AIRCRAFT SCRIBE MARKS USING PHASED ARRAY

Scribe marks on aircraft are nothing new; however, the way we inspect for them has changed in recent years, significantly reducing inspection times and expense. No longer does the paint have to be removed, avoiding long hanger stays and repainting. Visual inspection and multiple passes with conventional eddy current and ultrasonic’s have been replaced by a single pass with Phased Array and/or Eddy Current Array, enabling scribe mark inspection to be undertaken in short window turnarounds. Flight Standards Information Bulletin for Airworthiness (FSAW 03-10B) issued on November 2003 titled: Fuselage Skin “Scribe Mark” Damage on Boeing 737 Aircraft reports Damage has been reported along fuselage skin lap joints, butt joints, and other areas of several aircraft caused by the use of sharp tools used during paint and sealant removal Use of sharp instruments can result in lines scribed in the fuselage skin Lines scribed in the pressurized skin, if undetected, can result in cracks and possibly lead to widespread fatigue damage. All commercial aircrafts who went to a repaint and sealant removal process are susceptible to have scribe marks. Phased Array brings many benefits to the scribe inspection using software control of beam angle, focal distance, and spot size with off the shelf equipment, including a 10 MHz 16 element probe giving multiple-angle inspection with a single, small, electronically controlled multielement probe and 60 degree wedge enabling sector scan imaging ranging from 60 to 85 degree SW scans with no encoding necessary. Imaging is very easy to interpret with signal amplitude displayed using colours, where 0 to 99% screen height amplitude is green and 99 to 100% showing red. This gives an easy to use and interpret, go no go inspection. Rental kits are available on the shelf from Oceanscan for the Scribe line and most other aircraft maintenance procedures for both Phased Array and Eddy Current Array and include the Olympus Omniscan, Probe, wedge and calibration piece. Please call Oceanscan for more details. Information and pictures courtesy on Olympus NDT and Southwest Airlines.

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