pafi fuel testing
At Radial Engines Ltd we had heard for some years about proposals to do away with lead in avgas, the same way it had been removed from automobile use. Then, in early 2017, we were contacted by the FAA Technical Center to inquire if we would be interested in conducting fuel tests in conjunction with their PAFI (Piston Aircraft Fuel Initiative) program. We submitted a proposal for testing and were awarded a contract in 2018.
The contract specified both detonation surveys and performance/durability testing on three W670 Continental engines and one Pratt & Whitney R1830. Since our dynamometer had been constructed to test engines up to 450 hp, it became necessary for us to design a larger test cell and dynamometer to accommodate the larger engine. Models were constructed that helped us with layout for the dynamometer.
Ultimately, we decided on a building that could house the engines during testing, with a remote-control room to observe the test runs and record data.
The first order of business was to fabricate a tunnel
to provide a smooth flow of inlet air. Since the three bladed propeller we would use for the R1830 was eleven feet in diameter and we needed the prop to clear the tunnel by at least two feet all around, the inside diameter of the tunnel was set at sixteen feet
Sections of 2” square steel tubing were rolled and then welded together to give us two sixteen foot diameter rings, and then these were spaced from each other by other pieces of square tubing. The entire ring assembly was covered on the inside with .062” steel sheet and then painted.
One problem with running engines inside metal buildings vibration damage to the building. The decision was made to assemble the building inside out by first erecting the girder and girts, and then sheeting the inside of the building.
Spray foam was then applied to the outside of the inner liner panels, which both stiffened them against vibration but also helped to join the panels to the building’s structure. After the foam, the outer panels were installed.
All electrical wiring is surface mounted for ease in servicing it. The control room was then built with double insulated glass and staircases inside and out. Three 5,000 gallon fuel tanks were purchased and installed, one for 100LL reference fuel and two for the experimental fuels.
As all this construction was progressing, three Continental W670 engines were overhauled for testing purposes. Each part in the engines were serialized and carefully measured, and then those measurements were recorded so wear could be determined after the test runs. An overhauled Pratt & Whitney R-1830 was obtained and propellers were overhauled for the engines.
At this point in our preparations, we were contacted by the FAA and told to halt all work. Both Teledyne Continental and Avro Lycoming already had their infrastructure in place to begin testing opposed engines. And apparently during the early stages of testing, problems with the new fuels had surfaced which made it unnecessary for us to test with those fuels.
We have been informed that fuel testing will resume this summer under the new EAGLE (Eliminate Aviation Gas Lead Emissions) Program. At this point we are awaiting instructions to finish construction for that testing.