Description of Driving Event:
Wind Tunnel Fan Blade Cracking at Ames Research Center
Lesson(s) Learned:
The fan blades on the 40' x 80' x 120' wind tunnel at the Ames Research Center developed cracks after only 2,000 hours of operation. To preclude shutting down the tunnel for the 1 year required to procure and install a new set of blades, it was decided to repair the old blades while waiting for delivery of the replacements. The repair includes wrapping the root section of the blades, which eliminates the ability to detect crack growth by visual inspection.
Recommendation(s):
NASA should ensure that a suitable inspection program, including frequent checks using nondestructive evaluation methods, is implemented.
Evidence of Recurrence Control Effectiveness:
As part of the fan blade repair at the National Full-Scale Aerodynamic Complex (NFAC), quality assurance and inservice inspection procedures are being developed and applied to ensure functionality of the repair. All blades are being visually examined to assess and establish their condition prior to the start of repair. Throughout the repair process, both ultrasonic and acoustic tap testing is being performed to determine adequacy of the crack fill, as well as the wrap lay-up quality and bonding. After placing back in service, periodic inspections using acoustic tap testing and a series of full-scale fatigue tests will be implemented to monitor and characterize void growth. Based on these testing results, criteria for the periodic inspections, including frequency and size of indications, will be developed.
Documents Related to Lesson:
N/A
Mission Directorate(s):
- Exploration Systems
- Aeronautics Research
Additional Key Phrase(s):
- Aerospace Safety Advisory Panel
- Facilities
- Parts Materials & Processes
- Policy & Planning
- Research & Development
- Test Facility
Additional Info:
|
