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Primer line question
http://t18.net/thorpforum/viewtopic.php?f=19&t=6610		 Page 1 of 1
Author:  Tim Brown [ Fri May 06, 2011 7:48 am ]
Post subject:  Primer line question
I read through all the posts about the pros and cons of primers and learned a lot... this lead me to investigate the installation of the primer in my T-18.
I noted immediately that the lines are plastic and wondered if that was OK.
While not very happy about having fuel lines in the cockpit at all was even more concerned when I noted the lower line (in or out???) had a definite crease where it exits the coupling and curls upward, see photo.
This seems to me to be a point of impending failure or at the least if it doesn't weaken the tube wall would restrict the flow.
I know nothing about primers (other than the previous threads) and am cornered about getting my left pant leg caught on this tube and tearing it out of the primer or having it just fall out of its own volition.
I was considering building a guard panel that extends from the panel lip rearward to protect the primer; is that needed?
Any thoughts

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Author:  Rich Brazell [ Fri May 06, 2011 10:49 am ]
Post subject:  Primer line question
Tim: I am not a plumber (although I did stay in a Holiday Inn Express last nite !), but according to Tony Bingelis plastic line is acceptable along with "plastic fittings" that are made for that tubing. The more acceptable line is aluminum, followed by copper. Both of these lines also using the appropriate fittings. If you still want to use the plastic, it looks like you will need to change the fitting(s). From the pic I would install a 90 degree fitting rather than the straight fitting. Also if it were me, I would get rid of the plastic and go with a metal line. I would also like to be 6ft two and blonde !

I did not install a cockpit primer as I wanted to reduce the number of "fluids" in the First class section of the cabin. I went with the Electric firewall mounted (engine side) primer from Vans.

One last note with the metal lines you "flare" the ends, making that a more secure installation (IMHO) than the plastic line.

RB
Author:  admin [ Fri May 06, 2011 12:35 pm ]
Post subject:  Primer line question
Plastic is for baby dishes, metal is for primer lines. The last time you looked at a production airplane how many plastic fuel lines did you see? My 2 cents worth

*** admin posted for William Williams ***
Author:  fytrplt [ Fri May 06, 2011 3:22 pm ]
Post subject:  Primer line question
Related primer issue: We lost a T-18 and the two occupants in a take off accident at Sun 'n Fun several years back due to a primer that was not locked in. The fellow evidently started the engine after the airshow with the primer and did not fully seat it. The long taxi with the engine pulling fuel through the open primer carboned up the plugs. The engine quit just after T/O with insufficient altitude to establish a glide. Witnesses later reported an inordinate amount of black smoke coming from the exhaust during taxi and T/O.

An open primer plunger will draw fuel (rich) and a broken primer line will lean the engine to the point of possible detonation. Treat 'em with respect!
Author:  Les King [ Fri May 06, 2011 4:30 pm ]
Post subject:  Primer line question
Hey fytrplt;

Thanks for the post on primers. I'm putting "check primer" on my pre T/O check list.

Les King - N331A
Author:  Bill Williams [ Fri May 06, 2011 4:43 pm ]
Post subject:  Primer line question
I've found two different primers. One will rotate completely around and the other has a detent that will lock the primer. I have the later
Author:  Victor Thompson [ Fri May 06, 2011 6:39 pm ]
Post subject:  Primer line question
My Baby Ace has copper fuel primmer lines and so does this picture.

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I have seen plastic,copper, alumimun and steel fuel primer lines in home-built aircraft.

My military experience I have worked on fuel systems with rigid aluminum, stainless steel, titanium and nickle fuel lines. These installations are rigid, have compatible flared fittings and are bonded to structure. Most fuel lines have a wall thickness of 0.035 -0.050 thickness. Standard practice is to remove rigid lines with dents or nicks of 10% wall thickness.

In the picture supplied by Tim Brown the plastic fuel line could have been better secured and as pointed out, this line has been snagged a few times and is on it's way to failing. Plastic lines can not be bonded and often are secured with clips/ lockwire over stepped fittings. Not the best in my opinion.

My preference is aluminum tubing. Proper AN fittings, flared ends, overall rigid installation for fuel primer lines.
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