B737-700
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 131
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Fuel Issue
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew FLC Overrode Automation; Flight Crew Landed As Precaution; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport
Aircraft
On departure from ZZZ; passing through FL 230; we saw the following indications almost simultaneously: Master Caution lights with FUEL and ENG illuminated and left and right fuel Filter Bypass lights illuminated on the upper panel. There were also indications of a computer data problem as the aircraft went into CWS Pitch and out of VNAV with DISPLAY SOURCE 2 (amber; in the bottom left of the PFD). The flight director became unreliable to nonexistent and we began to hand fly off of the raw data; cross checking primary and standby instruments with minimal thrust lever movements. After we leveled off; we ran the QRH for Filter Bypass; [notified ATC]; and returned for a precautionary landing at ZZZ which was uneventful; below MGLW (Maximum Gross Landing Weight); with no hot brake concerns. There were no known deviations from QRH; ATC; or Company procedures despite the aircraft malfunction(s).The QRH is very straightforward regarding the dual Filter Bypass light condition; so we [notified ATC] and returned in a safe and expeditious manner. It wasn't until after we were on the ground and able to reflect on everything; that we began to figure that it was likely not a fuel contamination problem; but a DEU (Display Electronics Units) failure of some sort and we began researching possible connections between that and the Filter Bypass lights. There is nothing that we could find in [our electronic guides] or our manuals linking these conditions... which led to a little head-scratching during the event; although it would not have affected our clear decision to land as soon as possible. Looking back; I would have at least tried the other autopilot to see if maybe that would have alleviated some of the task load; but it was just so much simpler at the time to just hand fly and not spend time worrying about the automation. It would be nice to get some follow-up from Maintenance about what they found.
Climbing out of ZZZ to FL 190 we were cleared to maintain FL 230. As we were about to level off; we had a duel fuel filter bypass. We read the QRH; [notified ATC]; and returned to ZZZ. We do not believe we deviated or oversped; and we did follow QRH; ATC and Company procedures to the best of our knowledge. We did initially lose VNAV but still no deviation.
B737 flight crew reported Master Caution illuminating with Fuel and ENG warning lights led to a return to the departure airport.