Aircraft Door Research Articles

A multiple alternative processes-based cost-tolerance optimal model for aircraft assembly

In the aircraft manufacturing process, the tolerance allocation of complex components has an extremely important impact on the life cycle of the aircraft. With the increasing demand for aircraft assembly performance and reliability, tolerance allocation has become one of the most concerned issues for process designers. However, the traditional cost-tolerance models hardly took into account the effects of multiple alternative manufacturing processes. The global search strategy and convergence of optimization methods of the model were insufficient, and it was difficult to obtain more optimized results. Therefore, this paper proposed a novel cost-tolerance model that considers the impact of multiple alternative manufacturing processes on component manufacturing cost and quality loss. Then, a hybrid optimization algorithm combining Monte Carlo simulation and self-adaptive differential evolution (SADE) was presented to achieve cost minimization while ensuring high assembly accuracy. The Monte Carlo simulation was used to solve the problem of tolerance superposition and provided a proper initial population for SADE, which can accelerate the convergence speed and enhances the robustness of the SADE. Moreover, based on the traditional SADE, a new mutation strategy, which expands the diversity of the population, was proposed in combination with the Levy distribution. Improved SADE algorithm had a good optimization effect for large space, nonlinear and non-derivable discrete problems. Finally, a case study of aircraft door assembly was illustrated to verify the effectiveness of the proposed model. The experimental results show the advantage of the method in achieving the cost reduction compared with traditional method.

Design and characteristics of fabric rubber sealing based on microchannel model

In this paper, both the mechanical behavior and the leakage characteristics of fabric rubber composite in aircraft door are investigated in detail based on microchannel model, which consider the influences of the microchannel shape, the elastic modulus, and the contact stress on the gas leakage rate of the fabric rubber composite. First, the explicit expression of the gas leakage rate at the contact interface of the fabric rubber composite is established based on the contact interface properties. Second, the explicit dimensionless function of the gas leakage rate at the contact interface of the rubber seal is proposed by means of dimensional analysis, finite element analysis and computational fluid dynamics (CFD) method. Finally, the influences of the gas pressure on the gas leakage rate are studied under the same pressure difference at both sides of the fabric rubber composite. The predicted results of the gas leakage rate are in good agreement with the experimental results, which provide an effective model for evaluating the gas leakage characteristics at the contact interface of the fabric rubber composite under any gas pressure and compressive displacement.

LIGHTWEIGHT MACHINE ENCLOSURES FOR DYNAMIC AND EFFICIENT PRODUCTION PROCESSES

Usually machining centres for processing wood-based and composite materials have moving partial machine enclosures in the X-axis direction. Because the workpieces to be machined are often large (e.g. aircraft doors), these partial enclosures have prevailed on the market compared to voluminous complete enclosures. Owing to the general trend towards complete machining through process integration, an increasing number of additional units are integrated into machining centres in addition to the main spindle. This leads to an increase of the mass to be moved as well as a larger and thus heavier partial enclosure. This inevitable increase in mass leads to a deterioration of the dynamic properties of the machine. To counteract this increase in mass, the use of lightweight design materials for machine enclosures becomes in the focus of attention. The lightweight materials to be used must comply with the requirements of modern mechanical engineering and legislation: retention in the event of tool breakage, reduction in the noise exposure of the machine environment and cost-effective solutions compared to the materials used nowadays. The sheet steel used today as material for partial enclosures is therefore to be supplemented or replaced with suitable lightweight design materials. Different lightweight materials are qualified for suitability as machine enclosure. Apart from mass reduction, ecological as well as economic aspects of the used materials play an important role. For this purpose, the safety properties (impact resistance in case of tool breakage / collision) of these weight-reduced materials have to be determined. In addition, an improvement in the acoustic behaviour of the machine is achieved by the new lightweight materials since the machine enclosure shields the distinctive sound sources.

