Sealant Removal from A-10 Center Wing Fuel Tanks Using a Portable Hand-Held Nd: YAG Laser System

1. Sealant Removal from A-10 Center Wing Fuel Tanks Using a Portable Hand-Held Nd: YAG Laser System Norman J. Olson Pacific Northwest National Laboratory Richland, Washington 99352 Mitchell Wool General Lasertronics Corporation San Jose, California 95112 2005 CTMA Symposium – Tacoma, WA April 18-21, 2005

2. The Problem • > 300 A-10 Aircraft in Service • Center Wing Fuel Tank Cells Have Fasteners Covered with Sealant (Primer Coating Elsewhere) • Sealant in Fuel Tanks Needs to be Removed for NDE and/or Repair • Sealant Removal from Center Wing Tanks is Tedious and Expensive • Need a Less-Expensive, Faster Alternative 2

3. The Problem • Current Technology is Hand Scraping • Difficult and Slow • Incomplete Cleaning is Highly Likely • Damage to Substrate is Likely • Laser Coating Removal • Offers Potential • Minimal Experience in Confined Spaces • Many Unanswered Questions 3

4. Demonstration Objectives and Requirements • A portable Nd: YAG laser that can remove sealant more economically than current methods, • A hand-held delivery system that is capable of removing all sealant in the center wing section, • A hand-held delivery system that is easy and safe to use, • A system that has the potential to remove only sealant and not primer (color recognition), and • A system that has reasonable reliability so that it will be operational for long periods of time without maintenance. 4

5. Target for Demonstration • A-10 SPO Sent Retired Center Wing Fuel Tank Section to General Lasertronics Corporation Facilities in San Jose, CA • Demo Wing Section Had Eight (8) Access Ports to Fuel Cells • There Were Approximately 600 Fasteners Covered with Sealant in Each of the Eight (8) Fuel Cells • Access Ports Barely Large Enough for Operator Cell Opening 5

6. Attributes Needed to Meet Requirements for A-10 Center Wing Tank • Portability and reliability – DP Nd: YAG laser • Compact hand-held end effector that can operate in confined space – GLC SBIR design • Ability to see target area even if there are obstacles in line of sight • Meet laser safety and environmental issues • TWO-dimensional automated beam scanning to eliminate substrate damage potential and to ensure complete and systematic coating removal • Color recognition – potential to selectively remove sealant without disturbing other coatings 6

7. 200 and 500 Watt Demonstrations Using GLC-Developed Systems • 200 watt , 13 kHz, Nd: YAG Lamp-Pumped, Q-Switched System was Used for the Demo Conducted 9/21/2004 • US Laser 406Q laser • 500 watt, 10 kHz, Nd: YAG, Diode-Pumped, Q-Switched System was Used for the Demo Conducted 12/9-10/2004 • Cutting Edge Optronics Laser: Northrop-Grumman • Operator Uses Video Display if Line-of-Sight Obstructions Exist 7

8. GLC Confined Space Tool for Laser Coating Removal • End Effector Consists of: • Laser Aperture • Two-Dimensional Scanning • 25 cfm Air Blow from Aperture • Cooling • Clear Work Area • Video Camera • Optical Fiber Umbilical • Cell Waste Evacuation • Separate 300 CFM Purge • Remove Ablated Debris • Remove Sealant Vapors • Maintain Good Visibility Camera 8

9. Demonstration Results • Sealant Removed from Equivalent Fastener • 200 watt in ~ 1 Minute • 500 watt in < ½ Minute • Estimate of Labor for Entire Center Wing Fuel Tank • GLC Laser Tool Using the 500 watt SystemOne 8 Hour Shift • Conventional Scraping • Has never been fully completed • >> 800 work hours 24 Equivalent Fasteners 9

10. Demonstration Results • Color Recognition Potential Demonstrated on Automated System to Remove Coatings from Other Aircraft • Color Recognition Previously Demonstrated with a GLC Hand-Held Delivery Tool 10

11. Demonstration Objectives Met • A portable Nd: YAG laser can easily remove sealant more economically than current scraping methods • A hand-held delivery system could be configured to remove all sealant in the center wing section • With minimal operator training, a hand-held laser delivery system is easy and safe to use • The system could be configured to remove only sealant and not primer by implementing existing color-dependent sensing technology and automated laser firing controls • The system has reasonable reliability so that it will be operational for long periods of time without maintenance. 11

12. Safety • Requirements • Filtered (Clear) Glasses Worn by Operators • Work Area Secured the Same as a Welding Area • No Other Personal Protective Equipment Needed • Recommendations • Two Operators in Work Area • Improve Productivity by Maximizing Trigger Time • Keep Work Area Clear of Unauthorized Personnel • Could Enclose Work Area with Filtered Glass 12

13. Recommendation for NCMS/CTMA Project • Implement System at Hill AFB • Build hand-held laser system for test, evaluation, and subsequent installation • Develop laser system operating parameters to ensure sealant removal without 2024-T3 Al substrate damage • Systematic exposure over a range of laser conditions • Collect metallographic and SEM information and relate to mechanical test data over statistically significant data sets • Develop end-effector attachments for easier access to all fasteners within A-10 • Project Funding ~ $1500K, including cost-sharing 13