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Titanium is a difficult material to fabricate into complex configurations. There is several elevated temperature forming processes available to produce titanium components for aerospace applications. The processes to be discussed are Superplastic Forming (SPF), hot forming and creep forming. SPF uses a tool that contains the required configuration and seals around the periphery so inert gas pressure can be used to form the material. Of the processes to be discussed, this is the one that can produce the most complex shapes containing the tightest radii. A variation of the process combines an SPF operation with diffusion bonding (SPF/DB) of two or more pieces of titanium together to produce integrally stiffened structure containing very few fasteners. Another process for shaping titanium is hot forming. In this process, matched metal tools, offset by the thickness of the starting material, are used to form the part contour at elevated temperature.

We live in an era of increasing twin-engine commercial airplane operations, with large and very quiet high bypass ratio engines. At the same time, due to several decades of increased attention to the environment, we have large and increasing hazardous species bird populations. These trends, when combined, are not a prescription for continued assurance of a remarkable and enviable safety record for commercial aviation. Therefore, greater diligence must be placed on the evaluation of the current and future aviation wildlife hazard. We have some new weapons in this fight for greater capability to live with this situation. The basic problem is that different databases are populated independently from one another and often contain conflicting, contradictory, and erroneous data. Databases that were used individually, but not necessarily combined, are being utilized in a conjoined methodology to give us a better picture of the actual risk involved.

One of the most common damages occurred found on commercial airframes are dents and gouges. The usual repair for these damages includes installation of metallic doublers with rivets or with hi-loks. Sometimes these doublers are of complex design, because of multiple angles of the original damaged skin. Many times the damages are in hard to reach areas. In these cases the traditional metallic doubler repairs are not only time consuming and but also expensive. As the numerous holes are be drilled through the original structure, its fatigue life is adversely affected. For airline operators, time is valuable and they cannot afford to lose revenue by spending longer time for repairs. The use of bonded composite doublers offers the airframe manufacturers and aircraft repair facilities an alternative repair process that alleviates the abovementioned concerns.

A team from the USA rotorcraft industry, NASA, and academia was established to create a validated high-fidelity computational fluid dynamics (CFD) icing tool for rotorcraft. Previous work showed that an oscillating blade with a periodic variation in angle of attack causes changes in the accreted ice shape and this makes a significant change in the airfoil drag. Although there is extensive data for ice accumulation on a stationary airfoil section, high-quality icing-tunnel data on an oscillating airfoil is scarce for validating the rotorcraft icing problem. In response to this need, a two-dimensional (2D) oscillating airfoil icing test was recently performed in the Icing Research Tunnel at the NASA Glenn Research Center. Three leading-edge specimens for an existing 15-inch chord test apparatus were designed and instrumented to provide the necessary data for the CFD code validation.

Boeing needed a process to replace hand drilling for floor panel holes and galley and lavatory mounting locator holes in the floor grid of the completed 737 fuselage. Electroimpact developed a process, and the 737 AFDE machine, that is a substantial improvement over existing technology. It provides full CNC control, quick reconfiguration of hole patterns, fast drilling of up to 3000 holes in one 8-hour shift, drills both titanium and aluminum and works inside the fuselage.

The advantage of higher strength to weight and higher stiffness to weight ratios for composite structure compared to metallic structure is well known in the aerospace industry, especially to commercial airline world. Its increased usage in the airplane structure is a direct reflection of the benefit in reduction of operating costs by lowering the fuel usage. This factor turned out to be more important for the airlines after the September 11, 2001 incident and also due to the increase in fuel prices. Besides reduction in the operating costs, airlines are seeking ways to reduce their maintenance costs. Most of the damage to the aluminum structure airplanes is attributed to corrosion. The non-metallic composite structure has an excellent property of resistance to corrosion. The structure is more damage tolerant due to the absence of fastener holes. As a result, its increased usage serves the airlines by lowering the maintenance and inspection costs.

