September 17, 2013
Rolls-Royce (R-R) is modifying Trent 700 oil pressure sensor systems to prevent misleading readings that have led unnecessary engine shutdowns, a U.K. Air Accident Investigations Branch (AAIB) incident report says.
The changes, one to Electronic Engine Controller (EEC) software and one to oil pressure measurement system hardware, would minimize the possibility that excessive engine vibration causes the system to deliver warning messages normally triggered by an oil pump failure.
Trent 700 oil pressure monitoring includes a safety mode that overrides actual pressure readings in certain circumstances, such as when sensors disagree. Designed to protect engine bearings when the oil pump fails, the mode delivers a low oil pressure warning on the flight deck’s Electronic Centralized Aircraft Monitoring (ECAM) system. It also displays the pressure level as zero on the engine’s instrument display.
However, conditions that are not oil pressure-related, such as vibration from a damaged fan or Integrated Drive Generator (IDG), also can trigger the mode, generating false cockpit warnings.