point out someone's mistakes publicly, it can help others learn.

I think one of the best ways to attack this problem is what Van's has done with the Section 5 - focus on best practices and understanding why they are best practices. Highlighting these kinds of failures can help drive the point home.
 
Flying Canuck said:
So I'm going to betray my own ignorance here. The shield is attached to the exhaust and the fuel line runs through an adel clamp attached to the same shield? I don't doubt that this is terrible idea, but what is the proper way to use a heat shield to protect a fuel line that runs in past the exhaust? It the shield is attached to just the fuel line (curve on the fuel line side) and is adequately secured to never contact the exhaust, is that okay?
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The idea is that getting fuel hot should be avoided. The best way to do that is to route fuel lines and exhaust as far away from each other as practical. There are some areas where reducing radiant heat from an exhaust pipe going to a fuel line (or wiring) can be done with a heat shield. If your fuel line is about to touch an exhaust pipe or heat shield, then you have simply routed the fuel line wrong, and need to think of a better way. This better way might require different hoses, different routing, even different orientation of fuel servos, fuel flow sensors, gascolators, or fuel pumps.
 
Hopefully this was a learning experience for the owner. When something like this can't be rerouted I've used a standoff made from bushing and a longer screw to distance the Adel clamp from the undesirable location. That's just the easy fix but it works.
danny
 
Photos such as this are helpful to the entire EAB community, as everyone can potentially learn from this. Vic Syracuse has used many pics like this to try to get poor practices corrected across the fleet, and it's very effective. Let's not be too harsh on this individual, as it may dissuade others from seeking input and opinions on their build. If this aircraft owner is aware of the problem and chooses to ignore the advice from technical counselors and other knowledgeable sources...well, maybe then we can release the hounds. ;)
 
DanH said:
Seen recently. Yes, that's a fuel hose attached to an exhaust heat shield.
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Since this is your thread, and NOBODY else has responded - What EXACTLY are the hazards you see here? I agree this is sub optimal and should be avoided, but if we want to make this a learning experience for the new builder or owners, we owe it to them to explain WHY this is wrong. Not one response in that vein yet.
 
my take on this is that the fuel line is just too close to the shroud. the adel clamp also conducts heat from the shroud although the rubber in the clamp might insulate a bit. how about if the clamp was attached to a standoff attached to the shroud? sat a piece of 1'' to 11/4'' square tubing say 1/2'' long.
obviously just plain away from the shroud is best but how about a standoff?
 
Post #6 by PhatRV shows how it SHOULD be done, and he is a new builder too, so good job!
 
Toobuilder said:
Since this is your thread, and NOBODY else has responded - What EXACTLY are the hazards you see here? I agree this is sub optimal and should be avoided, but if we want to make this a learning experience for the new builder or owners, we owe it to them to explain WHY this is wrong. Not one response in that vein yet.
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OK: let me take a starting stab at this:

Let's see; where to begin. Fuel and heat together are NOT a good idea unless it is in the cylinder doing its exploding thing. Fuel lines should be kept as far away from heat sources (oh, say, exhaust pipes, for example :unsure: ) to avoid mixing the two. Is this airplane running 100LL or auto fuel? Vapor lock seems to be more frequent in aircraft using auto fuel, I believe, and the likelyhood is increased by heat. The insulated fuel line covering is called fire sleeve but does have some insulating properties. But why put that property to the test if it isn't necessary? If you look closely at the picture in the OP, there is discoloration of the fire sleeve where the Adel clamp attaches. Is this from the rubber itself (black not blue...) or from heat transfer? Difficult to tell. Attatching the fuel line to something that might have more independence of movement than the engine does, eg exhaust systems, might not be a good idea. They are long things extending down from something (the engine) that has a LOT of movement when it is running and especially at startup. (Those videos are enlightening!) The fulcrum of that movement would put an unneeded strain on the fitting that is attached to the throttle body as the two move independently of each other, even if it is a relatively small movement. That small movement can add up over time.

That's a start. Others might want to chime in and suggest other things and also tear my opinion apart. This is, after all, a LEARNING experience, this building of airplanes!
 
