Search Results

Fault-tolerance in commercial aircraft applications is typically achieved by redundancy. In such redundant systems the primary component is checked before the start of a flight to see if it operates correctly. The aircraft will not take off unless the primary is functioning. Airplane manufacturers must certify the airplane systems to be safe for flight. One means of safety certification is by safety analysis which shows that the probability of failure in a typical flight is bounded. The probability bound requirement for a system is based on the criticality of system failure. Usually backup components are checked at intervals that span multiple flights. The first backup may be checked more frequently than the second or higher levels. This leads to flights where the system may have latent faults in the backup components. The probability of failure in such cases varies from flight to flight due to the different exposure times for components in the system.

Developing the most advanced wing panel assembly line for very high production rates required an innovative and integrated solution, relying on the latest technologies in the industry. Looking back at over five decades of commercial aircraft assembly, a clear and singular vision of a fully integrated solution was defined for the new panel production line. The execution was to be focused on co-developing the automation, tooling, material handling and facilities while limiting the number of parties involved. Using the latest technologies in all these areas also required a development plan, which included pre-qualification at all stages of the system development. Planning this large scale project included goals not only for the final solution but for the development and implementation stages as well. The results: Design/build philosophy reduced project time and the number of teams involved. This allowed for easier communication and extended development time well into the project.

CFD now stands alongside the wind tunnel in terms of importance to aerodynamic design. Its usage by engineering designers involves many thousands of runs per year, and the rate is increasing. For the simpler aerodynamic flows where viscous effects are modest, CFD has become the dominant tool for aerodynamic design. The primary role of the wind tunnel for such flows is for validation of a design and for determination of aerodynamic characteristics over the broad flight envelope. For more complex flows that are dominated by strong viscous effects, CFD is beginning to make a contribution. It is thought by many that the principle challenge for the future is to develop better computers and algorithms in order to better address the computation of complex flows over complex airplane geometries. But recent experiences involving the application of CFD to the design of the new Boeing 777 airplane has taught us that the challenge for the future is really much broader.

A new portable floor drilling machine, the 767AFDE, has been designed with a focus on increased reach and speed, ease-of-use, and minimal weight. A 13-foot wide drilling span allows consolidation of 767 section 45 floor drilling into a single swath. A custom CNC interface simplifies machine operations and troubleshooting. Four servo-driven, air-cooled spindles allow high rate drilling through titanium and aluminum. An aluminum space frame optimized for high stiffness/weight ratio allows high speed operation while minimizing aircraft floor deflection. Bridge track tooling interfaces between the machine and the aircraft grid. A vacuum system, offline calibration plate, and transportation dolly complete the cell.

New and derivative commercial jetliner programs face increased pressure to reduce cost, shorten development cycles, increase production rates, and create an increasingly fuel efficient aircraft. The industry also has limited engineering resources and suppliers with manufacturing capacity constraints. Designing parts right the first time, while concurrently taking into account available and proven manufacturing techniques, is crucial to meeting product development schedule and profitability goals. New, knowledge-based software solutions bridge the gap between design, manufacturing, and the supply chain, assuring timely, cost effective, and correctly manufactured products. Boeing Commercial Airplanes used a unique knowledge-based software solution to analyze one of the most complicated jetliner parts: the titanium part joining the wing to the aircraft body.

Recent work has shown that when an aircraft encounters ambient ice-supersaturated conditions (where contrails may form and persist), it may be possible to avoid contrail formation by shifting cruise altitude up or down 2000 feet. If an aircraft's cruise altitude is shifted from the optimal profile during a portion of the mission, fuel consumption increases. Because on average approximately 20% of distance flown by commercial airliners is through ice-supersaturated regions, this study quantifies the fuel burn penalties for the notional scenario of flying the same fraction of cruise at altitude displacements of +2000, -2000, and -4000 ft. Present aircraft performance data was used to generate accurate fuel burn penalty estimates. This study finds that the net penalties for existing aircraft to fly contrail avoidance shifts vary between 0.2% and 0.7% increase in block fuel consumption.

One recent evolution in commercial transport structure has been the emergence of monolithic structure applications. Monolithic structure reduces the number of parts that must be managed, eliminates sub-assembly operations and contributes strongly to determinant assembly practices. The cost of three components from the Boeing 737-200 and their counterparts on the Boeing 737-600 will be compared. The mid 1960's 737-200 components were assembled from sheet metal details. The mid 1990's 737-600 components are monolithic designs and utilize superplastic forming, casting and NC machining technologies. The built-up solutions and the monolithic solutions are compared based on cost infrastructures from the 1960's and the 1990's.

