What happened
On 8 August 2017, a flydubai Boeing 737-80 and registration A6-FDS was operating a scheduled passenger service from Dubai International Airport to Bahrain International Airport. The flight carried 35 people, including 29 passengers and six crew members.
Shortly after departing from runway 12R, the aircraft began its climb. Once the landing gear was retracted and the aircraft reached approximately 250 feet radio altitude, the crew observed a pressure loss in Hydraulic System A. The flight crew notified Air Traffic Control of the hydraulic issue and requested to enter a holding pattern at the GINLA waypoint to troubleshoot the system. After performing the necessary non-normal checklists, the crew decided to return to Dubai. The aircraft landed safely on runway 12L and taxied to its parking stand without further incident.
The investigation
The GCAA AAIS investigation focused on the sequence of events leading to the hydraulic pressure loss. Investigators examined the aircraft's maintenance records, the damaged tire, and the landing gear retraction mechanism. The investigation specifically looked into the condition of the left main landing gear and the integrity of the hydraulic lines located within the wheel well.
Findings
Investigators determined that the primary cause of the incident was the rotation of a damaged portion of the number 1 tire tread inside the left main wheel well. This rotating debris struck and damaged various components and lines associated with Hydraulic System A, leading to the pressure loss.
Several contributing factors were identified:
- The left alternate antiskid valve operated intermittently, which likely allowed the two wheels of the left main landing gear to remain spinning as they entered the wheel well.
- A portion of the center tire tread rib on the number 1 wheel peeled away while rotating. This debris failed to trigger the frangible fitting, which allowed the gear retraction process to continue and permitted the tire fragment to strike the hydraulic lines.