Tag Archives: BRM AERO

Fuel System, Fuel Transducer

Wednesday 4th March 2020 – Fuel Flow Transducer

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Now the transducer is mounted the fuel lines are run from the 4-way connector to the unit and the output line is run to the ‘T’. At each stage of the installation the fuel line is purged with fuel to ensure no debris is present that could block the fuel flow to and from the unit. Once the fuel hose is connected and secured with pipe clips, fire resistant sleeving is added and secured into place with wire lock.
The 4-way and ‘T’ connectors can be positioned adjacent to each other allowing for a neater installation.
And the fuel lines are covered with fire and heat resistant sleeving and wire locked into position.
The finished installation with the fuel pressure switch just visible at the bottom of the photo.

So just enough time in the day to re-assemble everything before departing for Vienna leaving the wiring to the EMS and test runs for when I return. No rush to finish as the runway is still sopping wet at Maypole and there’s more rain to come!

Fuel System, Fuel Transducer

Tuesday 3rd March 2020 – Fuel Flow Transducer

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Due to Maypole’s runway and taxiways being waterlogged, it’s not been possible to fly since before Christmas. I decided to use the time to do some more work on the plane. I had originally made the decision not to fit a fuel flow transducer but after flying the aircraft a few times I realised that the addition of a transducer would help me understand how much fuel I’m using more accurately than I have been using a spreadsheet. It would also help me on some of the longer flights allowing me to balance fuel use against speed.

So on the 4th Feb I talked to the LAA and asked what was the best approach to carry out the mod. I didn’t want to start the mod only to wait ages for the approval to come through. They said that the best thing to do is send the paperwork in and await their approval as it could take a while to be approved. To my surprise I received an email from the LAA on Friday 28th to say that I could go ahead with the work.

First thing to do is make a bracket to mount the transducer on. I used a piece of aluminium angle which would be screwed to the firewall using M6 screws and thick rubber washers to absorb any vibration.
The transducer requires 1/4 NPT 27TPI fittings to connect to the fuel pipes. These are sealed with Loctite 577.
Part of me thought ‘if it ain’t broke don’t fix it’ but I think the work needed to fit the transducer will be worth it in the end. So it’s time to start removing parts…
With the parts removed I can try different positions to check the fuel fuel pipe runs and clearances. Despite quite a bit of space on the firewall there are very few places the transducer can be mounted as it has to be mounted with the wires at the top and with straight runs of fuel pipe each side to reduce any turbulence in the fuel flow as this may cause erratic readings.
The existing and proposed fuel feed schematic. Essentially the 3 way and 4 way connectors are swapped and the transducer is inserted in the line leading to the 2 carbs so only one transducer is required. Other installation options require two transducers, one on the feed and one on the return line but this is a much simpler method.
In the ‘as built’ scheme, the 4 way connector takes the fuel from the mechanical pump, splits to the carbs either side and the forth connection is restricted and returns any unused fuel to the left tank. In the new scheme the outlet of the transducer is fed into the 3 way connector which supplies the carbs. The 4 way will be inserted in the line between the mechanical pump and the transducer. The third spur will be connected to the fuel pressure sender and the forth, which is restricted, will be connected to the return line to the tank.
The mounted transducer with the fuel pipes connected but without the fire sleeving. Quite pleased with today’s progress but ran out of time so will hopefully finish the installation and wiring tomorrow and perhaps even carry out some test runs.