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. 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

3. 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

4. 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.

5. 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

6. 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

7. 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

8. 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

9. 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 System One 8 Hour Shift Conventional Scraping Has never been fully completed >> 800 work hours 24 Equivalent Fasteners

10. 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

11. 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.

12. 12 SafetySafety 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

13. 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