Fuel Flow Checks

Back from Vienna just before Corona Virus closed all borders! With the transducer installed before I went away I rechecked the installation and carried out pressure testing to ensure there’s no leaks and all seems to be secure.

Wiring up the transducer into the EMS220 is straightforward using 3 wires, a 12v supply, signal and ground. The SkyView panels need to be configured with the ‘K’ factor of the FT60 unit. This is the number of rotations per US Gallon. Entering the config screen I found that the SkyView had already detected the unit and configured itself which was handy.

Once configured a check needs to be carried out between measured and actual fuel flow. I removed one of the banjos from the carb and captured the flow in a measuring jug to carry this out. With no restriction the electric fuel pump delivered 66 litres per minute and when restricted to give 3 psi within the fuel system the flow rate was 44 litres per minute. This is significantly more than the 27 rpm that the engine needs at full throttle.

Testing throughout the RPM range was carried out switching between left and right tanks and using the engine pump and engine and electric pumps options to ensure there were no issues with fuel supply.

After the engine runs a thorough check of the installation was made to ensure there were no leaks or issues.

All’s fine so now for the paperwork for the LAA.
Worksheets covering the work carried out and a fuel flow check form needs to be completed. A suitable entry needs to be entered in the Airframe logbook signed by myself and a permit maintenance release needs to be signed off by and LAA inspector with the appropriate authority, in this case Ian Daniels.

One of the jobs that I’ve not looked forward to is the fuel flow test. Not because it’s difficult or complicated but more that it seems dangerous. It involves taking a feed off of the carb line and running a long pipe away from the engine and prop. Several timed measurements take place using the electric pump on it’s own with the engine stopped, one with the engine running at full bore using just the mechanical pump and one with the mechanical and electric pumps working together. The aircraft has to be choked and Ian offered to do the work outside the cockpit. We used radios to signal the start and stop of each engine run.