What happened
On October 23, 2007, a Cessna C152 II, registration CS-DDP, departed from Cascais Municipal Aerodrome (Tires) for a planned instructional flight to Coimbra under Visual Flight Rules (VFR). The crew, consisting of a flight instructor and a student pilot, reached Cabo da Roca before deciding to abort the trip and return to Cascais to perform circuit training.
After completing two successful touch-and-go landings, the crew prepared for a third and final landing on runway 35. At 09:46 UTC, the aircraft touched down on the main gear at approximately 65 knots. As the nose wheel made contact with the runway, the aircraft suddenly veered to the left. The pilot was unable to correct the deviation, causing the aircraft to depart the paved surface at an angle of approximately 35 degrees from the runway centerline. The nose wheel struck the adjacent terrain, causing the aircraft to overturn. The crew escaped the wreckage without injury, but the aircraft sustained significant damage, including a deformed fuselage, damaged horizontal stabilizer, and a twisted nose gear.
The investigation
The GPIAAF investigation focused on the mechanical state of the aircraft and the maintenance history. Investigators examined the wreckage and the tracks left on the runway and adjacent ground. They identified metallic streaks on the runway caused by the nose wheel rim scraping the asphalt.
Crucially, the investigation examined the nose gear assembly and discovered that the bolt securing the two arms of the nose gear torque link was missing. This bolt was not found at the accident site, leading investigators to conclude it likely detached during one of the previous landings. Furthermore, while a 100-hour inspection had been performed eight days prior to the accident, investigators found no evidence of recent lubrication on the torque link bolt seats, despite the maintenance protocol requiring such lubrication.
Findings
- The primary cause of the accident was the loss of directional control of the nose wheel due to the detachment of the torque link arms.
- A contributing factor was the loss of the securing bolt for the torque link arms, which resulted from a failure to properly follow the 100-hour inspection protocol, specifically regarding the lubrication and verification of the bolt's security.
- The aircraft's nose wheel was unable to maintain alignment, causing the sudden left veer and subsequent excursion from the runway.
- Meteorological conditions were ideal for flight and were not a factor in the accident.