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B737 flight crew reported the captain's pitch limit indicator came into view during cruise and a descent was initiated before the full clearance was received from ATC.
| Attributes | |
| ACN | 1617673 |
| Time | |
| Date | 201902 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.ARTCC |
| State Reference | US |
| Environment | |
| Flight Conditions | IMC |
| Aircraft 1 | |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Autoflight Yaw Damper |
| Person 1 | |
| Function | Captain Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 169 Flight Crew Type 6143 |
| Person 2 | |
| Function | Pilot Not Flying First Officer |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 144 Flight Crew Type 221 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Flight Deck / Cabin / Aircraft Event Other / Unknown |
Narrative:
While cruising at FL400; with a weight of approximately 130;000 pounds and about a 30 knot buffer between red line and top of the yellow arc; the pli (pitch limit indicator) displayed 1 above our pitch attitude. I did not realize that it was only on my (captain) side ADI (attitude director indicator); I asked the first officer (first officer) to request FL380 and I initiated a shallow descent with the ap (autopilot) off. I believe that the pli disappeared but then reappeared approaching FL380 with the pli still indicating only 1 above our pitch attitude. I continued descending to FL360 and asked [the first officer] to request FL360. It took ATC a short time to respond and issue clearance to FL360 and I may have deviated from our cleared altitude trying to ensure that we did not enter a stalled condition. The pli did appear a 3rd time; briefly at FL360 but then disappeared for good. I then switched the ap to the B ap. We had been in the tops of clouds and I initially thought the turbulence was causing the pli display but after leveling off at FL360; [the first officer] informed me that the pli never displayed on his ADI. We worked with maintenance control who informed us of a previous write up 7 days earlier of the #1 stall management yaw damper (smyd). After a short time we returned to FL400; and continued to destination uneventfully.
Original NASA ASRS Text
Title: B737 flight crew reported the Captain's Pitch Limit Indicator came into view during cruise and a descent was initiated before the full clearance was received from ATC.
Narrative: While cruising at FL400; with a weight of approximately 130;000 pounds and about a 30 knot buffer between Red Line and top of the yellow arc; the PLI (Pitch Limit Indicator) displayed 1 above our Pitch Attitude. I did not realize that it was only on my (Captain) side ADI (Attitude Director Indicator); I asked the FO (First Officer) to request FL380 and I initiated a shallow descent with the AP (Autopilot) off. I believe that the PLI disappeared but then reappeared approaching FL380 with the PLI still indicating only 1 above our Pitch Attitude. I continued descending to FL360 and asked [the FO] to request FL360. It took ATC a short time to respond and issue clearance to FL360 and I may have deviated from our cleared altitude trying to ensure that we did not enter a stalled condition. The PLI did appear a 3rd time; briefly at FL360 but then disappeared for good. I then switched the AP to the B AP. We had been in the tops of clouds and I initially thought the turbulence was causing the PLI display but after leveling off at FL360; [the FO] informed me that the PLI never displayed on his ADI. We worked with Maintenance Control who informed us of a previous write up 7 days earlier of the #1 Stall Management Yaw Damper (SMYD). After a short time we returned to FL400; and continued to destination uneventfully.
Data retrieved from NASA's ASRS site 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.