Right fuel line corrosion where it contacts black air duct

[M20 Ogler]

That black ductwork is terrible, every one should replace it with orange skeet IMO. 

I can see some blue dye starting to seep where this is occurring too. 

[PT20J]

There are four types of aviation ducts that have a spiral spring steel core:

SCAT — single wall silicone impregnated fiberglass

SCEET — double wall silicone impregnated fiberglass

CAT — single wall neoprene impregnated fiberglass

CEET — double wall neoprene impregnated fiberglass

In the engine compartment, I prefer SCEET made to length with cuffs on the ends. Guy @GEE-BEE AEROPRODUCTS will make them to order if you give him the length and diameter. The problem with SCAT cut to length in the shop is that no matter how you try to secure the cut ends of the wire, it will eventually wear a hole through the tubing. Also, the SCEET is stiffer and often requires less support to stay where you want it.

Color doesn’t necessarily determine the type of material. Guy made me SCEET hoses in black, though SCEET also come in orange.

Skip

AERODUCT-Aviation-Ducting-and-Hose-Products-Catalog.pdf

 

 

[carusoam]

The original ductwork fell out of my M20C around Y2K…

The spring support had turned to dust in some places…

No idea what the half life is on the old stuff, but by 35 years it was toast…

The small diameter probably isn’t very good at flowing air all the way to the back seats…

Things to Think about during the replacement process…

PP thoughts only, not a mechanic or hvac technician…

Best regards,

-a-

[N201MKTurbo]

Are you sure that is corrosion? It might just be crud.

[N201MKTurbo]

A piece of duct that only lasts 50 years is total crap.....

[M20 Ogler]

1 minute ago, N201MKTurbo said:

A piece of duct that only lasts 50 years is total crap.....

Durability is not the issue. It eventually corrodes aluminium where ever it contacts it.  

[M20 Ogler]

7 minutes ago, N201MKTurbo said:

Are you sure that is corrosion? It might just be crud.

Yeah I’m sure, my A&P also noticed the blue dye indicating fuel is starting to seep. So him and I need to figure out a repair 

Edited October 8, 2021 by M20 Ogler

[carusoam]

9 minutes ago, M20 Ogler said:

Yeah I’m sure, my A&P also noticed the blue dye indicating fuel is starting to seep. So him and I need to figure out a repair 

Lets focus on that for a moment….

If the steel duct support was in contact with the aluminum fuel line….  The steel wire is rubbing through the softer aluminum…

See if you can get a good pic of the fuel line and how it was getting cut…

Nobody is going to notice the crumbly hvac tube when you have a leaking fuel line…. 
 

Expect if the fuel line is leaking, it is coming out for replacement…  plenty of time to get a good pic.

 

A case of too many points in one post…

Best regards,

-a-

[M20 Ogler]

15 minutes ago, carusoam said:

Expect if the fuel line is leaking, it is coming out for replacement…  plenty of time to get a good pic.

I wonder if since the rest of this line is in good condition if it’s acceptable practice to use a splice in the affected area. 

[carusoam]

6 minutes ago, M20 Ogler said:

I wonder if since the rest of this line is in good condition if it’s acceptable practice to use a splice in the affected area. 

Depends on what your mechanic thinks…

From a failure point of view… fewer connections in a fuel line is better…

 

Somebody was replacing a similar tube around here yesterday…

Bending tube is an easy skill to have… but unfortunately, those mechanics are becoming harder to find…

Best regards,

-a-

 

[N201MKTurbo]

29 minutes ago, M20 Ogler said:

I wonder if since the rest of this line is in good condition if it’s acceptable practice to use a splice in the affected area. 

43.13 specifically says you can splice it.

But, making a new one is just as easy.

Edited October 8, 2021 by N201MKTurbo

[47U]

3 hours ago, M20 Ogler said:

I wonder if since the rest of this line is in good condition if it’s acceptable practice to use a splice in the affected area. 

This kind of stuff is why you pull the interior for the annual inspection.

My air ducts were replaced some 25 years ago, but the corrosion had begun.  Last year the blue stain was discovered.  I had not yet detected any fuel smell in the cockpit.  As you can see, the air duct wasn’t any where near the corroded section.

The fuel feed line from the right wing root is one continuous run all the way to the fuel selector.  Replacing it would be a huge PIA.  It would be easier to replace it with a hose, if that becomes necessary.  

I replaced the corroded section with AN fittings.  There’s just enough room to get the Roto Flare in there.

My IA agreed that this was the best solution.

 

 

 

[carusoam]

Nice work 47U!

Thanks for sharing those pics!

Go MS!

Best regards,

-a-

[N201MKTurbo]

8 hours ago, 47U said:

This kind of stuff is why you pull the interior for the annual inspection.

My air ducts were replaced some 25 years ago, but the corrosion had begun.  Last year the blue stain was discovered.  I had not yet detected any fuel smell in the cockpit.  As you can see, the air duct wasn’t any where near the corroded section.

The fuel feed line from the right wing root is one continuous run all the way to the fuel selector.  Replacing it would be a huge PIA.  It would be easier to replace it with a hose, if that becomes necessary.  

I replaced the corroded section with AN fittings.  There’s just enough room to get the Roto Flare in there.

My IA agreed that this was the best solution.

 

 

 

I have 3 different flaring tools. That one is my favorite.

[M20 Ogler]

Are these fuel tubes 3/8”? Looks like I need to order a B nut. A&P has flare tool already 

[Yetti]

14 hours ago, M20 Ogler said:

I wonder if since the rest of this line is in good condition if it’s acceptable practice to use a splice in the affected area. 

Not right there.  See all that white stuff down low?  That is the fuel line that has flaked off.   You are going to have to go really far in either direction to find good line.

[Guest]

7 hours ago, M20 Ogler said:

Are these fuel tubes 3/8”? Looks like I need to order a B nut. A&P has flare tool already 

Normally the lines are 3/8” diameter.  The B nut should be 11/16” 

Clarence

[mike20papa]

I bet that fuel line is some off spec material.  Absolutely weird.  5052 is highly corrosion resistant.  Especially weird considering the condition of the surrounding airframe.  Would make me wonder what the rest of my fuel system looked like.  Did someone fill the tanks with ?? pickle juice ??