Investigation into the effectiveness of certification and operational icing procedures for helicopters

Abstract

This paper presents information gathered from helicopter airframe and engine manufacturers, as well as operators, both in Europe and Canada. It details the measures taken to prevent accidents in icing conditions through helicopter design and operating procedures. The major conclusions of the paper are that a helicopter's operating procedures change, depending on whether the route is off-shore or overland. When flying over water, there is normally a positive temperature layer above the sea, which can be used as an escape route by helicopters that encounter icing conditions. The principle types of icing that affect helicopters are engine icing and main rotor icing. Ice accretion is a gradual process, which the pilot should be able to detect from visual cues, instrument levels and handling changes. Most helicopters are not cleared for flying in any icing conditions, although nearly all their engines have basic forms of ice protection. Rotor icing directly affects the manoeuvrability and performance of the helicopter. The helicopter industry felt that snow, slush and visibility were the biggest weather problems. Although icing was a hazard, owing to the types of operations flown by helicopters, it was of less importance. The methods used to certify helicopters have been adapted from those of fixed wing aircraft, so the applicability of the airworthiness requirements, such as appendix C should be validated for helicopter operations.