A new look at tactical combat V/STOL design and utility as affected by emerging technology and mission concepts is given in this paper. History has shown that a certain level of useful load fraction must be attained before an airplane system can be considered operationally successful. Technology trends reviewed in this paper suggest that the time is here or at least near for V/STOL tactical aircraft to achieve a truly viable useful load fraction. Propulsion, structure, and controls technologies will contribute to the success of the tactical V/STOL system. In addition, aerodynamic technology as related to interference effects in hover and transition, and as required for efficient supersonic cruise and combat, significantly impacts the design solution. A unique approach to system design risk assessment is described with results giving technology leverage as a function of design options.

The term “3 inch ice shapes” has assumed numerous definitions throughout the years. At times it has been used to generally characterize large glaze ice accretions on the major aerodynamic surfaces (wing, horizontal stabilizer, vertical stabilizer) for evaluating aerodynamic performance and handling qualities after a prolonged icing encounter. It has also been used as a more direct criterion while determining or enforcing sectional ice shape characteristics such as the maximum pinnacle height. It is the authors’ observation that over the years, the interpretation and application of this term has evolved and is now broadly misunderstood. Compounding the situation is, at present, a seemingly contradictory set of guidance among (and even within) the various international regulatory agencies resulting in an ambiguous set of expectations for design and certification specialists.

The formation of ice over lifting surfaces can affect aerodynamic performance. In the case of helicopters, this loss in lift and the increase in sectional drag forces will have a dramatic effect on vehicle performance. The ability to predict ice accumulation and the resulting degradation in rotor performance is essential to determine the limitations of rotorcraft in icing encounters. The consequences of underestimating performance degradation can be serious and so it is important to produce accurate predictions, particularly for severe icing conditions. The simulation of rotorcraft ice accretion is a challenging multidisciplinary problem that until recently has lagged in development over its counterparts in the fixed wing community. But now, several approaches for the robust coupling of a computational fluid dynamics code, a rotorcraft structural dynamics code and an ice accretion code have been demonstrated.

With the increasing usage of composites for aerodynamic surfaces, the use of bonded composite repair processes are becoming more common. The repair process remains a largely manual process, with repair technicians scarfing or stepping, tracing the plies, fabricating repair patches and finally bonding the patch. The patch fabrication process becomes increasingly tedious and tiring due to cutting and tracing of each individual ply twice for thermal surveying and the final repair patch. We have developed a system that can replace the tracing and cutting components of the fabrication process using low cost, commercial off the shelf (COTS) tools. We present the ply boundary extraction method used and detail the nesting algorithm used to produce the final plies. Our software is benchmarked against the manual process with a list of successfully cut materials using a low cost fabric cutter with a steel drag blade.

Flight in icing for transport category aircraft certification presents a particularly challenging set of considerations to establish adequate safety commensurate with the associated risk while balancing design complexity and efficiency. A review highlighting important aspects of the regulatory evolution and guiding principles for flight in icing certification is presented, including the current standards and recent rulemaking activity.

Determining local ice crystal icing concentration factors in the region of the forward fuselage is critical for setting the Total Water Content levels for air data probe qualification testing. Simulation, modeling, and testing techniques for this concentration-factor phenomenon are still in their infancy, and there is currently not a significant amount of this type of analysis in the literature. A representative, 3D analysis was conducted using transport airplane geometry and flight conditions that explored the sensitivities resulting from parametric changes to flight and ice crystal icing conditions, particle modeling parameters, and bouncing effects.

The Particular Risks Assessment Document (PRA) is the compendium of the assessments accomplished during the development of a new airplane that relate to threats to the airplane from the outside environment (e.g. birdstrike, lightning, hail) and threats to the systems from events originating in other systems (e.g. rotorburst, flailing shafts, tire and wheel burst). These assessments are accomplished to ensure the robustness of the design to survive these threats. An extensive list of threats is developed and teams are formed to evaluate each of them. The results of these studies are collated into a document that provides a single point reference for the new airplane with regard to its ability to survive all known external threats. If PRAs have been accomplished on previous programs they can be used as a starting point for the new assessment, then the systems are reevaluated against the new design and differences created by new design features need to be added to the list.