Process development work was conducted to develop a machined fuselage frame concept for a small (5 abreast) commercial airplane. To minimize detail fabrication cost and to facilitate lean manufacturing, roll forming was identified as the preferred forming process. To reduce assembly costs, long frame segments were desired to minimize the number of frame splices. Since plate stock is limited to lengths of approximately 3.66 meters (12 feet), formed aluminum extrusions were selected as the raw material form. Roll forming and stretch forming process paths were screened for both J section and rectangular bar extrusions. The post machining distortion produced in formed extrusion and plate hog-out frame segments was compared to each other and to process standards governing allowable fit-up forces. As a result of this process development activity, a producible roll forming process path was developed.

Historically the manufacturing of aircraft fuselages with capacities of 100+ passengers requires large panels and assemblies to be integrated through processes of manipulating them into proper alignment to one another, and then fastening the panels and assemblies together. The manipulating and alignment processes typically incorporate large handling devices and cranes to move the large panels and monolithic tools or measurement alignment systems to precisely align the aircraft components. After the individual panels and assemblies are properly aligned, they can be fastened together. Normally, the fastening process is performed manually with the aid of fastener location templates. There are problems with these processes. They require high capital investments for tooling and facilities; up to two shifts (16 hours) to complete the loading, indexing, and fastening operations; and depend on a highly skilled and knowledgeable work force to minimize discrepancies.

Determinant Spar Assembly Cell (DSAC) has been developed by Boeing to help reduce the cost of building commercial airplanes. This revolutionary system uses a state of the art 5 axis NC machine in conjunction with quick-change multi-function end effectors and a reconfigurable fixture, to provide the capability to assemble any Boeing heritage commercial airplane spar. This paper describes the high level aspects of this unique system.

The Safety Assessment Process, defined by SAE ARP4761 and associated regulatory guidance, is described in the context of conventional, crewed civil aircraft. While this material has been used for decades to evaluate airplanes and rotorcraft, the evolution of technology challenges it. As new entrants venture into aviation, they bring perspectives, which may not clearly align to those conventional concepts. For those skilled in the art of aviation safety assessment, the approach to new technologies might appear straight forward. Such an individual might easily perceive the accommodations for unconventional applications. Once accommodations are made, and failure conditions are established and classified to those new architectures, the rest of the process is somewhat mechanical -they flow out of these conditions. However, the context of their experience betrays the reality of the process description in the ARP and guidance.

Aerospace Recommended Practice (ARP) 4754 Revision A (ARP4754A), “Guidelines for Development of Civil Aircraft and Systems,” [1] is recognized through Advisory Circular (AC) 20-174 (AC 20-174) [2] as a way (but not the only way) to provide development assurance for aircraft and systems to minimize the possibility of development errors. ARP4754A and its companion, Aerospace Information Report (AIR) 6110, “Contiguous Aircraft/System Development Process Example,” [3] primarily describe development processes for an all new, complex and highly integrated aircraft without strong consideration for reused systems or simple systems. While ARP4754A section 5 mentions reuse, similarity, and complexity, and section 6 is intended to cover modification programs, the descriptions in these sections can be unclear and inconsistent. The majority of aircraft projects are not completely new Products nor are they entirely comprised of complex and highly integrated systems.

In the last several years, technical advances and regulatory pressures have motivated the need for flexible, simple, and performance-based solutions for conducting development assurance in support of a system safety assessment process. Additionally, the affected design space for commercial vehicles has been growing beyond the conventional regulations for airplanes, rotorcraft, engines, and propellers, addressed by current Aerospace Recommended Practices (ARPs). This space is beginning to include commercial technologies such as unmanned aerial systems, multi-stage spacecraft systems, and road-able aircraft. These developing areas are each accompanied with their own development assurance expectations in support of their safety criteria. Concurrently, the industry and regulators are working to simplify guidance for system safety and development assurance, which has been foundational in the aircraft industry for decades.

