When pilots turn their attention to icing, it’s the in-flight kind that garners the most attention and training focus. But ground icing is also critical and has been implicated in a number of accidents. Fortunately, the training material available on ground icing is as voluminous as it is for in-flight icing, and most of it is readily available online for individual use or incorporation into a training program.
A study conducted by NTSB researchers Kevin Petty and Carol Floyd found that ground icing was a serious issue for all types of aircraft operations. The results of the study, “A Statistical Review of Aviation Airframe Icing Accidents in the U.S.,” were presented in October 2004 at the 11th Conference on Aviation, Range and Aerospace.
The researchers studied icing-related accidents that occurred between 1982 and 2000. While nearly 40 percent of airframe-icing accidents (and 50 percent of fatal accidents) occurred in the cruise segment, takeoff accidents in which ice was a cause amounted to 19 percent of airframe icing accidents and 11.7 percent of fatal accidents. According to the report, “The number of takeoff accidents would have been cut considerably if proper preflight inspections and de-icing procedures were followed. Seven of the 10 air-transport category accidents reviewed in this study were takeoff accidents. Hence, attempting takeoff with frost/ice on an airframe is not only an issue in the general aviation community, but is a concern in all segments of aviation operations.”
FAA regulations are clear about the need to remove ice, snow and frost before takeoff in large and turbine-powered aircraft and for those operated under Part 91K fractional and Part 135 charter regulations. However, the same regulations also permit takeoff with frost if it “has been polished to make it smooth.”
Antonio Cortes, assistant professor at Embry-Riddle Aeronautical University’s Department of Aeronautical Science, has studied icing-related takeoff accidents and warns that any wing contamination can compromise takeoff performance. A Canadian study of the effect of roughness on airfoils found that particles as small as one to two millimeters (the size of a grain of salt) spaced at one particle per square centimeter caused a loss of lift of 22 percent in ground effect and 33 percent in free air. A wing that is 30 percent contaminated, according to Cortes, will see stall speed raised by 13 percent. What appears to be a small amount of contamination can be dangerous, he warned. “All it takes is just a little aggressive rotation, and you’re a test pilot.”
The FAA is not entirely comfortable with the idea of operators taking off with any frost on lifting surfaces and in 2006 published a Safety Alert for Operators (SAFO 06014) that attempted to clarify the agency’s position. Basically, the FAA is saying that the rule allowing polished frost should be tempered with aircraft manufacturer advice. Hawker Beechcraft, for example, allows some frost on the underside of the Hawker 800 wing but none on the upper surfaces.
Cortes applauds the FAA’s taking a more proactive stance on the polished frost issue before an accident happens because a pilot tried to split regulatory hairs and take off with some kind of frost that compromised aerodynamic performance enough to cause a problem.
To avoid any possible problems stemming from polished frost, Cortes offers this guidance, which could be incorporated into standard operating procedures: “Unless the AFM makes explicit reference to an approved procedure for takeoff with polished frost, you are prohibited from performing a takeoff with polished frost on any lifting surfaces and flight controls.”
Of equal concern to Cortes is that some operators allow pilots to visually assess ice contamination on wings through cabin windows, instead of using a tactile test with bare fingers. Those grains of salt spaced at one particle per square centimeter can be awfully hard to see through a window. “This is particularly poignant at night or when the window being used is wet, fogged over, scratched or warped,” he said.
“Furthermore, some operators still allow taxi out with loose snow adhered to wings under the hope that it will blow off before requiring lift on the takeoff roll. It is often left to the pilot’s untrained judgment to decide whether the snow will blow off or not. Naturally, the presence of snow also impedes the examination of the underlying wing surface to ascertain any other sources of contamination, such as dried de-icing fluids, frost or ice.”
Ten years ago, Walter Randa launched Leading Edge Deicing Specialists, a business that offers on-site ground de-icing training for both aircraft operators and de-icing providers, such as FBOs and airline service companies. Randa travels throughout the U.S. and Canada providing the de-icing training seminars.
A unique feature of the Leading Edge seminars is that participants get to try their hand at spraying an airplane with de-icing fluid, using an inflatable nearly life-size Learjet 40XR called the flexible jet. (The company uses the inflatable airplane because it is not always possible to borrow a real airplane for de-icing training.) At a recent seminar held at Stewart Airport in Newburgh, N.Y., participants got to practice spraying in real-life conditions, which were about 35 degrees F with a cold rain.
Randa believes that hands-on training is a much better way for de-icing operators to learn the skill. “There are companies that have computer-based training,” he said, “but if you’re using a truck that’s got a joystick and a closed cabin, you can’t simulate that.”
Randa has worked with NASA to help develop its online ground de-icing training program. This year, he plans to expand by offering training in Europe to help operators prepare for next winter’s icing season.
New De-icing Criteria for Part 135/125 Ops
On Dec. 20, 2007, the FAA published Notice 8900.27, which allows Part 125 and 135 operators to use data published in FAA holdover tables for their de-icing needs. According to the Regional Air Cargo Carriers Association, which worked with the FAA on this initiative, operators can use the FAA holdover times “if the de-icing/anti-icing is performed by an air carrier or contract service provider conducting ground aircraft deicing/anti-icing service under a current Part 121.629 approved program, and the implementation and training elements of FAA Order 8900.1, Flight Standards Information Management System, Volume 3, Chapter 18, Section 3, Part A Operations Specifications.
“Needless to say, the pilot-in-command will have an active role in directing and supervising de-icing/anti-icing applications to ensure they are appropriate to the aircraft type and individual operators’ requirements.”