 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
One of two B737 autoplt channels had a serious malfunction but was still available for selection because only a paper label warning disabled it.
| Attributes | |
| ACN | 753333 |
| Time | |
| Date | 200709 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-500 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : preflight |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 330 |
| ASRS Report | 753333 |
| Events | |
| Anomaly | aircraft equipment problem : less severe |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : unable |
| Supplementary | |
| Problem Areas | Aircraft Chart Or Publication Company |
| Primary Problem | Ambiguous |
| Situations | |
| Publication | MEL |
Narrative:
Flight was operated with the 'a' autoplt inoperative under the provisions of MEL; autoplt inoperative. These provisions do not include disabling a malfunctioning autoplt; an inoperative sticker is placed by the autoplt engage switch/paddle; in accordance with special procedure #1. The write-up that caused that MEL to be applied stated that if the 'a' autoplt was engaged; an abrupt pitch down would result. If engagement of an autoplt would result in an abrupt and unwanted movement of a flight control surface; I suggest that the autoplt be disabled by pulling and collaring the appropriate circuit breaker. There are many flight conditions in which an abrupt and unwanted flight control movement could be hazardous; and placement of a paper sticker on or near the enabling control is not sufficient protection against that possibility.
Original NASA ASRS Text
Title: ONE OF TWO B737 AUTOPLT CHANNELS HAD A SERIOUS MALFUNCTION BUT WAS STILL AVAILABLE FOR SELECTION BECAUSE ONLY A PAPER LABEL WARNING DISABLED IT.
Narrative: FLT WAS OPERATED WITH THE 'A' AUTOPLT INOPERATIVE UNDER THE PROVISIONS OF MEL; AUTOPLT INOPERATIVE. THESE PROVISIONS DO NOT INCLUDE DISABLING A MALFUNCTIONING AUTOPLT; AN INOPERATIVE STICKER IS PLACED BY THE AUTOPLT ENGAGE SWITCH/PADDLE; IN ACCORDANCE WITH SPECIAL PROCEDURE #1. THE WRITE-UP THAT CAUSED THAT MEL TO BE APPLIED STATED THAT IF THE 'A' AUTOPLT WAS ENGAGED; AN ABRUPT PITCH DOWN WOULD RESULT. IF ENGAGEMENT OF AN AUTOPLT WOULD RESULT IN AN ABRUPT AND UNWANTED MOVEMENT OF A FLT CTL SURFACE; I SUGGEST THAT THE AUTOPLT BE DISABLED BY PULLING AND COLLARING THE APPROPRIATE CB. THERE ARE MANY FLT CONDITIONS IN WHICH AN ABRUPT AND UNWANTED FLT CTL MOVEMENT COULD BE HAZARDOUS; AND PLACEMENT OF A PAPER STICKER ON OR NEAR THE ENABLING CTL IS NOT SUFFICIENT PROTECTION AGAINST THAT POSSIBILITY.
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.