Abstract Subject invention relates to novel and improved apparatus for non-destructible detection of flaws in aircraft fuel filtering or coalescing elements. The improved apparatus provides for the conduction of heated pressurized air through the coalescer element to be tested into contact with a plastic film which is positioned about the outer peripheral surface of the coalescer element. The outer surface of the film is coated with a predetermined cholesteric liquid crystal material or a combination of the same. Flaws present in the coalescer element produce uneven conditions of the heated air flow through the coalescer and temperature gradients on the liquid crystal coated film. Resulting color patterns on the coated film identify the location and nature of flaws in the coalescer element.