Dad's RV-10 said:
Maybe I'm stating the obvious but who knows how old this airplane is? It's possible this rigging might have been changed multiple times since the initial airworthiness inspection.
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I thought about that first but then figured if someone replaced the original hose later, why would they replace it with a longer more expense hose than they had to? So that's why I think this has been like this from day 1.
 
Scott Hersha said:
It’s because of the experimental nature of what we do - like bolting a fuel line to a shaking exhaust pipe.
Click to expand...

Have to interrupt you here. The fuel line is connected to the same shaking mass that the exhaust pipe is, so the pipe won't shake independently of the fuel line. The issue is bolting a fuel line to a hot exhaust shield.
 
bobnoffs said:
my take on this is that the fuel line is just too close to the shroud. the adel clamp also conducts heat from the shroud although the rubber in the clamp might insulate a bit. how about if the clamp was attached to a standoff attached to the shroud? sat a piece of 1'' to 11/4'' square tubing say 1/2'' long.
obviously just plain away from the shroud is best but how about a standoff?
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Any object that can transfer heat to a fuel line is a big NO-NO
 
I’ve been in the industry for a few decades now, and in that time I have participated in a fair number of FRR (Flight Readiness Review) and TRR (Test Readiness Review) exercises prior to flight or test of a new weapon system. One of the key elements of that process is a THA (Threat Hazard Analysis), and it details the inevitable sub optimal conditions that exist in a flight test environment of a new system. This thread is EXACTLY the type of discussion that happens in a THA, but unlike a real THA, this thread is lacking the “analysis” part. Dan had identified an undesirable condition, but nobody has described the “why” yet. The thread has been nothing but a dogpile of “me too” opinions, but no substance. In a “real” THA, the team get to discuss and challenge the perceived threat proposed by the interested party (Safety, usually), and generally, the discussion involves the mechanics and probability of failure which results in the decision to move forward with the flight, or further mitigate the risk.

In all cases, the DISCUSSION of the analysis is the important part. That is absent in this thread.
 
Toobuilder said:
I’ve been in the industry for a few decades now, and in that time I have participated in a fair number of FRR (Flight Readiness Review) and TRR (Test Readiness Review) exercises prior to flight or test of a new weapon system. One of the key elements of that process is a THA (Threat Hazard Analysis), and it details the inevitable sub optimal conditions that exist in a flight test environment of a new system. This thread is EXACTLY the type of discussion that happens in a THA, but unlike a real THA, this thread is lacking the “analysis” part. Dan had identified an undesirable condition, but nobody has described the “why” yet. The thread has been nothing but a dogpile of “me too” opinions, but no substance. In a “real” THA, the team get to discuss and challenge the perceived threat proposed by the interested party (Safety, usually), and generally, the discussion involves the mechanics and probability of failure which results in the decision to move forward with the flight, or further mitigate the risk.

In all cases, the DISCUSSION of the analysis is the important part. That is absent in this thread.
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There has been a few WHY’s posted now.
 
Roadjunkie1 said:
OK: let me take a starting stab at this:
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Good start. I also mostly agree with your assessment. But a THA typically weighs “Likelihood” and ”Impact”, each with a score of 1-5 on a decision matrix. A possible THA hazard statement in this scenario is “Fire, due to ———“. If you fill in the blank, (chafe, burn through, radiation, conduction, etc), then you assign a number for likelihood (never, to frequent) and then Impact ( benign, to catastrophic) the matrix will inform you of the relative hazard. One can have a catastrophic failure mode and fly safely - we have many on our airplanes - but the likelihood of so low that we score a green on the matrix. The single bolt that holds the crank gear on is an example.
 
I don't think the WHY is missing (hot fuel line=bad), it's the HOW. You have hot exhaust, you have a fuel line that has nowhere else to go (say 2-3" clearance). How do you install a radiant heat shield to protect the fuel line? Which way does the shield face? What is it connected to? What is it not connected to? How do you connect it?

