What happened
On December 23, 2008, a Cessna Citation C525, registration F-HAJD, operated by Star Service International, was performing a commercial air transport operation from Paris-Le Bourget to Cascais Aerodrome. During the landing phase, the crew noted an unusual aerodynamic noise after extending the landing gear.
Upon touchdown on runway 35, the crew attempted to use the primary braking system but found the pedals fully deflected without any corresponding braking effect. An inspection of the cockpit instruments revealed a significant drop in hydraulic pressure. To prevent a runway excursion, the pilot utilized the pneumatic emergency brake, successfully stopping the aircraft within the first two-thirds of the runway. There were no injuries and no damage to the aircraft. Following the stop, a post-flight inspection revealed a hydraulic leak in the left main landing gear and a fractured hinge on the landing gear door link.
The investigation
The GPIAAF investigation focused on the mechanical failure of the landing gear components. The investigation established that the aircraft's maintenance records were up to date and that all flight documentation was valid. The investigators examined the physical state of the landing gear door hinge and the hydraulic lines to determine how the pressure loss occurred.
Findings
- The unusual aerodynamic noise heard during descent was caused by a piece of the landing gear door link vibrating due to airflow.
- The hinge of the landing gear door link had failed, causing the link to split into two separate pieces.
- The portion of the link still attached to the gear leg was subjected to repeated impacts against the hydraulic brake piping due to aerodynamic buffeting.
- These repeated impacts weakened the hydraulic tubing, which eventually ruptured under the internal pressure applied when the pilot engaged the brakes.
- This rupture led to a rapid hydraulic fluid leak, resulting in the loss of the primary braking system's functionality.