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B757-200 flies off course when they receive IRS navigation only message on domestic flight. Distractions led to failure to write up concurrent fuel imbalance issue.
| Attributes | |
| ACN | 797136 |
| Time | |
| Date | 200807 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : iad.airport |
| State Reference | VA |
| Altitude | msl single value : 31000 |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : shnon |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 80 flight time total : 7000 flight time type : 150 |
| ASRS Report | 797136 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 200 flight time total : 14000 flight time type : 3000 |
| ASRS Report | 797140 |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : clearance non adherence : far other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : eicas warning message other controllera |
| Resolutory Action | controller : issued advisory controller : issued new clearance flight crew : overcame equipment problem |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Aircraft |
Narrative:
About 25 mins after takeoff; got IRS navigation only message on FMC. Checked progress page 1; it showed 2 vors being tuned and apparently updating. Referenced additional section of flight manual regarding IRS navigation only message. 1.5 hours later; same situation and 1 hour after that; again same IRS navigation only message; with same FMC depiction. Coming into iad on shnon.2 arrival; ZDC cleared us direct druzz. Shortly thereafter; we were told to turn 20 degrees left and that we were 15 mi off course. All navigation presentations looked normal. Informed center that normal navigation was unavailable and received vectors for ILS runway 19C approach. During this time we were also dealing with a fuel imbal and associated fuel confign light that we determined was not due to a fuel leak. Because of our concerns about the IRS problem; we forgot to write up the fuel imbal.
Original NASA ASRS Text
Title: B757-200 FLIES OFF COURSE WHEN THEY RECEIVE IRS NAV ONLY MESSAGE ON DOMESTIC FLT. DISTRACTIONS LED TO FAILURE TO WRITE UP CONCURRENT FUEL IMBALANCE ISSUE.
Narrative: ABOUT 25 MINS AFTER TKOF; GOT IRS NAV ONLY MESSAGE ON FMC. CHKED PROGRESS PAGE 1; IT SHOWED 2 VORS BEING TUNED AND APPARENTLY UPDATING. REFED ADDITIONAL SECTION OF FLT MANUAL REGARDING IRS NAV ONLY MESSAGE. 1.5 HRS LATER; SAME SITUATION AND 1 HR AFTER THAT; AGAIN SAME IRS NAV ONLY MESSAGE; WITH SAME FMC DEPICTION. COMING INTO IAD ON SHNON.2 ARR; ZDC CLRED US DIRECT DRUZZ. SHORTLY THEREAFTER; WE WERE TOLD TO TURN 20 DEGS L AND THAT WE WERE 15 MI OFF COURSE. ALL NAV PRESENTATIONS LOOKED NORMAL. INFORMED CTR THAT NORMAL NAV WAS UNAVAILABLE AND RECEIVED VECTORS FOR ILS RWY 19C APCH. DURING THIS TIME WE WERE ALSO DEALING WITH A FUEL IMBAL AND ASSOCIATED FUEL CONFIGN LIGHT THAT WE DETERMINED WAS NOT DUE TO A FUEL LEAK. BECAUSE OF OUR CONCERNS ABOUT THE IRS PROB; WE FORGOT TO WRITE UP THE FUEL IMBAL.
Data retrieved from NASA's ASRS site as of May 2009 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.