Increasing Rotor Blade Durability in Erosive Environments

U.S. military helicopters are used extensively in the harsh environments of the Middle East. Increasing rotor blade durability has the potential for both a significant reduction in direct operating costs and an increase in mission availability.

Most untreated rotor blades utilize a metallic leading edge made of titanium, stainless steel, or nickel, and operation in desert conditions results in significant degradation of these materials. Additionally, a visible halo is generated around titanium blades, which can distract pilots and make the aircraft visible to potential threats.

The current erosion protection approach includes application of an engineered polyurethane layer. This approach provides a 4-6 times improvement over unprotected blades, and can be reapplied in the field when wear does occur. While an improvement, it still requires an effort to maintain protection; furthermore, it is susceptible to impact damage caused by rocks and other harsh airborne debris.

As part of the Rotor Durability technology investment agreement between Sikorsky and AATD, the next generation erosion resistant solution for helicopter main and tail rotor blades is under development. Requirements are a 1,000 hour life within erosive environments, compatibility with the deice system, and the option for replacement by spares on a legacy aircraft. Achieving these goals requires an in-depth understanding of various environmental conditions and impact mechanisms.

A wide variety of materials were screened for their ability to resist sand and rain erosion. Trades driven by aircraft design specifications, impact speeds, strain tolerances, and environmental exposures have refined the candidates.  Additionally, manufacturability and repairability characteristics were considered. The combined outcome of these efforts will be demonstrated by the manufacture of rotor blades enhanced with the selected solution.

The presentation describes the down selection process, the outcomes of the various trades and studies, and the plans to implement the durability solution on the demonstration articles.

This research was partially funded by the Government under Agreement No. W911W6-08-2-0006. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon.

The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Aviation Applied Technology Directorate or the U.S. Government.