Scribe Marks Inspection with No Paint Removal

The Flight Standards Information Bulletin for Airworthiness (FSAW 03-10B) issued on November 2003, entitled: Fuselage Skin "Scribe Mark" Damage on Boeing 737 Aircraft, reports the following:
• 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 marks scribed in the fuselage skin.
• Marks scribed in the pressurized skin, if undetected, can result in cracks and possibly lead to widespread fatigue damage.
• All commercial aircraft who went to a repaint and sealant removal process are susceptible to have scribe marks.

Advantages of Ultrasonic Phased Arrays for Scribe Mark Detection Phased-array technology offers the following capabilities:
• Software control of beam angle, focal distance, and spot size
• Multiple-angle inspection with a single, small, electronically controlled, multielement probe
• No paint removal necessary to carry the inspection (huge time saving)
• Sector scan imaging
• The least expensive configuration of the OmniScan® PA (16:16) is sufficient to carry the inspection.

Advantages of OmniScan for Scribe Mark Detection
• The OmniScan is built to work in the harshest field conditions.
• The OmniScan is compact and lightweight (only 4.6 kg).
• The OmniScan will run 6 hours with its two Li-ion batteries.

Defects to Be Detected
• Scribe marks of 0.200 in. long (5.08 mm) or more
• Scribe marks should be 50% of the skin thickness in skins that are from 0.032 in. to 0.044 in. (0.81 to 1.10 mm) thick.

Scribe Marks Inspection

• The inspection is done with an OmniScan PA 16:16.
• The phased-array probe used is a 10-MHz 16-element probe (10L16)
• The probe is mounted on a SA1N60S5X5 wedge.
• Sector scans range from 60º to 85º SW.
• No encoder is needed.

OmniScan PA Imaging

Conclusions about Scribe Marks
• Inspection for scribe marks can be done without paint removal.
• OmniScan PA is now referenced in the Boeing NTM manuals, 737 NDT Manual, Part 4, 53-30-06, July 2005.
• Many airlines are already inspecting for scribe marks using this procedure and have dozens of technicians trained to use the OmniScan. Airlines report an extremely fast payback.
Other Maintenance Procedures Already Qualified

Airplane	Part	Service Bulletin	Qualified Instrument
Boeing 737	Doubling edge	737 NDT 53-30-25 part 6, Dec. 2004	OmniScan ECA with ECA probe
Boeing DC-9	Landing gear	DC9-32A350, Dec. 2004	OmniScan PA with PA probe

Ordering Information

These items are required to perform the inspection:

Description	Ordering Number
OmniScan Phased Array 16:16	OMNI-P-1616
Phased array angle-beam probe	10L16
Wedge	SA1-N60S5x5
Option	Ordering Number
NDT Engineering Special Purpose EC Reference Standard	NDT3065

Products used for this application OmniScan PA