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Captain of B747 reports receiving a 2000 pound increase in ZFW well after takeoff. When entered into FMC resulting FMC generated app speeds appear low when compared to CADC derived stick shaker speeds.
| Attributes | |
| ACN | 670334 |
| Time | |
| Date | 200508 |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : iad.airport |
| State Reference | VA |
| Altitude | msl single value : 2000 |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Controlling Facilities | tower : iad.tower |
| Operator | common carrier : air carrier |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 108 flight time total : 14500 flight time type : 4500 |
| ASRS Report | 670334 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : company policies non adherence : published procedure non adherence : far other anomaly other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : air spd indicator other flight crewa |
| Resolutory Action | flight crew : overrode automation flight crew : overcame equipment problem |
| Consequence | other |
| Supplementary | |
| Problem Areas | Company Flight Crew Human Performance Aircraft |
| Primary Problem | Company |
Narrative:
In cruise we received a zero fuel weight change. I remember it only being 2000 pounds and entered it into the FMC and did a rechk for accuracy. On approach at iad the FMC flaps 30 speed was 131 KIAS and so target 136 KIAS was selected. As flaps were lowered; the flap min maneuver speed was only 2 KIAS above the amber stall warning speed indicator. At gear down and flaps 30 target speed 136 was 4-5 KIAS below the amber stall warning indicator. I set a new target speed of 145 KIAS and landed normally. Callback conversation with reporter revealed the following information: reporter advised he had investigated the discrepancy after the fact and determined the results were consistent with a difference of about 20000 pounds between programmed and actual aircraft weight. He was apologetic that he hadn't retained the tardy revision and was unable to state whether the message itself might have actually said 20000 pounds vs 2000 pounds or whether he and the first officer may have misread it.
Original NASA ASRS Text
Title: CAPT OF B747 RPTS RECEIVING A 2000 LB INCREASE IN ZFW WELL AFTER TKOF. WHEN ENTERED INTO FMC RESULTING FMC GENERATED APP SPDS APPEAR LOW WHEN COMPARED TO CADC DERIVED STICK SHAKER SPDS.
Narrative: IN CRUISE WE RECEIVED A ZERO FUEL WT CHANGE. I REMEMBER IT ONLY BEING 2000 LBS AND ENTERED IT INTO THE FMC AND DID A RECHK FOR ACCURACY. ON APCH AT IAD THE FMC FLAPS 30 SPEED WAS 131 KIAS AND SO TARGET 136 KIAS WAS SELECTED. AS FLAPS WERE LOWERED; THE FLAP MIN MANEUVER SPD WAS ONLY 2 KIAS ABOVE THE AMBER STALL WARNING SPD INDICATOR. AT GEAR DOWN AND FLAPS 30 TARGET SPD 136 WAS 4-5 KIAS BELOW THE AMBER STALL WARNING INDICATOR. I SET A NEW TARGET SPD OF 145 KIAS AND LANDED NORMALLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED HE HAD INVESTIGATED THE DISCREPANCY AFTER THE FACT AND DETERMINED THE RESULTS WERE CONSISTENT WITH A DIFFERENCE OF ABOUT 20000 LBS BETWEEN PROGRAMMED AND ACTUAL ACFT WT. HE WAS APOLOGETIC THAT HE HADN'T RETAINED THE TARDY REVISION AND WAS UNABLE TO STATE WHETHER THE MSG ITSELF MIGHT HAVE ACTUALLY SAID 20000 LBS VS 2000 LBS OR WHETHER HE AND THE FO MAY HAVE MISREAD IT.
Data retrieved from NASA's ASRS site as of January 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.