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Technical Paper

Study of Positive Feed Drilling Parameters for Optimized Drilling in Stackups of Composite/Metallic Materials

Design limits in aerospace are constantly being challenged forcing engineers to look for materials and material combinations that will provide the strength needed, yet meet the lightweight requirements demanded throughout the industry. These material combinations provide demanding and unique challenges to all involved in the development of robust, reliable assembly processes. As advancements are pushed forward in aircraft materials, advancements must also be made in the technologies/methodologies used to drill close tolerance holes in these complex materials. These advancements will be discussed in the following paper. Common stack-ups of aircraft materials include various combinations of graphite, aluminum, and titanium. Many problems arise when trying to drill the different combinations of these materials due to the extreme differences in physical properties.
Technical Paper

Empirical Wake Turbulence Model of Tiltrotor Aircraft

This paper describes the methods used to collect and reduce wake turbulence data behind two distinct types of tiltrotor aircraft using a Light Detection and Ranging (LIDAR) measurement system, which uses laser velocimetry to measure the velocity of dust particles in air that has been disturbed by the passage of an aircraft. The test aircraft flew at various combinations of weight, rotor speed, airspeed and configuration. The MIT LL LIDAR system measured the wake vortices with minimal pre-test preparation; we obtained a large quantity of high quality data in only a few days of testing. The data shows tiltrotor and fixed-wing wake characteristics are very similar. Data reduction methods used a classical horseshoe vortex system as a template, and employed a vortex that had a rotational core and an irrotational outer field. Intersecting polynomials that are linear in downstream distance and bi-linear in downstream distance and mast angle adequately modeled vortex strength.
Technical Paper

Peck Drilling of Composite/Metal Assemblies

Under Contract No. N00019-93-C-0006 EMD with the Department of the Navy, Bell Helicopter Textron Inc. (BHTI) conducted a Manufacturing Process Verification Test as part of the V-22 Engineering Manufacturing Development process. The objective of this test was to develop a “One Step” drilling solution for peck drilling close tolerance holes in V-22 major assemblies. These assemblies consist of Titanium / Graphite / Titanium and Aluminum / Graphite compositions. The V-22 is a graphite / epoxy composite structure that has metal detail parts mechanically attached to the basic structure. Attachment of these detail parts is accomplished with two piece titanium fasteners that require a close tolerance of .003″ per hole. To achieve this tolerance a drill / ream process is currently used.
Technical Paper

Designing the v-22 “Osprey” Tiltrotor V/Stol Aircraft for Maintenance and Serviceability

This paper deals with the development and application of maintenance and serviceability-related design constraints during the design of the V-22 “Osprey” multi-service aircraft. The V-22 program has been unique in its early and continuous application of supportability emphasis during the aircraft development process. Integrated teams of logistics and design engineers were formed commencing with the beginning of the preliminary design phase to ensure maximum aircraft supportability. Mockups were used extensively to develop serviceability concepts and evaluate conceptual designs. Design approaches to enhance supportability were stressed throughout the development process. This paper highlights the effectiveness of the supportability enhancement process by reviewing the process itself and describing some of its resulting effects on the design of the “Osprey.”
Technical Paper

Evaluation of Current Conductivity of Composite Wiring Integrated Assembly for use on Bell / Agusta 609 Tiltrotor Aircraft

Electrical characteristics of composite Wiring Integrated Assembly (WIA) chassis’s when subjected to lightning environment are studied. The wiring architecture of the Bell Agusta Tiltrotor civil aircraft designated as Model BA609 includes WIAs that are shielded junction boxes. The WIAs are required to maintain wire bundle shield continuity to ground when exposed to the effects of a lightning event. Test results demonstrate that the composite WIAs having copper and nickel plating can withstand lightning currents up to 20 KA. A description of the WIAs, as well as lightning test procedure and results using waveforms 5A and 5B are presented.