US Navy E2C Propeller Inspection
ProblemThe E-2 Hawkeye is the Navy's all-weather, carrier-based tactical battle management airborne early warning, command and control aircraft, providing the eyes and ears for carrier task forces and ground operations. An emergency situation developed when 16 catastrophic propeller failures occurred, destroying the engines and nearly bringing the planes down.
The cause of the failures was determined to be due to anomalies in the bond between the fiberglass skin and the foam core of the propeller. However, the combination of foam, fiberglass and coating on the propeller presented significant challenges to conventional inspection methods including x-ray and ultrasound. As a last resort, the props were being inspected by coin tap, which was ineffective for detection of cracks in the foam.
Subsurface crack in E2-C propeller
SolutionThe Navy implemented TWI�s EchoTherm inspection system at NADEP Cherry Point in 1998, for in-service maintenance and acceptance testing of new propellers. A 100% inspection of every E2C blade is performed to identify skin-foam bonding problems as well as fluid ingress and impact damage. Inspection procedures have been developed and over 30 inspectors have been trained to perform the inspection.
Recently, an automated system was implemented to handle increased workload. Since implementation of the TWI system, no prop failures have occurred.