An analysis of prop-fan/airframe aerodynamic integration

An approach to aerodynamic integration of turboprops and airframes, with emphasis placed upon wing mounted installations is addressed. Potential flow analytical techniques were employed to study aerodynamic integration of the prop fan propulsion concept with advanced, subsonic, commercial transport airframes. Three basic configurations were defined and analyzed: wing mounted prop fan at a cruise Mach number of 0.8, wing mounted prop fan in a low speed configuration, and aft mounted prop fan at a cruise Mach number of 0.8

The role of dedicated freighter aircraft in the provision of global airfreight services

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.In 2014, over 51 million tonnes of cargo, valued at over US$6.8 trillion, was flown around the world. Approximately 56% of this total (by global revenue tonne kilometres (RTKs)) was flown on dedicated freighter aircraft which were either manufactured specifically for this purpose or converted from passenger use. The remaining 44% (by total global RTK) travelled as belly-freight in the holds of passenger flights or on combi (combination) or QC (quick change) aircraft that can accommodate both passengers and freight. Although both sources of capacity offer the same basic service – the aerial carriage of time sensitive and/or high value-to-weight goods – they exhibit different cost structures, operating characteristics and spatial patterns of demand and supply. Using empirical data on the contemporary scale and scope of global freighter operations, this paper examines the role of dedicated freighter aircraft in the provision of global airfreight services and identifies a range of exogenous and internal factors which may affect the demand and supply side characteristics of all-cargo air services in the future

Langley rotorcraft structural dynamics program: Background, status, accomplishments, plans

Excessive vibration is the most common technical problem to arise as a show stopper in the development of a new rotorcraft. Vibration predictions have not been relied on by the industry during design because of deficiencies in finite element dynamic analyses. A rotorcraft structural dynamics program aimed at meeting the industry's long-term needs in this key technical area was implemented at Langley in 1984. The subject program is a cooperative effort involving NASA, the Army, academia, and the helicopter industry in a series of generic research activities directed at establishing the critical elements of the technology base needed for development of a superior finite element dynamics design analysis capability in the U.S. helicopter industry. An executive overview of the background, status, accomplishments, and future direction of this program is presented

The NASA/industry Design Analysis Methods for Vibrations (DAMVIBS) program : Bell Helicopter Textron accomplishments

Accurate vibration prediction for helicopter airframes is needed to 'fly from the drawing board' without costly development testing to solve vibration problems. The principal analytical tool for vibration prediction within the U.S. helicopter industry is the NASTRAN finite element analysis. Under the NASA DAMVIBS research program, Bell conducted NASTRAN modeling, ground vibration testing, and correlations of both metallic (AH-1G) and composite (ACAP) airframes. The objectives of the program were to assess NASTRAN airframe vibration correlations, to investigate contributors to poor agreement, and to improve modeling techniques. In the past, there has been low confidence in higher frequency vibration prediction for helicopters that have multibladed rotors (three or more blades) with predominant excitation frequencies typically above 15 Hz. Bell's findings under the DAMVIBS program, discussed in this paper, included the following: (1) accuracy of finite element models (FEM) for composite and metallic airframes generally were found to be comparable; (2) more detail is needed in the FEM to improve higher frequency prediction; (3) secondary structure not normally included in the FEM can provide significant stiffening; (4) damping can significantly affect phase response at higher frequencies; and (5) future work is needed in the areas of determination of rotor-induced vibratory loads and optimization

Advanced composite airframe program: Today's technology

The Advanced Composite Airframe Program (ACAP) was undertaken to demonstrate the advantages of the application of advanced composite materials and structural design concepts to the airframe structure on helicopters designed to stringent military requirements. The primary goals of the program were the reduction of airframe production costs and airframe weight by 17 and 22 percent respectively. The ACAP effort consisted of a preliminary design phase, detail design, and design support testing, full-scale fabrication, laboratory testing, and a ground/flight test demonstration. Since the completion of the flight test demonstration programs follow-on efforts were initiated to more fully evaluate a variety of military characteristics of the composite airframe structures developed under the original ACAP advanced development contracts. An overview of the ACAP program is provided and some of the design features, design support testing, manufacturing approaches, and the results of the flight test evaluation, as well as, an overview of Militarization Test and Evaluation efforts are described

"Supplier Networks and Aircraft Production in Wartime Japan"

