The FAA's latest bulletin asks inspectors, owner, operators and repair technicians to be cautious in the handling of flexible lines and hoses that carry flammable fluid to aircraft engines. The SAIB also advises maintenance personnel against overbending of flexible lines and hoses and to treat them as hard lines. The FAA advises inspection of flexible lines and hoses, because engine fires may occur if these lines or hoses fail after overbending or kinking.
The bulletin follows the investigation of a fire in a Pratt & Whitney PW4062 engine that was caused by a leak in the Turbine Case Cooling air valve actuator fuel pressure line. During a recent overhaul, the line was apparently removed and then, after replacement, was moved aside during replacement of a TCC actuator.
Metallurgical examination of the CP11 line showed the line ruptured in an area of broken wires in the braid directly adjacent to a kink in the line. The CP11 line is identified by a metal band wrapped around the outside of the external fire sleeve. This metal band, acting like a hinge when the flexible line is bent, is believed to have caused the kink in the CP11 line. The investigation noted the rupture in the CP11 line was adjacent to the identification band.