An Independent Check of the Performance of Two M2208 Fatigue Meters
Abstract
Aircraft Structural Integrity section of Directorate General Technical Airworthiness (ASI-DGTA) has concerns about the current accuracy of the ageing M2208 electro-mechanical fatigue meters fitted to RAAF P-3C and C-130H aircraft. An examination of relevant documentation was undertaken and tests performed on two meters, one deemed unserviceable and the other fresh from an overhaul. The results of this investigation are presented and implications discussed. The variable frequency closed box style testing performed in this study on two M2208 meters indicated these meters may produce readings of questionable accuracy due to errors not easily detected using current operational testing procedures of monitoring the G4/G3 ratio. When comparing the measured lock thresholds to the nominal lock thresholds, for the positive g counters, using a reference value of 0 g, the observed discrepancy varied between about 2% to 14% of the nominal value for both meters. A basic analysis of the significance of meter readings with fatigue consumption suggested that if the positive readings from the overhauled meter were employed as the sole source of fatigue life data, then the errors observed in threshold values in this study may lead to an underestimation of aircraft life consumption by about 40%. Currently, operational readings from these M2208 meters are not used for executive airframe life analysis, but are only used in a confidence building capacity by comparing Nz exceedances measured to the Nz exceedance spectrums used in the executive life analysis. Thus, although this limited study has indicated that observed performance for the overhauled meter differed significantly from the original specifications, the impact of this discrepancy is minimal given the current manner in which the data from these meters are used. The limited testing performed here, and taking into account the continual wear and tear expected with these types of electro-mechanical meters, would suggest that t
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2011
- Accession Number
- ADA550588
Entities
People
- Ian Powlesland
- Quang Nguyen
- Steve Galea
Organizations
- Defence Science and Technology Group