What happened
On November 29, 2017, during a routine daily pre-flight inspection at EPLL Łódź, the crew of an EC 135 P2+ identified a warning message on the Centralized Aircraft Display (CAD). The message, indicating a "BLEED AIR" condition, appeared before the engine had been started, suggesting a potential malfunction within the cabin heating system.
Following standard procedures, the pilot notified the Technical Coordination Center (CKT). Per instructions from the center, a ground engine run was performed, which confirmed the malfunction of the cabin heating system. Consequently, the aircraft was immediately removed from flight service.
The investigation
Technical maintenance personnel from the Warsaw-Babice Maintenance Station (SOT) were dispatched to diagnose the fault. Upon inspection, the team identified a failure in the electrically controlled valve responsible for mixing engine compressor air with cabin air. To rectify the issue, the faulty valve was replaced with a new component. Following the replacement, a successful ground test was conducted, confirming the aircraft was airworthy and allowing it to be returned to service.
Findings
- The primary cause of the incident was a malfunction of the electrically controlled mixing valve used to regulate the temperature between engine compressor air and cabin air.
- The issue was detected during a standard pre-flight inspection, preventing an operational flight with a known defect.