Operating an In-Cabin Femto-Cellular System Within a Given LTE Cellular Network

An onboard mobile communication system can be operated when the height of an aircraft is above 3000 m and the maximum equivalent isotropic radiated power outside an aircraft is below $-$ 13 dBm for 200 kHz bandwidth in a 1800 MHz system based on the Electronic Communications Committee reports. However, in order to provide seamless connectivity for aircraft passengers, the onboard communication system should be in operation in every phase of the flight. Therefore, in this paper, the compatibility of an in-cabin long term evolution (LTE) 1800 MHz femto cellular system with the current terrestrial LTE 1800 systems are investigated when an aircraft is stationary on the ground. Edinburgh Airport in Scotland and the existing LTE cells that provide network coverage at the airport are modeled through a simulation platform. Three Airbus A321 aircraft are modeled, while stationary, in the parked position on the apron and an in-cabin LTE femto cellular system is deployed within each aircraft. Signal-to-noise-plus-interference ratio and power leakage from the in-cabin evolved NodeBs in the downlink direction are considered as performance metrics to investigate the coexistence of the terrestrial and in-cabin systems. The simulation results show that the in-cabin LTE 1800 MHz femto cellular system can be operated without causing any significant interference to the existing terrestrial LTE 1800 MHz system while the aircraft is parked on the apron. However, it may be advisable to only operate the system when the aircraft doors are closed, in order to mitigate any possible interference effect on the users who are boarding the aircraft through the passenger boarding bridge. According to the results shown for a linear apron concept, the legislation governing the onboard mobile communication systems should be revised, in order to pave the way to the goal of seamless mobile connectivity in the next generation of communication systems.

Redundancy system design for an aircraft door management system

The door management system (DMS) is a safety-critical system in an aircraft which checks if all doors are properly closed and the cabin has the correct pressure. As for every safety-critical system in an aircraft, it has to meet some safety regulations and it should be designed optimally in terms of weight, cost or power consumption. This paper studies the problem of designing a DMS optimally as per the previous objectives while guaranteeing that the system is k-redundant. We call this new problem the DMS design problem with redundancy. First, we propose a new MILP model for the DMS problem which includes redundancy. Because the model is too difficult to be solved efficiently by standard MILP solvers, we introduce specialized branching rules and a new heuristic. Computational tests are run for example instances of the DMS problem by implementing these new rule in CPLEX. It is shown that the solving time is significantly reduced through the new branching rules and heuristic.

An analytical scaling approach for low-velocity impact on composite structures

For the analysis of low-velocity impact, this work provides an analytic scaling approach, permitting to analyze structural impact scenarios on a small reference coupon. Thus, the numerical prediction of impact damage on large structures through high-fidelity methods is made possible. Yet, the massive computational effort needed for these virtual tests even on a coupon level means a major challenge to their application in the design process of a structure. To reduce the computational effort, local analysis approaches consider only damage-prone areas for an actual damage analysis.Our approach permits the analysis of structural impact scenarios on a much smaller reference coupon that represents the damage-prone area. An analytical spring-mass model transfers the impact parameters between the structural and the coupon level. For this purpose, the spring-mass model captures the impact-damage state by a scalar parameter. The transfer between the reference coupon and the structure is based on the equivalence of this damage parameter. Thus, a coupon simulation or coupon test result is given validity for a structural impact scenario. So, based on a single coupon simulation, areal impact assessment of a structure is made possible.This methodology is validated through experiments and a demonstrated on a generic aircraft door structure.

Configuration Optimization of Laser Tracker Stations for Large-scale Components in Non-uniform Temperature Field Using Monte-carlo Method

The laser trackers play an important role in fabrication and assembly of aircraft, spacecraft and other large-scale products, and optimization of laser tracker configuration station is one of the core issues. When laser trackers are used on the shop floor, environment factors, especially non-uniform temperature can induce considerable measurement uncertainty. Aiming to reduce measurement uncertainty of laser tracker, optimization of laser tracker configuration station for large-scale components in non-uniform temperature field using the Monte-Carlo method is proposed. Firstly, an improved mathematical model for measurement uncertainty of laser tracker is established. This mathematical model is more applicable to measurement uncertainty evaluation of laser tracker because it takes main measurement uncertainty sources (mechanism system and non-uniform temperature) into account. Secondly, the Monte-Carlo method is used to evaluate measurement uncertainties of laser tracker in different configuration stations. Based on the measurement mathematical model, a serial of simulation data can be generated to evaluate the uncertainty of measurement task. Through iterations, the optimal configuration station of laser tracker, in which measurement uncertainty is minimal, can be obtained. Finally, an example of measurement scenario about measuring the inspection jig of an aircraft door demonstrates that the proposed method is feasible and effective. The proposed approach to identify the optimal position of laser tracker is intuitionistic and efficient.

