Reprinted from The Wall Street Journal

Written By: Andy Pasztor

Cockpit instruments apparently indicated that onboard anti-icing systems were operating normally on a Continental Connection turboprop shortly before it stalled and crashed near Buffalo, N.Y. Thursday night from what now appears to be deadly accumulation of ice on some critical flight surfaces, according to federal investigators.

The latest information released by the National Transportation Safety Board raises questions about the operation and design of the mechanical de-icing systems, or so-called rubber boots, that inflate to shed ice off the leading edges of the wings and some tail surfaces on the widely-used Bombardier Q400 aircraft. Steve Chealander, the safety board member serving as spokesman for the roughly 150 investigators, law enforcement officials and others sifting through the wreckage, told reporters earlier Saturday that the plane had “very sophisticated de-icing systems” that the pilots turned on.

Based on information gleaned from the cockpit-voice recorder, according to Mr. Chealander, there was no discussion of any kind before the crash indicating that the systems were not working properly. “We hear no indication thus far” that lights in the cockpit alerted the crew to problems with anti-icing equipment, Mr. Chealander said. Once turned on, the anti-icing systems are designed to cycle automatically until the pilots turn them off.

This image from television shows an aerial view of the crash site of Continental Connection Flight 3407 and the surrounding neighborhood on Feb. 13, 2009 in Clarence Center, N.Y.The findings are important because investigators Saturday described a sequence of events further buttressing preliminary indications the twin-engine turboprop lost its ability to fly due to severe icing.

In his press conference, for example, Mr. Chealander said a “cursory visual look” at the engines indicated they were operating before the impact. Investigators have said that so far they have found no indications of engine or flight-control system malfunctions.

Mr. Chealander also revealed that the plane’s cockpit-voice recorder and flight-data recorder indicate that stall warnings came on immediately before the crash, which would be consistent with ice build-up causing the plane to lose lift.

The latest details released by the safety board shot down earlier speculation that some kind of mechanical problem delayed the plane’s takeoff from Newark, N.J. the board determined that takeoff was delayed due to high winds.

In a surprise from what investigators may have expected to find, analysis of the wreckage shows that the 74-seat turboprop didn’t smash into a house at a steep angle. Mr, Chealander said “all four corners” of the plane were in their proper position, indicating that instead of hitting nose first the plane struck the ground at a relatively flat angle.

Adding further support to the notion that icing brought down the plane, the safety board said the pilots had been flying using the autopilot during an earlier part of the descent toward the airport, when they noticed significant ice build-up on parts of the cockpit windshield and windshield wipers. The flight-data recorder indicates the plane went out of control almost immediately after the pilots disconnected the autopilot and started extending the wing flaps.

In a classic icing accident, such actions suddenly put a plane into a stall. The Q400 has anti-icing devices on the leading edge of its wings as well as parts of its tail, including the horizontal stabilizer. As a result, the investigators are expected to look at the impact of ice buildup in both areas, according to safety officials. A gradual loss of speed points to possible icing on the tail, portions of the wings and other aircraft parts, which would reduce lift and increase the weight of a plane.