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Probable electronic spike when electrical power was transferring from the APU to the generator, gave momentary erroneous heading information. Flight crew noticed discrepancy and used the other FMS for navigation.
| Attributes | |
| ACN | 323229 |
| Time | |
| Date | 199512 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : bhb |
| State Reference | ME |
| Altitude | msl bound lower : 3000 msl bound upper : 3000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : bgr |
| Operator | common carrier : air carrier |
| Make Model Name | Challenger CL601 |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | Other Other |
| Flight Phase | climbout : initial climbout : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : commercial pilot : cfi pilot : atp pilot : instrument |
| Experience | flight time last 90 days : 90 flight time total : 13000 flight time type : 700 |
| ASRS Report | 323229 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : commercial pilot : instrument |
| Experience | flight time last 90 days : 75 flight time total : 7500 flight time type : 125 |
| ASRS Report | 323232 |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : clearance other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
We were released for departure off of runway 04 at bhb and cleared direct alb. Captain was navigating off of left side FMS which showed an erroneous easterly heading which we turned to and proceeded on that heading for approximately 2-3 mi before realizing and turning back onto course. After turning on course direct to alb we navigated off of the right side FMS while the left FMS finally depicted correct course information. Callback conversation with reporter revealed the following information: aircraft type was challenger 601-3A. There are 2 FMS on the aircraft and usually the heading information can be transferred between the two, ie, the first officer setting the heading and transferring to the captain side. In this case, the heading information was in error and the reporter can only attribute it to an electronic glitch, possibly due to the APU being shut down just prior to the erroneous information. When the APU was shut down the power source transferred on the captain FMS, and it is assumed that an electronic 'spike' caused the anomaly. The error was noticed, and navigation was continued using the right side FMS. Shortly thereafter, the #1 was again accurate.
Original NASA ASRS Text
Title: PROBABLE ELECTRONIC SPIKE WHEN ELECTRICAL PWR WAS TRANSFERRING FROM THE APU TO THE GENERATOR, GAVE MOMENTARY ERRONEOUS HEADING INFO. FLC NOTICED DISCREPANCY AND USED THE OTHER FMS FOR NAV.
Narrative: WE WERE RELEASED FOR DEP OFF OF RWY 04 AT BHB AND CLRED DIRECT ALB. CAPT WAS NAVING OFF OF L SIDE FMS WHICH SHOWED AN ERRONEOUS EASTERLY HEADING WHICH WE TURNED TO AND PROCEEDED ON THAT HEADING FOR APPROX 2-3 MI BEFORE REALIZING AND TURNING BACK ONTO COURSE. AFTER TURNING ON COURSE DIRECT TO ALB WE NAVIGATED OFF OF THE R SIDE FMS WHILE THE L FMS FINALLY DEPICTED CORRECT COURSE INFO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ACFT TYPE WAS CHALLENGER 601-3A. THERE ARE 2 FMS ON THE ACFT AND USUALLY THE HEADING INFO CAN BE TRANSFERRED BTWN THE TWO, IE, THE FO SETTING THE HEADING AND TRANSFERRING TO THE CAPT SIDE. IN THIS CASE, THE HEADING INFO WAS IN ERROR AND THE RPTR CAN ONLY ATTRIBUTE IT TO AN ELECTRONIC GLITCH, POSSIBLY DUE TO THE APU BEING SHUT DOWN JUST PRIOR TO THE ERRONEOUS INFO. WHEN THE APU WAS SHUT DOWN THE PWR SOURCE TRANSFERRED ON THE CAPT FMS, AND IT IS ASSUMED THAT AN ELECTRONIC 'SPIKE' CAUSED THE ANOMALY. THE ERROR WAS NOTICED, AND NAV WAS CONTINUED USING THE R SIDE FMS. SHORTLY THEREAFTER, THE #1 WAS AGAIN ACCURATE.
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.