Variable coefficients reciprocal squared model based on multi-constraints of aircraft assembly tolerance allocation

In order to improve product quality and enhance economic returns, the research about tolerance allocation under multi-constraints including assembly and manufacturing accuracy is done. On the basis of cost-tolerance relationship, this paper introduces variable coefficients reciprocal squared model (VCRSM) into tolerance allocation process and thus constructs the tolerance allocation optimization objective model. Aiming at resolving multi-constraints problem within allocation process, the penalty items are added into allocation optimization objective model, and an analytic equation based on multi-constraints is proposed. The equation is solved using the Newton iteration method in consideration of the assembly and manufacturing accuracy constraints. Finally, a tolerance allocation instance about aircraft door component assembly is given. The numerical results show the method can achieve optimal tolerance allocation and the VCRSM is more suitable than other cost-tolerance models in multi-constraints tolerance allocation.

민항기 door damper용 칼날형 댐핑 오리피스의 설계

In this paper a sharp-edged type damping orifice for an aircraft door damper were designed, where the dynamic viscosity of working fluid were assumed to change up to 400cSt. The discharge coefficient of the damping orifice were investigated by CFD analyses and experiments. In particular, the influences of orifice diameter, edge angle, flow direction and the Reynolds number were taken into consideration. Based on this, it has been deduced how high Coulomb friction forces of damper seals is to be allowed to meet the performance criterion with respect to the orifice size.

항공기의 도어 댐퍼용 교축 오리피스의 설계

In this study the flow rate-to-pressure difference characteristics of short-tube type damping orifices for an aircraft door damper were investigated by CFD analyses and experiments. As the design parameters of the damping orifice its diameter, inlet and outlet angle, tube length and the viscosity of the working fluid were taken into consideration. The results showed that the discharge coefficient of the orifices are dependant on the inlet and outlet angle and the oil viscosity, while their length plays an little significant role. Although the short-tube type damping orifice was employed to induce a turbulent flow, their discharge coefficient decreases rapidly as the oil viscosity gets higher than 50mm2/s. Therefore, in order to determine the orifice size, satisfying the working temperature range of the door damper, the oil viscosity as well as the friction force on the damper piston should be kept within proper values. For the verification of the CFD analysis results the actual performance of a door damper was measured and compared with them.

Non-linear MSD crack growth by DBEM for a riveted aeronautic reinforcement

A special specimen is created cutting a rectangular notched area from the surrounding of the upper left corner of a wide body aircraft door. Then a constant amplitude fatigue traction load is applied by a special servo-hydraulic machine, in order to induce a Multi Site Damage (MSD) scenario. The Dual Boundary Element method (DBEM), as implemented in a commercial code, is adopted for a three-dimensional MSD crack growth simulation of such multi-layer and multi-material component. To this aim, the cracked part of a pre-existing global two-dimensional model is extracted and “extruded” in order to generate a three-dimensional submodel, whose boundary conditions are imposed displacements, calculated by the two-dimensional model, along a virtual line corresponding to the submodel boundary. Non-linear contact conditions are applied between the mating plate surfaces in the area surrounding the cracks, in order to precisely model the plate interactions in the area of interest. The three-dimensional approach is aimed to improve, with respect to the two-dimensional approach, the correlation between numerical and experimental results (e.g. by an accurate assessment of the secondary bending effects). The obtained improvements on crack growth rates, in the initial part of the crack propagation, justify the increased computational effort that a three-dimensional non-linear approach involves. The proposed numerical procedure, based on DBEM, is successfully validated for the virtual testing of a complex aeronautic reinforcement.

DBEM Crack Growth Simulation for a Riveted Aeronautic Reinforcement under Non-linear Contact Conditions

A special specimen was created cutting a rectangular notched area from the surrounding of the upper left corner of a wide body aircraft door. Then a fatigue traction load was applied in order to induce an MSD crack initiation and propagation. An innovative DBEM (Dual Boundary Element Method) modelling approach was devised, capable of explicitly modelling the different test article layers with their rivet connections even in a 2d approach. The rivets that are close to the propagating crack are coupled with the corresponding holes by non linear contact conditions, and the accuracy improvements are assessed in comparison with a previous linear analysis, in which traction and displacements continuity conditions on the hole-rivet interface had been imposed. The importance of such influence on the simulation precision need to be assessed due to the strong impact that a non linear analysis produces on computational times. For such a complex problem (three different panels, made of different materials, each one with a variable thickness and connected by numerous rivets), experimental crack propagation data were available for the numerical-experimental comparison. With such non linear approach, a significant improvement on the growth rate correlation is obtained, that justify the increased computational effort.

