previous experience with metallic and composite structure in the current fleet. These lessons provide evaluation criteria in the application and servicing of new materials and structures.

An International Air Transport Association survey estimates that 36–40 percent of damage to aircraft is from ramp and maintenance damage, sometimes called friendly foreign object damage (IATA, 1991). Figure 7-1 shows a diagram of the Boeing 777 aircraft interfaces with servicing and other equipment (Boeing, 1994b). These areas are especially prone to damage and require robust material performance in these locations.

To determine the extent of groundhandling damage, 11 airline operators were queried for ground damage history during the years 1990 to 1993 (Boeing, 1994a). Of the 2,241 incidents reported, more than a third were from unknown causes. A tabulation of the causes of damage is given in table 7-2.

Ramp and maintenance damage can represent significant costs to the airlines. The repair of a damaged component is only part of the cost. The airline also bears the cost of flight delay or cancellation and the effects on connections and aircraft rotations.

In April 1988, an Aloha Airlines Boeing 737-200 experienced an in-flight structural failure in which a large section of the upper fuselage ripped open and separated from the aircraft. The failure resulted from multiple-site damage (MSD) and corrosion. In this case, MSD was the link-up of

Front Matter (R1-R14)

Executive Summary (1-4)

1 Requirements and Drivers (5-10)

2 Structural Concepts (11-25)

3 Metallic Materials and Processes (26-35)

4 Polymetric Composite Materials and Processes (36-44)

5 Environmentally Compliant Materials and Processes (45-48)

6 Methodologies for Assessment of Structural Performance (49-56)

7 Aircraft Maintenance and Repair (57-66)

8 Nondestructive Evaluation (67-70)

9 Committee Findings (71-76)

References (77-82)

Appendix: Biographical Sketches of Committee Members (83-84)