On December 10, 2019, a crew of Boeing 737-400 belonging to South African low-cost carrier Safair experienced an incident reminiscent of a Hollywood action movie, as sparks started flying and smoke filled the cockpit.
The final report on the incident was published by the South African Civil Aviation Authority (SACAA) on September 9, 2020.
According to the report, the aircraft took off from O.R. Tambo International Aerodrome (JNB) at 4:36 local time. Sometime after the takeoff, a drain tube, located on the left of the cockpit, above the pilot-in-command head, started leaking.
At 4.48, the first drops fell on the instrument panel. The equipment became lit up with arcing electricity and smoke started filling up the cabin. The pilot-in-command broadcasted a Mayday and stated that they had a fire.
Seconds later, he corrected himself: it was just smoke, not fire. The crew followed emergency procedures, fitting smoke goggles and oxygen masks, and requested a turn back to JNB. The request was granted, and the aircraft landed safely, 32 minutes after the takeoff.
The investigation revealed that the drain tube at fault dislodged itself from the fitting. The aircraft in question was continuously operated since 1989, and it is likely that the tube was never changed. Being constantly exposed to the light, the plastic lost its flexibility and became brittle, which led to the dislocation.
Although the dislodged tube was visible, it was slightly out of the pilot’s peripheral vision, and was not noticed. Small amount of water accumulated in the upper cockpit drip pan and was therefore drained into the cockpit instead of through the external drain valve via the tube.
An immediate special inspection of all Boeing 737s was issued by the operator, with an emphasis on the security of the tubing leading from the drip pan.