Search Results

The aircraft employs a unique V/STOL design, which places all control for hover and transition in the twin turbofan nacelles. This paper presents design and development of the aircraft propulsion system, covering a span of seven years. ...Initial developmental testing concentrated on two of the key components of the nacelle, the inlet and the control vane assembly. Isolated testing was used to establish baseline designs which eventually were adapted to a TF34 engine for a full scale powered model test of a proposed manned flight demonstrator at the Ames Research Center. ...Isolated testing was used to establish baseline designs which eventually were adapted to a TF34 engine for a full scale powered model test of a proposed manned flight demonstrator at the Ames Research Center.

Aircraft nacelles were originally fabricated completely out of sheet metal. Advances at Rohr have enabled the implementation of new materials in an overall effort to reduce weight and improve aircraft performance.

A semirobotic part-positioning system and elevated automatic riveter used for the assembly of aircraft engine nacelles and extremely contoured panels including control schemes, applications, and implementation are discussed.

A general method for the preliminary design of a single, straight-sided, low subsonic ejector is presented. The method is based on the information presented in References 1, 2, 3, and 4, and utilizes analytical and empirical data for the sizing of the ejector mixing duct diameter and flow length. The low subsonic restriction applies because compressibility effects were not included in the development of the basic design equations. The equations are restricted to applications where Mach numbers within the ejector primary or secondary flow paths are equal to or less than 0.3.

This SAE Aerospace Information Report (AIR) has been prepared by a panel of the SAE A-5A Committee and is presented to document unique design approaches used for aircraft wheels and brakes.

This paper traces the use of FRP composites on nacelle structures designed and manufactured at Westland Aerospace over the last decade. The paper highlights the design, development and manufacturing processes that have had to be evolved, in order to achieve sound structural composite primary structures.

A flow modeling method has been developed to analyze the flow in the annular base (rear-facing surface) of a circular engine nacelle flying at subsonic speed but with a supersonic exhaust jet. Real values of exhaust gas properties and temperature are included.

This paper describes the second government-conducted, piloted flight simulation of the Grumman Design 698 V/STOL (vertical and short takeoff and landing) aircraft. Emphasis is on the aircraft's handling qualities as rated by various NASA, Navy, and GAC pilots with flight experience ranging from CTOL (conventional takeoff and landing) to V/STOL aircraft. The Design 698 had been modified to resolve the flight problems that were of most concern to the pilots in the first investigation (Phase I). Those problems included an adverse nonminimum phase (NMP) acceleration response in both the longitudinal and lateral axes, a large thrust-response lag, and adverse ground effects. The adverse NMP acceleration is an attribute of the vertical vanes (a Grumman patent) positioned in the fan exhaust flow.

This paper aims to conduct a comparative computational analysis encompassing seven distinct chevron designs and one without chevrons. It also summarizes the previous works that led to the advancement of this technology. ...The size and configuration of the chevrons with the jet engine nacelle were designed to match the nozzle diameter of 100.48mm and 56.76mm, utilizing the advanced SolidWorks CAD modeling software. ...The results were obtained in the form of acoustic power level contours and turbulent energy contours which unambiguously exhibit the effectiveness of each of the chevron designs that were taken into consideration for study. The acquired solutions were finally used for a comparative study among the designs.

The aerodynamic development of the engine nacelle for the Boeing 767 airplane is described from configuration development model tests to FAA certification flight tests.

The main engineering problems requiring solution in a development programme aimed at the application of composite materials to selected nacelle components are reviewed. The components chosen were characterised by important special features including acoustic performance, fireproof capability and resistance to fan-blade off effects. ...The subsequent application of the developed technology to meet production nacelle requirements and Airworthiness compliance needs is discussed.

The acoustic treatment requirement for jet engine nacelle inner flowpath leads to using perforated skin. Formerly in light alloy these skins are now composite and new techniques have been developped to achieve the perforation.

In addition, the system has been used to experimentally investigate the influence of nacelle type afterbodies on the propeller blade pressure distribution.

Composite structures used in jet engine nacelle applications designed by Rohr Industries and advantages of this type of construction are briefly reviewed.

Based on the results for the water catch rate on the basic nacelle configuration in snow conditions it is concluded that the ‘cheeks’ of the duct are more susceptible to impingement of larger snow crystals (>75 μm), whereas the ‘chin’ of the duct is more susceptible to impingement of smaller droplets (<75 μm).

A one-seventh scale model of a high bypass turbofan inlet/nacelle was tested with and without V-groove riblets applied to the external surface. Tests were conducted in the French ONERA S1 transonic atmospheric wind tunnel in Modane. Before the test was finished riblets came off in two places and other problems with the riblet arose. These problems were partially solved by selective use of the drag data. Drag reductions up to 6.4%, depending on flow conditions, were obtained. Locally, reductions up to 8% were attained. In general, the higher drag reductions were attained when shocks were present.

The first government-conducted piloted flight simulation of the Grumman-designed twin turbofan-powered tilt-engine V/STOL aircraft (design 698) was conducted at NASA Ames Research Center. The aircraft is discussed with an emphasis on its unique hover characteristics. These characteristics include the adverse nonminimum phase that occurs in lateral and longitudinal translation, and the large attitude control power available. Both of these features are attributes of the control vanes (a Grumman-patented concept) buried in the fan exhaust flow. The simulation used the following NASA Ames Research Center facilities: The Vertical Motion Simulator with the interchangeable cab, the Sigma 8 computer, and the Computer-Generated Image system with a four-window display.

The current trend of flying aircraft in a severe environment; i.e., high mach numbers at low altitudes, has created interest in the impact of dynamic pressure fluctuations on nozzle hardware durability. Because of this interest, methods have been developed to obtain dynamic pressure data in the internozzle region of twin-jet aircraft models during wind tunnel testing. Results from the wind tunnel tests have been analyzed to establish trends, such as the effect of flight variables and engine operating variables, on the dynamic pressure fluctuations. Comparisons have also been made between wind tunnel test results and flight test data.

The main objective of this work is to investigate, by means of numerical simulations, the performance of the engine nacelle ventilation cooling system of a helicopter under hover and forward flight conditions, and to propose a simplified method of evaluating the performance based on rotor downwash flow by taking the synthetical effect of engine nacelle, exhaust ejector and external flow of a helicopter into account. ...The main objective of this work is to investigate, by means of numerical simulations, the performance of the engine nacelle ventilation cooling system of a helicopter under hover and forward flight conditions, and to propose a simplified method of evaluating the performance based on rotor downwash flow by taking the synthetical effect of engine nacelle, exhaust ejector and external flow of a helicopter into account. For the engine nacelle of a helicopter, an integrated model of the nacelle and exhaust ejector was set up including the domain of external flow. ...For the engine nacelle of a helicopter, an integrated model of the nacelle and exhaust ejector was set up including the domain of external flow. The unstructured grid and finite volume method were applied for domains and control equations discreteness, and the standard k-ε model was applied for solving turbulent control equations.

The flow around the nacelles of high altitude airships is very important in order to assess the inlet conditions and losses associated to their propulsion systems. ...Herein we present a laminar kinetic energy transitional model that is then applied on the analysis of the flow around an example of the MAAT airship nacelle. The model is also validated using several well known test cases from the literature. Results indicate the effects of accurate transition prediction in the redesign of the nacelle for improvement in efficiency. ...Results indicate the effects of accurate transition prediction in the redesign of the nacelle for improvement in efficiency.