B737-800 flight crew reported severe weather on approach leading to a flap overspeed and unstabilized approach.
Synopsis
B737-800 flight crew reported severe weather on approach leading to a flap overspeed and unstabilized approach.
Narrative
First Officer was pilot flying. There was a thunderstorm on final for Runway XX at ZZZ. We were cleared to cross ZZZZZ at 3000 feet; cleared for the ILS XX. At ZZZZZ; the First Officer lost his Autopilot and Flight Director in IMC conditions; heavy rain; and fluctuating winds. I still had my Flight Director so I took over the flight controls and started to descend to catch the glide slope as we were high. I called for flaps 15 after extending the landing gear. It was at this time that the flaps were oversped due to fluctuating wind speed. After coming into visual contact with the runway; we realized we were high and the approach could not be salvaged. It was at this point we decided to initiate a go around. I pressed the TOGA buttons and lost my Flight Director. We were at an altitude of 1500' when we initiated the go around. In the confusion; we got behind cleaning up the aircraft but once we caught up; our Flight Directors reappeared and the Autopilot worked. The First Officer took the controls back and we opted to shoot an RNAV approach to Runway XYL. We successfully landed the aircraft and proceeded normally to the gate where we wrote up the flap overspeed and the anomaly of the disappearing flight directors and Autopilot. We theorized that we may have had a lightning strike seeing there was lightning in the vicinity of the storm we were flying through. We were unable to verify this as the ramp was closed due to lightning when we got off of the aircraft in ZZZ.
Second reporter narrative
I was the First Officer and Pilot Flying on Flight ABCD from ZZZZ to ZZZ. When arriving in the ZZZ terminal area; we encountered storms in the area and ATC was vectoring aircraft around them. We were vectored and cleared onto the ILS Runway XX into ZZZ. The weather radar was showing weather around the final approach course but other aircraft were able to proceed on the ILS and make the runway so we elected to continue. When we were approaching point ZZZZZ at 3000 feet AGL and the aircraft was about to intercept glideslope; I lost all flight director guidance and 'raw data' from LOC and G/S which caused Autopilot 'B' to disengage. We were IMC at the time. I noticed the Captain still had his Flight Director and I passed him the controls; at which point we continued to configure gear and flaps. Throughout this we were experiencing heavy rain; turbulence and possible windshear. We over sped flaps 15 while trying to configure. We did eventually break out of the weather and had visual of the runway but we were high and unstable so we elected to go-around at about 1500 feet AGL. When the Captain pressed the TOGA button; he lost his Flight Director; as well. At this point we were very task saturated and got behind the aircraft on the go-around and clean up. I was eventually able to get my Flight Director back and the Captain passed me the controls. I then climbed to 3000 feet AGL and was able to reengage the Autopilot. We then elected to shoot the RNAV to Runway XYL and landed without further incident and were able to taxi to our gate.Cause: The primary factor to this incident was weather. There were thunderstorms in the area along the final approach course. The Captain and I suspected a possible lightning strike is what caused our automation issues but were unable to do a post-flight inspection due to the ramp being closed for lightning. There were a number of aircraft shooting approaches into ZZZ which is why we elected to continue but it may have been more prudent to hold or divert. Another factor was our task saturation in IMC and turbulence while losing automation and flight guidance. Captain and I were able to execute a go-around and stabilize the aircraft.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.