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Flight crew of a fokker 100 FK10 cut short their flight plan route over the VOR during a course turn caused by the aircraft FMS program leading the course turn. Captain notified the manufacturer prior to this incident and was given a reply that the system was FAA certified the way it was designed.
| Attributes | |
| ACN | 383944 |
| Time | |
| Date | 199710 |
| Day | Tue |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : psb |
| State Reference | PA |
| Altitude | msl bound lower : 18000 msl bound upper : 18000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zny |
| Operator | common carrier : air carrier |
| Make Model Name | Fokker 100 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | other other : other pilot : commercial pilot : atp pilot : flight engineer pilot : instrument |
| Experience | flight time last 90 days : 150 flight time total : 14500 flight time type : 4500 |
| ASRS Report | 383944 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | non adherence : clearance other anomaly other other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
Flying filed route syr to dca. A large bend occurred at psb to change course from sws to ese. ZNY made a comment about missing the VOR. I watched it pass off to the right by 3-5 mi. I have seen this happen before on other rtes. The FMS is programmed to take many parameters into consideration to stay centerline on the airways during course changes. Sometimes it leads the turn and leaves the 4 NM width of the airway. I presented this problem to my flight manager about 6 yrs ago. He forwarded the data to fokker aircraft. Their response was that the navigation system is FAA certified and that is acceptable. Most all drifting during FMS navigation has dissipated and ATC never asks to correct heading to rejoin the airway as with vors. This one area of leading turns needs to be addressed so ATC and FMS operators are in common agreement on turns.
Original NASA ASRS Text
Title: FLC OF A FOKKER 100 FK10 CUT SHORT THEIR FLT PLAN RTE OVER THE VOR DURING A COURSE TURN CAUSED BY THE ACFT FMS PROGRAM LEADING THE COURSE TURN. CAPT NOTIFIED THE MANUFACTURER PRIOR TO THIS INCIDENT AND WAS GIVEN A REPLY THAT THE SYS WAS FAA CERTIFIED THE WAY IT WAS DESIGNED.
Narrative: FLYING FILED RTE SYR TO DCA. A LARGE BEND OCCURRED AT PSB TO CHANGE COURSE FROM SWS TO ESE. ZNY MADE A COMMENT ABOUT MISSING THE VOR. I WATCHED IT PASS OFF TO THE R BY 3-5 MI. I HAVE SEEN THIS HAPPEN BEFORE ON OTHER RTES. THE FMS IS PROGRAMMED TO TAKE MANY PARAMETERS INTO CONSIDERATION TO STAY CTRLINE ON THE AIRWAYS DURING COURSE CHANGES. SOMETIMES IT LEADS THE TURN AND LEAVES THE 4 NM WIDTH OF THE AIRWAY. I PRESENTED THIS PROB TO MY FLT MGR ABOUT 6 YRS AGO. HE FORWARDED THE DATA TO FOKKER ACFT. THEIR RESPONSE WAS THAT THE NAV SYS IS FAA CERTIFIED AND THAT IS ACCEPTABLE. MOST ALL DRIFTING DURING FMS NAV HAS DISSIPATED AND ATC NEVER ASKS TO CORRECT HDG TO REJOIN THE AIRWAY AS WITH VORS. THIS ONE AREA OF LEADING TURNS NEEDS TO BE ADDRESSED SO ATC AND FMS OPERATORS ARE IN COMMON AGREEMENT ON TURNS.
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.