Aircraft icing has been a focus of the aviation industry for many years. While regulations existed for the certification of aircraft and engine ice protection systems (IPS), no FAA or EASA regulations pertaining to certification of ice detection systems existed for much of this time. Interim policy on ice detection systems has been issued through the form of AC 20-73A as well as FAA Issue Papers and EASA Certification Review Items to deal mainly with Primary Ice Detection Systems. A few years ago, the FAA released an update to 14 CFR 25.1419 through Amendment 25-129 which provided the framework for the usage of ice detection systems on aircraft.
As a result of the ATR-72 crash in Roselawn, Indiana due to Supercooled Large Droplets (SLD) along with the Air France Flight 447 accident and numerous engine flame-outs due to ice crystals, both the FAA and EASA have developed new regulations to address these concerns. These new regulations are focused on aircraft-level ice protection certification and do not require a new type of ice detection technology. However, they do imply the need for ice detection systems which can detect and differentiate 14 CFR Part 25 Appendix C from Appendix O (SLD) as well as the ability to detect and differentiate Part 25 Appendix C or O from 14 CFR Part 33 Appendix D (ice crystals).
To meet these evolving industry needs, many new ice accretion and icing conditions detector technologies are being developed. Designing an ice detection system which has the sensitivity to detect and differentiate these different types of icing environments can be challenging enough, but integration with the aircraft systems, installation effects and freezing fraction differences between the ice detector technology and the aircraft surface of interest must be considered as well. This paper will review the regulation changes that impact ice detection system design and certification and discuss the necessary analyses and testing required to demonstrate the ability of ice detection technologies to meet these requirements and achieve successful Primary Ice Detection System certification.