This work forms part of a larger investigation into fatigue crack detection using acoustic emission (AE) during landing gear airworthiness testing. It focuses on the use of principal component analysis (PCA) to differentiate between fatigue crack propagation (FCP) signals and high levels of background noise. An artificial AE fracture source was developed and additionally five sources were used to generate differing artificial AE signals. Signals were recorded from all six artificial sources in a real landing gear component subject to no load. Furthermore, artificial FCP signals were recorded in the same component under airworthiness test load conditions. PCA was used to automatically differentiate between AE signals from different source types. Furthermore, successful separation of artificial FCP signals from a very high level of background noise was achieved. The presence of a load was observed to affect the ultrasonic propagation of AE signals.