Solutions to helicopter blade erosion - Improving aircraft availability and reducing costs

Abstract

Helicopters engaged in military operations conduct a large number of take-offs and landings in “brownout” conditions. “Brownout” is a result of surface particles such as dust and sand being stirred up by the downwash from helicopter rotor blades causing a large cloud which can completely envelop the platform. Flying in “brownout” conditions can impact operational effectiveness in a number of ways including; loss of aircrew spatial awareness, damage to the helicopter in the form of erosion (particularly the engines and rotor blades) and scintillation from particle impacts with the rotor blades that creates a bright light source reducing the effectiveness of night vision devices. This paper concentrates on activities to reduce the effects of operation in “brownout” conditions on rotor blades. The study initially concentrated on characterising the type of damage caused to blades by operating in sand/dust environments with a number of damage mechanisms being identified. Maintenance records for the majority of helicopter types in UK service were interrogated with the results indicating that damage to blades from operation in sand/dust environments is a significant problem. The cost of reworking severely damaged blades has been quantified and is considerable, generally requiring that the blades are returned to the manufacturer for an extended period of time. A range of protection technologies were identified which largely mitigate blade erosion. Whilst work continues to investigate and develop new solutions it has been concluded that at present blade tape that is maintained effectively provides the most cost effective solution for UK military helicopters. To support the selection of future materials; a dynamic test facility has been developed which will allow samples of candidate mitigations to be tested in a representative sand/dust environment. The facility is novel in that it provides the capability to test a number of samples simultaneously ensuring that all of the materials are subjected to a similar level of damage. This approach will allow a simple comparison to be made between known “best of breed” solutions with new candidates.