Certification and operation of helicopters in icing environments

This paper presents the issues gathered from a survey carried out on helico pter airframe and engine manufacturers, and helicopter operators and aircre ws, throughout Europe and Canada. The work focused on in-flight icing and t he problems of manufacturing, testing, and subsequently, operating helicopt ers in such conditions. Most commercially operated helicopters are not perm itted to fly in known icing conditions, because they are not certified to d o so by the aviation authority. However, during the survey it was establish ed that owing to commercial pressures, aircrews do fly in icing conditions, using helicopters that do not have an icing clearance, In addition, there is a disparity between what the airframe manufacturers and icing specialist know are the most dangerous icing conditions, and the knowledge held by he licopter aircrews. Aircrews would like a better method of ice detection and would prefer an ice predictor, which indicates that an icing environment i s approaching, rather than a detector, which tells them that they are alrea dy in icing. Furthermore, operators would like all helicopters to have a fu ll icing clearance if there were no operational penalties. In conclusion, t he industry as a whole would like to verify that the icing envelope describ ed in the certification regulations is applicable for helicopters. The curr ent parameters have been modified from fixed-wing aircraft, which tend to c ruise at much higher altitudes and in colder, drier conditions.