DBEM Crack Growth Simulation and Experimental Results for a Multi-Layer and Multi-Material Aeronautic Panel

A special specimen was created cutting a rectangular notched area from the surrounding of the upper left corner of a wide body aircraft door. This part of the aircraft skin is made of different layers with variable thickness and material (titanium or aluminum). Then a fatigue traction load was applied and some notches were cut in the different layers in order to speed up the crack initiation and reproduce a realistic crack scenario. Such through cracks were monitored during their propagation along the specimen width, in order to have available for the simulation a realistic initial scenario and experimental propagation data useful for the correlation with the simulated crack path and growth rates. In particular an innovative DBEM modelling approach was devised, using a commercial code (BEASY), capable of explicitly modelling the different test article layers with their rivet connections even in a two-dimensional approach. The results of the simulation show a satisfactory correlation with the experimental crack path and growth rates even for such a complex problem: three different panels (one skin with two doublers), made of different materials, each one with a variable thickness and connected through numerous rivets (whose shear stiffness is taken into account for the simulation).

Patents

Sealing a gap on a roller strip casting machine Repairing an aircraft door pressure seal Liquid seal for a wet roof bit Seal for a cable entry or pipe penetration Notched blade seal for high performance aircraft Piston seal Dynamic end seal for image forming apparatus Rearward wash basin with neck seal Gap seal for injection moulding apparatus Premixed and frozen seal caps Cylinder head gasket

Shape memory wire improves sealing of aircraft doors

In aviation safety, providing maximum security for door seals is a crucial part of the specification. Other factors include ease of passenger entry and egress. Such doors require opening and closing only whilst on the ground. Other types of doors are required which can be opened in flight such as weapons bay doors on military aircraft not to mention doors for the undercarriage. But present generation aircraft seals have many deficiencies. To try to overcome these shortcomings Northrop Grumman has patented a new seal based on the special characteristics of a material new to the sealing industry, that of ‘shape memory alloys’.

Variable-Geometry Motion Control of an Aircraft Door

The paper deals with the motion control of an aircraft door hinged at its lower edge. The door opens under the influence of weight, restrained by cross-mounted air springs and dampers. The goal is to mechanically control the motion so as to bring the door in a specified time from rest at a specified initial position to rest at a specified final position, while minimizing the peak force in the dampers. It is shown that such a velocity profile requires to engage the dampers at an optimized position and simultaneously start to modulate the spring moment so that it equals the weight moment at the final position. A variable-geometry solution is proposed consisting of a mechanical feedback in which the door rotation drives an elongation of the spring levers via bevel gears and screw leads. The associated double two point boundary value problem is solved by casting it into a constrained optimization form, yielding the required damper engagement position, the amount of spring lever extension and the damper lever length. The approach is illustrated by a design example.

Studies in the matrix dominated failures of composite joints

The potential use of composites for weight savings is now widely recognised and they are extensively used in both aircraft control surfaces and doors. However, if major weight savings are to be realised it is essential that composites be used in ‘primary’ structural components, i.e. wing and fuselage skins. Before this can be achieved it must be shown that means of transmitting the load from the composite structure to the underlying, or adjacent structure, are both safe and meet the FAA damage tolerance certification requirements. For stiffened composite panels, one potential failure mechanism is the separation of the skin from the stiffeners; resulting from excessive ‘through the thickness’ stresses. This failure mechanism is also present in bonded composite joints and composite repairs. Currently, failure prediction due to in-plane loading appears to be relatively well handled. Unfortunately, this is not yet true for matrix dominated failures. Consequently, it is essential that a valid certification methodology, which addresses all of the possible failure mechanisms, including failure due to interlaminar failure, be developed. To aid in the understanding of such failures the present paper outlines the results of a series of experimental, analytical and numerical studies into the matrix dominated failures of bonded joints, composite repairs and rib stiffened post buckled structures.

Le développement de pièces structurales moulées en fonderie d'aluminium à la cire perdue

Thanks to progress achieved in the past decade, shell investment casting allows the manufacture of aircraft structural parts of high complexity and enables extremely attractive weight and cost benefits when compared to traditional solutions such as machining as a hog-out, sheet metal assembly or sand casting. Specific technological aspects are presented, as well as static and dynamic data obtained on D357 castings obtained through premium quality casting processes. The comprehensive data base generated on premium quality investment castings offers airframe and aeroengine designers a unique chance to achieve substantial gains on major structural parts such as aircraft doors or highly loaded gearbox housings.

The Manufacture of Military Aircraft Doors from Alloy 8090

The Manufacture of Military Aircraft Doors from Alloy 8090

4720065 Translatable outward opening plug-type aircraft door and actuating mechanisms therefor: Tomio Hamatani assigned to The Boeing Company

4720065 Translatable outward opening plug-type aircraft door and actuating mechanisms therefor: Tomio Hamatani assigned to The Boeing Company