Military Specifications Research Articles

Ba1-x Sr x TiO3 ELECTRICAL PROPERTIES-SCALE AND THERMAL PROCESSING

ABSTRACT Bulk charge-balance substituted Ba1-xSrxTiO3 provides a benchmark for low-loss, tunable ferroelectric phase shifter performance over US Military and commercial temperature specification ranges. Thin film dimensions and processing techniques are more amenable to portability requirements. Thin-film Ba0.6Sr0.4TiO3 was deposited on Pt/Si(100) at 400 to 700°C. At room temperature, state-of-the-art thin-film tunability was obtained and was found to improve with deposition temperature, but losses also increased. The results are compared to those of bulk charge-balance substituted Ba1-xSrxTiO3.

History of Low-Order Equivalent Systems for Aircraft Flying Qualities

Introduction F ROM the beginnings of the evolution of flight, there evolved an appreciation of the advantages of an aircraft that was easy for the pilot to fly. Among the insights for which they are famous is the Wright brothers’ realization that when the ability to balance and steer became understood, then aviation would truly have arrived. As the balance between stability and control became better understood, aircraft emerged with sufficiently good flying (or handling) qualities to allow air-to-air combat, reliable passenger transport, and a host of other uses. As aeronautical engineers examined the measurable factors that seemed to bestow good flying qualities, they followed the urge of all engineers, which is to write down those lessons, rules of thumb, and guidelines that make the job easier the next time. From the observations of these engineers, and especially from dedicated research using special-purpose variable-stability aircraft, the community began to document characteristics that were preferred for good flying qualities, along with characteristics that would indicate poor qualities. Most of the early flying-qualities work involved essentially steady-state characteristics like stick force variation with steady, trimmed speed. Dynamic behavior was not so well understood, though early aviators did comprehend the slow tradeoff between altitude and speed in Lanchester’s phugoid mode. They also knew all too well the sinister origins of the slow divergence called the spiral mode. The quick lateral-directional oscillations of the Dutch roll were commonly experienced. Appreciation of the rigidbody modes of motion greatly improved in the first half of the 20th century, including the faster lateral roll mode and the quick angle-of-attack oscillations of the short-period mode. By the middle of the 20th century, engineers realized that the time constants, damping ratios, and natural frequencies of all of these modes could be correlated with flying qualities, good or bad. The stage was set for formal requirements, in the form of military specifications, to define the good and bad values of these modal parameters.

Sample preparation and characterization of artificially aged aircraft coatings for microstructural analysis

The paper describes a method for metallographic preparation of artificially aged aircraft coatings. In order to better understand the in-service performance and identify degradation mechanisms of an aircraft coating, complete characterization of the microstructure is essential. This paper discusses metallographic sample preparation and subsequent microscopy techniques (light optical microscopy, scanning electron microscopy) for characterization of a standard polyurethane aircraft coating system. The preparation method has proven to produce good, consistent results on a wide range of laboratory-produced simulated environmental exposures. The military specification coating system under study (MIL-PRF-85285C and MIL-PRF-23377G) degrades severely after accelerated weathering. Typical degradation includes deterioration of the polyurethane-based resin system in the topcoat and is observed as a visible change in the color. Increased porosity and some physical deterioration were also observed. In addition, some inorganic pigments in the primer appear to migrate into the topcoat during simulated exposure.

Differentiation of Composition C-4 Based on the Analysis of the Process Oil

Abstract United States military Composition C-4 explosive contains 91% cyclotrimethylene trinitramine (RDX), 5.3% dioctyl sebacate or adipate (DOS or DOA), 2.1% polyisobutylene (PIB), and 1.6% oil. The original military specification required low viscosity engine oil, but this has since been changed to a specially manufactured mineral oil, also called “process oil.” Differentiation of military and commercial Composition C-4 may be possible by analyzing the oil. In this study, samples of Composition C-4 were taken from various lots of U.S. military M112 demolition blocks from two commercially manufactured brands sold in the U.S. The oil and plasticizer were extracted with pentane, and the plasticizer was removed using silica solid phase extraction cartridges. The oil was then analyzed by high-temperature gas chromatography/mass spectrometry (HTGC/MS). Results indicated that HTGC/MS is an excellent discriminating technique for oil comparisons; however, differentiation of Composition C-4 is limited by manufacturer production and distribution practices.

