TABLE OF CONTENTS Damage present at the first flight after a major inspection can constitute a significant safety problem. The situation has been recognized, in the discussion of risk management, as the main element in establishing an acceptable safety level for flight vehicles.
There are a few situations that need further scrutiny. Some of the more severe are:
Damage initiated in the manufacturing process has insignificant external damage size indicators and grows to "region 5 internal damage during service";
Severe damage (region 5) initiated after major inspection but before start of the first flight and not accessible to "preflight walk-around inspections";
Unreported and undetected major damage resulting from ground accidents for cases when external damage size is disproportionately small compared to internal damage size;
Accidental in-service damage with "faint" and fading external damage indicators;
Significant strength reduction due to processing failures or in-service degradation;
Selection of maximum damage size for ultimate static strength requirements.
Damage, detection and inspection approaches are important ingredients in design to avoid "Unsafe States" in composites. A detailed investigation of the probability of an unsafe state for a specific PSE is conducted in the next section.
Inspection methods selected for service can depend on both internal and external damage sizes for detection. "Visual" inspection would depend on external damage size for detection. The "tap-test" would be expected to depend on a combination of the two. And inspections based on acoustic response would be dominated by internal damage size. The critical situation would deal with loss...
