B737 flight crew reported flap malfunction resulted in priority handling to a safe landing.
Synopsis
B737 flight crew reported flap malfunction resulted in priority handling to a safe landing.
Narrative
During cruise flight; but within approximately 20 minutes of Top Of Descent; left flap needle on flap position indicator gauge started bouncing intermittently between the 12 O' clock and 6 O' clock position without any noticeable yaw or LE FLAP TRANSIT OR LE FLAPS EXT LIGHTS . The AFT OVERHEAD PANEL flap extension indication lights also remained extinguished. Captain (pilot monitoring (PM)) and First Officer (FO) (pilot flying (PF)) discussed this situation and initially assumed it was a faulty gauge; but both gave the flap malfunction section of the QRH a quick review before and during initial descent into ZZZ. Electronic Logbook entry was sent to Maintenance; and a note to ZZZ station ops was sent requesting to have Maintenance meet us on arrival.Normal briefs were conducted and Descent Checklist was completed prior to top of descent.After switching to ZZZ Final Approach Controller; crew was cleared to ZZZZZ for the ILS XXL approach.Over ZZZZZ at 8000 ft.; PF called for FLAPS 1 and PM moved the flap handle to FLAPS 1 position; but both flap position indicators displayed FLAPS 0 without any LE FLAP TRANSIT light illumination. The flaps were stuck at 0.Captain (PM) [requested priority handling] with ATC; had FO (PF) continue flying; and told FO to handle the comms while Captain found; and started running the FLAPS- TRAILING EDGE FLAP DISAGREE checklist. FO worked with ATC to fly to and hold south of ZZZ1 VOR. Captain noted that Fuel On Board was 6200# and; knowing that running flap malfunction checklists can be complex; decided to get started with finding the correct checklist prior to FO entering the ATC assigned holding pattern. Captain was reading QRH checklist titles and unaware that FO was struggling to properly enter the assigned holding pattern into the FMC; and only discovered it after hearing a TCAS TA and the Approach Controller called to tell us to get back into our holding pattern (There was NO TCAS Resolution Advisory). Captain took a look at the holding pattern depicted on the Navigation Display (ND); saw that FO was reloading a correct pattern into FMC; then FO returned aircraft to holding fix and continued flying the aircraft in the holding pattern.The TE FLAP DISAGREE checklist was completed which directed us to the ALTERNATE FLAP EXTENSION checklist. This checklist was completed while we were in the holding pattern and prior to heading back to ZZZ for landing.Flight attendants were briefed (no prep for evacuation was ordered); and passengers were informed about our flap malfunction prior to final approach.Captain elected to fly the approach and landing. FO requested Tower to roll the firefighting trucks for our landing.Uneventful FLAPS 15 landing; and taxi to the gate with firefighting equipment in trail. At the gate; Fire fighters reported that our brakes were warm; but no fire threat existed. Passengers deplaned normally; and crew debriefed Maintenance Technician at the gate.
Second reporter narrative
Inbound to ZZZ; while vectoring around cells near ZZZ2; The Captain identified the left flap gauge needle flickering up and down; then back to the up position.We discussed the threat and concluded the flaps were in the up position. Captain sent and ACARS maintenance report.I briefed the ZZZZZ2 2 arrival Runway XXL transition. We discussed our plans if the flaps did not extend for the ILS XXL.We vectored around more weather cells until ZZZZZ1 intersection and then were cleared to descend via the ZZZZZ2 2 and intercept the XXL localizer. At ZZZZZ intersection inbound; 8000 ft. Speed 210; the flaps did not extend. The Captain [requested priority handling] with the Approach Controller and we were cleared to hold south of the ZZZ1 VOR on the 180 radial. I was the pilot flying (PF) and radio while the Captain ran through the Trailing Edge Flap Disagree non normal checklist. For this particular flap malfunction we selected step 5; alternate flap extension to flaps 15. When we were ready for the approach; Approach cleared us direct to ZZZZZ3 intersection 5000 ft. until established cleared ILS XXL. The Captain transitioned to pilot flying for the approach and landing. He asked me to verify the Landing checklist again from the non normal checklist. We requested fire trucks to stand by and were cleared to land. Vref was 152 and v target was 157. We landed and were cleared to the gate. The approach speed was standard range so we continued to taxi to the gate. The Captain asked the fire crew to check the brake temperature when we parked at the gate.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.