 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Flight crew of MD83 encounter heading anomalies between the navigation displays and the repeater RMI's. Ultimately discover the true-navigation switch had been activated, thus displaying true heading on the navigation displays.
| Attributes | |
| ACN | 638733 |
| Time | |
| Date | 200411 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : pdx.airport |
| State Reference | OR |
| Altitude | msl single value : 3000 |
| Environment | |
| Weather Elements | Rain |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : p80.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | MD-83 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 10r |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| ASRS Report | 638714 |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : clearance other anomaly other other spatial deviation |
| Independent Detector | other flight crewa other flight crewb |
| Resolutory Action | flight crew : overcame equipment problem flight crew : overrode automation flight crew : executed go around other |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
Narrative:
Approach control assigned a heading downwind for sequence to the final approach. We complied and they asked what our heading was. There was an approximately 15-20 difference with the navigation display and the RMI. Both the captain and the first officer's RMI's agreed. Both navigation displays agreed, but the navigation displays were the problem -- they were inaccurate. Checked wet compass. Did not see a 'heading' on the FMA, that would have denoted a conflict with the 2 system. Went to the book to see if this issue was addressed and it was not. Began an automatic-coupled ILS runway 10R and the localizer capture did not properly align and we had a full scale needle deflection. Requested a turn out of the final approach course, climbed to 3000 ft. ATC was aware of our compass conflict. Commenced our second approach using raw data to a successful landing. While constructing my logbook entry and further discussing the situation with the first officer, I discovered that the green, true/magnetic light was illuminated to true, thus eliminating variation on our navigation displays. I pushed the button to magnetic and the system returned to normal. It had been turned on accidentally. This is an item that should be addressed. This could be a very serious issue if the visibility was at minimums.
Original NASA ASRS Text
Title: FLT CREW OF MD83 ENCOUNTER HDG ANOMALIES BTWN THE NAV DISPLAYS AND THE REPEATER RMI'S. ULTIMATELY DISCOVER THE TRUE-NAV SWITCH HAD BEEN ACTIVATED, THUS DISPLAYING TRUE HDG ON THE NAV DISPLAYS.
Narrative: APCH CTL ASSIGNED A HDG DOWNWIND FOR SEQUENCE TO THE FINAL APCH. WE COMPLIED AND THEY ASKED WHAT OUR HDG WAS. THERE WAS AN APPROX 15-20 DIFFERENCE WITH THE NAV DISPLAY AND THE RMI. BOTH THE CAPT AND THE FO'S RMI'S AGREED. BOTH NAV DISPLAYS AGREED, BUT THE NAV DISPLAYS WERE THE PROB -- THEY WERE INACCURATE. CHKED WET COMPASS. DID NOT SEE A 'HDG' ON THE FMA, THAT WOULD HAVE DENOTED A CONFLICT WITH THE 2 SYS. WENT TO THE BOOK TO SEE IF THIS ISSUE WAS ADDRESSED AND IT WAS NOT. BEGAN AN AUTO-COUPLED ILS RWY 10R AND THE LOC CAPTURE DID NOT PROPERLY ALIGN AND WE HAD A FULL SCALE NEEDLE DEFLECTION. REQUESTED A TURN OUT OF THE FINAL APCH COURSE, CLBED TO 3000 FT. ATC WAS AWARE OF OUR COMPASS CONFLICT. COMMENCED OUR SECOND APCH USING RAW DATA TO A SUCCESSFUL LNDG. WHILE CONSTRUCTING MY LOGBOOK ENTRY AND FURTHER DISCUSSING THE SIT WITH THE FO, I DISCOVERED THAT THE GREEN, TRUE/MAGNETIC LIGHT WAS ILLUMINATED TO TRUE, THUS ELIMINATING VARIATION ON OUR NAV DISPLAYS. I PUSHED THE BUTTON TO MAGNETIC AND THE SYS RETURNED TO NORMAL. IT HAD BEEN TURNED ON ACCIDENTALLY. THIS IS AN ITEM THAT SHOULD BE ADDRESSED. THIS COULD BE A VERY SERIOUS ISSUE IF THE VISIBILITY WAS AT MINIMUMS.
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.