Fuel flow transducer mounting question

lostpilot28 · #1 12-26-2011, 11:09 AM

I've spent a lot of hours reading the various threads on mounting a fuel flow transducer. I plan on buying the Floscan (flowscan?) unit and my initial idea was to buy an extra 6-inch piece of fuel line and mount the transducer between the carb and the mechanical pump. I've seen another installation where the flow sensor just hangs there (wrapped with firesleeve and aluminum heat shield wrap) and it appears to provide great results.

I'm planning on doing the same thing, and want to make sure just letting it hang wouldn't be a problem. I only ask because many of the threads I've read have the sensor mounted to a plate somewhere. Does anyone see a problem with doing this?

One last bonus question - how critical is it to add a fuel filter upstream of the sensor? I have the gascolator (mounted on the firewall) between the boost pump and mechanical pump...is this good enough, or do I need to add another filter?

Mark12A · #2 12-26-2011, 11:26 AM

In general, it's a good idea to add a filter between something that might create debris if it came apart and the point of final use. However, a filter will always call a pressure drop. If your flow transducer doesn't have anything in the fuel stream, you don't gain anything by adding a filter. However, turbine flow meters (if that's what you're using) are often a little twitchy. I would imagine there are some old military specifications that might be some help to you.

lostpilot28 · #3 12-26-2011, 03:26 PM

Thanks, Jay. I think the manufacturer recommends a filter...I just want to know if the firewall mounted gascolator is sufficient.

My biggest question is about the transducer not being mounted to anything. I'm sure someone has an opinion about that...

Ron Lee · #4 12-26-2011, 03:37 PM

My concern is whether doing it your way could lead to a fatigue in the fuel line. I don't know if that is a valid concern but it needs to be considered. The fact that someone else did it that way does not make it a sound method. Perhaps theirs has not had time to fail.

Tom Martin · #5 12-26-2011, 03:48 PM

Mine has been mounted like that for almost six hundred hours and six years of flying. I have the unit wrapped in fire sleeve with a dab of high temp RTV between the fire sleeve and the oil sump. No problems so far and none expected. Over the years I have mounted them in all sorts of locations and they seem to work well in every installation.

Walt · #6 12-26-2011, 04:02 PM

Electronics International has some excellent info in their manual on installing the FF xdr, starts on page 26...

Link to MVP-50 install manual

As long as your gascolator has some kind of filter or screen in it you'll be ok with it as the "pre-filter".

lostpilot28 · #7 12-26-2011, 04:43 PM

Quote:

Originally Posted by Tom Martin

Mine has been mounted like that for almost six hundred hours and six years of flying. I have the unit wrapped in fire sleeve with a dab of high temp RTV between the fire sleeve and the oil sump. No problems so far and none expected. Over the years I have mounted them in all sorts of locations and they seem to work well in every installation.

Thanks, Tom. You wouldn't happen to have a picture of your installation, would you?

lostpilot28 · #8 12-26-2011, 04:48 PM

Quote:

Originally Posted by Walt

Electronics International has some excellent info in their manual on installing the FF xdr, starts on page 26...

Link to MVP-50 install manual

As long as your gascolator has some kind of filter or screen in it you'll be ok with it as the "pre-filter".

Walt, that's great info. Thanks!

lostpilot28 · #9 12-27-2011, 06:31 PM

What do you guys think of making your own fuel lines? I made 2 of them before when running from the fuel tanks to the selector valve...the hose and fittings are from Pegasus Racing. They don't leak, which I'm guessing is the important part!

I could build the same thing for my FWF section from the mechanical fuel pump to the carb. Being that it's low pressure, I think this would be OK. Again, what do you guys think?

lostpilot28 · #10 01-15-2012, 05:29 PM

OK, this is prompting me to wonder how you guys did this. I've built two sections of fuel line, one is about 9 inches long & the other is about 5 inches long (including the fittings).

My questions are:
1. In looking at the aircraft standards handbook, I couldn't see any reason to worry about making a short run of fuel line, such as my 5 incher.

2. There is NOT a lot of room in that area to run fuel line - see the pictures below. Is there any concern with the way I'm doing this?

3. The very front section of fuel line (to the carb) actually touches the engine mount (middle picture), which I'm not happy about. So did the old hose, although I don't see any wear on the hose or mount. I don't think running the hose on the OUTSIDE of the mount is a good idea because it's too close the exhaust. What do you guys think?

4. I bought AN6 straight fittings for the flow meter, but they force the hose to bend pretty sharply by the firewall, so I put in that aluminum 45 degree fitting to see if it would make it better - and it does. I will use Steel if I go this route...any reason I shouldn't use a 45 degree fitting?

As always, much thanks to all of you guys...you're much smarter than I am!