statistical analysis

FAA Issues Draft “Sample Size” Advisory Circular that Would Apply to PMA, STC, and RS-DER applications

The FAA has issued for comment a draft Advisory Circular focused on sample size for statistical analysis in PMA applications. As many of you remember, there was a draft on statistical analysis issued several years ago. MARPA objected to that draft because it implied that every PMA application needed to be based on statistical analysis, … Continue reading →

FAA Issues Statistical Analysis Guidance – Are You Testing Enough Parts?

The FAA has issued new guidance for how to use statistics in your PMA and STC applications. They have also set minimum sample sizes that seem unrealistically high for many parts. The guidance is limited to sample sizes for engine parts and APU parts, but it sets a precedent that could be followed for other parts. Continue reading →

Comments Sought on Proposed FAA Advisory Circular for Engine and APU Comparative Test and Analysis

The FAA has released a new draft Advisory Circular that is intended to describe acceptable statistical methods for developing substantiating data for comparative test and analysis compliance findings to support FAA approval of turbine engine and APU parts produced under a PMA, TC, STC, repair or alteration.

Several members have brought this AC to our attention and expressed their concerns about the details of this guidance. We welcome specific comments from members about problems and/or ways to improve this document. Based on member comments we have received so far, the proposed guidance appears likely to discourage applications to produce replacement parts. One reason for this is the large suggested sample size, and associated high costs, necessary to satisfy the proposed statistical analysis metrics. Continue reading →