2022-02 · NASA ASRS report 1884943
DA40NG Flight Crew flew a non airworthy aircraft with inoperative fuel transfer pump; resulted in fuel imbalance and diversion.
Fuel transfer pump was found to be inoperative in flight requiring a diversion. On a time-building flight we left ZZZ with full fuel with the intention of flying ZZZ-ZZZ1-ZZZ2-ZZZ3 then taking a break. I flew ZZZ-ZZZ1; then the other pilot took controls from ZZZ1-ZZZ2 and I took comms/checklist verification. Approximately 35nm from ZZZ2 I prompted the PF (Pilot Flying) that we needed to do a fuel transfer. He initiated the transfer and set a timer and we continued talking. After a couple minutes I noticed there was no annunciation on the PFD of an active transfer; and the fuel level was not increasing in the main tank. I brought it to the PF's attention. I cycled the fuel transfer switch and again noticed no annunciation. I tried pulling and resetting the CB; and again tried to transfer with no result. I then grabbed the QRH and ran the checklist which called for the use of the fuel valve set to emergency. We delayed going fuel valve emergency as we had yet to reach our max imbalance; and decided to divert to ZZZ4 which was about 20nm off our left and closer to ZZZ. As we setup for ZZZ4 and were on with approach our fuel reached max imbalance and I used the fuel valve to select emergency which immediately began filling our main tank with unused fuel. After we touched down the left tank was full so I turned the valve back to normal. On the ground we got a top off of Jet A. I called Maintenance to discuss our options. I walked through 91.213 reviewing our document and TCDS (Type Certificate Data Sheet) for fuel transfer pump. I did not see it listed; but overlooked a final sentence at the bottom noting all engine systems and equipment must be operational. In hindsight; I realized that the fuel transfer pump is technically a piece of equipment that is required to be operational before takeoff due to it belonging to the fuel system - one of the engine's systems. Since I did not think the pump was required; I proceeded with the other areas of 91.213. I checked 91.205; airworthiness directives; and the TCDS. I discussed with the other pilot his comfort level with deactivating and flying back to ZZZ on a lower power setting to avoid any need of fuel transfer. We both agreed this was an acceptable and safe decision. I pulled the circuit breaker and tied it off with wire to securely deactivate it; and labeled the transfer pump as inoperative. We calculated at 40% we would only burn approximately 3.5 gallons roughly from ZZZ4-ZZZ with a tailwind. We arrived back at ZZZ and grounded the plane for maintenance.Unfortunately in missing that last sentence in the company document I failed to realize that we departed in an unairworthy condition. Although the flight was conducted safely; it was no in accordance with 14 CFR Part 91; and more attention needs to be placed on reading these documents more closely going forward as pilot in command responsible for the aircraft.
Flew a DA-40NG from ZZZ4 to ZZZ with an inoperative fuel transfer pump.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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