B737-800 flight crew reported diverting to an alternate airport after experiencing leading edge flap issues.
Synopsis
B737-800 flight crew reported diverting to an alternate airport after experiencing leading edge flap issues.
Narrative
Bad weather at ZZZ. Completing the landing was in question due to heavy rain on the field. Turning final extended flaps to 1; 2; 5. At flaps 5 amber bands on airspeed converged at flaps 2 green bug flying airspeed on both pilot's airspeed indicators. Momentarily got 'Airspeed Low' Aural alert. This caused confusion as LE FLAPS TRANSIT was the actual problem; but we did not recognize it and thought there was a standalone airspeed malfunction. Performed AIRSPEED UNRELIABLE QRC action items and executed go-around out on final approach (10 miles) and cleaned up flaps. Airspeed returned to normal. Diverted to ZZZ1 as a ZZZ landing in approaching heavy rain was not desirable with malfunction. Extremely busy in divert with briefing Flight Attendants; Dispatch; Passengers; ATC. and deviating around weather. Two separate ATC Controllers requested same details on emergency status FOB etc.; and Dispatch requested we divert to ZZZ2. Fifteen minutes after initial problem and very busy with flying; diverting; etc.; we still weren't sure of what our problem was. I read through AIRSPEED UNRELIABLE QRH Checklist items after transferring aircraft control to the First Officer. We discussed it and decided it was not applicable now as airspeed was normal with flaps up. Decided to go hold and reattempt flap setting to analyze airspeed and flaps. In holding; after lowering flaps we got the same indications and it was then that we observed the LE FLAPS TRANSIT amber light on the forward panel with no green light (all green LE indicator lights on overhead panel) with flaps at 1. Thereafter was able to run the proper QRH and performance data associated non-normal procedures and land flaps 15 at ZZZ1; which was VMC conditions and dry runway. Fuel was about 6000 pounds on landing after the delay with the holding pattern. Had we gone to ZZZ2; we would have been lower fuel state with some weather en route. We were so busy in the flight deck with non-normal checklists; setup for divert etc. decided to stay with nearest suitable field (ZZZ1); which was our precoordinated alternate prior to our ZZZ arrival and the initial occurrence of the malfunction. Uneventful flaps 15 landing was accomplished and 30 minute holdout for a gate due to brake cooling.Monitor the flaps indications better at each separate extension setting. We regularly by standard operating procedures perform the Before Landing Checklist after final configuration and we acknowledge flaps 'green light'; but we may not always notice the leading edge green light(s) at each extension point where it should be illuminated.
Second reporter narrative
Weather: storms on/around ZZZ during ILS approach with a 7-knot tailwind and RA showers on the field. Turning to final we extended the flaps to 5 and began to slow towards approach speed and initiated a descent to 2500 ft. per ATC instructions for the ILS. The minimum maneuver speed did not decrease as expected while configuring to land. The max maneuvering speed and minimum maneuvering speeds came within 5 knots of touching quickly followed by 'Airspeed Low' when slowing towards the flaps 5 maneuver speed. (I saw the LE FLAPS TRANSIT amber light in my peripheral vision; but it did not register until later due to the concern for the 'Airspeed Low' alert.) The pilot flying (PF) initiated a stall recovery and go-around; asked that I turn off the Flight Directors; and make inputs into the Mode Control Panel (MCP) to comply with ATC instructions. I advised Tower that we needed to stay VMC and requested vectors to the east to remain clear of the storms so we could determine the malfunction. Tower coordinated with Departure for us to turn towards the northeast (towards storms) and climb to 4000 ft. MSL (into IMC) and to contact Departure. I contacted Departure and requested to return to 3000 ft. and to turn east to remain VMC and mitigate increasing workload by flying in the storm clouds. Upon consulting with the Captain I [requested priority handling]. Departure acknowledged our [request]; allowed us to remain VMC at 3000 ft. MSL; and turn towards the east to remain clear of storms. We were then handed off to Center. I asked the Captain if I could fly while he coordinated with the Flight Attendants; the Passengers; and Dispatch. I contacted Center and requested to hold so we could determine the malfunction. The Captain said we would divert to ZZZ1 since it was VMC and was added as an alternate by Dispatch via ACARS while on the STAR. I advised Center we would eventually divert to ZZZ1 after holding. Center cleared us direct ZZZ1 and asked if we wanted a higher altitude. I responded 'yes'; and we climbed to 10;000 ft. MSL. En route to ZZZ1; Center cleared us to the Arrival to ZZZ1. I advised Center we needed to hold. Center cleared us to hold as published. I programmed the FMC to hold. During the climb; we discussed the Airspeed Unreliable QRC/QRH items. We determined that all three sets of instruments were in agreement. ATC also provided us with our ground speed; which matched our instruments. We determined the Airspeed Unreliable Checklist was not applicable to our situation. Enroute the Captain let me know that he finished coordinating with the Flight Attendants and Passengers. Center relayed that Dispatch requested that we divert to ZZZ2. The Captain relayed that ZZZ1 was the nearest suitable airport and we were diverting there due to fuel concerns; the longer runway at ZZZ1; and unknown weather at ZZZ2. Approaching holding; we changed PF duties (the Captain flew); noted our airspeed; and began to extend flaps as if we were landing in order to determine the malfunction. The same sequence of events occurred as on final to ZZZ; minus the airspeed low. The Captain accelerated and we started to retract the flaps. I saw the LE FLAPS TRANSIT Amber light this time with flaps 1.The Captain called for the LE FLAPS TRANSIT QRH. We completed this QRH; computed non-normal performance data and brake cooling; briefed the approach and actions and after landing; and requested vectors to final for the ILS at ZZZ1. At some point; Center asked if we were still a [priority] aircraft. We responded in the affirmative and passed all requested information. Center passed us to ZZZ1 Approach. Approach Control asked for the souls on board; fuel on board; and any other requirements. We requested [assistance] due to potential hot brakes. The Captain flew an uneventful approach and landing; braking manually upon touchdown. After landing we coordinated with ATC and Crash Fire Rescue (CFR) for remote parking. I re-ran brake cooling based on manual braking and the brakes on speed I noted during touchdown. The inputs returned a required 30 minutes of cooling prior to approaching the gate and an additional one hour before departure. Although not required by the Brake Cooling module we coordinated for CFR to measure the brake temperature; chock the nose wheel and right wheel set; release the parking brake; and cool the brakes with fans once the engines were shut down; since they offered; while we waited for the expiration of the brake cooling time. The highest brake temperature recorded was 340 degrees Fahrenheit on the right brakes.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.