Fuel transducer installation

N

n12365

Pre-takeoff checklist
Joined
Oct 5, 2010
Messages
182
Location
Charleston, IL
Display Name
Display name:
Ryan
I recently had a local A&P install a JPI fuel transducer in my 172. Attached is the best picture I was able to take of the installation. Is it permissible to use a hose support clamp over the firesleeve that is over the AN816 fitting used to connect the fuel hose to the transducer?

The use of plastic tie wraps on the firesleeve and the routing of the transducer that puts it above the carburetor are also concerns, but the hose clamp location is what worries me the most.

Ryan
 

Attachments

  • IMG_5740.JPG
    IMG_5740.JPG
    790.4 KB · Views: 80
I'll be interested to hear what the mechanics here say.

The Adel clamp technically isn't "holding" anything there, it'll just hold on to the fire sleeve and let it rub back and forth over everything underneath it, under vibration. Just looking at it, anyway. Sloppy.

I don't like the radius of the bend on the left side either... Seems silly to put that much stress on the hose when there's oodles of space there for a more "gentle" routing.

Just a non-mechanic's opinion. I'll let Duncan, Mike, and Tom comment -- but I think Tom's off fishing somewhere right now. ;)
 
n12365 said:
I recently had a local A&P install a JPI fuel transducer in my 172. Attached is the best picture I was able to take of the installation. Is it permissible to use a hose support clamp over the firesleeve that is over the AN816 fitting used to connect the fuel hose to the transducer?

The use of plastic tie wraps on the firesleeve and the routing of the transducer that puts it above the carburetor are also concerns, but the hose clamp location is what worries me the most.

Ryan
Click to expand...
That looks like a common and even recommended mounting for a fuel flow transducer. The manufacturers like to keep the engine vibration away from the transducer as much as possible. One other alternative would be mounting it rigidly to the firewall.
 
The installation instructions for the JPI fuel flow transducer can be found here - http://www.jpitech.com/manuals/01/In503ffRevC+Diff.pdf
The Adel clamp installation looks to be in accordance with the JPI guidance. They do call out Aeroquip 900591B steel clamps to secure the ends of the fire shield over the transducer rather than plastic tie wraps (which would not be very fireproof). The JPI drawings also show fireshield over the fuel lines on both sides of the transducer and call out hoses that meet TSO-C53a type C or D. Your hoses look like Aeroquip 303, I'm not sure if they meet this spec without a firesleeve. There is also a note to include a hose loop if the transducer is mounted above the carburetor.
 
Last edited:
Looks ok to me, but I don't use zip ties on fire sleeve, I'll give it a couple of wraps with safety wire and spin it snug.
 
Firesleeving the transducer with a non firesleeved hose... is like wearing a rubber with a hole punched in it. Might as well leave it off for convenience.
 
I went through this stuff on my airplane (TB20) some years ago, and wrote up the notes here.

In short, there are very subtle issues with these flow transducers, which is some installations cause them to misread massively. The installer then tweaks the K-factor and the customer thinks all is OK, until he does a different flight profile and then he gets an error of say 5% or 10%.

It seems to be related to where the transducer is located, and the radii of any bends in the pipe before and after it. Both of these are critical, but differently so on different engines because different engines have different fuel pumps that generate differently pulsating flow.

The transducer is a Flo-Scan 201 in nearly all installations, and if one looks at the manufacturer notes on it one can see it really is not suitable for the pulsating flow in most aviation apps, but many years ago somebody (Shadin?) picked up this transducer, found that it "worked" and got it certified, and started selling it at a 4x markup :)

If one copies the Shadin STC mounting instructions exactly then one gets an installation which works well, but even small deviations from the layout can cause very inaccurate/unstable readings.
 
You must log in or register to reply here.
Back
Top