I was looking at this on my plane just 2 days ago, I thought that it was okay, but this thread has me second guessing the installation.
 
rvbuilder2002 said:
There has been a few WHY’s posted now.
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Not good enough to form a decision, unfortunately.

In the OP, the airplane has apparently flown a few hours. The evidence is the discoloration of the fire sleeve near the adel clamp. This is typical of any installation, regardless of heat. There is zero evidence of heat discoloration on the fire sleeve anywhere else, including those areas not shielded from the radiant barrier. Heat shields are very effective at reducing radiant energy, Adel clamps are poor paths for conduction, and then to top it off, the firesleeve is an added insurance against conduction and radiation...

So again, what is the mechanism for failure - please spell it out as a representative from the mothership. Everyone on this thread agrees this is a sub optimal situation - let’s hear the step by step failure chain.
 
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Toobuilder said:
What is the “object” and what is the transfer mechanism?
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A metal standoff is a conductor of heat ergo transfer; a heat muff on heat source ( exhaust pipe) with 1 inch of air or more between heat source and fireproofed fuel line is my recommendation. Or reroute the fuel line ...:cool:
 
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I believe that the issues discussed were, the heat radiating from the exhaust pipe through the shield and clamp into the fuel line could cause possible vapour lock issues and the potential resonance and dissimilar vibration from the exhaust pipe putting strain on the fuel line and fitting potentially resulting a failure. A few possible solutions come to mind. Post #6 shows a solution if there is or can be a fitting on the top of the fuel servo. Another possible solution is a slightly shorter fuel line which is then supported by a standoff and Adell clamp from one of the servo mounting studs keeping it away from the exhaust. Lastly if using the existing hose it appears from the original photo that it could be moved away from the exhaust and supported by a standoff and clamp from one of the servo inlet mounting screws. I think most agree that there are better options than the one in the picture.
 
Toobuilder said:
Not good enough to form a decision, unfortunately
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Fair enough, but that is different than saying, there has been no explanations offered of why it is a problem.

My personal opinion is that routing a fuel line almost in contact with an exhaust pipe is a bad idea from a heat transfer standpoint Period
Yes, there is a heat shield between the hose and the pipe but I think it is undebatable that the hose is still getting some amount of heating influence that wouldn’t occur if it was 6 inches away.
It is fully possible that the airplane has operated normally for many hundreds of hours with the hose installed that way, but it could have reduced the safety margin, and it is clearly not best practice.
 
Bad mechanics are in all industries..
I'll add in a little story here.
I used to own a TD-8 International dozer. Took it to the dealer (professionals Right?) to get the transmission rebuilt and new undercarriage. Big job requiring dissembling the dozer.
After I picked it up and drove to the job and was off the machine looking at something, I notice a nut loose on the back. It was on the end of a 7' long 1 3/8" rod and supposed to be torqued to 660 foot pounds of torque. It was one of two that basically holds the machine together front to back. Both nuts On both rods were finger tight.
That was profession work for you.
Stuff happens in all phases of life.
But my luck varies Fixit
 
rvbuilder2002 said:
Fair enough, but that is different than saying, there has been no explanations offered of why it is a problem.
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Let’s go deeper, for the new builder…. Most of us think this is bad, yet we can’t agree on the hazard. Some imply ”fire”, others imply ”vapor lock”. Which is it? Or is it both? And once we decide on that, then the path to mitigation may be very different
 
Should we do this like flight test professionals?

1. Define the hazard presented in the OP. Let’s say it’s “fire”
2. Define the mechanism that results in fire. Let’s say it’s due to “fuel line failure because of chafing with the adel clamp, caused by excessive heat conducted, resulting in failure of the adel insulator cushion“. Or something like that.
3. Given that “hazard”,whats the “score” based on likelihood and impact? https://securityexecutivecouncil.com/insight/program-best-practices/the-risk-assessment-threat-matrix-and-heat-map-1332#:~:text=In order to effectively analyze,of damage to the organization.
 
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Pilot135pd said:
Asked and answered many times, here's one of them
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Opinion, not analysis.

You are promoting “Vapor lock” as well as “mechanical overload/failure of the fuel fittings”...