The unrestrained design space for unmanned aerial systems (UAS) presents challenges to accurate safety assessment and the assurance of development to appropriate levels of rigor within those systems. The established safety and development assurance standards and practices were developed for vehicles operating in highly controlled conditions with continuous oversight. The very nature of unmanned systems introduce new failure conditions, even in those systems operating within the strict rules of the National Airspace System (NAS), particularly failures of control and command, situational awareness, and control security. Beyond those, the new concepts of operation being conceived by UAS developers introduce their own new set of considerations with regards to operating in uncontrolled airspace, often in close proximity to bystanders. These new concepts require new technologies beyond those currently supported by the hardware and software development assurance processes.

In the last several years, the aviation industry has improved its understanding of jet engine events related to the ingestion of ice crystal particles. Ice crystal icing has caused powerloss and compressor damage events (henceforth referred to as “engine events”) during flights of large transport aircraft, commuter aircraft and business jets. A database has been created at Boeing to aid in analysis and study of these engine events. This paper will examine trends in the engine event database to better understand the weather which is associated with events. The event database will be evaluated for a number of criteria, such as the global location of the event, at what time of day the event occurred, in what season the event occurred, and whether there were local meteorological influences at play. A large proportion of the engine events occur in tropical convection over the ocean.

The Systems Engineering (SE) “Vee” is generally recognized as one of the primary identifying features of Systems Engineering processes. While there are many specifications which include SE in their titles and show a version of the “Vee” in their process descriptions, there are other specifications which make no claim to be an SE standard but show a “Vee” describing the processes in the specification. There are also specifications which appear to be completely unrelated to SE but describe processes which are very much SE. This wide variety of documents points to the possibility of identifying the common core which composes SE (the soul of Systems Engineering). To search for the soul of SE, the words in two recognized SE standards along with the National Aeronautics and Space Administration (NASA) SE standard and multiple Federal Aviation Administration (FAA) standards have been analyzed for alignment of and differences between the models.

Aerospace Recommended Practice (ARP) 4754 Revision A (ARP4754A), Guidelines for Development of Civil Aircraft and Systems [1], and ARP4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment [2], together describe a complex set of intertwining processes which comprehensively prioritize development activities for a product's systems based on their safety criticality. These processes work at specific levels of detail (aircraft and system) and interact with a set of processes at lower levels of detail (item) defined by Radio Technical Commission for Aeronautics (RTCA) standards. The aircraft and system development process (ARP4754A) supplies functions, requirements, and architectural definitions to the System Safety process (ARP4761), which in turn supplies Development Assurance Levels back to the development process and on to the RTCA processes.

This paper discusses the process development and implementation of an Electric Boring process for boring the Frame Lug for the Main Landing Gear (MLG) Swing Link bushing on the 777 Airplane. Due to the process reliability issues associated with the equipment traditionally used for this process, primarily air driven right angle motors, a boring process using electric motors was developed and implemented for this application. The process development focused on equipment selection based on horsepower/torque requirements, laboratory testing for cutting parameters and bore quality generation, equipment reliability testing under operational loads and process efficiency validation. The implementation programme involved the detail design and fabrication of protective enclosure (explosion proof) hardware to prevent the electric motor and its connections from being contaminated by various fluids used in processes in the vicinity of this application.

The Safety Assessment Process defined by SAE ARP4761 [1] and associated regulatory guidance and the system development process defined by SAE ARP4754 [2] are built on an understanding of the functions performed by a system or systems. SAE Technical Paper 2022-01-0008 [3] proposes a process to assist the system or product developer with identifying and describing functions at each level of abstraction used in describing the architecture. This paper walks through the process described in SAE Technical Paper 2022-01-0008, examining some of the issues and considerations encountered using this approach, and resulting in an example function list for a passenger aircraft. The example aircraft is typical except that an autonomous operating mode is included.

The Safety Assessment Process, defined by SAE ARP4761 and associated regulatory guidance and the system development process defined by SAE ARP4754 are built on an understanding of the functions performed by a system or systems. [1, 2] These recommended practices do not provide, or reference, specific guidance regarding function definition, though they do provide some conventional airplane examples. ASTM E2013-20 describes function identification principles for cost evaluations, but does not consider how functions are used in safety assessments.[3] Without a systematic process for establishing and describing functions for safety assessments, the application of the development and safety assessment processes can be complicated by inappropriate function selections. Such functions may be overly inclusive, applied at the wrong level of abstraction, or might not describe the intended behaviors adequately.