by: Paul D. Faltyn – Commercial Pilot and A&P Mechanic
A common misleading scenario concerning engine instrumentation among piston engine helicopter operators is that you do not repair or calibrate them unless they fail or there accuracy is suspect. All mechanically driven instruments have a ( TBO ) ” time between overhaul “, most manufacturers recommend that there instruments be overhauled between 1500 to 2500 hours in service.
Manifold Pressure and Oil Pressure Indicators:
These very important indicators are basically a pressure sensing element transmitting a reading to the pointer via a mechanical linkage. Most indicators will run in excess of 5000 hours without any indication of degraded accuracy or
I would recommend that the gages at be tested or accuracy at engine overhaul. Most repair stations or FBO’s have ramp test equipment where the calibration can be easily verified.
One of the most neglected part of the indicating system is the pressure lines installed behind the instrument panel. Have your mechanic inspect the lines at the annual inspection. If the lines which are generally rubber hoses are hard or brittle, replace them.