Studies of 18650 cylindrical cells made with doped LiNiO2 positive electrodes for military applications

Abstract We studied GP 18650 cylindrical cells made with doped LiNiO 2 positive electrode for military application. The studied cells should deliver about 184 Wh/kg according to the military specification MIL-PRF-320521 while it delivers about 201 Wh/kg according to the general commercial standard. The difference in the cell specific energy is mainly caused by the difference in the charging voltage. It is 4.1 V in the military specification compared to 4.2 V in the general commercial standard. Clearly, to take full advantage of the commercial lithium-ion cell, either the military increases the voltage limit to 4.2 V from 4.1 V or the cell manufacturers redesign their cells according to the 4.1 V charging voltage limit. The studied cell exceeds all major military requirements including high rate discharging, high current pulse discharging, low temperature discharging, cycle life, high temperature storage, and abuse tolerances such as the overcharging, forced discharging, and external short. Specifically, the capacity of the cell exceeds the requirement by 51% at a high discharging rate (3.3 A) and by 39% with a high current (6 A) pulse. The cell can discharge not only ∼62% of the expected capacity at −30 °C but also ∼47% at −40 °C and at 0.67 A, which means that the military can extend their specification to −40 °C. The cell still retained 1.97 Ah (or 92%) after 224 cycles, which exceeds the requirement by ∼9%. The cell retained 1.95 Ah (or 95%) after one-week storage at 50 °C and at 4.1 V, which exceeds the requirement by 8%. The abuse tolerance is also very high. The maximum cell temperature ranged only from 62 to 70 °C during overcharging, external short, and forced discharging. Directions for the improvement are also discussed.

T-50 전기체 내구성시험 시험하중 설계기술 연구

항공기 구조 개발에 관련된 MlL-HDBK-1530 에는 구조 건전성을 확보하기 위한 요구사항이 기술되어있다. 기체 구조의 내구성 및 손상허용성은 요구항목 중의 하나로서 관련 규격서의 요구조건과 절차에 따라 해석 및 시험을 통하여 입증되어야 한다. 본 논문에서는 T-50 항공기 (고등 훈련기)의 안전성 및 내구성 평가를 위한 전기체 내구성 시험하중 설계에 대하여 기술하였다. 내구성 시험하중 설계는 대한민국 공군과 미군사규격서의 요구조건 및 절차에 따라 수행되었다. 실제 비행상태 구현을 위한 전기체 부유식 시험조립 기법과 비행대비행 하중 스펙트럼의 모든 하중을 정확하게 모사 할 수 있는 시험 하중 최적화 기법 및 6-자유도 평형기법을 개발하여 적용하였다. 개발된 기법은 향후 항공기 전기체 구조시험을 수행하는데 있어서 유용한 시험하중 설계 기법임을 확인하였다. The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-HDBK-1530. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper describes the full scale durability test load simulation to evaluate the structural safety and durability of the advanced trainer, T-50. The test load simulation was performed according to the procedure in the military specification and the KAF contract requirements. The durability test design technique which involve the floating test set-up, the optimal test load simulation method, and the 6-DOF test article balance method to secure the real flight conditions as many as possible. It was confirmed that this method will be available in a similar full-scale airframe structural test in future.

Opinion Item: Cancelled US-Military Specifications

The US Military Specification and Standard system has evolved over the years from simple documents to today's complex documents containing the collected knowledge of both the government and industry. Specifications define materials & processes, performance, quality assurance, and packaging of everything from nuts & bolts to weapons systems, and handkerchiefs to gunpowder. Standards identify preferred or acceptable materials, processes, and procedures. Handbooks contain compilations of data regarding particular subjects. The US Military Specification and Standards system was modified as part of the DoD Acquisition Reform program, resulting in cancellation of many of the specifications, standards, handbooks, and supporting documents.

The Microstructural Changes and Mechanical Properties of 7175 Aluminum Alloy Die Forgings

The aim of this study is to investigate the effect of process conditions on the microstructual changes and mechanical properties of large 7175 aluminum die forgings. The cast billets of 370 and 720 mm in diameter were homogenized and die forged after direct chill casting. The size and volume fraction of second phase particles in 720 mm billet were larger than those of 370 mm billet. The interdendritic sites containing the second phase particles was considered to be a crack initiation region in the process of cold upsetting. The tensile and yield strength of die forged specimens of 720 mm billet in the direction of Land L T were higher than those of 370 mm billet. However, the tensile strength of these specimens were 5 to 10% lower than that of American military specification. The plane strain fracture toughness of die forged specimens of 370 mm cast billet showed almost the same level of 720 mm billet, which was die forged after free forging.

Boundary Lubrication RCF Performance of 4 cSt Gas Turbine Engine Oils at 204 °C

The rolling contact fatigue (RCF) and wear performance of three qualified formulations of MIL-L-7808K (4 cSt at 100 °C) were evaluated using AISI VIM-VAR M50 steel. The RCF tester differentiated the fatigue life and wear performance of gas turbine engine lubricants in boundary lubrication regime. Tests were conducted using a ball-on-rod type RCF tester at a maximum Hertzian stress of 4.8 GPa and temperature of 204 °C. Although all the three lubricants meet the military specification, the RCF results suggest that life and wear in the boundary lubrication regime are significantly affected by the formulation. Changes in physical and chemical properties of post test lubricants such as viscosity, acid number and additive concentration were minimal. However, the lowest Fe concentration and COBRA reading, which is a measure of the electrical property of the lubricant, correlated with the highest RCF life and lowest wear.

