37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Attributes | |
ACN | 421745 |
Time | |
Date | 199811 |
Day | Tue |
Local Time Of Day | 1801 To 2400 |
Place | |
Locale Reference | atc facility : vxv |
State Reference | TN |
Altitude | msl bound lower : 30650 msl bound upper : 31000 |
Environment | |
Flight Conditions | Mixed |
Light | Night |
Aircraft 1 | |
Operator | common carrier : air carrier |
Make Model Name | MD-88 |
Operating Under FAR Part | Part 121 |
Navigation In Use | Other |
Flight Phase | cruise other |
Route In Use | enroute : direct enroute airway : ztl |
Flight Plan | IFR |
Person 1 | |
Affiliation | company : air carrier |
Function | flight crew : captain oversight : pic |
Qualification | pilot : flight engineer |
Experience | flight time last 90 days : 180 flight time total : 9000 flight time type : 6500 |
ASRS Report | 421745 |
Person 2 | |
Affiliation | company : air carrier |
Function | flight crew : first officer |
Qualification | pilot : commercial |
Events | |
Anomaly | altitude deviation : excursion from assigned altitude other anomaly other |
Independent Detector | aircraft equipment other aircraft equipment : unspecified |
Consequence | Other |
Supplementary | |
Air Traffic Incident | Pilot Deviation |
Narrative:
We fly, deviating around thunderstorm at night, with autoplt coupled, using both radar and visual means to identify cells. I was looking out of the windshield (face nearly pressed against the glass, so I could see better), and was controling my heading with the heading select knob on the flight guidance control panel. The first indication that we had left FL310 was from the altitude alert device, chiming at 250 ft below selected altitude. At that point, I disconnected the autoplt and climbed back to FL310. While we're not sure why the aircraft left altitude, I think that I may have inadvertently brushed against the pitch control wheel, which is adjacent to the heading select knob on the flight guidance control panel. Often, the altitude hold detent on this wheel is less secure than on other units. This incident could have been prevented had the pitch wheel detent been more secure. Also, one of us in the cockpit should have been watching the instruments and the flight guidance control panel. Instead, we were both looking outside at the cells. It was due to the altitude alert device that I only descended 350 ft below assigned altitude.
Original NASA ASRS Text
Title: MD88 CREW HAD ALT EXCURSION.
Narrative: WE FLY, DEVIATING AROUND TSTM AT NIGHT, WITH AUTOPLT COUPLED, USING BOTH RADAR AND VISUAL MEANS TO IDENT CELLS. I WAS LOOKING OUT OF THE WINDSHIELD (FACE NEARLY PRESSED AGAINST THE GLASS, SO I COULD SEE BETTER), AND WAS CTLING MY HDG WITH THE HDG SELECT KNOB ON THE FLT GUIDANCE CTL PANEL. THE FIRST INDICATION THAT WE HAD LEFT FL310 WAS FROM THE ALT ALERT DEVICE, CHIMING AT 250 FT BELOW SELECTED ALT. AT THAT POINT, I DISCONNECTED THE AUTOPLT AND CLBED BACK TO FL310. WHILE WE'RE NOT SURE WHY THE ACFT LEFT ALT, I THINK THAT I MAY HAVE INADVERTENTLY BRUSHED AGAINST THE PITCH CTL WHEEL, WHICH IS ADJACENT TO THE HDG SELECT KNOB ON THE FLT GUIDANCE CTL PANEL. OFTEN, THE ALT HOLD DETENT ON THIS WHEEL IS LESS SECURE THAN ON OTHER UNITS. THIS INCIDENT COULD HAVE BEEN PREVENTED HAD THE PITCH WHEEL DETENT BEEN MORE SECURE. ALSO, ONE OF US IN THE COCKPIT SHOULD HAVE BEEN WATCHING THE INSTS AND THE FLT GUIDANCE CTL PANEL. INSTEAD, WE WERE BOTH LOOKING OUTSIDE AT THE CELLS. IT WAS DUE TO THE ALT ALERT DEVICE THAT I ONLY DSNDED 350 FT BELOW ASSIGNED 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.