A rule issued by the U.S. FAA on Aug. 3 requires that makers of new transport category airplanes certified for flight in icing conditions ensure the timely activation of ice-protection systems. The rule does not apply to existing airplanes (unless they undergo extensive design changes), but the agency is considering one. Amendments to the airworthiness standards that are addressed in the new rule for new airplanes take effect Sept. 9. The rule provides makers with three options for certification: a primary ice-detection system (IDS), which automatically activates or alerts the flight crew to activate the airframe ice-protection system (IPS); a definition of visual cues for recognition of the first sign of ice accretion on a specified surface (e.g., wings), combined with an advisory IDS that alerts the flight crew to activate the airframe IPS; or identification of conditions conducive to airframe icing that would tip off pilots to activate the IPS. The major difference between the first and second options is that in option No. 1 the IDS is the principal means to determine when the airframe IPS should be activated and has two ice detectors. Option No. 2, an advisory IDS, serves as a backup to the flight crew and has only one ice detector. Ice detectors cost about $6000 each, the FAA noted.