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Journal Article

Improving the Modelling of Dissociating Hydrogen Nozzles

2019-11-21
Abstract While the design of nozzles for diatomic gases is very well established and covered by published works, the case of a diatomic gas dissociating to monatomic along a nozzle is a novel subject that needs a proper mathematical description. These novel studies are relevant to the definition of nozzles for gas-core Nuclear Thermal Rockets (NTR) that are receiving increased attention for the potential advantages they may deliver versus current generation rockets. The article thus reviews the design of the nozzles of gas-core NTR that use hydrogen as the propellant. Propellant temperatures are expected to reach 9,000-15,000 K. Above 1500 K, hydrogen begins to dissociate at low pressures, and around 3000 K dissociation also occurs at high pressures. At a given temperature, the lower the gas pressure the more molecules dissociate, and H2 → H + H. The properties of the gas are a function of the mass fractions of diatomic and monatomic hydrogen x H2 and x H = 1 − x H2.
Journal Article

Conceptual Design, Material, and Structural Optimization of a Naval Fighter Nose Landing Gear for the Estimated Static Loads

2019-12-13
Abstract The Naval Nose Landing Gear (NLG) structural assembly consists of components with complex structural geometry and critical functionalities. The landing gear components are subjected to high static and dynamic loads, so they must be appropriately designed, dimensioned, and made by materials with mechanical characteristics that meet high strength, stiffness, and less weight requirements. This article contributes to the shape, size, and material optimization for the NLG of a supersonic naval aircraft for the estimated static loads. The estimated modal frequency values of the NLG assembly using Finite Element Analysis (FEA) software were compared with available Ground Vibration Test data of an aircraft to literally prove the accuracy and suitability of finite element (FE) model that can be used for any further analysis.
Journal Article

Parametric Studies on Airfoil-Boundary Layer Ingestion Propulsion System

2020-03-11
Abstract From the fact that a propulsor consumes less power for a given thrust if the inlet air is slower, simulations are conducted for a propulsor imposed behind an airfoil as ideal boundary layer ingestion (BLI) propulsor to stand on the benefits of this configuration from the point of view of power and efficiency and to get a closer look on the mutual interaction between them. This interaction is quantified by the impact on three main sets of parameters, namely, power consumption, boundary layer properties, and airfoil performance. The position and size of the propulsor have great influence on the flow around the airfoil. Parametric studies are carried out to understand their influence. BLI propulsor directly affects the power saving and all of the pressure-dependent parameters, including lift and drag. For the present case, power saving reached 14.4% compared to the propeller working in freestream.
Journal Article

Analytical Estimation of Infrared Signature of Converging and Converging-Diverging Nozzles of Jet Engine

2021-04-21
Abstract Jet engine hot parts (e.g., jet nozzle) are a crucial source of aircraft’s infrared (IR) signature from the rearview, in 1.9-2.9 μm and 3-5 μm bands. The exhaust nozzle design used in a jet aircraft affects its performance and IR signature (which is also affected just by performance) from the engine layout. For supersonic aircraft (typically for M ∞ > 1.5), a converging-diverging (C-D) nozzle is preferred over a convergent nozzle for optimum performance. The diverging section of the C-D nozzle has a full range of visibility from the rearview; hence, it was not considered a prudent choice for low IR observability. This theoretical study compares the IR signature of the C-D nozzle with that of the convergent nozzle from the rearview in 1.9-2.9 μm and 3-5 μm bands for the same thrust.
Standard

Nitrogen Absorption/Desorption (Gas Dissolution) in Aircraft Shock Absorbers

2019-04-18
WIP
AIR6942
This document outlines the current state of the art in the understanding of gas in solution in shock absorber oils in unseperated shock absorbers. A literature review, overview of Henry's law, Henry's law coefficients for known gas and oil couples, in-service operational problems, lessons learned, and potential future work will be discussed in the document.
Standard

Landing Gear Based Weight and Balance Systems

2019-04-18
WIP
AIR6941
This document outlines historical systems which have used the landing gear as a sensor or installation point for full aircraft weight and balance systems. A number of systems have been developed, installed, certified, and placed in service but few systems remain in regular use. The document will capture the history of these systems, reasons (where known) for their withdrawal from service, and lessons learned.
Standard

Runway Condition Monitoring Systems

2022-04-13
WIP
AIR6697
This report will document Runway Condition Monitoring systems that provide information intended to reduce or eliminate aircraft runway excursions or overruns that may occur as a result of poor runway conditions.
Standard

SAFE-LIFE LIMITS FOR LANDING GEAR STRUCTURES

2018-04-26
WIP
AIR6949
This document describes the approaches taken to define safe-life limits for the management of fatigue in landing gear structures, and the substantiation of those limits through full-scale fatigue testing. The safe-life scatter factors considered in a range of military and civil regulatory standards are also reviewed.
Standard

Test Method for Catalytic Carbon Brake Disk Oxidation

2013-12-04
WIP
AS6289
The scope of the test method is to provide stakeholders including fluid manufacturers, brake manufacturers, aircraft constructors, aircraft operators and airworthiness authorities with a relative assessment of the effect of deicing chemicals on carbon oxidation. This test is designed to assess the relative effects of runway deicing chemicals by measuring mass change of contaminated and bare carbon samples tested under the same conditions.
Standard

Minimum Environmental Performance Standard for Parts 23, 25, 27, and 29 Aircraft Wheels Brakes, and Wheel and Brake Assemblies

2021-04-27
WIP
AS6961
This SAE Aerospace Standard (AS) prescribes the Minimum Performance Standards (MPS) for environmental conditions that wheel, brake, and wheel and brake assemblies to be used on aircraft certificated under 14 CFR Parts 23, 25, 27, and 29. The environmental requirements in this document shall be used in conjunction with other MPS defined in Technical Standard Orders for the applicable equipment.
Standard

In-Flight Thrust Determination for Aircraft with Thrust Vectoring

2022-06-14
CURRENT
AIR6007
The purpose of this document is to provide guidance on in-flight thrust determination of engines that are impacted by intentional or unintentional thrust vectoring. However, as indicated in the Foreword, the field of aircraft thrust vectoring is varied and complex. For simplicity and coherence of purpose, this document will be limited in scope to multi-axis thrust vectoring nozzles or vanes attached to the rear of the engine or airfame; single-axis thrust vectoring and unintentional thrust vectoring (fixed shelf or deck configuration) are special cases of this discussion. Specifically excluded from this scope are thrust vectoring created primarily by airframe components such as wing flaps, etc.; lift engines, propulsive fans and thrust augmenting ejectors; and powerplants that rotate or otherwise move with respect to the airframe.
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