After determining that operations with polished frost increases the risk of unsafe flight, the Federal Aviation Administration issued a Notice of Proposed Rulemaking, proposing to remove provisions in its regulations that allow for operations with ``polished frost'' (i.e., frost polished to make it smooth). The proposed rule would impact aircraft operated under parts 125, 135, and certain airplanes operated under part 91. Comments are due August 6.
The FAA cited 11 known accidents in which individuals attempted to smooth or polish frost, but the aircraft failed to generate enough lift and crashed shortly after takeoff. Although the agency found that nine of the 11 accidents would not have been prevented by the proposed rule, since the aircraft were involved in non-part 91 subpart F operations, it believes they illustrate the risk involved in flying with polished frost, adding there have been a number of other takeoff accidents and fatalities that have occurred when flight crews have consciously decided to take off without removing frost from the wings of their aircraft. The agency also cited National Transportation Safety Board’s (NTSB) numerous safety alerts as well as recommendations made by the Part 125/135 Aviation Rulemaking Committee.
Currently, regulations, dating back to 1960, allow pilots to take off with frost adhering to wings or stabilizing or control surfaces if that frost has been polished to make it smooth. Since 1960, the FAA and others have accumulated an extensive amount of data that would indicate that any amount of contaminants on wings or critical surfaces could be detrimental to the flight characteristics of an aircraft. The agency issued Advisory Circular (AC) 135-17, recommending all wing frost be removed prior to takeoff, and states that if an operator desires to polish the frost, the aircraft manufacturer's recommended procedures should be followed. However, no current aircraft manufacturer has issued any recommended procedures for polishing frost or conducting operations with polished frost. In addition, the FAA has no data to support practical guidance on determining how to polish frost on a surface to make it acceptably smooth, other than completely removing the frost and returning the airplane's critical lifting surfaces to uncontaminated smoothness. Finally, it cited the impracticability in trying to achieve smoothness equivalent to uncontaminated surfaces and said the term, polished frost, is ambiguous since no standard of acceptable smoothness is provided. The FAA is recommending that all authorities delete all references to polished frost and ensure the term is expunged from operations manuals.