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A B737-700 FMC database update erroneously coded RNAV mandatory speeds as below the required speed rather than at the required speed.
| Attributes | |
| ACN | 786350 |
| Time | |
| Date | 200805 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 254 flight time type : 4000 |
| ASRS Report | 786350 |
| Events | |
| Anomaly | aircraft equipment problem : less severe |
| Independent Detector | other flight crewa |
| Supplementary | |
| Problem Areas | Company Aircraft |
| Primary Problem | Aircraft |
Narrative:
The current FMC database appears to have added the ability to code airspds 'B' (below) much like it has always been able to do altitudes (a or B). The EAGUL2 arrival was coded as follows: 'payso 280B/240' 'pichr 280B/160' 'homer 250B/120' 'queny 210B/080.' the altitudes are correct but the airspds on the arrival are at exactly that airspeed; not below. This change did prevent us from getting all kinds of warnings about 'unable payso at 280 KTS' due to our cost index dscnts. But; it does not seem correct for the arrival in the box to differ from the plate. I also find it disconcerting that such a fundamental change happens to our FMC with no notice or information to the pilots about it. I think that this arrival (and any others that got the 'below airspeed' treatment) should be put back to its original and correct state and that we should do a 280 KT descent into places like phx and lax rather than have the FMC arrs be modified to suit our 'needs' for a 261 KT descent. I think we're getting enough ATC queries about our descent speeds without having our FMC information being wrong. Callback conversation with reporter revealed the following information: the reporter stated that after this report was filed; his air carrier notified pilots about the coding error and cautioned them to disregard constraints.
Original NASA ASRS Text
Title: A B737-700 FMC DATABASE UPDATE ERRONEOUSLY CODED RNAV MANDATORY SPDS AS BELOW THE REQUIRED SPD RATHER THAN AT THE REQUIRED SPD.
Narrative: THE CURRENT FMC DATABASE APPEARS TO HAVE ADDED THE ABILITY TO CODE AIRSPDS 'B' (BELOW) MUCH LIKE IT HAS ALWAYS BEEN ABLE TO DO ALTS (A OR B). THE EAGUL2 ARR WAS CODED AS FOLLOWS: 'PAYSO 280B/240' 'PICHR 280B/160' 'HOMER 250B/120' 'QUENY 210B/080.' THE ALTS ARE CORRECT BUT THE AIRSPDS ON THE ARR ARE AT EXACTLY THAT AIRSPD; NOT BELOW. THIS CHANGE DID PREVENT US FROM GETTING ALL KINDS OF WARNINGS ABOUT 'UNABLE PAYSO AT 280 KTS' DUE TO OUR COST INDEX DSCNTS. BUT; IT DOES NOT SEEM CORRECT FOR THE ARR IN THE BOX TO DIFFER FROM THE PLATE. I ALSO FIND IT DISCONCERTING THAT SUCH A FUNDAMENTAL CHANGE HAPPENS TO OUR FMC WITH NO NOTICE OR INFO TO THE PLTS ABOUT IT. I THINK THAT THIS ARR (AND ANY OTHERS THAT GOT THE 'BELOW AIRSPD' TREATMENT) SHOULD BE PUT BACK TO ITS ORIGINAL AND CORRECT STATE AND THAT WE SHOULD DO A 280 KT DSCNT INTO PLACES LIKE PHX AND LAX RATHER THAN HAVE THE FMC ARRS BE MODIFIED TO SUIT OUR 'NEEDS' FOR A 261 KT DSCNT. I THINK WE'RE GETTING ENOUGH ATC QUERIES ABOUT OUR DSCNT SPDS WITHOUT HAVING OUR FMC INFO BEING WRONG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT AFTER THIS REPORT WAS FILED; HIS ACR NOTIFIED PILOTS ABOUT THE CODING ERROR AND CAUTIONED THEM TO DISREGARD CONSTRAINTS.
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.