Yikes
Ya gotta wonder how some people are even alive to do this stuff. That's just plane crazy. Ya can't fix stupid just steer clear of it.Yikes
Seen recently. Yes, that's a fuel hose attached to a exhaust heat shield.
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.Yep, thatās pretty scary if this got by any accepted standard of pre first flight inspection, but letās 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 donāt 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 āwho did your inspectionsā. We arenāt 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) couldnāt pass anyoneās 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?? Itās not because of the Vans aircraft design. Itās because of the experimental nature of what we do - like bolting a fuel line to a shaking exhaust pipe. Iām sorry if it sounds like Iām blaming the builder - Iām 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 letās not make them easier to certify with relaxed periodic safety inspections.
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.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?
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.Seen recently. Yes, that's a fuel hose attached to an exhaust heat shield.
Isn't the DAR supposed to catch something like this during the AW inspection?
OK: let me take a starting stab at this: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.
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.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.
What is wrong with "this"? Please be explicit. What is the failure mode? What is the hazard?Isn't the DAR supposed to catch something like this during the AW inspection?
Itās because of the experimental nature of what we do - like bolting a fuel line to a shaking exhaust pipe.
Any object that can transfer heat to a fuel line is a big NO-NOmy 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?
What is the āobjectā and what is the transfer mechanism?Any object that can transfer heat to a fuel line is a big NO-NO
There has been a few WHYās posted now.Iāve 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 āanalysisā part. Dan had identified an undesirable condition, but nobody has described the āwhyā yet. The thread has been nothing but a dogpile of āme tooā opinions, but no substance. In a ārealā 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.
Good start. I also mostly agree with your assessment. But a THA typically weighs āLikelihoodā and āImpactā, each with a score of 1-5 on a decision matrix. A possible THA hazard statement in this scenario is āFire, due to āāāā. 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.OK: let me take a starting stab at this:
Not good enough to form a decision, unfortunately.There has been a few WHYās posted now.
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 ...What is the āobjectā and what is the transfer mechanism?
Fair enough, but that is different than saying, there has been no explanations offered of why it is a problem.Not good enough to form a decision, unfortunately
Letās go deeper, for the new builderā¦. Most of us think this is bad, yet we canāt agree on the hazard. Some imply āfireā, others imply āvapor lockā. Which is it? Or is it both? And once we decide on that, then the path to mitigation may be very differentFair enough, but that is different than saying, there has been no explanations offered of why it is a problem.
Asked and answered many times, here's one of themWhat is wrong with "this"? Please be explicit. What is the failure mode? What is the hazard?
Opinion, not analysis.Asked and answered many times, here's one of them
...letās take a closer look....Is this her/his first build?
...this airplane could possibly win awards for its attention to detail and beauty of its construction...
Do you know how many hours the aircraft has flown like that?
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.
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.
Well, Iām willing to add my opinion.Letās go deeper, for the new builderā¦. Most of us think this is bad, yet we canāt agree on the hazard. Some imply āfireā, others imply āvapor lockā. Which is it? Or is it both? And once we decide on that, then the path to mitigation may be very different
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.Seems like most of us are landing on āVapor Lockā as the primary hazard. Iām more nervous about āfireā, personally. But thatās precisely WHY we propose and discuss specific hazards. This same discussion is common before every test event in ābig aerospaceā 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.
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.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
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.....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.
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....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...
Well, thatās the problemā¦. The builder of this airplane WAS sure.Guys---it you arent sure--ASK someone. LOTS of members on VAF with the knowledgeā¦