02.13.09

Behind the Buffalo Crash

It’s too early to tell what caused last night’s crash of a Continental Airlines plane near Buffalo. But Clive Irving points to some troubling instances in which other turboprop planes failed in icy weather.

There is something hauntingly familiar about the crash of the Bombardier Dash 8 commuter plane in Buffalo. While a lot more information is needed before investigators can be sure of the cause, there are precursors that suggest a pattern.

It begins with the crash of American Eagle Flight 4184 at Roselawn, Indiana, in October 1994. It was a different type of plane, a European-built ATR-72 (the Bombardier is a Canadian plane). All 49 people on board died. The cause was ice on the wings.

The ATR-72 had been in a holding pattern, flying through sleet that caused a build-up of ice on the wings. When this happens at a critical point the ice effectively destroys the power of the wings to provide lift. Flight 4184 lost lift, rolled over, and crashed.

What urgently needs to be looked at is whether the basic configuration of all turboprop commuter planes, and particularly their flying characteristics in ice-making weather, leaves them unusually exposed to ice build-up on the wings and control surfaces.

This has been a hazard since the first days when planes encountered ice. And usually it can be disregarded because all airliners have what are called de-icing boots—vulnerable parts of the wings are heated to prevent ice forming.

The Roselawn crash led to investigations that revealed that the ATR-72 had a history of being vulnerable to ice formation. ATR-72s were later modified to correct the problem, and flight crews were alerted to the dangers of flying in weather that could cause rapid ice build-ups.

In 1997, a Comair commuter flight, this time involving the Brazilian-built EMB-120, crashed near Detroit, killing 3 crew and 26 passengers. Again, ice was the cause and the National Transportation Safety Board discovered that the plane maker, Embraer, had warned the airline that the EMB-120 could be uncontrollable if flown too slowly in icy conditions. The airline had not passed this warning to the crew.

As recently as January 27 this year, a FedEx ATR crashed on landing at Lubbock, Texas, in a freezing mist. Officials are still disputing the role of ice in that incident. The crew was able to walk away, but the crash has every appearance of ice build-up affecting the controllability of the plane at a critical moment.

So here there are at least three different types of commuter planes—European, Brazilian and Canadian—involved in crashes where ice was almost certainly a factor. What do they have in common?

They are all turboprops—each with two engines in which a gas turbine, as in a jet, drives propellers. When turboprops descend for a landing, as the Buffalo flight was, they fly more slowly than a jet, which means that they spend longer at the altitude where sudden, unpredictable bursts of ice can appear.

The Bombardier Dash 8 Q400 is state of the art as turboprops go, with extremely sophisticated equipment and, until now, a good safety record. However, what urgently needs to be looked at is whether the basic configuration of all turboprop commuter planes, and particularly their flying characteristics in ice-making weather, leaves them unusually exposed to ice build-up on the wings and control surfaces. In other words, whether those heated “boots” can be so suddenly overwhelmed by sudden flashes of rapid ice formation that the pilots have no chance of retaining control.

This comes at a time, incidentally, when these turboprops, which are more fuel efficient for short commuter flights than jets, are experiencing a big boost in demand from cash-strapped airlines.

Clive Irving is Senior Consulting Editor at Conde Nast Traveler, specializing in aviation. He has flown the A320 in a simulator and earned an “Honorary Captain” certificate for making a perfect approach and landing at JFK—thankfully, he says, not for real.