Evolution, Revolution, and Challenges of Handling Qualities

Abstract : The need for good aircraft handling qualities has been apparent since the days of the Wright Flyer. In the past decade, there has been a perception that this need has lessened as advanced concepts have evolved, in parallel with acquisition reform. The former has led those who are unfamiliar with the field of handling qualities to conclude that quantitative requirements are not necessary, as the latter has resulted in the elimination of the military specifications for handling qualities. This paper reviews the evolution of handling qualities and their specifications. It presents some ongoing challenges in the field to illustrate that handling qualities are still a critical issue for future aircraft.

Multi-Purpose, Moisture-Resistant, High Load Carrying Polyalphaolefin Based Grease, MIL-PRF-32014

A lithium-soap-thickened synthetic hydrocarbon (polyalphaolefin) grease was developed in response to failure of a sodium-soap-thickened mineral oil grease on long term storage in the F-107 engine of the Cruise Missile. The new grease was heavily fortified with performance improving additives and has demonstrated excellent results in bench tests, in an engine test and in the actual application. The superior capabilities of the grease include very high speed (30,000 rpm), high load, high temperature, low water washout, excellent corrosion inhibition and excellent wear resistance. A military specification, MIL-PRF-32014, was written to procure this grease. Testing of the grease in C-5 aircraft landing gear is currently underway and new applications are being investigated. This grease is anticipated to meet most of the military applications and is being proposed as a new multipurpose grease that could significantly reduce the number of greases in the military inventory. Presented at the 57th Annual Meeting in Houston, Texas May 19–23, 2002

Desirable eigenstructure for good short-term helicopter handling qualities: The attitude command response case

The eigenstructure necessary to achieve a good short-term attitude command response in a generic single-rotor helicopter is presented. It achieves appropriate mode decoupling and is consistent with the physical relationships between the state variables. This eigenstructure translates exactly into ideal transfer functions for use with a variety of control design methodologies. The paper discusses how such an eigenstructure is defined to satisfy the requirements of two important military rotorcraft specifications: US ADS 33 and UK DEF STAN 00970.

Updated US Military Specification

Updated US Military Specification

기본 훈련기 실기체 내구성시험

항공기 구조 개발에 관련된 MIL-STD-1530A에는 구조 건전성을 확보하기 위한 요구사항이 기술되어 있다. 기체 구조의 내구성 및 손상허용성은 요구사항 중의 하나로서 관련 규격서의 요구조건과 절차에 따라 해석 및 시험을 통하여 입증되어야 한다. 본 논문에서는 기본 훈련기의 안전성 및 내구성 평가를 위한 실기체 내구성시험에 대하여 소개하였다. 내구성시험은 미군사규격서의 요구조건 및 절차에 따라 수행되었다. 내구성시험의 시험하중은 비행대비행 하중 스펙트럼으로 기본 훈련기의 피로하중 기준에 의거하여 개발되었다. 4배 설계수명 동안의 내구성시험을 성공적으로 완료하였으며, 기본훈련기 구조가 내구성 요구조건을 만족하고 있음을 확인하였다. The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-STD-1530A. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper introduces the full scale durability test to evaluate the structural safety and durability of the basic trainer, KT-1. The test was performed according to the procedure in the military specification. The flight by flight load spectrum was developed by KT-1 fatigue load criteria and used for the durability test. The durability test had been performed for 4 service lives and was completed successfully. Therefore, it was shown that KT-1 airframe satisfied the durability requirements.

Performance of Hydrotalcite Conversion Treatments on AA2024-T3 When Used in a Coating System

Abstract Hydrotalcite (HT) conversion coatings are a possible alternative to chromate conversion coatings (CCC) for the pretreatment of aluminum aerospace alloys, but they must meet several criteria for acceptance. Relevant to acceptance are the abilities of these coatings to provide stand-alone corrosion protection, suitable adhesion with subsequent organic layers, and overall corrosion protection when used within a coating system. This study examines the salt spray performance of nine different HT treatments on AA2024 (UNS 92024) as stand-alone conversion coatings and as a substrate for an epoxy primer. In addition, the adhesion of epoxy to the HT and the corrosion characteristics of HT coatings as assessed by electrochemical impedance spectroscopy (EIS) were determined. Salt spray testing was performed under pertinent military specifications, and CCC was used as the benchmark. Two epoxy primers were evaluated: one with a chromate inhibitor (Class-C) and one with a nonchromate inhibitor (Class-N). The s...

