What happened
On July 7, 2018, a Learjet 45XR, registration CS-TFQ, was operating an air taxi flight from Malaga-Costa del Sol Airport to Cascais, Portugal. While cruising at FL320, approximately 11 km east of Seville Airport, the crew observed a "MAIN HYD QTY LO" warning on the EICAS display. As the flight continued, the situation escalated to an amber "MAIN HYD PRESS" caution, accompanied by visible fluctuations in hydraulic pressure on the multi-function display and signs of pump cavitation.
In response to the continuous drop in pressure, the crew declared an emergency and diverted to Seville Airport (LEZL). During the descent at FL170, the crew attempted to extend the landing gear using the normal checklist, but after no success, they transitioned to the emergency gravity extension procedure. To preserve remaining hydraulic fluid for the auxiliary system and conventional brakes, the crew opted to perform the approach without flaps. The aircraft landed safely on runway 2/27; however, while taxiing on taxiway A1, the hydraulic pressure depleted entirely, rendering the normal brakes inoperable and forcing the use of the emergency brakes. The aircraft was subsequently towed to the stand.
The investigation
The CIAIAC investigation focused on the source of the hydraulic fluid loss and the maintenance history of the aircraft. Investigators examined the hydraulic system, the aircraft's maintenance records, and the implementation of manufacturer service bulletins. The investigation confirmed that hydraulic fluid had leaked from the electrical connector of a specific pressure switch. Physical evidence, including fluid stains on the fuselage and spills on the runway, aligned with the identified faulty component.
Findings
- The primary cause of the incident was the loss of fluid from the main hydraulic system due to leaks occurring through the electrical connector of the pressure switch (P/N 7629001004-001).
- A contributing factor was the failure to implement Bombardier Service Bulletin (SB) 45-29-17, which recommended replacing the existing pressure switch with an improved version (P/N 6629101004-001) to prevent such leaks.
- The crew managed the emergency effectively, following all applicable checklists and procedures.
- There were no injuries to the two crew members or three passengers, and the aircraft sustained no damage.
Safety action
- The operator was recommended to enhance organizational procedures for assessing and implementing manufacturer Service Bulletins to minimize risks to airworthiness.