G SERIES PILOT’S GUIDE .
INSIGHT
INSTRUMENT CORPORATION BOX 122, FORT ERIE, ONTARIO, L2A 5M6
31
VIBRATION SPECTRUM
Engine Vibration Screen
Decibels (dB)
RPM
(Fundamental)
Harmonics - Vibration at multiples of RPM
PERIODIC TEMPERATURE
Variation Screen
Periodic Temperature Variation
is a new form of engine analysis. Some valve related engine faults produce a slow periodic
variation in EGT. The oscillation rate is on the order of one cycle every minute or two.
This is just too slow to be identified by casual observation of the temperatures alone.
Yet it is very important to discover this phenomenon because it may eventually lead to a catastrophic engine failure.
It readily appears in a slow sampled spectrum analysis.
A normal indication will be a flat line with a little noise, while a trouble indication will show as an obvious spectral peak.
This analysis should only be performed in cruise at a constent altitude and power setting. Press and hold bottom button to
reset screen. Press and release bottom button to select cylinder (1-6, all) to view.
Variation degrees
Time in minutes
While in-flight with the vibration
sceen showing on G3-4.
Pressing and holding the PG
button will trigger the G3-4 to
save the present vibration
waveform for future reference.
Hold PG button in until G3-4
screen says it is data logging
vibration data.
