Typically, “divergence” is calculated for 5 parameters: • Core Speed • Fuel Flow • Nacelle Temperature • DEGT • EGTHDM
“Divergence” can be trended for other engine parameters, as specified
Alerts can be defined based on “divergence” trends
EFFECTIVITY
ALL DIVERGENCE GE PROPRIETARY INFORMATION
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DIAGNOSTICS TRAINING MANUAL THE POWER OF FLIGHT
Divergence (cont)
Divergence is very useful for finding slight movement in parameters that have excess noise in ambient condition data. • Post water wash DEGT and Fuel Flow • Nacelle temperature [Ambient conditions cause significant variation in Nacelle Temperature. This variation can not be reliably modeled. But the Divergence functionality removes variation due to ambient conditions. Thus, more effective alerting can be set up.]
Divergence is used to help confirm potential trend shifts.
Divergence trends are independent of standard monitoring trends from engine “deviation” models (i.e. “divergence” parameters calculated from aircraft average-measurements, instead of from “cruise reference baselines” or from “takeoff EGT-redline limit”)
Note: • Divergence trends for engines on a twin-engine aircraft are mirror images of each other. • Divergence trends can indicate a shift, but other data must be reviewed to determine which engine drove the shift.
ALL DIVERGENCE GE PROPRIETARY INFORMATION
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DIAGNOSTICS TRAINING MANUAL THE POWER OF FLIGHT
Nacelle Temp Divergence Nacelle Temperature (ZTNAC) has stayed in a normal range. There is enough scatter that a real change can not be detected
Nacelle Temperature Divergence (ZTNAC_D) tells a different story. The relationship between this engine and the others has changed.
