What happened
On August 26, 2009, a Beech 4000, registration N-413HB, was parked at the Líder Signature S/A apron at Congonhas Airport (SBSP) in São Paulo. The crew, consisting of two pilots and a mechanic, was preparing for a ferry flight to Rio de Janeiro.
Prior to starting the Auxiliary Power Unit (APU), the mechanic on board removed the aircraft's chocks and placed them beside the wheels. Once the crew was seated and the doors were closed, the APU was activated. Shortly after startup, a "park brake low pressure" warning appeared on the flight deck, indicating insufficient hydraulic pressure in the parking brake circuit. Despite the crew activating the auxiliary hydraulic pump, the pressure remained low.
Due to a slight gradient in the apron leading toward a hangar, the aircraft began an uncontrolled movement. An ground mechanic attempted to stop the motion by placing a single chock under a wheel, but the Beech 4000 bypassed the obstacle and collided with three parked aircraft: a Learjet 45 (PR-ONE), a King Air C-90 (PR-SJE), and a Hawker 800 (PT-WVG). The aircraft finally came to a stop after the third impact. All occupants of the N-413HB were unharmed.
The investigation
CENIPA's investigation focused on the sequence of events leading to the loss of ground control. Investigators examined the aircraft's hydraulic systems, the apron's topography, and the coordination between the flight crew and the ground support personnel. The investigation established that the aircraft was within weight and balance limits and that the pilots held valid licenses and medical certificates. The investigation also reviewed the procedures for chock removal and the communication between the foreign crew and the local ground support company.
Findings
- Improper chock removal: The mechanic on board removed the chocks before the APU and engines were started, which was contrary to standard procedure.
- Lack of coordination: There was a failure in coordination and potential communication barriers between the foreign crew and the local ground support personnel regarding who was responsible for removing the chocks.
- Mechanical failure: The parking brake system experienced a loss of hydraulic pressure that could not be rectified by the auxiliary pump.
- Environmental factors: The slight downward slope of the apron contributed to the uncontrolled movement once the brakes failed.
- Inadequate ground intervention: The attempt by a ground mechanic to stop the aircraft with a single chock was insufficient to halt the momentum of the moving aircraft.