# SDR CA110318002

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: November 15, 2010
- Submitted: September 14, 2015
- Operation: General aviation
- System (JASC): [3461 · Flight Management Computing Software System](https://openairdocs.org/jasc/3461)
- Part: Fms
- Part number: 100601951
- Condition: Defective
- Location: Cockpit
- Stage of operation: UK
- How discovered: O
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/CA110318002

## Discrepancy

(CAN) PROBLEM ORIGINALLY OCCURRED LAST YEAR, HOWEVER WAS ONLY RECENTLY REPORTED TO THE EQUIPMENT MANUFACTURER.  TWO ACFT PH-PXB & PH-PXE AFFECTED.  WHEN FLYING IN REGION WHERE MAGNETIC VARIATION IS CLOSE TO ZERO DEGREES, THERE IS A POSSIBILITY THAT THE FMS CAUSES A 180 DEGREES INVERSION OF THE COMPASS MAP ON THE HSI DISPLAY.  THE FOLLOWING HSI PICTURE TAKEN IN FLIGHT SHOWS THE HELICOPTER FLYING TOWARD 297 DEGREES WHILE THE ACTUAL TRACK & DESIRED TRACK ARE 117 DEGREES.  PROBLEM IS OBSERVABLE ON INSTALLATION USING THE FMS PROVIDED MAGNETIC VARIATION ENCODED IN ARINC 429 LABEL 147.  CMC HAS CONVENED SAFETY REVIEW BOARD & HAS LOGGED FAULT INVESTIGATION WITH INTENT TO PROVIDE CORRECTIVE ACTION.

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