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Air carrier medium large transport's loss of IRU's after takeoff in IMC conditions creates a heading track deviation in departure procedures. Non adherence to ATC clearance instruction procedure.
| Attributes | |
| ACN | 242266 |
| Time | |
| Date | 199305 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : atl |
| State Reference | GA |
| Altitude | msl bound lower : 1500 msl bound upper : 1500 |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : atl |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | climbout : initial climbout : takeoff |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 9000 flight time type : 1200 |
| ASRS Report | 242266 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial pilot : atp |
| Experience | flight time last 90 days : 225 flight time total : 4800 flight time type : 225 |
| ASRS Report | 242269 |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : clearance other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | controller : provided flight assist controller : issued new clearance flight crew : overcame equipment problem flight crew : declared emergency flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Approximately 20 seconds after takeoff, we lost our inertial reference unit (IRU) system, which resulted in loss of our primary flight director (pfd) indications and loss of navigation map (nd) display. Crew completed straight ahead departure in compliance with abnormal checklist with wings level climb out while PNF initiated abnormal checklist procedures. This resulted in a delayed turn from runway heading (272 degrees magnetic to assigned heading of 250 degrees at middle marker). Upon contacting departure control, crew advised departure of our degraded heading system and positioning indications. Departure control advised/directed a further turn to the left to direct us to a 250 degree heading for their departure corridor. After turning to a heading of 250 degrees (with ATC assistance) due to continued degraded flight direction and attitude information in IMC conditions, the crew completed the abnormal checklist (abnormal section 'navigation' page 4, 'attitude heading selection'). In the 'attitude' mode of the IRS, we continued to climb into VMC conditions. Primary attitude references were restored and reliable. We were able to restore IRS heading information, but heading information continued to drift, requiring frequent updates. VOR and ILS raw data information was available. ATC vectored crew for ILS to runway 17 at pensacola municipal (pns). WX was greater than 5000 ft and 5 mi. A visual approach was made to runway 17 with an ILS backup. Approach and landing were uneventful.
Original NASA ASRS Text
Title: ACR MLG'S LOSS OF IRU'S AFTER TKOF IN IMC CONDITIONS CREATES A HDG TRACK DEV IN DEP PROCS. NON ADHERENCE TO ATC CLRNC INSTRUCTION PROC.
Narrative: APPROX 20 SECONDS AFTER TKOF, WE LOST OUR INERTIAL REF UNIT (IRU) SYS, WHICH RESULTED IN LOSS OF OUR PRIMARY FLT DIRECTOR (PFD) INDICATIONS AND LOSS OF NAV MAP (ND) DISPLAY. CREW COMPLETED STRAIGHT AHEAD DEP IN COMPLIANCE WITH ABNORMAL CHKLIST WITH WINGS LEVEL CLBOUT WHILE PNF INITIATED ABNORMAL CHKLIST PROCS. THIS RESULTED IN A DELAYED TURN FROM RWY HDG (272 DEGS MAGNETIC TO ASSIGNED HDG OF 250 DEGS AT MIDDLE MARKER). UPON CONTACTING DEP CTL, CREW ADVISED DEP OF OUR DEGRADED HDG SYS AND POSITIONING INDICATIONS. DEP CTL ADVISED/DIRECTED A FURTHER TURN TO THE L TO DIRECT US TO A 250 DEG HDG FOR THEIR DEP CORRIDOR. AFTER TURNING TO A HDG OF 250 DEGS (WITH ATC ASSISTANCE) DUE TO CONTINUED DEGRADED FLT DIRECTION AND ATTITUDE INFO IN IMC CONDITIONS, THE CREW COMPLETED THE ABNORMAL CHKLIST (ABNORMAL SECTION 'NAV' PAGE 4, 'ATTITUDE HDG SELECTION'). IN THE 'ATTITUDE' MODE OF THE IRS, WE CONTINUED TO CLB INTO VMC CONDITIONS. PRIMARY ATTITUDE REFS WERE RESTORED AND RELIABLE. WE WERE ABLE TO RESTORE IRS HDG INFO, BUT HDG INFO CONTINUED TO DRIFT, REQUIRING FREQUENT UPDATES. VOR AND ILS RAW DATA INFO WAS AVAILABLE. ATC VECTORED CREW FOR ILS TO RWY 17 AT PENSACOLA MUNICIPAL (PNS). WX WAS GREATER THAN 5000 FT AND 5 MI. A VISUAL APCH WAS MADE TO RWY 17 WITH AN ILS BACKUP. APCH AND LNDG WERE 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.