PA30 Fuel Flow Gauge (one vent input vs two)

[William Flood]

Hi,
My fuel flow gauge is gone tech. I got a known good dual fuel flow gauge, it seems to be a more modern type than the one thats broken. It has two vent line and two pressure line inputs at the rear. My old gauge has just one vent input I think. Can this gauge be used or has anyone come across this one before?

Regards

William

[Charles Schefer]

William,

I just had my factory fuel flow overhauled by Air Parts of Lockhaven (and did both oil temp and pressure gauges at the same time). Like your original fuel flow mine has just one vent (pic below).

To install a new gauge of a different type I would think you would need paperwork to show that it is approved. Either an STC or paperwork showing it's PMA approved for the aircraft as a replacement for the original. If you are able to install the new gauge you have one thing we learned is it is very important to blow the lines out before installing the gauge. The Fuel Flow gauge and the oil pressure gauges (factory ones that is) have a "wet line" to the gauge as you know but it is somewhat a misnomer because fuel (or oil in the case of the oil pressure) should never reach the gauge itself. Rather the fuel / oil comes part way up the line and compresses a column of air. We learned that if fuel gets into the bellows of the fuel flow gauge it can cause it to read inaccurately. Fuel lines can be disconnected at the divider, blown out with compressed air and reinstalled.

Regarding replacement options - Osborne has an STC to allow installation of a Shadin fuel flow as a substitute for the factory original.

- Charles

[William Flood]

Thanks Charles,
That does indeed look like mine, and I guess I need to procure the older type one now of which I have an offer from the other forum. I'll put the newer type 2 vent one up for sale. It is a nice instrument and indeed clearer in it's display. I guess it must have been used for PA39's and very high SN PA30's.

Will post it in the relevant section. By the way what sort of money did air parts of lockhaven charge to refurb your one?

William

[Charles Schefer]

William,

I just checked my file and Air Parts charged me $185 for the OH on the factory fuel flow. For that it came back looking like new - even the face was re-painted / silk screened. Looks like it's fresh from the factory. That did not count shipping or labor installing / reinstalling.

If the gauge you have was a factory installed version on later PA-30s then maybe it is PMA approved for install??? You'd have to check and research. Alternately I'd be you have a good shot at a field approval if in fact it was used on later PA-30 / 39s. It would seem a reasonable substitution to me. But if you have to get into running a second vent line or somehow tie in to your existing vent line with the two vents on the new gauge then you might find it more time and cost effective to simply contact Air Parts of Lockhaven for an overhaul of your original.

I actually also have and older Shadin Fuel Flow and transducers that are STCed (Osborne now holds the STC) but the owner prior to me removed it and reinstalled the factory gauge (which I then OHed). I like the factory gauge as I find it easier to glance at an analog gauge and see the angle of the needles for a quick reference. I would put the Shadin back in but it's pretty old and the rubber on the switches is cracking. Needs to be overhauled or replaced. It's such an old model that it does not interface to the GPS. All that said, I'm planning to keep my factory FF gauge but later instal a JPI engine monitor or perhaps the Insight G4 Twin once available and that will have digital fuel flow in addition.

- Charles