EC135
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Company Policy; Aircraft; Procedure
On startup of our EMS helicopter I noticed 'Batt Cal Due 0 Days' message on our ESI-200 Standby Attitude Instrument. I had reviewed all of our Company's maintenance tracking documents as I assumed the shift and there was no mention of a calibration inspection required for the standby attitude indicator. We did not have an AMT on duty at the base. Thinking this was one of the myriad of nuisance indications common to this Airbus product I elected to continue the flight. Landing at a sister base for fuel I asked their mechanic what that message meant. He was initially dismissive; but called the only other base in the company that has this attitude gyro installed and was told by that AMT that this message meant there was a calibration inspection required and that we had likely overflown the inspection.As I wait for the AMT to complete the inspection I have been reviewing what information is available to the pilot concerning this system. The only mention of this equipment is an out-of-focus; difficult to read reproduction of the face of the instrument in the STC included in the RFM. There is no other mention of this system in the RFM. The Maintenance Tracking Documentation software that the pilots are required to review; print; and carry with them in the aircraft does not mention this inspection requirement. An Internet search for 'ESI-200 Standby Attitude Indicator' leads you to the manufacturer's website; but there is no information available for this system on that website; the -200 apparently has been superseded by the -500. The -500 has a similar indication - 'CAL DUE' and it says 'the accuracy of the battery capacity meter may be degraded and require a calibration discharge cycle. The battery charging and discharging continues to work; but the battery capacity is unknown. A battery calibration is required to remove this indicator from the screen. Contact an Avionics System authorized dealer.' This statement is not particularly helpful; but to take the most conservative approach I've called the aircraft 'not airworthy' until someone can prove differently or complete the required calibration.
Eurocopter EC-135 Captain reported over flying a required inspection of the standby attitude. He also stated that the guidelines regarding the inspection requirement were not clear.