Date: 201307
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Engine Fuel Filter
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Detector: Automation Aircraft Other Automation
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; General Declared Emergency
Contributing factors: Company Policy; Aircraft; Manuals; Procedure
Primary problem: Aircraft

Narrative: During final climbout the Master Caution illuminated with a fuel 'six pack' warning and accompanying FUEL FILTER BYPASS light ENG 2 message. Aircraft was passing FL 340; slightly nose high; wings level with 32;000 LBS FOB. Immediate level off executed; The QRH Fuel Filter Bypass procedure was accomplished and an emergency declared with Center. An immediate return to our departure airport was issued and executed. Overweight checklist and Emergency Landing checklist accomplished as well as all required coordination. Captain executed flawless overweight landing at 151;500 LBS less than 100 FPM; 29;300 FOB and very soft landing followed by a normal taxi to a gate where the aircraft was removed from service. The Fuel Filter Bypass QRH for one engine is very vague and non-directive. It offers no remedy or [directed] course of action re continued flight or landing. It has a note that you may encounter erratic engine operation or flameout and that is all. With 2 lights it states to land at nearest suitable airport.


Second narrative: Our logic for the decision to return was that the light reflects an abnormal operation/malfunction; we don't know the cause. It may have been caused by contaminated fuel; the condition may lead to loss of one or both engines; the mountain range and darkness lie ahead; let's return to the airport. The QRH lacks specific guidance to continue or land in the case of a single filter bypass light; but in the case of both left and right lights [directs flight crews] to land at the nearest suitable field. I would have appreciated more refined text to guide us through the continue or land decision process. The day following this event; I received a call from the B-737 Fleet Manager inquiring as to my decision process leading to our return. Although she stated time and again that she was not 'second guessing' my decision; I felt strongly that she was. There was a condescending tone and she stated that other pilots fly with that condition; but should probably not fly over [large bodies of] water. I'm shining a light on this Fleet Manager's conversation because I feel that it was inappropriate in this context. While it may not be rated as 'pilot pushing' it was somewhat intimidating and might play a role in a future wrong choice as this conversation replays in my head.


Synopsis: A B737NG flight crew declared an emergency and returned to their departure airport following receipt of a FUEL FILTER BYPASS warning. The crew stated they believed the QRH procedure addressing a single filter bypass provided insufficient guidance with respect to continuing their flight when only one engine displayed the condition. A call to the Captain requesting justification for his decision was deemed by the Captain to have been coercive and intended to intimidate against future decisions which might compromise normal operations.