Thu, Sep 9, 2010 — Admin
The FAA issues an emergency directive for Bell 222 and 430 helicopters.
1 September 2010 FAA
Emergency Airworthiness Directive (AD) for Bell 222 and 430 Helicopters
Prompted by a main rotor hydraulic servo actuator malfunction, which suggests an “unsafe condition” exists on other helicopters of the same design. A piston rod had fractured because of stress corrosion cracking; a nonconforming grind was discovered on a separate piston rod. It is not clear if this AD results from an accident or just from an inspection during maintenance. This emergency AD is considered “interim action” pending a reduced life limit and overhaul of the affected service actuators.
The interim action, which must be done “before further flight,” is pretty detailed:
– Disassembling the actuator to gain access to the piston rod.
– Cleaning the piston rod and nut using Acetone and a nylon brush.
– Inspecting the piston rod and nut and examining the grind relief for conformance. Replace if not in conformance.
– Using a 10x or higher magnifying glass, inspecting for corrosion or damage to the threads. Replace if corrosion/damage is found.
– If cadmium plate (gold or grey color) is lacking, replace the piston rod.
– If red or orange color corrosion is found, conduct a magnetic particle inspection of the piston rod for a c rack. If cracked, replace piston rod.
– Apply brush cadmium plating to all bare and reworked areas.
– Reassemble servo actuator. Mark it with the letter “B” following the serial number using a scribe or vibrating stylus.
The AD illustrates the extent to which helicopters depend on scrupulous maintenance for safe flight.