Small transport aircraft captain reported experiencing a drastic compass heading deviation allegedly...

Attributes
ACN	1464161
Time
Date	201707
Local Time Of Day	0601-1200
Place
Locale Reference	BGR.Airport
State Reference	ME
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Small Transport
Operating Under FAR Part	Part 91
Flight Phase	Taxi
Flight Plan	IFR
Component
Aircraft Component	Compass (HSI/ETC)
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Ground Event / Encounter Other / Unknown

Narrative:

While on taxiway M; holding short of rwy 15 at bgr; the compass deviation increased to over 60 degrees; apparently due to a high capacity underground power line. We had HSI1 and HSI2 caution messages. The cautions went out when we were cleared to 'line up to wait' on the runway; however the heading was still 089 degrees while lined up on runway 15. As the weather was VFR; we elected to takeoff and continue the flight; navigating via pilotage.recommend the airport authority provide signs to warn crews of potential compass deviations and avoid holding for any length of time on taxiway M. Also; add a comment about this phenomenon in the airfield notes.

Original NASA ASRS Text

Title: Small transport aircraft Captain reported experiencing a drastic compass heading deviation allegedly caused by underground power lines on Taxiway M at BGR.

Narrative: While on Taxiway M; holding short of Rwy 15 at BGR; the compass deviation increased to over 60 degrees; apparently due to a high capacity underground power line. We had HSI1 and HSI2 Caution messages. The Cautions went out when we were cleared to 'line up to wait' on the runway; however the heading was still 089 degrees while lined up on runway 15. As the weather was VFR; we elected to takeoff and continue the flight; navigating via pilotage.Recommend the airport authority provide signs to warn crews of potential compass deviations and avoid holding for any length of time on Taxiway M. Also; add a comment about this phenomenon in the airfield notes.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Small transport aircraft captain reported experiencing a drastic compass heading deviation allegedly caused by underground power lines on taxiway M at bgr.