 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
A B737-300 flight crew cruising through ZMP airspace tests the fuel gauges and takes the autoflt system out of VNAV. The aircraft has an altitude excursion of 400 ft.
| Attributes | |
| ACN | 409112 |
| Time | |
| Date | 199807 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : obh |
| State Reference | NE |
| Altitude | msl bound lower : 34600 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zmp |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 20000 flight time type : 3000 |
| ASRS Report | 409112 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 240 flight time total : 12500 flight time type : 3000 |
| ASRS Report | 409108 |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : regained aircraft control flight crew : overcame equipment problem flight crew : became reoriented |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
B737-300 in cruise at FL350, autoplt engaged in VNAV. I tested the fuel gauges, and for some reason the VNAV disconnected and the autoplt did not default to altitude hold, but rather started a slow descent. We did not pick up the descent until the altitude alert horn sounded at 300 ft below FL350. I took corrective action by disengaging the autoplt and returning to FL350. The aircraft descended to about 400 ft below our assigned altitude of FL350. Testing the fuel gauges resulted in VNAV disengagement. However on each subsequent test the autoplt defaulted to altitude hold and did not change altitude.
Original NASA ASRS Text
Title: A B737-300 FLC CRUISING THROUGH ZMP AIRSPACE TESTS THE FUEL GAUGES AND TAKES THE AUTOFLT SYS OUT OF VNAV. THE ACFT HAS AN ALT EXCURSION OF 400 FT.
Narrative: B737-300 IN CRUISE AT FL350, AUTOPLT ENGAGED IN VNAV. I TESTED THE FUEL GAUGES, AND FOR SOME REASON THE VNAV DISCONNECTED AND THE AUTOPLT DID NOT DEFAULT TO ALT HOLD, BUT RATHER STARTED A SLOW DSCNT. WE DID NOT PICK UP THE DSCNT UNTIL THE ALT ALERT HORN SOUNDED AT 300 FT BELOW FL350. I TOOK CORRECTIVE ACTION BY DISENGAGING THE AUTOPLT AND RETURNING TO FL350. THE ACFT DSNDED TO ABOUT 400 FT BELOW OUR ASSIGNED ALT OF FL350. TESTING THE FUEL GAUGES RESULTED IN VNAV DISENGAGEMENT. HOWEVER ON EACH SUBSEQUENT TEST THE AUTOPLT DEFAULTED TO ALT HOLD AND DID NOT CHANGE ALT.
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.