Date: 201911
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Fuel
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Troubleshooting; Workload; Confusion
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition
Contributing factors: MEL; Aircraft; Procedure
Primary problem: Ambiguous

Narrative: Dispatched on Aircraft X with 3 MEL items; 25-XX; 28-XX; and 28-XXA. I reviewed the MELs in OPS. Per 28-XX knew to look for a fueling slip and a form XXXXX; though I was not familiar with that form. Once at the aircraft during preflight we did receive both forms from different fuelers. Release was 14;612; fuel slip showed a total of 14;800 lbs. At the gate the #1 tank showed 7.40; the center 0.00; the #2 tank was blank; and the totalizer was blank. Spending some time attempting to understand the form XXXXX; I discerned it was our aircraft and date; and the stuck tank measured to an equivalent volume of 7400 lbs. So it looked we had a balanced load of empty center and 7400 lbs in each wing tank. I filled in 14.8 in the fuel block on the INIT REF page; as that block was blank.During pushback and engine start the ground crew reported a fuel leak from the #2 engine. I had him stay connected during the five minute warm up period. By the end of the 5 minutes the leak stopped. Taxi; takeoff; climb; and cruise were normal. ATC gave us 2 shortcuts; one direct ZZZZZ after ZZZZZ1; then later direct ZZZZZ2. Fuel check at ZZZZZ was right on. I subsequently did the MEL recommended fuel check using fuel used. That showed 2.7 used by each engine (5.4 total). Deducted from the starting fuel of 14.8 gave us 9.4. Just after that we passed abeam ZZZZZ3; where I recorded 9.2; compared to the MISC 14 prediction of 9.5.Shortly thereafter the #2 tank FWD pump LOW PRESSURE light began to flash. I pointed this out to the FO (First Officer) and commented something like 'well that's not right!' then 'well now why would that be happening?' Subsequently that light came on steady; followed by the AFT LOW PRESSURE light beginning to flash. I told the FO we had a big problem and that we needed to consider that the only fuel we might have available was the #1 tank fuel; as I pointed to the left quantity. We agreed; and at that point the #2 AFT LP light came on steady; both MC lights came on; and the #2 engine began rolling back.At this point it appeared we had a right engine failure. We ensured the FO had the aircraft; he clicked off the automation and managed the yaw and loss of thrust. I reached up and opened the fuel crossfeed. Our estimate was that N1 decreased to about 20-30 %. After a very mild audible and tactile vibration; the right engine began to recover; increasing N1 and N2 and returning to normal thrust and indications. The FO and I agreed on the diversion to ZZZ which was ahead at 11:30 clock code and by then about 100 miles ahead. I [spoke with] ATC and told them we were diverting to ZZZ. I had been to ZZZ before and knew the station had [company] maintenance. I asked for a series of right 360s to descend. ATC said they had traffic over there; asked if we could take a left vector heading to absorb the altitude loss and I said yes. The FO continued to manage energy while flying the aircraft. From there it was the normal ACARS MISC [message]; backing up the FO as he deftly flew the aircraft and got us down expeditiously; running regular checklists; completing non-routine landing consideration tasks; talking to the #1 FA (Flight Attendant); making PAs; etc. The FO flew a flawless visual approach and spectacular touchdown; backed up by the ILS; to RW XXL.After landing on RW 1XXL and clearing the Runway I asked the ARFF commander if he saw any fuel leaking from the right wing or engine and he said no. Proceeded to gate XX. On the gate the indicating fuel gauges showed 3.52 in the #1 tank; 0.00 in the center tank. No other fuel light had ever annunciated (e.g. 'LOW' or 'IMBAL'). Maintenance was on the jet bridge; boarded on our arrival and we began the conversation; relating the details of what we saw over time. We agreed with their plan to stick the right wing; look for fuel leaks; talk to [Maintenance Control]; and eventually refuel to a known quantity and stick again. The fueler reported the #2 wing tank was 'bone dry'. We discussedpossible causes of our symptoms: a fuel leak; bad fuel; fuel sticking inconsistencies. They began their work; saying eventually they would be doing an engine start and run to look for leaks; all of which would take some time.In speaking with dispatch to determine a rough fuel load that maintenance could use in their work; [I was asked] to speak to a maintenance manager who was there. The manager asked for a recap; what lights we had; what paperwork we had received in ZZZ1; what RPM the #2 had spooled down to; and asked if we could send him copies of the fuel slip and form XXXXX. I later had the FO do that. ZZZ maintenance continued to work with us. They reported there was no placard out on the refueling panel for the 28-XXa.I made periodic PAs to the passengers. The #1 FA indicated there were some passengers that wanted to deplane. I went up to the gate to retrieve an agent. We discussed the options and mutually decided to deplane everyone. Back on the aircraft calls with dispatch resulted in us learning the aircraft was taken OTS. 3 AML entries were made reporting the fuel tank LOW PRESSURE lights and subsequent rollback with empty #2 tank upon arrival at gate; the engine rollback; and the pulled CVR CB.We began to get texts from ZZZ1 Chief Pilots supporting us and offering assistance.


