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A non GPS B737-400's flight guidance did not track an RNAV departure correctly and caused a track deviation.
| Attributes | |
| ACN | 826085 |
| Time | |
| Date | 200903 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Climb |
| Route In Use | SID X |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | FMS/FMC |
| Person 1 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Commercial Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor |
| Experience | Flight Crew Last 90 Days 120 Flight Crew Total 9600 Flight Crew Type 1100 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types |
Narrative:
About XA45 we departed ZZZ to ZZZ1. We were filed and cleared for the RNAV departure off of runway xx. During preflight the route was entered and reviewed by me and the captain before pushback. The route and runway was confirmed by both of us with the RNAV departure; runway xx and zzzzz as our first fix. All VOR's were operational; and full alignment of all IRS's with most accurate position had been completed prior to push back. During taxi I confirmed again zzzzz as the first fix and advised ground control of zzzzz as our first fix. During taxi I verified the captain had his HSI switch to navigation and I had my HSI switch in navigation. We were cleared into position and hold on runway xx. As we lined up on the runway I updated the aircraft position on the takeoff page using the runway xx update prompt and announced runway updated. I then verified the CDI needle centered and aligned with initial heading and yellow waypoint pointer pointed to zzzzz. After takeoff at 400 ft the captain called for LNAV and I selected LNAV and confirmed LNAV on the MCP and the FMA. ATC advised us to contact departure. At a 1000 ft afe the captain called for climb thrust; 220 kts; flaps 1 and then he engaged the 'a' autopilot. CDI needles were centered the entire climb. I contacted departure and then the captain called for flaps up after takeoff checklist. The ATC advised us to turn to a heading of 130. We turned to heading 130 and then ATC advised us of a deviation of track. Both CDI needles were centered during the entire RNAV departure. Later in ZZZ1 we called maintenance to advise them that there may be a problem with the navigation system on the aircraft. Maintenance informed us that 3 or 4 other company boeing 737 airplanes had the same problem on the X RNAV departure that day.callback conversation with reporter revealed the following info: the reporter stated that the flight guidance indicated precisely on track. There did not appear to be any deviation indicated until ATC called to give them a new heading. The air carrier maintenance stated that three previous aircraft that day had similar deviations but the equipment appeared to be functioning normally.
Original NASA ASRS Text
Title: A non GPS B737-400's flight guidance did not track an RNAV departure correctly and caused a track deviation.
Narrative: About XA45 we departed ZZZ to ZZZ1. We were filed and cleared for the RNAV Departure off of Runway XX. During preflight the route was entered and reviewed by me and the Captain before pushback. The route and runway was confirmed by both of us with the RNAV Departure; Runway XX and ZZZZZ as our first fix. All VOR's were operational; and full alignment of all IRS's with most accurate position had been completed prior to push back. During taxi I confirmed again ZZZZZ as the first fix and advised ground control of ZZZZZ as our first fix. During taxi I verified the Captain had his HSI switch to NAV and I had my HSI switch in NAV. We were cleared into position and hold on Runway XX. As we lined up on the runway I updated the aircraft position on the takeoff page using the Runway XX update prompt and announced runway updated. I then verified the CDI needle centered and aligned with initial heading and yellow waypoint pointer pointed to ZZZZZ. After takeoff at 400 ft the Captain called for LNAV and I selected LNAV and confirmed LNAV on the MCP and the FMA. ATC advised us to contact departure. At a 1000 ft AFE the Captain called for Climb thrust; 220 kts; flaps 1 and then he engaged the 'A' autopilot. CDI needles were centered the entire climb. I contacted departure and then the captain called for flaps up after takeoff checklist. The ATC advised us to turn to a heading of 130. We turned to heading 130 and then ATC advised us of a deviation of track. Both CDI needles were centered during the entire RNAV departure. Later in ZZZ1 we called maintenance to advise them that there may be a problem with the navigation system on the aircraft. Maintenance informed us that 3 or 4 other company Boeing 737 airplanes had the same problem on the X RNAV Departure that day.Callback conversation with reporter revealed the following info: The reporter stated that the flight guidance indicated precisely on track. There did not appear to be any deviation indicated until ATC called to give them a new heading. The air carrier maintenance stated that three previous aircraft that day had similar deviations but the equipment appeared to be functioning normally.
Data retrieved from NASA's ASRS site as of April 2012 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.