Originally Posted by
KRviator
What'd cause the descent from FL280 -> FL150 and climb back to 280 early in the piece? Do the firescan ops require that, or could it be indicative of a pressurisation issue?
-HPY was also the rego of the Twotter we lost in PNG when the students turned up the wrong valley and couldn't outclimb the terrain.
My first thoughts were pressurization with the altitude involved. The speed seems to indicate that perhaps there was quite a bit of headwind at 280 giving them a GS of around 220kts, then descent to 150 and they were making 250kts, possibly indicating less headwind. The track also looks like it made a slight right turn at one point and is missing Isa by some distance, which further lends to possible pressurization issues. The final part looks like possibly power loss, windmilling prop would slow it down fast at that level, left engine, slows, stall warning disconnects autopilot and it rolls and descends to the left, which is the path it would follow if the crew were not in a position to control it. I'm not familiar with the 695A but if it has multiple tanks it could have run one dry by then if the pilot was unconscious. In any case it's another bad day for GA. Does the 695A have recording equipment? if so that might be the only real clue to what has happened.