Among in-flight hazards related to weather conditions, aircraft icing has always been one of the biggest issues in commercial aviation. Since major efforts in the 1940s and 50s to investigate and document environmental conditions prone to the formation of ice on aerodynamic surfaces, the resulting regulations, such as the Federal Aviation Regulations (FAR) 25 Appendix C, have not been re-assessed in detail.
Due to a general increase in air traffic, and in particular the growing number of regional aircraft, which are more sensitive to icing, there is renewed interest in this subject.
EURICE aimed to carry out a co-ordinated effort within Europe to examine current aircraft icing problems and the related certification process, operational requirements and finally the flight standards for icing. The results could be used to revise the Joint Aviation Authorities' Airworthiness Requirements (JAR) and its associated advisory documentation.
The main objectives of EURICE were to:
- tackle critical aspects of the icing certification process of aircraft and rotorcraft through the revision of the standard icing atmosphere, and identification of operational weaknesses that would require new or modified requirements;
- create a European database, complemented by flight testing, to be used as the scientific platform for the revision of the icing atmosphere data, and to elaborate on new probabilistic atmosphere models, which could be used to enhance the development of real time forecasting of snow, freezing drizzle and freezing rain;
- survey future developments for icing protection systems, procedures and corresponding regulations and evaluate the impact of possible changes in regulations in terms of design process and means of compliance modifications.
- reviewed the scope of icing hazards in aviation, developing a database of world-wide icing-related accidents and incidents from 1980 to 1995;
- collected and analysed existing icing atmosphere data, and developed a relational database accessible via the Internet;
- carried out flight tests with twin engine turboprop aircraft employed by three national research centres to investigate Supercooled Large Droplet (SLD) conditions that trigger ice formation on the airframe and wing, achieved by using the latest measuring equipment
- reviewed existing regulations for design and certification of fixed-wing aircraft and helicopters with respect to operation in icing conditions, and sought feedback from manufacturers of turboprop aircraft and rotorcraft on their experience with current icing standards;
- interviewed operators about specific ice information and crew training aspects;
- proposed several updates and extensions to the existing FAR 25 Appendix C regulation to cover SLD conditions, the instrumentation to measure these conditions and the characterisation of atmospheric phenomena;
- compared current 'means of compliance' in certification and design, such as the analysis of ice accretion, system safety, laboratory trials and flight tests.
Co-ordinated efforts by Europe's Joint Aviation Authorities (JAA), the US Federal Aviation Administration (FAA) and others, such as Transport Canada, will be beneficial in developing harmonised design and certification rules concerning icing hazards. The EU's R&D programmes in collaboration with the JAA's Flight Study Group may help to update and extend airworthiness regulations, found to be insufficient at the moment.