The way in which 'icing conditions' are defined for large (transport) aircraft has in recent years come under close scrutiny on both sides of the Atlantic because it has become apparent that icing can occur at static air temperatures much colder than those adopted in the longstanding current definitions. Each document posted on the site includes a link to the Condition 1 does not mention “ known icing conditions”.

documents in the last year, 32
We construed the request as seeking clarification of the meaning of “known icing conditions” as that term appears in the Airplane Flight Manuals (AFM) or Pilot Operating Handbooks for many general aviation aircraft. documents in the last year, 616 from 49 agencies. Does the FAA define it? (The envelopes use the term mean effective diameter, but this equates to the MVD for the Why is there no AIRMET for icing?

They could end there with a big fat period, but they add: Note- In many cases, especially for smaller general aviation aircraft, it may be intended to allow for just a temporary period of operation in icing conditions during which the horizontal or vertical extent of the icing is vacat… (1) The aircraft has functioning deicing or anti-icing equipment protecting each rotor blade, propeller, windshield, wing, stabilizing or control surface, and each airspeed, altimeter, rate of climb, or flight attitude instrument system; (2) The airplane has ice protection provisions that meet section 34 of appendix A of this part; or.

Use the PDF linked in the document sidebar for the official electronic format.

Send your comments on or before May 3, 2007. While various FAA regulations contain limitations on flight in known icing conditions, the regulatory provision that most commonly affects general aviation operators in this respect applies the term only indirectly.

Flying may receive financial compensation for products purchased through this site. Both airframe and engine icing have resulted in numerous fatal accidents in aviation history.

Order No. In aviation, icing conditions are atmospheric conditions that can lead to the formation of water ice on an aircraft.

This draft letter of interpretation addresses a request by the Aircraft Owners and Pilots Association (AOPA) that the FAA rescind a letter of interpretation dated June 6, 2006 regarding “known icing conditions”.

Saved and put in to circulation!

About the Federal Register Turbine engine certification has historically been focussed on inlet ice protection which is addressed in CS E-780 in CFR14- Part 33.68 with reference currently made, as in the airframe case, to Appendix C conditions. A jet requires other procedures than Part-NCO aircraft

The Public Inspection page may also

In their current version, these require that an aircraft should be able to "operate safely" when the stated definition of icing conditions exist. Personally I consider any visible moisture at around 0° as expected icing conditions that I avoid. documents in the last year. We’ve made big changes to make the eCFR easier to use. Be sure to leave feedback using the 'Help' button on the bottom right of each page!


This feature is not available for this document. Appendix C did not address the presence of supercooled large droplets (SLD) - water droplets which persist in subfreezing temperatures and have a median diameter usually defined as greater than 40 microns.