Second narrative: Flight X from ZZZ1 to ZZZ2 departed the Gate [a few] minutes ahead of schedule after having spent the night at the airport. While familiarizing and setting up for the preflight I noticed two of the three MEL's on the release were for fueling which showed the right gauge blank from the flight deck and a discrepancy on the fueling panel quantity indicator (option 2). While walking around the plane there were three men consulting on the fueling as this required a non-normal fueling procedure. After walk around completion; fuelers came to the flight deck and handed two pieces of paper to the Captain: a form and a Jet Fuel Service Record showing 7;400 pounds of fuel on each side of the aircraft (14;800 total). Sufficient fuel complying with the release (14;612 lbs.) After pushing back; the ground crew noticed fuel dripping from the right engine. Starting both engines with a follow up wait period of five minutes the drip had disappeared and we continued on. It was a normal takeoff on a good VFR weather day and the light load allowed us to climb quickly to flight level 390. Approximately 40 minutes into the flight the forward Number Two Fuel Pump Low Pressure light illuminated which caught our attention perhaps a minute later the aft number two fuel pump came on also. There was a brief pause when the N1 on the number two engine began to roll back. The Captain (non-flying pilot) quickly selected the fuel cross feed to open and the engine continued to operate normally. There was a momentary slight yaw and audible change discernible to the passengers as well. I turned off the autopilot. After assessing we may now only have the fuel showing on the left side; getting on the ground as soon as possible became the priority. The Captain [requested priority handling] and chose ZZZ as our new destination. The Captain was quite busy running checklists; informing the Flight Attendants and making PA's; in addition to monitoring pilot tasks. With so much altitude to lose we got vectors from the air traffic controllers for the descent and then lined up visually for Runway XXL and used the ILS for guidance. After I made a normal landing; the ARFF standing by the runway then cleared the aircraft of showing any fuel visibly leaking at the Captain's request. We continued taxiing to the gate where maintenance met the aircraft and after completing our shutdown checklist; they joined us on the flight deck while the passengers deplaned. Their measurement of the number two fuel tank showed it completely empty and 3;520 pounds remaining in the number one. We then began relaying information to dispatch; chief pilots; and union aids.For whatever reason the right fuel tank was not correctly measured and the information we received was false. We thought we had sufficient fuel but because of the absent fuel indicator for the right side tank and the belief that the tank had been fueled and measured properly we were wrong.The easiest correction would be to have the MEL address and corrected earlier; after that I would recommend when there is a question of fuel load that both sides of the aircraft be measured using the stick method.


Synopsis: B737 flight crew was dispatched with several MELs regarding fuel system. During flight crew received several fuel warning lights and the right engine rolled back. Crew diverted; landed safely; and learned their right wing fuel tank was empty.