The Japanese aircraft industry, which operated on a very small scale before World War II, became Japan's largest manufacturing industry by the end of the war. In this paper, we explore the causes of the growth of the aircraft industry during this time by focusing on the No. 5 Works of Mitsubishi Heavy Industries Co. We find that during the war, the supply of basic inputs increased substantially: the labor force, equipment and "machinery parts" were in sufficient supply, and none of them were binding constraints on production. A binding constraint existed in the supply of "special parts." Put differently, aircraft production expanded as the supply of special parts increased. This increase in the supply of special parts and even faster growth in the supply of machinery parts came about through the expansion of supplier networks in terms of both the number of suppliers and the geographical area in which they were located. These findings imply that outsourcing played a key role in the rise of aircraft production in wartime Japan.

"Supplier Networks and Aircraft Production@in Wartime Japan"

The Japanese aircraft industry, which was of very small scale before World War II, became Japanfs largest manufacturing industry by the end of the war. In this paper, we explore the basis for the growth of the aircraft industry during this time by focusing on the No. 5 Works of Mitsubishi Heavy Industries Co. It was revealed that during the war, the supply of basic inputs increased substantially: the labor force and gmachinery partsh were in sufficient supply and neither was a binding constraint on production. The binding constraint existed in the supply of gspecial parts.h Put differently, aircraft production expanded as the supply of special parts increased. This increase in the supply of special parts and still faster growth in the supply of machinery parts came about through the expansion of the supplier network in terms of both the number of suppliers and the geographical area in which they were located.

The NASA/industry design analysis methods for vibrations (DAMVIBS) program: Accomplishments and contributions

A NASA Langley-sponsored rotorcraft structural dynamics program, known as Design Analysis Methods for VIBrationS (DAMVIBS), has been under development since 1984. The objective of this program was to establish the technology base needed by the industry to develop an advanced finite-element-based dynamics design analysis capability for vibrations. Under the program, teams from the four major helicopter manufacturers have formed finite-element models, conducted ground vibration tests, made test/analysis comparisons of both metal and composite airframes, performed 'difficult components' studies on airframes to identify components which need more complete finite-element representation for improved correlation, and evaluated industry codes for computing coupled rotor-airframe vibrations. Studies aimed at establishing the role that structural optimization can play in airframe vibrations design work have also been initiated. Five government/industry meetings were held in connection with these activities during the course of the program. Because the DAMVIBS Program is coming to an end, the fifth meeting included a brief assessment of the program and its benefits to the industry

The NASA/industry Design Analysis Methods for Vibrations (DAMVIBS) program: McDonnell-Douglas Helicopter Company achievements

This paper presents a summary of some of the work performed by McDonnell Douglas Helicopter Company under NASA Langley-sponsored rotorcraft structural dynamics program known as DAMVIBS (Design Analysis Methods for VIBrationS). A set of guidelines which is applicable to dynamic modeling, analysis, testing, and correlation of both helicopter airframes and a large variety of structural finite element models is presented. Utilization of these guidelines and the key features of their applications to vibration modeling of helicopter airframes are discussed. Correlation studies with the test data, together with the development and applications of a set of efficient finite element model checkout procedures, are demonstrated on a large helicopter airframe finite element model. Finally, the lessons learned and the benefits resulting from this program are summarized

Experiences at Langley Research Center in the application of optimization techniques to helicopter airframes for vibration reduction

A NASA/industry rotorcraft structural dynamics program known as Design Analysis Methods for VIBrationS (DAMVIBS) was initiated at Langley Research Center in 1984 with the objective of establishing the technology base needed by the industry for developing an advanced finite-element-based vibrations design analysis capability for airframe structures. As a part of the in-house activities contributing to that program, a study was undertaken to investigate the use of formal, nonlinear programming-based, numerical optimization techniques for airframe vibrations design work. Considerable progress has been made in connection with that study since its inception in 1985. This paper presents a unified summary of the experiences and results of that study. The formulation and solution of airframe optimization problems are discussed. Particular attention is given to describing the implementation of a new computational procedure based on MSC/NASTRAN and CONstrained function MINimization (CONMIN) in a computer program system called DYNOPT for the optimization of airframes subject to strength, frequency, dynamic response, and fatigue constraints. The results from the application of the DYNOPT program to the Bell AH-1G helicopter are presented and discussed