AC for fuel systems and experiementals

[LSaupe 123]

Hey All:

Had a guest speaker at our last EAA meeting.  He was a CFI, A&P and AI.  His talk was on fuel systems.  Particularly fuel system design in Experimentals.  He mentioned an A.C. that experimental birds must comply with (cant recall the number of the AC unfortunately, my bad).  He was also adamant that fuel lines in the cockpit need to be metallic (aluminum or stainless etc), and cannot be soft flex lines (such as Tygon).  He spent a lot of time going over proper routing, static head, pressure drops, correct filters and general orientation.  Very good talk overall.

I know my bird has flex line (Tygon) at the wingroot to allow for wing fold.  All other lines are aluminum in the cockpit. Tygon again from the firewall to the engine (liquid cooled 2 stroke) as there is relative motion.  Also use Tygon for my wing tank sight glasses.

I had no problems however during my DAR inspection with this.

Couple questions. As experimental birds what AC sections are we bound to (fuel delivery wise) with regard to air worthiness?  I just followed the Kitfox plans (and general hydraulic knowledge) and all has been well.  But.... it did get me thinking.

Can anyone point me to the AC we need to be following?  I am sure that flex hose can be accommodated legally as Kitfox and other product factory built SLSA's.  Also several LSA's (EAB and ELSA) running around here are running flex line (Tygon and other) exclusively throughout the cockpit and to the engine.

 

Edited 2 Dec 2016 by LSaupe

[EDMO 1078]

Hey All:

Had a guest speaker at our last EAA meeting.  He was a CFI, A&P and AI.  His talk was on fuel systems.  Particularly fuel system design in Experimentals.  He mentioned an A.C. that experimental birds must comply with (cant recall the number of the AC unfortunately, my bad).  He was also adamant that fuel lines in the cockpit need to be metallic (aluminum or stainless etc), and cannot be soft flex lines (such as Tygon).  He spent a lot of time going over proper routing, static head, pressure drops, correct filters and general orientation.  Very good talk overall.

I know my bird has flex line (Tygon) at the wingroot to allow for wing fold.  All other lines are aluminum in the cockpit. Tygon again from the firewall to the engine (liquid cooled 2 stroke) as there is relative motion.

I had no problems however during my DAR inspection with this.

Couple questions. As experimental birds what AC sections are we bound to (fuel delivery wise) with regard to air worthiness?  I just followed the Kitfox plans (and general hydraulic knowledge) and all has been well.  But.... it did get me thinking.

Can anyone point me to the AC we need to be following?  I am sure that flex hose can be accommodated legally as Kitfox and other product factory built SLSA's.  Also several LSA's (EAB and ELSA) running around here are running flex line (Tygon and other) exclusively throughout the cockpit and to the engine.

 

I have some doubts that the AC applies to Experimental, but would like another opinion, or several, about the Regs.   Doesn't AC stand for "Advisory Circular"?  How can that be mandatory unless it is stated in the FARs?   Factory planes have to comply with their TCDS which must have been approved by some FAA authority, but Experimentals are each built to the builder's specifications.  I read that Canada once had the same rules for solid fuel tubing inside the cabin, but was told that they usually now don't enforce it for experimentals.  I have tossed this back and forth thinking whether the solid tubing would be any safer than flex tubing in case of a crash, and cant come up with a reason why if each is properly installed.  I sure as hell cant make my Kitfox type sight gauges out of solid tubing, although there were some metal shielded (glass or hard acrylic?) in some factory planes, and if one of them gives way you have got the whole tank of gas to come out with no shutoff valve to stop it.   EDMO

Edited 2 Dec 2016 by EDMO

[1avidflyer 1983]

I think your speaker doesn't know what he is  talking about when it comes to experimental aircraft.  Until he can prove it with an FAR, I will believe otherwise.   I've had 6 or 7 experimentals, and all of them had plastic tubing for fuel lines.  They were all Kitfoxes and Avids.  All of them received an airworthiness certificate with those lines.    I'm sure every Kitfox and Avid has that type of fuel line so the wings can fold as Ed mentioned.  JImChuk 

[EDMO 1078]

I didn't see that the guy with an alphabet ratings was a DAR or an AWI for FSDO or an FAA engineer, so I just have to believe that this is "his opinion", and that don't count.  I would not want him for an A&P or AI.  I would like to see the AC.  EDMO

Edited 3 Dec 2016 by EDMO

[RobS 52]

This info, found in FAR 25.993, does say flexible hose has to be approved but contradicts the notion of only being able to use rigid lines.

