Quote Originally Posted by IanD View Post
On this aircraft deicing equipment was installed. Can you confirm if this applies only to carb. deicing? Presumably nothing to do with heating leading edges or similar. Also, could the erratic decrease, increase, decrease in altitude be partly explained by localised downdrafts, updrafts and wind shear associated with with an approaching cold front? Could the aircraft have been battered by hail?
The PA46 Malibu range nearly all have FIKI ( Flight Into Known Icing ) capabilities. I believe N264DB had de-icing boots on the leading edges of the wings & leading edge of tailplane & also the leading edges of the elevator ( highlighted in yellow boxes )
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These are hydraulically inflated to break off Ice build on these surfaces ( if they have a pin hole or leak, they fail to work )

It is not known (by me) if they were serviceable on N264DB or whether the pilot understood the procedure to use them correctly

The engine in the PA46 Malibu is a fuel injected engine so carb icing isn't an issue.

My assumptions on the erratic decrease, increase, decrease in altitude are one of two scenarios:
(1) The pitot head froze up & instruments failed to function correctly, thereby the pilot chasing the needles was fighting to keep what he thought was level flight
(2) He got Spatially disorientated & just simply lost control & was pulling & pushing at the controls trying to regain level flight.