Hi all,
I have posted about this before, but have never been completely satisfied that I understood, and I am getting very close to first flight, and so would like to understand everything, especially FWF, 100%.
The KB-090-T fitting connects to the output of the engine driven fuel pump. A picture is here: http://www.aircraftspruce.com/catalog/eppages/lycomingfitting00782.php
From previous threads on the topic, Vans and others suggest to install this to the correct orientation, and then tighten down the jamb nut to compress the o-ring. Here's the thing - the jamb nut just turns against a steel flange that is fixed in place on the KB-090-T fitting. It does not compress the o-ring at all. It simply bottoms out on the flange. If I want to compress the o-ring further I need to turn the entire fitting, thus getting it out of the correct orientation. In fact, I don't even see the purpose of tightening the jamb nut, it does nothing. If it turned against a washer or something else moveable, now that would make sense. But a fixed flange that doesn't move or compress makes no sense to me.
As it is now, the fitting in my installation will turn several degrees back and forth with just a tug of the fuel line attached to it. I have run the engine and pressure tested everything with the boost pump on, and there are no leaks, but a fitting that loose doesn't seem right, and I would have to tighten it another full turn to keep it in the proper orientation, which I think would be way too tight on the o-ring, if it would even go that far.
There is no potential for this fitting to back out more than a couple degrees due to the two fuel lines attached to it, but that fact that it wiggles at all concerns me. Should I try to get another full turn out of it? How thin can I crush that o-ring? Or is the slight play normal?
There is something very simple my feeble mind is missing here...
Chris
I have posted about this before, but have never been completely satisfied that I understood, and I am getting very close to first flight, and so would like to understand everything, especially FWF, 100%.
The KB-090-T fitting connects to the output of the engine driven fuel pump. A picture is here: http://www.aircraftspruce.com/catalog/eppages/lycomingfitting00782.php
From previous threads on the topic, Vans and others suggest to install this to the correct orientation, and then tighten down the jamb nut to compress the o-ring. Here's the thing - the jamb nut just turns against a steel flange that is fixed in place on the KB-090-T fitting. It does not compress the o-ring at all. It simply bottoms out on the flange. If I want to compress the o-ring further I need to turn the entire fitting, thus getting it out of the correct orientation. In fact, I don't even see the purpose of tightening the jamb nut, it does nothing. If it turned against a washer or something else moveable, now that would make sense. But a fixed flange that doesn't move or compress makes no sense to me.
As it is now, the fitting in my installation will turn several degrees back and forth with just a tug of the fuel line attached to it. I have run the engine and pressure tested everything with the boost pump on, and there are no leaks, but a fitting that loose doesn't seem right, and I would have to tighten it another full turn to keep it in the proper orientation, which I think would be way too tight on the o-ring, if it would even go that far.
There is no potential for this fitting to back out more than a couple degrees due to the two fuel lines attached to it, but that fact that it wiggles at all concerns me. Should I try to get another full turn out of it? How thin can I crush that o-ring? Or is the slight play normal?
There is something very simple my feeble mind is missing here...
Chris
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