Ice gets blame for fatal Convair crash

A plane which crashed into the sea near Paraparaumu with the loss of two lives is believed to have become heavily iced up shortly before the crash, according to an investigation report released early today.

The Convair 580, operated by Air Freight New Zealand, was on a scheduled freight flight. It crashed in extreme weather about 9.30pm on October 3 last year, killing pilot Barry Cowley, 58, of Kaiapoi, near Christchurch, and co-pilot Paul Miller, 50, of Thames.

The Transport Accident Investigation Commission report into the crash points to a critical period of just 15 seconds when the plane levelled, for an unknown reason, around 4700m during descent.

Investigator-in-charge Ian McClelland said the aircraft had descended through an area of severe icing that was probably beyond the design and certified icing capabilities of the aircraft.

The build-up of ice had become critical to the point that the aircraft stalled and went into a spiral dive.

The report said that because the plane had levelled for those 15 seconds, a build-up of ice probably reached a point where continued controlled flight was not possible.

Mr McClelland said "rare and extreme" weather had probably been responsible for a particularly dangerous form of aircraft icing - freezing rain ice.

That type of icing could form quickly, disrupting the normally smooth flow of air over the wings and increasing aircraft weight, resulting in a stall.

Anti-icing equipment had probably been working satisfactorily.

It was reasonable to assume the crew of the Convair had not been aware of the severity of the icing and the rate it was building up on the tailplane and other surfaces out of their sight.

"The first indication of anything untoward may have been when the aircraft stalled, by which time recovery was probably impossible," Mr McClelland said.

"This accident was the result of an unfortunate set of circumstances.

"Without knowing why the aircraft was levelled during the descent, had any other crew been placed in the same situation and had the same information available, they may well have completed the same actions."

The investigation had probably been prolonged and limited by the lack of cockpit voice recorder (CVR) information, and to a lesser extent aircraft flight data recorder information, he said.

"The failure of the CVR to record any cockpit communications was unacceptable, but steps have been taken by the operator and regulator to address this subject."

The commission recommended that the report into the crash be used to emphasise to pilots and operators the hazards of icing, in particular tailplane icing and the danger of freezing rain.

It also wants to see pilots educated about the benefits of transmitting reports from the air on conditions such as wind shear, turbulence and icing.

The accident file shows that an aircraft reported a severe ice encounter about 7.40pm west of Otaki, but did not report it until after the crash.

Mr McClelland said the two-person crew on the Convair had been experienced and capable.

The flight had proceeded normally until, after passing Paraparaumu during the descent, the aircraft had levelled, then shortly after entered a steady turn to the left.

During that time the co-pilot made a routine radio transmission.

At the end of the transmission the plane had started to descend rapidly, entering a tightening spiral dive.

Flying at about 400 knots (740km/h), it had started to break up about 2073m over the sea.

- NZPA