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Technical Analysis

Summary

Fairchild Industries Inc., SA227-DC, VH-DMI

1. FACTUAL INFORMATION
1.1 Introduction

Extensive radial cracking of the flangeOn 12 August 2001, the take-off of a Fairchild Metro 23 aircraft (VH-DMI) was discontinued as a result of the failure of the left engine. To investigate the event, the Australian Transport Safety Bureau carried out an examination of major components from the first, second and third turbine stages of the affected engine.

  • Centre rotating air seal plate (p/no. 3103839-3, s/no. 2-23315-945)
  • First-stage turbine wheel (p/no. 3103897-10, s/no. 3-03229-1075)
  • Second-stage nozzle guide vane assembly
  • Second-stage turbine wheel (p/no. 3103927-5, s/no. 981217201126)
  • Third-stage nozzle guide vane assembly
  • Third-stage turbine wheel (p/no. 3103838-2, s/no. 0-01345-1837)

An earlier disassembly of the engine had found these components damaged to varying degrees.

To further assist the examination, two additional rotating air seal plates were supplied. Extensive radial cracking of the flange section had rendered both of these items unserviceable.

1.2 Component history

The failed engine was an Allied Signal (Garrett) TPE331-12UHR-701G, serial number P-70210. At the time of failure, the engine had operated for a total of 9,140 hours and through 15,585 flight cycles. The following life information was also provided for the rotating components.

Item TSN (hours) CSN Life Limit (cycles)
Air Seal Plate
9,140
15,585
20,000
S1 Turbine Wheel
9,140
15,585
20,000
S1 Turbine Blades
3,067
5,728
Unknown
S2 Turbine Wheel
6,073
9,857
15,000
S3 Turbine Wheel
4,614
8,545
12,000
 
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