Corrosion Performance of Field-Applied Chromate Conversion Coatings

Abstract Alternative conversion coatings designed to replace chromate conversion coatings (CCC) are typically compared to laboratory-prepared CCC with regard to stand-alone corrosion performance. This study seeks to determine the stand-alone corrosion resistance of field-applied CCC to establish a more realistic benchmark for new nonchromate conversion coatings. Salt spray exposure, wet tape adhesion tests, and measurement of electrical contact resistance were performed according to the military specifications that govern what conversion coatings are accepted for use by the U.S. Department of Defense (DOD) facilities. In addition, other analytical techniques such as electrochemical impedance spectroscopy and Auger electron spectroscopy depth profiling were used. In an initial study, all of the field-applied coatings on AA2024 (UNS A92024), AA6061 (UNS A96061), and AA7075 (UNS A97075) displayed significant pitting after 168 h salt spray exposure. Additionally, attention to pre-cleaning the surface prior to...

Tailoring of Vibration Test Specifications for a Flight Vehicle

Most equipment are subjected to vibration environment during their useful life. It is seen that nearly half of the failures observed during the flights of. satellite launch vehicles or missiles are due to mechanical vibration and shock. Thus, these stresses must be carefully considered while defining the specifications. Specifications are established for a system for use during a simulation test to show that a product meets the requirements concerning resistance to the environment. If the equipment operates smoothly during a test, there should be a very strong probability that it will perform its intended task correctly in the real environment and vice versa. Hence, the specification must be at least as severe as the real environment and also representative of the real environment. It is also required that no other item of the equipment built according to the same design should fail in operation. Specifications should take care of this and thus the envelop of data obtained during the real world environment should be considered. Generally at the design stage and the initial development stage, existing standards like the Military Specifications or Joint Service Specifications are used as guidelines for formulating the specifications. This causes either an overtest or an undertest with regards to the overall spectrum or in specific frequency bands for any given structure. To overcome this, it is essential to develop a correct specification using the telemetry data acquired for a few flights and a method is required to be formulated for deriving the specifications out of the telemetry data so obtained. This paper discusses the formulation of a specification methodology, and algorithm in general. The above method is applied to a series of flight data obtained for a particular flight vehicle to derive a specification representative of the real world environmental conditions (tailoring).

The application of COTS technology in future modular avionic systems

Current avionic systems make extensive use of military specifications and standards but are based on dedicated implementations for individual avionic functions. The result is a proliferation of military devices, software and support environments that are expensive to develop, procure and support. Future systems will be based on integrated modular avionic concepts in which all functions are implemented on a common processing platform constructed from a standard set of hardware and software modules. The paper describes the approach being taken to optimise the application to future modular systems: an architecture based on standardised interfaces will allow modules to be based on commercial components and standards to achieve affordability and exploit rapid advances in commercial technology. At the same time, approaches are being developed to deal with COTS (commercial off-the-shelf) application problems such as short commercial time-scales and loss of control over specifications and standards.

On Acquisition Reform, Risk and Structural Reliability

ABSTRACTU.S. Navy acquisition reform is presented as a means of reducing costs and risks in the acquisition process, while providing improved mission performance for Navy assets. The DD 21 acquisition program is an outgrowth of this desire, with the attainment of the U.S. Navy's performance goals by new designs being demonstrated by commercial design teams instead of being based upon traditional, detailed military specifications. One role of the U.S. Navy technical community will be to certify that the design meets the program performance goals. Because of an absence of formal performance metrics, there may be unmitigated risks that the certification process will either approve an unacceptable design or reject an acceptable design. Both types of risk would negatively impact the U.S. Navy acquisition process. This paper discusses the programmatic risk reductions inherent in adopting a technical risk‐based approach by identifying the role of reliability‐based acceptance criteria for ship structures.

Multi-gigabit WDM optical networking for next generation avionics system communications

It is envisaged that photonic networking will play a significant role in improving performance and reliability in both civil and military avionics systems. Of all the available photonic multiplexing technologies, wavelength-division multiplexing (WDM) has been the primary focus of attention within mainstream telecommunications offering increased throughput at a reasonable cost, with scope for enhanced routing flexibility, connectivity and network survivability. A direct mapping of techniques and devices from the maturing telecommunications sector is, however, not possible because of the stringent requirements of systems operating in the hostile aerospace environment. This paper gives an outline of these requirements and discusses, in detail, the design and development of a multi-gigabit, broadband optical WDM network architecture, specifically for use on aerospace platforms. The paper will also discuss a key element in the system, the arrayed-waveguide grating (AWG) wavelength multiplexing component, which has been designed to allow operation over the full military temperature specification without environmental conditioning.