Aircraft Design最新文献

A new aircraft configuration to employ a rotary cockpit compartment (RCC) is proposed to allow an arbitrary line of sight and visibility pattern. In addition to being a manually controlled system, the rotary cockpit control system is linked to the aircraft flight control computer and therefore automatically reacts to high speed turns, giving a wider view of the scene of the rear of the aircraft. To ensure the highest degree of reliability, in case the aircraft conducts a compound maneuver consisting of successive turns, two different strategies to rotate the cockpit have been investigated. A complete set of nonlinear and coupled equations of motion are used to prove the effectiveness of RCC in a complex maneuver in 3/D space. More research might be needed to investigate the possibility of pilot confusion.

This paper addresses the necessity to incorporate an intake-engine matching procedure in any procedure to analyze the off-design performance of engines designed to power high-speed civil transport aircraft. Most methods known to the author that are useable in the conceptual design phase of the aircraft (a phase characterized by the fact that very few design variables are known) only analyze the performance of the engine, without taking into account the design and performance of the intake. It will be shown in this paper, that the intake and the design exhibit a strong mutual influence, that cannot be neglected. An alternative method of analysis is presented. Particular reference will be made to the phenomenon of excess air and the resulting spillage drag. It will be shown that spillage air can be quite large in case of an HSCT design, especially in case the engine is designed for a high cruise Mach number. Assuming the presence of a sophisticated intake system generating multiple shocks in order to optimize the intake efficiency at the cruise condition, excess air at lower Mach numbers can amount to more than 60%.

The paper describes the results from a concept exploration study to assess the feasibility of a modular/reconfigurable rotorcraft designated the “multirole, mission-adaptable air vehicle (MRMAAV)”. The initial phase of the study consisted of developing mission and operational requirements for the vehicle. This phase resulted in the assessment that the aircraft should be considered primarily an attack vehicle but with the capability, through reconfiguration, for performing several alternate missions. Evaluation of several high-speed rotorcraft concepts led to the selection of two platform configurations for further study. These included the variable-diameter compound helicopter (VDCH) and the joined-wing tilt rotor (JWTR). Detailed sizing efforts focused on the VDCH as the more feasible of the two concepts. Innovative aspects of the air vehicle include variable-diameter main rotor, turboshaft/turbofan convertible engine, virtual-canopy cockpit, and reconfigurable payload bay. The mission-equipment package is highlighted by an autonomous remote sensor platform. The study identifies areas which best lend themselves to a modular or reconfigurable design approach and describes in detail a candidate vehicle meeting the MRMAAV objectives.

The paper introduces an autonomous vehicle concept (ALSR AV) that is air-launched and self-recovering. The aircraft has a rotor wing lifting surface that is fixed perpendicular to the fuselage during flight operations, windmills during autorotative self-recovery, and is stowed parallel to the fuselage for transport. The vehicle has advantages over other proposed autonomous aircraft in that fuel requirements are minimized since it is transported to the objective area, separate launch and recovery facilities are not necessary, and it has a relatively compact size and low complexity relative to other V/STOL autonomous vehicles. The ALSR AV is proposed for remote sensing, surveillance, and scout military missions, as well as search-and-rescue and law-enforcement civil operations. The analysis indicates that the ALSR AV represents a viable candidate for such applications, and can be sized to be carried by and perform a mission complimentary to the AH-64 Apache.

This paper presents a conceptual project of a high-altitude long-endurance unmanned aerial vehicle. It describes a number of historical, current and prospective HALE aircraft and considers existing four serious obstacles, to overcome them can mean the successful building of HALE aircraft. Among these obstacles there are very special aerodynamic (low Reynolds numbers together with transonic speeds), very light structures usually of high aspect ratio, propulsion technology (usually propeller driven by turbocharged piston engines) and flight control system (usually combining the best features of preprogrammed and hand-flown modes). Four aerodynamic design concepts are presented and their performances are compared. Among them is a biplane, considered mainly because of its moderate wing span, which can be obtained for a relatively big wing area and a high effective wing aspect ratio, a relatively stiff wing structure, and lower induced drag being possible to be obtained at the same lift and wing area as for the equivalent monoplane. It is shown that an attentively designed biplane can be efficient aerodynamically for high altitude patrol missions having almost the same endurance, using the same fuel to reach a service ceiling and having the take-off mass (and the payload) considerably bigger than a corresponding, equivalent monoplane. The paper is completed with selected considerations about dynamic stability.

