Follows Reports Of Two Failures Of PW4000-94 Model Engines

The FAA has issued a revised Special Airworthiness Information Bulletin (SAIB) for PW4000 engines following two reports of LPT 4th stage vane liberations, which have resulted in two engine failures with low-energy case uncontainment events on PW4000-94 model engines. In both cases, the pilots of the airplanes that suffered the engine failures made safe landings.

Investigations revealed sulfidation of the vane internal passages corroding the parent material, weakening the structure and inducing lean back or liberation of vane clusters.

This SAIB provides information on LPT 4th stage vane fractures and lists service information intended to prevent further occurrences of vane weakening and possible engine failure. PW4000 series engine Clean, Inspect, Repair (CIR) Manual, P/N 51A357, Task No. 72-53-24-200-002, dated January 15, 2015 was issued to inspect the LPT 4th stage vane airfoil permeability using a magnetoscope. This method is indicated because the material degradation occurs largely from the inside of the vane passages. While general borescope inspection is useful to identify sulfidation of the external airfoil surfaces, it is unable to detect deterioration of internal surfaces prior to failure of the part. Magnetoscope inspection allows for the remainder of the unaffected airfoil material to be measured by nondestructive means.

The FAA recommends that upon piece part exposure of LPT 4th stage vanes with a hollow internal airfoil configuration you perform a magnetoscope inspection per the instructions in PW4000 series engine CIR Manual, P/N 51A357, Task No. 72-53-24-200-002, dated January 15, 2015 and remove the degraded parts.

(Image from file)

FMI: SAIB