History of Flight
On 21 February 2008, at 0215 UTC (0745 local time), Expo Aviation flight EXV 711, a Fokker F27 registration 4R-MRA, departed Colombo Airport Ratmalana on a scheduled domestic passenger flight to Jaffna. After becoming airborne, at an altitude of 200 feet on takeoff, the fire warning bell and light illuminated. The first officer took immediate action and subsequently silenced them after realizing the problem. Following the pilot-in-command's instructions, the first officer performed the fire drill in accordance with the emergency checklist. The aircraft returned and landed safely approximately 15 minutes after takeoff with the left engine feathered.
Injuries to Persons
No injuries were sustained by the four crew members, 38 passengers, or one other person on board.
Damage to Aircraft
The accessory gearbox (AGB) drive shaft sustained damage including bending, discoloration, and shearing at the coupling flange. The cover of the coupling shaft universal joint was sheared. The combustion chamber No. 1 had the expansion chamber and outer air casing flange damaged with dents and cracks. The AGB drive coupling at the engine end was completely broken. Other damaged components included the coupling shaft cover air seal, the driven AGB drive gear wheel (teeth damaged), the cover assembly at the gearbox end (completely damaged), one engine mount strut (dent), LH inboard engine cowling (burnt hole), LH top two reinforce frames (damaged), bracket cable guide gearbox drip tray (damaged), gearbox drip tray (damaged hole), and the fire sense element (discolored and broken).
Personnel Information
The pilot-in-command was Captain S. Boentoro, a 41-year-old male holding a valid Airline Transport Pilot License issued by the DGAC Indonesia and validated by the DGCA Sri Lanka. He had 9,725 total flying hours, including 6,184 hours on type. The first officer was Mr. K.I. Sarathchandra, holding a valid Commercial Pilot License issued by the DGCA Sri Lanka, with 364 total flying hours, including 68 hours on type.
Analysis
The aircraft was in satisfactory condition after pre-flight checks. During climb at 200 feet, the No. 1 engine fire warning activated. On-ground inspection revealed that the AGB drive shaft of No. 1 engine had come out from the bearings of the universal joint assembly at the engine end. Consequently, the shaft rotated without coupling, striking combustion can No. 1 and causing impact damage to the outer casing and expansion chamber. The flame tubes of the combustion chambers did not suffer impact damage. There was no evidence to indicate that fire emanated from the damaged combustion can. The fire warning was attributed to hot cooling air exiting from combustion chamber No. 1 and being sensed by the fire warning system.
Conclusion
The investigation concluded that the AGB drive shaft had failed from its universal joint assembly. The shaft had been recently installed and had operated only two flights (4.58 hours) since overhaul. The strip report of the overhaul was unsatisfactory, showing considerable deviations from the Dowty Rotol Overhaul Manual No. 83-10-9 for gear box drive. Essential parts such as oil seal rings were found missing.
Probable Cause
The probable cause of this incident is the failure of the AGB drive shaft due to unsatisfactory overhaul of the AGB drive shaft.