What happened
Two distinct incidents involving a Bombardier Learjet 60 occurred during operations from Modlin Airport (EPMO) in April and May 2018.
On April 21, 2018, while flying from Modlin to Zurich (LSZH) at FL400, the aircraft experienced a cabin depressurization. The crew followed standard operating procedures, the aircraft flying manual (AFM), and the operator's operational instructions. The crew decided to abort the flight and return to the departure airport, Modlin, where the aircraft landed safely without exceeding any structural or operational limits. Following the event, maintenance was performed between April 23 and April 28, which included implementing manufacturer recommendations from Bombardier Inc. A successful test flight up to FL450 was completed, and the aircraft subsequently performed four flight segments.
On May 8, 2018, during a flight from Modlin to Geneva (LSGG), a second incident occurred. While descending from FL410, the crew heard a loud bang from the rear of the cabin and observed a rapid increase in differential pressure on the cockpit instruments. The crew immediately donned oxygen masks and followed the Quick Reference Handbook (QRH) procedures for cabin depressurization. The aircraft continued the flight at FL200, with the crew setting the transponder to Squawk 7700 as instructed by Rhein Radar air traffic control. The aircraft landed safely at Geneva.
The investigation
The investigation, conducted by the PKBWL and AMC Aviation, examined the sequence of events and the technical state of the aircraft. The investigation focused on the mechanical failure that led to the loss of pressure in both instances and reviewed the maintenance actions taken following the first event.
Findings
- The primary cause of both depressurization events was a failure of the vacuum line, which resulted in a loss of pressure integrity within the pressurization system.
- The crew's adherence to emergency procedures and oxygen mask usage ensured the safety of the flight during both occurrences.