Pilot vigilance can prevent icing accidents

 - October 31, 2006, 4:05 AM

As I prepared to pen yet another article dealing with winter operations, the realization hit me that we will likely have ice-related accidents. It seems that every winter we are peppered with articles dealing with many of the issues that need to be addressed to maintain safe flight under some challenging conditions.

However, every year after an accident or serious incident we are also struck by the realization that some of us have difficulty recalling what we have learned through training or from reading. During my years as an NTSB member we were well aware of the statistics that indicated we would experience a number of fatalities and lose a number of aircraft to winter operations that failed to prepare using all that is known and available. I live in the Northeast and–along with most of my peers–I conduct myself with great caution during winter operations.

I include both ground and flight operations in the term winter operations. While they are not exactly the same they both have a major effect on a safe flight. I have always been taken aback by pilots who elect not to spend the few hundred dollars it costs to de-ice frost. I have been amazed at the justification these pilots use to convince themselves that a required de-icing is not necessary. I wonder how many pilots realize how much even slight contamination affects the aerodynamic performance of a wing. A simple review of the accident record would lead us to believe there are enough to cause concern.

In-flight Icing Issues

In-flight icing raises similar concerns. Flights into icing conditions require a pilot to devote considerable mental effort to stay on top of the situation. In icing conditions it can be a short transition from safe flight into big problems. Flying modern aircraft with all the state-of-the-art avionics can be demanding, particularly given the large amount of data displayed and available to the pilot.

In addition to the volume of information displayed, the pilot has the added challenge of thinking about the information that is not displayed. Determining whether ice is building on an aircraft requires a visual check of usually the wing leading edge and a judgment call about how much has adhered to the wing. On aircraft equipped with de-icing boots these are critical decisions, and pilots must stay focused on following the established procedures, including maintaining proper airspeed. Even airline flight crews have failed to recognize that their aircraft had slowed to a critical point in icing conditions, with disastrous results. In December last year a Cessna 208B Caravan crashed in icing conditions and the NTSB cited inadequate airspeed as a factor in the accident.

There is a huge amount of information available on aircraft icing. Our knowledge base was expanded considerably as a result of the 1994 ATR icing accident in Roselawn, Ind. In the efforts to determine the cause of that accident, the federal government– through a coordinated research effort involving the NTSB, FAA and NASA’s Lewis Research Center–conducted icing tunnel tests, icing computer simulations, airflow simulations and actual flight tests using a tanker aircraft to provide the moisture in the form of controlled-size droplets.

As a result, we learned much about ice accumulation–not only on the leading edges of wings but also aft of the de-icing boot and forward of the ailerons. On the accident aircraft this ice buildup rendered the ailerons ineffective in controlling the aircraft. We also learned that pilots should not accept prolonged holds in icing conditions.

A huge amount of data was collected, and work continued on icing using this data long after the issues surrounding that accident were resolved. What are we doing with the considerable amount of data that has been collected? Are we using it to conduct a safe flight? The answer to these questions is as close as our nearest flying publication.

Every year about this time there are many articles written about the full spectrum of icing issues, including ground de-icing and in-flight icing. Our special-interest magazines and trade publications can provide a wealth of knowledge on icing and de-icing. In addition, our aviation organizations such as NATA and NBAA offer information and seminars to bring all operations personnel, both flight and ground, up to speed on the latest information, procedures and best practices.

The FAA also provides considerable information on icing as well as the rules we must follow to comply with the FARs. Some of the icing information we have is the result of other pilots’ accidents and the lessons learned from those events. We are not required to repeat their mistakes. If we consistently apply what we know, winter operations can be as safe as operations during any other season. We do a good job of safe operations, but we could do even better if we improve our winter operations through information and training.