This wasn’t discovered for some six seconds as noted by the CAM?statement 'Altitude' at Time 13.4. The first anomaly begin at Time 08 when the flight first departed from thealtitude it had held for over 30 minutes, probably when the autopilot wasdisconnected. 'CAM?' denotes that the location from which a sound came wasunidentified. 'CAM1' is on the left side of the cockpit, while 'CAM2' is on the rightside. NOTE: In the CVR transcript at left, 'CAM' denotes cockpit areamicrophone. Increasing wind noise (airspeed increasing) 'Altitude' deviation from normal first noticed Here’s a transcript of the final22 seconds of the CVR:

There were some earlier comments on the CVR about a problemwith the co-pilot’s attitude indicator, but after switching its souce to thecaptain’s vertical gyro, operation was normal. The flight was entirely normal up to Time 08 (i.e., eight seconds into theplot above), and had been on autopilot in 'altitude hold' mode forover 30 minutes. The triangular symbols mark the time of relevant CVRcomments and other key events. Times of significant events (in seconds) are read against the horizontalscale at the bottom. (Thecaptain’s activities are relevant to what happened, and will be discussedshortly.) To appreciate what happened to the flight during the next 30 seconds,look at this plot of data from the flight data recorder (FDR) and cockpit voicerecorder (CVR): The co-pilot was doing the flying, navigating, communicating everything and the flight engineer was attending to normal duties at his panel. The flight was cruising at 22,000 feet at night, between layers, in smoothair.

The co-pilot was relativelyinexperienced but had received all required training and was certified and fullyqualified. The captain and flight engineer were highlyexperienced and both had many hours in type. The airplane involved was a four-engine turboprop in airline cargo service.The only occupants were the captain, co-pilot, flight engineer, and adeadheading pilot in the jump seat. To illustrate that TDS can happen even with highly experienced pilots,consider the following two case studies that involved high-time airline crewsflying large transport aircraft: Case Study A

Death spiral on its side completely