HELICOPTER DE-ICING SYSTEM DEVELOPMENT AND QUALIFICATION FLIGHT IN NATURAL ICING VERSUS SIMULATION AND ANALYSIS

The qualification of helicopters for flight into known icing conditions has assumed greater importance as equipment which allows for flight in instrument meteorological conditions (IMC) has become a common sub-set of the avionics systems of most modern helicopters. The method of ensuring that the helicopter can safely operate in the icing environment it may encounter (qualification), is currently based largely on actual flight test in natural or simulated icing conditions. This basis for qualification can either result in a lengthy and expensive program to gather a large data base or, if the testing is limited, a level of confidence in the test results which may be unacceptable. The Boeing Company has recently completed an intensive test program to qualify a helicopter for flight in icing conditions, based on flight tests in natural icing while concurrently conducting studies to investigate simulation and analysis as a means of qualification, in lieu of flight testing. This paper will discuss the current criteria applied for qualification, review Boeing's natural icing flight test experience and discuss the alternate approach of simulation and analysis. The paper will also discuss some methods which may be developed to predict the effects of flight in icing conditions and further how these methods might be used to supplement and, in time, replace much of the current emphasis on flight in natural icing as the qualification basis.