What happened
On 24 November 2018, a Pakistan International Airlines Corporation (PIAC) ATR 72-212A, registration AP-BKW, was undergoing engine performance ground run-up checks at Jinnah International Airport (JIAP), Karachi. The aircraft had recently undergone a Check-A maintenance inspection and engine replacements.
During the testing of the engines at maximum reverse thrust, the aircraft initially rolled backward approximately 10 feet. Due to an incorrect selection of engine controls by the ground crew, the power levers were moved to flight idle instead of ground idle or fuel shut-off. This generated sufficient thrust to propel the aircraft forward.
The aircraft traveled approximately 450 feet, striking two parked Shaheen Air International (SAI) aircraft. The first collision involved a B737-400 (AP-BJT), where the PIAC aircraft's left wing tip made contact with the fuselage. The movement continued until the PIAC aircraft struck the nose radome of a second B737-400 (AP-BJU), at which point the No. 1 engine propeller became embedded in the parked aircraft's fuselage. One senior technician sustained a minor leg injury during the sudden stop.
The investigation
The Safety Investigation Board (SIB) Pakistan examined the maintenance history and mechanical state of the aircraft. The investigation established that the aircraft had been grounded for 84 days prior to the event, during which time various components, including brake assemblies, had been removed to service other aircraft in the fleet.
Investigators reviewed flight data recorder (FDR) information, which showed hydraulic brake pressure was between 39-45 psi, significantly below the required 3000 psi. The investigation also examined the equipment used for the run-up, noting that the wheel chocks utilized were non-standard, smaller than recommended by the OEM, and intended for ground power units rather than aircraft stabilization.
Findings
- Inadequate brake maintenance: The high-pressure hydraulic lines for the brakes had not been properly bled or purged after the installation of new brake assemblies, leaving air in the system and rendering both normal and emergency brakes ineffective.
- Improper equipment: PIAC failed to procure OEM-recommended wheel chocks, instead using undersized, non-standard chocks that were only placed in front of the wheels rather than both sides.
- Human error: The ground operator, reacting to the initial backward movement, incorrectly selected flight idle power, providing the thrust necessary for the forward collision.
- Maintenance deficiencies: The investigation identified significant deficiencies in maintenance practices, documentation, and the availability of required support equipment.
Safety action
- PIAC is required to ensure strict compliance with OEM requirements for high-performance ground run-ups.
- The airline must immediately procure the correct OEM-recommended wheel chocks for its ATR fleet.
- PIAC must revise its authorization process for engineers, incorporating practical aircraft evaluations rather than relying solely on theoretical tests.
- The Civil Aviation Authority (PCAA) was requested to audit PIAC's maintenance practices regarding support equipment and personnel competence.