Assessing the Performance CVM Sensors for Monitoring the 737 Aft Pressure Bulkhead

Abstract

Current maintenance operations and integrity checks on aircraft require personnel entry into normally-inaccessible or hazardous areas to perform necessary nondestructive inspections. To gain access for these inspections, structure must be removed, sealant must be removed and disassembly processes must be completed. The use of in-situ sensors, coupled with remote interrogation, can be employed to overcome a myriad of inspection impediments stemming from accessibility limitations, complex geometries, the location and depth of hidden damage, and the isolated location of the structure. Reliable Structural Health Monitoring (SHM) systems can automatically process data, assess structural condition, and signal the need for specific maintenance actions. This paper presents an OEM-airline-SHM vendor-regulator effort to realize these benefits by moving Comparative Vacuum Monitoring (CVM) technology into routine use in airline maintenance programs. A certification program has been completed to validate CVM sensors for surface crack detection on the 737 Aft Pressure Bulkhead (APB). Formal and comprehensive CVM technology validation and certification was guided by a recently-released FAA Issue Paper which addresses the full spectrum of issues including design, deployment, durability and performance. For accurate SHM validation to occur, all relevant environments - which may include separate fatigue and environmental response components - were properly simulated in the tests. Flight tests also played an important role in assessing overall CVM system performance under normal aircraft operations. Validation tests were designed to address the CVM equipment, the health monitoring task, the resolution required, the sensor interrogation procedures, the conditions under which the monitoring will occur, and the potential inspector population. The test results will be presented in light of the overall CVM certification plan. Such SHM deployment programs are allowing the aviation industry to confidently make informed decisions about the proper utilization of SHM. These programs also streamline the regulatory actions and certification measures needed to ensure the safe application of SHM solutions.