Rans S20: Fuel Pump & Servo Tray

by | Feb 19, 2023 | Rans S20 Build, Rans S20 FWF

Rans S20 Fuel Pump Tray Fabrication

This panel was both an original design and fabrication. I have been researching the location of the fuel pumps for over a year. My original plan was to mount it on the firewall in the engine compartment. Still, the more I read and communicated with other builders, especially Rans builders (and the Rans organization as well), it became obvious that the pumps needed to be installed closer to the header tank that sits right behind the pilot’s seat.

Below are the steps I took to build and install the Rotax Fuel Pumps:

  • I analyzed the installation data provided by Rotax. To reduce the risk of a vapor lock in the fuel system, which can occur between the header tank and the pumps, I realized that installing the pump on the firewall would increase the risk of a vapor lock because of the distance between the head tank and the fuel pumps. The Rotax manual for the 912is recommends reducing the distance. If the fuel pumps ever get 10 degrees above the header tank (in the case of a steep climb), the potential for vapor is must greater. Therefore, installing the pumps under the pilot’s seat became the most logical choice.
  • The next step was to decide on the best possible tray design that needed to be built to hold both the autopilot pitch servo and the fuel pumps. This was much more difficult than I originally anticipated. There were several designs that I wanted to replicate, but those designs were installed in the Rans S21 with the aluminum skin. Additionally, Rans installed the pumps upside down without protective housing underneath the pilot’s seat. Although the casing is designed to reduce the fire risk when installed in the engine compartment, I thought the casing would reduce the risk of gas spraying in the cockpit if a leak were to develop. Also, the casing will significantly reduce the motor noise on the two pumps.
  • With the decision to install the pumps with the casing, I then needed to figure out the best location underneath the pilot’s seat so that The fuel hoses would not cross, if possible. After multiple attempts, I installed the pumps with the inlet and outlet face forward.
  • Like all other fabricating projects, building the tray required much time and patience. I had originally built a tray almost two years ago but was unhappy with the design. And at that time, I wasn’t 100% certain where I would ultimately install the pumps anyway. Building the tray was trying different designs to see which made the best sense. Using 6160 aircraft-grade aluminum and 1/16″ thickness, I laid out a piece of aluminum centered underneath the pilot seat area. I planned to attach it to several 4130 Chrom-Molly tubes of the fuselage. I bent the forward and back ends of the tray upward with the metal brake. I then riveted 6160 Right Angles on the left and right sides of the aluminum sheet. The Right Angles were used to provide additional strength to the tray and attach points to the fuselage. Once the tray was completed and test-fitted, I began working on the two parts that would be installed on the tray. First, I laid out the autopilot pitch servo and connected the housing that holds the servo. I built the housing myself – I did not like the one provided by Rans. Using Riv-Nuts, I installed three for the servo mount, ensuring not to hit the fuselage tube below. The installation went well. My next task was to drill the holes for the pumps and mount them to the tray. I drew out the lines/holes on the tray and then drilled the holes.

 

 

 

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