8KCAB Fuel Pressure Snubber

Bartman said:
what is that piece in the middle? the thread looks like pipe thread
Click to expand...

You mean the greasy black elbow? Damned if I know. Chad says that piece has a restricted orifice too. I asked if I could buy one. But the factory elbow terminates at a hose fitting, while I need a bubble flare fitting, or whatever the hell terminates my stainless gauge line.

This thing is turning into a debacle.
 
No, the brassy plug looking part. Does the hole go all of the way through? You might want to call a shop that overhauls fuel system components, they would probably be able to help explain some of this stuff.

Poor Chad, he must be swamped with all of us building airplanes and constantly calling him for parts and with whacked out questions! lol
 
Bob Turner said:
A lot of IAs get really uptight about TSO. The original Bellanca Champs came with auto gauges, so one can assume they can be replaced with same. Mine have never failed, so they remain in place, but I did the panel so I can easily bolt in standard 2 1/4” instruments.
I would have to see the regulation on TSO - I am only an expert on non-TSO avionics.
Click to expand...

As I understand it, if the factory uses a non-aircraft part and the FAA approves it, it then becomes an aircraft grade part for that aircraft design only. Replacing auto gauges with auto gauges would be allowed, in my humble opinion.
 
Bartman said:
what's on the other side of that fitting? it kind of looks like a plug for a hole that is supposed to have compression fitting in it.
Click to expand...

The other side of the hole is the middle picture in post #9.

Spoke to Chad more today. Here are the two fittings available. The brass fitting at left is for my setup, which is a stainless line to a mechanical gauge. The black fitting at right is for a hose connection to an electronic sender. I will order both, so I have an upgrade option.

fittings - Copy.webp
 
I installed the snubber and flew today. HUGE improvement. Zero flutter on the gauge needle. I highly recommend this little gadget.

I have been obsessed with getting rid of my mechanical fuel gauge, because I did not feel safe with that pressurized line running into the cockpit. With this setup, I am rethinking that. The mesh snubber is G grade, meaning it is only permeable by gasses (not gas, as in avgas). Even a complete break of the gauge line would result in very minimal leakage, just the contents of the line from the break to the gauge. And the elbow would provide redundancy.
 
Big Ed. Old post but did you use the 90deg brass “restrictor” (in the airline world, those fluid loss traps are called hydraulic fuses) or just go straight into the servo? In other words, no additional parts except the snubber. Hope you can answer this. Thanks.
 
He can't. But this is a topic that was left hanging - he apparently got the correct part for most of us with older Decathlons, then left the forum without giving us the part number.
I still haven't fixed this area, and someday may regret it - $35 for peace of mind and a non-fluctuating gauge? Worth it!
 
Just got the part number from Chad at ACA. . It’s
PART #:
4034K68
$29.56 before shipping. Have it ordered and will take pics as I install it.

I saw in another post by Big Ed that the snubber replaces a hydraulic fluid loss “fuse” that is already on the line. This what he said, Chad told him.
 
We need a part number for the 90deg elbow fitting. And lots of NPT fitting to make it work. This is a real PITA. And Chad is no help, he is always busy and he doesn’t know or remember what goes where or what was installed from the factory in the older Decathlons. $35 for a part that isn’t working.
 
I sent a text to retired ACA guru Dale G., he said the piece mounts to the back of the gauge, I guess just put it inline right at the gauge and the mesh should dampen the pulses. I assume it can only go one way due to male/female threads.

Hope that helps
 
If it is at the gauge, its fuel-snubbing ability will be of no effect. Fuel snubbing (or actual cutoff if the line breaks) is best done right at the fuel control unit.

Perhaps this is a Lycoming issue, not really an ACA issue?
 
I ordered one today, will install it and see what happens.

I don’t think the anticipated fuel leak is from the thin tube as much as it is the gauge itself so the location of the device at the gauge would make sense.
 
The snubber is a Chemiquip model 12S G porosity. On Chemiquip’s site it says a G allows air and gasses to pass. So I assume it will stop fluid loss. Attaching it to the gauge should work since there is also a fluid loss trap/fuse already on the throttle body. Ideally on the throttle body is best but there are numerous additional fitting that have to go on since the snubber is not a direct fit. My 8KCAB has an aluminum hard line with a bubble flare end from the throttle body to the gauge which makes switching to 1/8” NPT a PITA. I’m not an A&P but I might just redo the whole setup to AN braided fuel line to bring it up to modern fittings. It works in my race car so it should work on my plane.
 
A number of Lycomings I have seen recently have the braided line. My Dec has a 1/8" stainless line, much like the injector lines on top. We did have a line break and a fire on another Dec a few years back (during taxi out - no real damage).
 
It’s incredible that we have, and that the FAA allowed, a fuel line to run into the cabin. Of course we have a 1.5 gal aux tank and overhead fuel lines but still. I talked to a Tech at Stewart Warner that makes the pressure gauge in our 8KCAB and he was shocked we had a fuel line under pressure running into the cabin. That isn’t even allowed in cars. Wishful thinking but I think ACA should sell at cost us older 8K owners a kit with a sender and new electric gauge package. This mechanical direct reading gauge is a law suit and a half waiting to happen. Also the SW Tech advised trying to bleed the line first before doing the snubber.
 
Even the electric sender has to have a stainless line from the injector body - too sensitive for engine vibration. I wonder if a fuel leak in the engine compartment is less bad than one in the cockpit.

Yeah, there has to be a better way. See if your racing buddies have solved the problem - I am fairly sure we could do it as a minor alteration - for safety of flight, often a field approval can be expedited with a little prodding.
 
You must log in or register to reply here.
Back
Top