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Scribe Marks Inspection with No Paint Removal


Scribe Mark detection

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 lowest 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.

Scribe Marks on Boeing 737

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
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.

Scan

OmniScan PA Imaging
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-PA1616M or higher configuration
Phased array angle-beam probe 10L16-A00
Wedge SA1-N60S5x5
Option Ordering Number
NDT Engineering Special Purpose EC Reference Standard varies
Olympus IMS

Products used for this application


OmniScan MX PA

The OmniScan PA performs manual and automated phased array inspections. It offers full-featured A-scan, B-scan, S-scan and C-scan displays, and advanced real-time data processing. Configurable in 16:128 elements, also 16:16M, 16:64M, 32:32, and 32:128

OmniScan MX2

The OmniScan MX2 now features a new phased array module (PA2) with a UT channel, and a new two-channel conventional ultrasound module (UT2) that can be used for TOFD (Time-of-Flight Diffraction), as well as new software programs that expand the capabilities of the successful OmniScan MX2 platform.
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