Whats the probability and severity of each of those failures?
 
Scott Hersha said:
...let’s take a closer look....Is this her/his first build?
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Noted during a pre-buy. My friend and I are much appreciative of the owner's hospitality, and he will remain anonymous.

I don't know the original builder personally. Said to be a repeat offender. Sold unpainted at 62 hours to second owner. You can fill in the blanks.

2021, 2022, and 2023 annuals done by an established A&P shop. Based in a group hangar with other owners. Cowl was off at a paint shop too.

Scott Hersha said:
...this airplane could possibly win awards for its attention to detail and beauty of its construction...
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Unfortunately, no. The aileron stops were missing, a miss-drilled HS front spar attach point, under-driven or bent nail rivets, automotive grade crimp terminals on rat nest wiring, and more.

ronrapp said:
Do you know how many hours the aircraft has flown like that?
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Little over 250.

rv8ch said:
The idea is that getting fuel (or hoses) hot should be avoided. The best way to do that is to route fuel lines and exhaust as far away from each other as practical. There are some areas where reducing radiant heat from an exhaust pipe going to a fuel line (or wiring) can be done with a heat shield. If your fuel line is about to touch an exhaust pipe or heat shield, then you have simply routed the fuel line wrong, and need to think of a better way. This better way might require different hoses, different routing, even different orientation of fuel servos, fuel flow sensors, gascolators, or fuel pumps.
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Precisely. Well said Mickey.

Toobuilder said:
What EXACTLY are the hazards you see here? I agree this is sub optimal and should be avoided, but if we want to make this a learning experience for the new builder or owners, we owe it to them to explain WHY this is wrong.
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Excellent point Mike.

First, for perspective...it may not be a "failure guaranteed" sort of error, but it has potential. For sure it is bad practice, for several reasons.

The divider line operates at relatively low pressure (typically 2 to 10 psi), so it is more prone to vapor bubble formation than the feed line from engine driven pump to servo. Fuel heating is a particular problem at idle and after shutdown, near the 2+ end of the pressure scale. Turning on the electric pump won't help. More line length makes the problem worse. Closer to a heat source makes the problem worse.

It will decrease the safe lifespan of the hose. We don't know if it is a rubber lined or teflon lined hose. If rubber, the liner will age and/or bake hard pretty quickly, which could indeed be a disaster (example below). Good teflon hose can handle 450F, so lifespan may be reasonable. In any case, a hose this close to a heat source must come off at every annual for the Rice Krispies test (flex and listen for snap, crackle, pop). I doubt this one has ever been off.

Baked Hose.jpg

So how to do it better, and why?

Too many builders fail to appreciate the limitations of the typical exhaust heat shield, or how it actually works. Radiant energy from the hot pipe strikes the inner surface of the shield. Some is reflected and some is absorbed, heating the shield. Some of the absorbed energy is subsequently conducted to the moving air in the lower plenum, and the rest is conducted to the opposite side of the shield, where it is re-radiated. Point is, the typical exhaust pipe shield does not block all the energy.

For our purposes here, let's assume an old oxidized stainless steel heat shield. It could re-radiate as much as half the energy striking its hot side, but here let's assume just 25%. Now, for comparison, consider the effect of distance. Detailed analysis is complicated, but a basic rule says the amount of energy received is inversely proportional to the square of the distance from the source. It means doubling the distance reduces heat transfer to 1/4, and doubling it again reduces it to 1/16. Think about that in terms of 1" separation, 2" separation, and 4" separation. A heat shield has its uses, but distance is better.

The amount of radiant and conducted energy received is also a function of area. Reducing the surface area of the hose reduces the quantity of energy reaching both hose material and fuel.

A good installation merely required obtaining a shorter hose, which would have moved the hose away from the pipe and reduced its surface area. More than anything, it says a lot about the builder's mindset. Using the longer hose was just lazy and cheap. Don't be that guy.
 
