CASE STUDIES

ITT DROP INDICATION

Decrease in ITT prior to planned maintenance work, helps find unexpected part failure and optimises downtime.

INTRODUCTION

The aircraft was due in maintenance for two weeks during which the Honeywell Service Bulletin SB 76-5121 (Replacement/Upgrade of the DEEC’s) was to be embodied. Prior to the work being carried out, the SB requires that a DEEC download is carried out.

GAS PATH ANALYSIS

The analysis of the trend from the engine showed a gradual decrease in ITT through out the period covered by the download. This was worth looking at while the engine was down for maintenance.

ACTION/FOLLOW UP

Investigation of the ITT system revealed curling of most of the ITT probe tips as shown in the photographs. The entire harness was replaced.

CONCLUSION:

The engine was saved from continued operation with defective temperature indication, which could have impacted engine reliability, safety and cost of operation.

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