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.
And from the Dominion Post
Crash pilots fought for control till last moment
08 September 2004
By KIM RUSCOE
The pilots of a mail plane that crashed into the sea off the Kapiti Coast fought for control till the last second, a Transport Accident Investigation Commission report says.
Barry Cowley, 58, of Kaiapoi, Christchurch, and Paul Miller, 50, of Thames, died when their Convair 580 crashed in a violent storm on October 3 last year.
The Airfreight New Zealand plane was on a night flight from Christchurch to Palmerston North when it hit the tail of an extreme weather band north of Paraparaumu about 9.30pm.
The storm, so severe that its damage isolated much of the Wellington region, hit the Kapiti Coast the hardest.
Transport Accident Investigation Commission air accident investigator Ian McClelland said the plane was descending as it went over Paraparaumu. For reasons unknown, it levelled out about 4700 metres (14,400ft) and turned left, away from the Kapiti Coast.
The "experienced and capable" pilots might have mistaken the extreme weather band for turbulence, and slowed and levelled the plane to lessen the impact, he said.
The investigation said the Convair had descended through an area of severe icing, probably beyond the aircraft's design and certified icing capabilities. "The buildup of ice became critical to the point that the aircraft stalled and entered the spiral dive," Mr McClelland said. "The short period of level flight, about 15 seconds, probably contributed to the buildup."
Spiralling toward the sea at 725km/h – more than 130km/h over its maximum speed – the plane started to break up at 2200m (6800ft). "It was under great stress and well over the design limits."
Injuries to the pilots' forearms and legs suggested they were conscious and still fighting for control when the plane hit the water at about 740km/h.
It took just 15 seconds from the time the plane stalled till it hit the sea, Mr McClelland said. "The weather conditions encountered by the crew on the night were both rare and extreme. They were also probably responsible for a particularly dangerous form of aircraft icing – freezing rain ice."
After the accident, crew on another plane reported a severe ice encounter just west of Otaki and photographed ice building on its front window.
Though flight recorders were recovered from the crash, they recorded only conversations with air traffic control and some background noise. They did not record cockpit conversations between the two pilots. Mr McClelland said he could not, therefore, know why the plane levelled out, or even if the pilots knew ice was building on the exterior.
"The first indication of anything untoward may have been when the aircraft stalled, by which time recovery was probably impossible."
Safety recommendations had been made to the Civil Aviation Authority and Airfreight about the need for pilots and operators to better understand aircraft icing, the role of cockpit and flight data recorders, and the need for all pilots to report extreme weather conditions even when warnings had already been issued.
Mr Cowley's family said they were "extremely disappointed" the chance to find out exactly what the pilots experienced was lost with the cockpit voice recorder's failure.
"While nothing can alter the outcome of the tragedy, that information could have provided us with invaluable answers."
AND FROM THE TAIC WEBSITE
Convair 580, ZK-KFU, loss of control and in-flight break-up, Kapiti Coast, 3 October 2003
On Friday 3 October 2003 at 2126, Convair 580 ZK-KFU was on a scheduled night freight flight from Christchurch to Palmerston North, when it was observed on radar to enter a tightening left turn and disappear. Attempts to contact the aircraft were unsuccessful and a search for the aircraft was started.
The aircraft had impacted the sea about 10 km north of Paraparaumu about vertically and at high speed. The crew of 2 was killed on impact.
After crossing Cook Strait the aircraft probably became heavily iced up while descending through an area of severe icing, and stalled after flying level for a short time. The crew was unable to recover from the ensuing spiral dive and the aircraft broke up as it descended.
Safety issues identified included:
* the need for all pilots and operators to have a better understanding of aircraft icing
* the use of air reports to alert pilots to hazardous meteorological conditions
* the adequacy of aircraft, operator and CAA documentation to assist pilots encountering adverse weather conditions, particularly for IFR and night freight operators in icing conditions
* the adequacy of the installation, performance and capabilities of cockpit voice and flight data recorders
* the requirement for a suitable tracking device to be readily available to find underwater location beacons.
Safety recommendations were made to the Director of Civil Aviation and the operator to address these issues.