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High altitude turbulence caused mdt jet to disconnect from autoplt altitude hold and lose 400 ft altitude from assigned before recovery was made by the flight crew.
| Attributes | |
| ACN | 328880 |
| Time | |
| Date | 199602 |
| Day | Sat |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : bld |
| State Reference | NV |
| Altitude | msl bound lower : 36600 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zla tower : apa |
| Operator | general aviation : corporate |
| Make Model Name | Medium Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 140 flight time total : 9300 flight time type : 1500 |
| ASRS Report | 328880 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Weather |
| Air Traffic Incident | Pilot Deviation |
Narrative:
En route from pvu to vny at FL370, .82 mach cruise, we had been experiencing intermittent moderate mountain wave (wind at FL370, 250 degrees, 95 KTS). The afcs altitude hold function disengaged on a sharp down cycle and the aircraft departed the assigned cruise altitude. At the altitude alert warning, I disengaged the autoplt and recovered the aircraft to assigned altitude after an approximately 400 ft loss.
Original NASA ASRS Text
Title: HIGH ALT TURB CAUSED MDT JET TO DISCONNECT FROM AUTOPLT ALT HOLD AND LOSE 400 FT ALT FROM ASSIGNED BEFORE RECOVERY WAS MADE BY THE FLC.
Narrative: ENRTE FROM PVU TO VNY AT FL370, .82 MACH CRUISE, WE HAD BEEN EXPERIENCING INTERMITTENT MODERATE MOUNTAIN WAVE (WIND AT FL370, 250 DEGS, 95 KTS). THE AFCS ALT HOLD FUNCTION DISENGAGED ON A SHARP DOWN CYCLE AND THE ACFT DEPARTED THE ASSIGNED CRUISE ALT. AT THE ALT ALERT WARNING, I DISENGAGED THE AUTOPLT AND RECOVERED THE ACFT TO ASSIGNED ALT AFTER AN APPROX 400 FT LOSS.
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.