What happened
On March 22, 2009, a Cessna 500 Citation I, registration I-CLAD, was performing a ferry flight from Bologna to Milan Linate. During the landing on runway 36, the crew heard a noise coming from the nose gear, which was immediately followed by intense vibrations and loud noises from the left engine. A "LH Engine Fire" warning light illuminated in the cockpit.
The crew responded by executing the engine failure and precautionary shutdown procedures, moving the left engine throttle to the "Cut Off" position. This action extinguished the fire warning, and no fire extinguishers were required. Upon parking the aircraft, a physical inspection revealed extensive damage to the left engine's air inlet section and nearly all the fan blades.
The investigation
The ANSV investigation focused on identifying the nature of the debris that caused the damage. An initial inspection at Milan Linate confirmed damage to the air inlet, fan, and visible internal components of the left engine. The engine was subsequently transported to Canada for a detailed teardown, supervised by the TSB Canada.
During the removal of the air intake flex joint, investigators discovered several metal leaves (lamellae) that likely belonged to a feeler gauge. Further microanalysis of metallic fragments found throughout the engine and lubrication circuit, conducted by the Italian Air Force Experimental Flight Center, confirmed that while most debris originated from the engine itself, some low-alloy steel fragments were foreign to the engine and matched the pieces found in the air intake joint.
Findings
- The primary cause of the serious occurrence was the ingestion of foreign object debris (FOD) into the left engine at the moment the nose gear touched runway 36.
- The ingested object was identified with high probability as a feeler gauge, a tool typically used for automotive valve adjustments rather than aircraft maintenance. It is believed the tool was likely lost from an airport service vehicle.
- The existing runway inspection procedures at Milan Linate were insufficient to detect small-sized FOD, especially when such objects are located several meters away from the runway centerline.
Safety action
- The ANSV issued a safety recommendation to ENAC to evaluate and ensure that runway inspection procedures at Italian airports are capable of detecting small foreign objects, even when they are located at a distance from the runway axis.