Narrative:

Aircraft has an FMS (single) with no GPS. Uses VOR/DME to update position. (Ams-850 full keypad, limited database). In this aircraft, as equipped, it is common to have a yellow dead reckoning flag until aircraft is airborne and able to update its position. During the westchester 1 departure (hpn) while flying the 295 degree heading as depicted in the STAR, we were given a right turn direct merit. FMS course needle centered 056 degree course to merit, dead reckoning flag cleared, then reappeared. ATC inquired our heading to merit. We responded 055 degrees. Controller said 'that's nowhere near merit, turn right 110 degrees.' we informed ATC that we were having FMS problems. We were given a 90 degree heading to intercept lga 055 degree radial to merit. The rest of the flight was uneventful.

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Original NASA ASRS Text

Title: A BE40 FO CLAIMED THAT HIS ACFT IS INSUFFICIENTLY EQUIPPED TO NAV PRECISELY WHICH CAUSED A HDG DEV IN N90 AIRSPACE.

Narrative: ACFT HAS AN FMS (SINGLE) WITH NO GPS. USES VOR/DME TO UPDATE POS. (AMS-850 FULL KEYPAD, LIMITED DATABASE). IN THIS ACFT, AS EQUIPPED, IT IS COMMON TO HAVE A YELLOW DEAD RECKONING FLAG UNTIL ACFT IS AIRBORNE AND ABLE TO UPDATE ITS POS. DURING THE WESTCHESTER 1 DEP (HPN) WHILE FLYING THE 295 DEG HDG AS DEPICTED IN THE STAR, WE WERE GIVEN A R TURN DIRECT MERIT. FMS COURSE NEEDLE CTRED 056 DEG COURSE TO MERIT, DEAD RECKONING FLAG CLRED, THEN REAPPEARED. ATC INQUIRED OUR HDG TO MERIT. WE RESPONDED 055 DEGS. CTLR SAID 'THAT'S NOWHERE NEAR MERIT, TURN R 110 DEGS.' WE INFORMED ATC THAT WE WERE HAVING FMS PROBS. WE WERE GIVEN A 90 DEG HDG TO INTERCEPT LGA 055 DEG RADIAL TO MERIT. THE REST OF THE FLT WAS UNEVENTFUL.

Data retrieved from NASA's ASRS site as of July 2007 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.