(a) Each fuel line must be installed and supported to prevent excessive vibration and to withstand loads due to fuel pressure and accelerated flight conditions. 

(b) Each fuel line connected to components of the airplane between which relative motion could exist must have provisions for flexibility. 

(c) Each flexible connection in fuel lines that may be under pressure and subjected to axial loading must use flexible hose assemblies. 

(d) Flexible hose must be approved or must be shown to be suitable for the particular application. 

(e) No flexible hose that might be adversely affected by exposure to high temperatures may be used where excessive temperatures will exist during operation or after engine shut-down. 

(f) Each fuel line within the fuselage must be designed and installed to allow a reasonable degree of deformation and stretching without leakage.

[EDMO 1078]

I believe I would inform any doubters that both the Avid and Kitfox kits were approved with the flexible fuel lines by the FAA under the 51% rule for Amateur-Built Experimental Aircraft.  EDMO

Edited 3 Dec 2016 by EDMO

[1avidflyer 1983]

FAR 25 is for transport category aircraft.  I don't think that's our category. Hopefully the link works. Jim Chuk

http://www.ecfr.gov/cgi-bin/text-idx?SID=3b7ce73203302fd3dd6864a1d4e33a54&mc=true&node=pt14.1.25&rgn=div5

[EDMO 1078]

FAR 25 is for transport category aircraft.  I don't think that's our category. Hopefully the link works. Jim Chuk

http://www.ecfr.gov/cgi-bin/text-idx?SID=3b7ce73203302fd3dd6864a1d4e33a54&mc=true&node=pt14.1.25&rgn=div5

Agree - FAR 25 would not apply to our birds - but if it's good enough for them it should be good enough for experimental.   EDMO

[1avidflyer 1983]

I'm not saying we shouldn't be safe, but using that argument then we should also follow all the other rules for certified planes.   I thought one of the nice things about experimental category was we aren't under near as many rules and restrictions.  JImChuk

[Geoffrey Thorpe 31]

Lots of people like to make up their own regulations to back up their opinions on how the world should be run, though this is the first time I've heard this one. Flexible fuel lines are pretty common.

FWIW, I replaced all of the rubber line from the tank to the gascolator with aluminum and AN fittings on my Merlin GT just because I felt better about it. It's not that challenging.  There is even some really bad video that I made while doing this on my youtube channel if you are having trouble getting to sleep at night... 49 minutes of your life that you will never get back.

[LSaupe 123]

Just spoke with the AI.  The referenced doc is AC43-13.  The flex lines were just one part of the conversation.  The rest of the experimental fuel system must comply as well.  As a counter discussion, is there something to say that AC43-13 does not apply?

[Geoffrey Thorpe 31]

Just spoke with the AI.  The referenced doc is AC43-13.  The flex lines were just one part of the conversation.  The rest of the experimental fuel system must comply as well.  As a counter discussion, is there something to say that AC43-13 does not apply?

IN general, acceptable methods and practices is a good idea - but it's not regulatory - first of all it covers MAINTENANCE when the MANUFACTURER doesn't provide guidance. You, as the manufacturer of your E-AB, so what you do during construction or write in any sort of manual would overrule the AC. Second, the intent of the AC is to provide guidance for complying with FAR part 43 which, according to 43.1 does not apply.

So, yea, it's a good idea, but someone is making up regulations to get you to do it the way that he/she/it thinks it should be done.

