Engine trend monitoring: reading EGT margin, N2 and oil before a shop visit

What is tracked

• EGT margin: the gap between the exhaust gas temperature at take-off and the red line, corrected for conditions. It erodes as the engine wears; when it reaches zero the engine must come off wing.
• Rotor speeds (N1, N2): shifts at a given thrust point indicate compressor or turbine changes.
• Fuel flow: rising fuel flow for the same thrust is lost efficiency.
• Oil: pressure, temperature and consumption; a change in consumption is one of the earliest signs of a bearing or seal problem.
• Vibration: the fan and core vibration levels and their trend.

The data comes as take-off and cruise snapshots from the aircraft, processed by the operator's condition monitoring system or the manufacturer's.

Shifts and steps

A slow drift over months is normal wear and sets the shop visit date. A step change on one day is an event — a bird strike, a surge, a sensor fault — and a reason to look. A sudden change in EGT margin or vibration is the classic trigger for an unscheduled borescope inspection.

Why owners and lessors watch it

EGT margin is value. Two engines with the same hours and cycles can be worth very different amounts if one has twice the margin left. Lessors read trend data at mid-lease inspections for exactly this reason, and buyers ask for it at pre-purchase.

How InspectView uses it

A trend that moves is a reason for a borescope inspection; the inspection report then records what the trend was pointing at. Keeping both in the same file for the same ESN is what makes the next decision easy.