This paper presents a computational investigation of a tangential slot blowing concept for generating lateral control forces on an aircraft fuselage forebody. This work is aimed at aiding researchers in designing future experimental and computational models of tangential slot blowing. The effects of varying both the jet width and jet exit velocity for a fixed location slot are analyzed. The primary influence on the resulting side force of the forebody is seen to be the jet mass flow rate. This influence is insensitive to different combinations of slot widths and jet velocities over the range of variables considered. Both an actuator plane and an overset grid technique are used to model the tangential slot. The overset method successfully resolves the details of the actual slot geometry, extending the generality of the numerical method. The actuator plane concept predicts side forces similar to those produced by resolving the actual slot geometry.

The Concurrent Subspace Design (CSD) framework has been used to conduct a preliminary design optimization of an electric-powered, unmanned air vehicle operating at low Reynolds number. A multidisciplinary system analysis has been developed for this class of vehicles and includes aerodynamics, weights, propulsion, performance and stability and control. The CSD framework employs artificial neural network-based response surfaces to provide approximations to the design space. This approach was applied to a number of conceptual aircraft design studies. In each case the CSD framework was able to identify feasible designs with significant weight reductions relative to any previously considered (i.e. initial database) designs. This was accomplished with a reasonable number of system analyses. The results also demonstrate the adaptive nature of this design framework to changes in design requirements.

Flight dynamics courses are exciting except for the part where instructors derive long and complicated equations for seemingly endless time. Most students are left bewildered at the dull algebra. A refreshing approach to present the derivation of the equations of motion of aircraft is exemplified in this paper. The method is based on the finding that the students appreciate the algebra better if they are enlightened about the logic behind it. The derivation of the perturbed equations is unfolded through the theory of stability in the first approximation. Although the concept is as old as the equations themselves, it is amazing that it is not explained in this manner in books. The author’s teaching experience has shown that this approach has led to substantial amelioration of the course. Students who are learning the course for the first time find the derivation of equations as gripping as the remaining portion when taught in this fashion.

Recent aerospace industry interest in developing subsonic commercial transport airplanes with at least 50% greater passenger capacity than the largest existing aircraft in this category (e.g. the Boeing 747-400 with approximately 400–450 seats) has generated a number of proposals based primarily on the configuration paradigm established 50 years ago with the Boeing B-47 bomber. While this classic configuration has come to dominate subsonic commercial airplane development since the advent of the Boeing 707/Douglas DC-8 in the mid-1950s, its extrapolation to the size required to carry more than 600–700 passengers raises a number of questions, including:

• 1.

  How large can an airplane of 707/747 configuration be built and still remain economically and operationally viable?

• 2.

  What configuration alternatives might allow circumvention of practical size limitations inherent in the basic 707/747 configuration?

• 3.

  What new and/or dormant technology elements might be brought together in synergistic ways to resolve or ameliorate very large subsonic airplane problems?

To explore these and a number of related issues, a team of Boeing, university and NASA engineers was formed under the auspices of the NASA Advanced Concepts Program during 1994. The results of a Research Analysis contract (NAS1-20269) focused on a large, unconventional (C-wing) transport configuration for which Boeing and the authors were granted a design patent in 1995 is the subject of this paper which is based on information contained in McMasters et al. (NASA CR 198351, October 1996).

It is very important to have minimum weight of aircraft equipment. It allows to increase the payload or flight range or to improve some other aircraft characteristics. For the systems that are consuming energy during the flight it is not less important to save the power spent on their functioning. “Starting mass” gives the opportunity to combine these two heterogeneous sides of the equipment properties into one complex characteristic, which depends on the flight duration and on the aircraft engine parameters. The main idea in solving the problem of combining mass and energy in one complex parameter arises from the fact that practically the only on-board source of energy is the fuel stored in the aircraft tanks. Therefore, the energy consumed by the system may be substituted by the equivalent mass of fuel. Another component of the “starting mass” is the fuel spent on the transportation of the first two parts. The necessity of this third part arises from the differences in fuel expenditure on transportation of unchangeable and changeable loads during the flight. The summation of these weight components is called “starting mass” because all of them should be present in the aircraft before take-off.

The core of the method was developed by Bulaevsky and myself. It is refined and partially corrected in this paper.