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Toobuilder said:
Let’s go deeper, for the new builder…. Most of us think this is bad, yet we can’t agree on the hazard. Some imply ”fire”, others imply ”vapor lock”. Which is it? Or is it both? And once we decide on that, then the path to mitigation may be very different
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Well, I’m willing to add my opinion.
I think the likelihood of it increasing fire risk is low.
I think the likelihood of it increasing the fuel temperature is high, Which we know can have an influence on the likelihood of fuel vaporization issues, and for that reason, routing close to an exhaust pipe, should be avoided.
Additionally, as already noted, depending on the specific hose being used exposure to excess heat, can accelerate the degradation of the hose.
 
Seems like most of us are landing on “Vapor Lock” as the primary hazard. I’m more nervous about “fire”, personally. But that’s precisely WHY we propose and discuss specific hazards. This same discussion is common before every test event in “big aerospace” too. And sometimes, the hazards are reshuffled and or retired at the table. Thoughtful input concerning the specific hazard is valuable, while rote opinion does not survive critical deconstruction in my experience.
 
Toobuilder said:
Seems like most of us are landing on “Vapor Lock” as the primary hazard. I’m more nervous about “fire”, personally. But that’s precisely WHY we propose and discuss specific hazards. This same discussion is common before every test event in “big aerospace” too. And sometimes, the hazards are reshuffled and or retired at the table. Thoughtful input concerning the specific hazard is valuable, while rote opinion does not survive critical deconstruction in my experience.
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OH BOY---its a bunch easier and dafer to swap the outlet fitting to the top of the servo and shorten the hose. JUST because the provided hose from the engine builder is used, the 'safer' way would be to route it differently away from the exhaust. YES, the temp there is lower that at the cylinder, BUT it most likely will still create enough heat to damage the firesleeve, also damage the hose liner. YES, teflon will withstand 500*+ for 15 minutes, but who wants to take the chance.

Guys---it you arent sure--ASK someone. LOTS of members on VAF with the knowledge.

Tom
 
TS Flightlines said:
OH BOY---its a bunch easier and dafer to swap the outlet fitting to the top of the servo and shorten the hose. JUST because the provided hose from the engine builder is used, the 'safer' way would be to route it differently away from the exhaust. YES, the temp there is lower that at the cylinder, BUT it most likely will still create enough heat to damage the firesleeve, also damage the hose liner. YES, teflon will withstand 500*+ for 15 minutes, but who wants to take the chance.

Guys---it you arent sure--ASK someone. LOTS of members on VAF with the knowledge.

Tom
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And it has an extra piece of firesleeve over the orginal firesleeved hose---at least it looks that way---so the intent was to coble a 'fix' instead of doint a better reroute.
 
Snowflake said:
Have to interrupt you here. The fuel line is connected to the same shaking mass that the exhaust pipe is, so the pipe won't shake independently of the fuel line. The issue is bolting a fuel line to a hot exhaust shield.
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Mmmmmmm......I might respectfully disagree. If you think of the length of the exhaust pipe, the end is a long way from where it is attached to the engine. It's this big potential pendulum of a thing. My Vetterman exhaust is attached to the engine just before it exits the lower cowling. That attachment is not a solid mount; it is a suspension with rubber hose as the go-between from the engine (to which it is firmly attached) to the exhaust (also firmly attached). If independent movement of the exhaust system was not a concern, there would be no need for that suspension system; it could be a solid mount from the engine to the exhaust support system. And, as I said in post #24, it might not be a large movement but consistent over time might have an effect on the hose fittings. It's that dynamic frequency thing, going back to my days in physics and wave formation. Go out to your airplane and grab that exhaust pipe as it exits the cowl. Give it a good shake and see how much movement there actually is! 😲 IMHO, of course.. YMMV.....
 
Toobuilder said:
Heat shields are very effective at reducing radiant energy, Adel clamps are poor paths for conduction, and then to top it off, the firesleeve is an added insurance against conduction and radiation...
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But the Adel clamp will decrease the area of protection under the clamp as it has to smash the insulation down as a matter of function making the fire sleeve properties in that area less effective, right? Just thinking....

This is the type of thread that gets people THINKING and looking at their own airplanes to see if there are any Oh, Dears....😊
 
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