 

From the AC

REFERENCE:

Title 14 of the Code of Federal Regulations part 43, section 43.13(a) states that each

person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or

appliance shall use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance

manual or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques,

or practices acceptable to the Administrator, except as noted in section 43.16. FAA inspectors are prepared to

answer questions that may arise in this regard. Persons engaged in the inspection and repair of civil aircraft

should be familiar with 14 CFR part 43, Maintenance, Preventive Maintenance, Rebuilding, and Alteration, and

part 65, Subparts A, D, and E of Certification: Airmen Other Than Flight Crewmembers, and the applicable

airworthiness requirements under which the aircraft was type certificated.

 

From part 43

 

§43.1   Applicability.

(a) Except as provided in paragraphs (b) and (d) of this section, this part prescribes rules governing the maintenance, preventive maintenance, rebuilding, and alteration of any—

(1) Aircraft having a U.S. airworthiness certificate;

(2) Foreign-registered civil aircraft used in common carriage or carriage of mail under the provisions of Part 121 or 135 of this chapter; and

(3) Airframe, aircraft engines, propellers, appliances, and component parts of such aircraft.

(b) This part does not apply to—

(1) Any aircraft for which the FAA has issued an experimental certificate, unless the FAA has previously issued a different kind of airworthiness certificate for that aircraft;

(2) Any aircraft for which the FAA has issued an experimental certificate under the provisions of §21.191(i)(3) of this chapter, and the aircraft was previously issued a special airworthiness certificate in the light-sport category under the provisions of §21.190 of this chapter; or

(3) Any aircraft subject to the provisions of part 107 of this chapter.

(c) This part applies to all life-limited parts that are removed from a type certificated product, segregated, or controlled as provided in §43.10.

(d) This part applies to any aircraft issued a special airworthiness certificate in the light-sport category except:

(1) The repair or alteration form specified in §§43.5(b) and 43.9(d) is not required to be completed for products not produced under an FAA approval;

(2) Major repairs and major alterations for products not produced under an FAA approval are not required to be recorded in accordance with appendix B of this part; and

(3) The listing of major alterations and major repairs specified in paragraphs (a) and (b) of appendix A of this part is not applicable to products not produced under an FAA approval.

[wypaul 448]

+1 Geoffrey.  Also reference AC20-27G 8(h-I) which deal with the cockpit area and the fuel system for amateur built experimental aircraft.  Even in these sections, and note the word "Should" there is no mention of metal fuel lines.  I am sure the speaker was well meaning but in this instance at least, not well informed. If you still have doubts I suggest you contact the EAAhttps://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/99737

Edited 4 Dec 2016 by wypaul

[LSaupe 123]

Thanks for the feedback on this.  What you describe is what my "impressions" were before the talk.  Good stuff.

[C5Engineer 1170]

There is NO SUCH THING as must comply with experimental amateur built aircraft. Not sure why you guys keep insisting on adding additional regulation to yourselves. If your concerned about having a reg governing an 18" hose go buy a Cessna. 

[EDMO 1078]

There is NO SUCH THING as must comply with experimental amateur built aircraft. Not sure why you guys keep insisting on adding additional regulation to yourselves. If your concerned about having a reg governing an 18" hose go buy a Cessna. 

Amen Joey - Most of the experimental builders have no idea how many hundred$, or thou$ands, it costs for an STC to make some simple change to a factory aircraft - and if it isn't on the TCDS, then you cant do it without getting an STC or a field approval, which is nonexistent in Missouri.... And this can be as simple as changing tire sizes!   EDMO

Edited 5 Dec 2016 by EDMO

[LSaupe 123]

Hi Joey:

I think this thread was about the opposite.  Trying to point out that these regs dont really apply here, as far an not being bound to them (i.e. provide arguments and evidence and to why this AI might be a bit off base here).

 

[1avidflyer 1983]

Well I think with the info that came together here, you could win the argument with him.  JImChuk

[C5Engineer 1170]

Hi Joey:

I think this thread was about the opposite.  Trying to point out that these regs dont really apply here, as far an not being bound to them (i.e. provide arguments and evidence and to why this AI might be a bit off base here).

 

your right sorry this one struck a nerve. I flew with a guy yesterday that pays someone else to work on his plane. I don't understand it. There's been a few threads lately regarding rules and regs that don't apply to us. We've got a great thing going here. Take advantage.