Incident Details
On Tuesday, 10 December 2019, at approximately 0436Z, a Boeing 737-400 aircraft with registration ZS-DMI departed O.R. Tambo International Aerodrome (FAOR) on a scheduled domestic flight to Port Elizabeth Aerodrome (FAPE). The aircraft was operated by FlySafair under Part 121 of the Civil Aviation Regulations. On board were 6 crew members and 166 passengers. The first officer was the pilot flying, and the pilot-in-command was the pilot monitoring.
During the climb, at about 0448Z, the crew declared an emergency by broadcasting Mayday, initially reporting fire in the cockpit, but two seconds later the pilot-in-command clarified it was smoke, not fire. The smoke was emanating from behind the instrument panel on the left side. The crew referred to the Quick Reference Handbook (QRH) for fire, smoke, and fumes. They requested an air turn back to FAOR, which was approved by the radar controller. The aircraft was cleared to turn right and descend to flight level 110 with no speed restrictions. The pilot-in-command donned smoke goggles and an oxygen mask; the first officer also confirmed wearing his oxygen mask. The pilot-in-command informed passengers via the public address system that the aircraft was returning due to a technical difficulty. The smoke had subsided by that time.
The aircraft landed safely on Runway 03L at FAOR and taxied to the parking bay, where passengers disembarked normally. No injuries were reported.
Investigation Findings
The investigation revealed that during the climb phase, the water drain pipe connected to the overhead cockpit drip pan became dislodged. This allowed water to drip onto the aircraft’s instrumentation panel, causing smoke in the cockpit. Damage to the aircraft was limited to the dislodged tubing; no evidence of damage was observed to the instrumentation or avionics.
Probable Cause
The probable cause of this serious incident was the dislodgement of the water drain pipe connected to the overhead cockpit drip pan, which allowed water to drip onto the aircraft’s instrumentation panel, causing smoke in the cockpit.