What happened
On July 24, 2006, a Boeing 737-700, registration PH-XRE, was parked at Stand 3 of Pisa Airport during baggage unloading operations. While approaching the aircraft's forward cargo hold, a motorized baggage belt operated by the airport management company (SAT) lost control and struck the lower cowling of the aircraft's right engine. There were no injuries to the flight crew or the ground personnel, but the impact caused damage to the engine cowling.
The investigation
The ANSV investigation focused on the mechanical failure of the baggage belt's steering and braking systems. The operator reported that both the steering and the brakes became extremely stiff and unresponsive, preventing the driver from avoiding the collision despite applying the handbrake.
Technical examinations revealed that the vehicle's battery was nearly depleted. While the battery indicator showed a sufficient charge (two green lights) upon startup, the voltage dropped significantly once the drive motor was engaged. This drop in voltage caused the hydraulic pump, which powers the power steering and power braking systems, to lose functionality. The investigation found that the battery indicator provided a misleading reading because it measured voltage under no-load conditions rather than the actual state of charge during operation.