Pre Flight Inspection and Ice and Frost
Official and Technical Information on Icing and Frost and Pre-Flight Inspection.
Sections (3) and (6) below quoted from the NTSB Advisory dated December 2009, 2004
(3)-- Ice accumulation on the wing upper surface is very difficult to detect. It may not be seen from the cabin because it is clear/white and it is very difficult to see from the front or back of the wing. The Safety Board believes strongly that the only way to ensure that the wing is free from critical contamination is to touch it.
(6)-- The Safety Board believes that even with the wing inspection light, the observation of a wing from a 30-to 40-foot distance, through a window that was probably wet from precipitation, does not constitute a careful examination, the Safety Board acknowledges that the detection of minimal amounts of contamination, sufficient to cause aerodynamic performance problems, is difficult and may not be possible without a tactile inspection.
“Frost” can form in two ways: Either by deposition or freezing. Depositional frost is also known as white frost or hoarfrost. It occurs when the dew point (now called the frost point) is below freezing. When this frost forms the water vapor goes directly to the solid state. Depositional frost covers the vegetation, cars, surfaces, etc. with ice crystal patterns (treelike branching pattern). If the depositional frost is thick enough, it resembles a light snowfall.
Frost that forms due to the freezing of liquid water is best referred to as frozen dew. Initially, both the dew point and temperature are above freezing when dew forms. Longwave radiational cooling gradually lowers the temperature to at or below freezing during the night. Cold air advection can also do the trick (e.g. Cold front moving through in the middle of the night after dew has formed). Once the temperature falls to freezing, the condensed dew droplets freeze. Frozen dew looks different from white frost. Frozen dew does not have the crystal patterns of white frost. White frost tends to looks whiter while frozen dew tends to look slicker and more difficult to see.
Pre flight inspection regarding the TKS Fluid De-Icing System is covered on Page 4 of 12 of the Cirrus SR22 Supplement Revision 04 dated 01-30-05 under Section 4 Normal Procedures lists pre-flight Inspection procedures regarding the De-Icing System. We also highly recommend incorporating the above Sections (3) and (6) into your pre flight inspection when in cold weather conditions.
Contact D.W. Davies & Co., Inc. with any questions. We are a recent new member to offer answers to all questions general or technical on icing, de-icing fluids, and the TKS Fluid De-Icing system.