Predicting the certification basis for airliner air-to-air refuelling

2015 ◽  
Vol 119 (1220) ◽  
pp. 1175-1192 ◽  
Author(s):  
R. J. Spencer
Keyword(s):  
Structural Integrity ◽  
Hazard Analysis ◽  
Aircraft Design ◽  
System Level ◽  
Handling Qualities ◽  
Close Proximity ◽  
Testing Techniques ◽  
Economic Necessity ◽  
Failure Conditions ◽  
Certification Requirements

Abstract The premise is that in the future civil Air-to-Air Refuelling (AAR) will become an economic necessity if popular mass air travel is to continue. What is attempted is to provide a contemporary view of how such future operations could be safely undertaken. The intention is to predict the certification basis for demonstrating safe AAR operation of Cruiser-Feeder concepts. The necessary systems and aircraft functions are treated very much as they are today when civil certifying a large aeroplane type. The compliance demonstration required for environmental conditions, flight envelope, systems providing the necessary functionality, structural integrity, weight and balance are discussed. Applicable existing civil certification requirements are identified and where necessary expanded in scope to accommodate AAR operation. Where contemporary material does not supply appropriate guidance then corresponding safety criteria are proposed to address the deficiency. Lessons learnt from military AAR include the drive for interoperability. This has resulted in extensive efforts to standardise equipment and systems, which are equally applicable to civil AAR. Extremely useful advisory material exists, ranging from flight testing techniques to related safety. The importance of ensuring the consistency of failure condition categorisation at system and aircraft level is highlighted. The treatment of failures when two aircraft are in close proximity is something not considered by civil functional hazard analysis. The concept of AAR as an additional flight phase is introduced and affected system safety analyses identified. Examples of failure conditions that are not catastrophic at system level, but potentially could be at aircraft level during AAR are provided. Rendezvous scenarios are described to illustrate their influence on the certification basis. Combining such considerations with the factors that influence aircraft design leads to ramifications for handling qualities, performance and fuel system design. A viable and certifiable AAR configuration is consequently proposed. Consideration is given to treating operational certification in a progressive manner similar to existing LROPS (Long Range Operations).

scholarly journals Efficient SMT-Based Analysis of Failure Propagation

2021 ◽  
pp. 209-230
Author(s):  
Marco Bozzano ◽  
Alessandro Cimatti ◽  
Anthony Fernandes Pires ◽  
Alberto Griggio ◽  
Martin Jonáš ◽  
...  
Keyword(s):  
Safety Assessment ◽  
Hazard Analysis ◽  
Aircraft Design ◽  
Modern Approach ◽  
Safety Requirements ◽  
Failure Propagation ◽  
Important Challenge ◽  
Failure Conditions ◽  
Model Failure

AbstractThe process of developing civil aircraft and their related systems includes multiple phases of Preliminary Safety Assessment (PSA). An objective of PSA is to link the classification of failure conditions and effects (produced in the functional hazard analysis phases) to appropriate safety requirements for elements in the aircraft architecture. A complete and correct preliminary safety assessment phase avoids potentially costly revisions to the design late in the design process. Hence, automated ways to support PSA are an important challenge in modern aircraft design. A modern approach to conducting PSAs is via the use of abstract propagation models, that are basically hyper-graphs where arcs model the dependency among components, e.g. how the degradation of one component may lead to the degraded or failed operation of another. Such models are used for computing failure propagations: the fault of a component may have multiple ramifications within the system, causing the malfunction of several interconnected components. A central aspect of this problem is that of identifying the minimal fault combinations, also referred to as minimal cut sets, that cause overall failures.In this paper we propose an expressive framework to model failure propagation, catering for multiple levels of degradation as well as cyclic and nondeterministic dependencies. We define a formal sequential semantics, and present an efficient SMT-based method for the analysis of failure propagation, able to enumerate cut sets that are minimal with respect to the order between levels of degradation. In contrast with the state of the art, the proposed approach is provably more expressive, and dramatically outperforms other systems when a comparison is possible.

scholarly journals A Review of Recent Advancements in Offshore Wind Turbine Technology

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 579
Author(s):  
Taimoor Asim ◽  
Sheikh Zahidul Islam ◽  
Arman Hemmati ◽  
Muhammad Saif Ullah Khalid
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Offshore Wind ◽  
System Level ◽  
Offshore Wind Turbine ◽  
Component Level ◽  
Foundation Design ◽  
Offshore Wind Turbines

Offshore wind turbines are becoming increasingly popular due to their higher wind energy harnessing capabilities and lower visual pollution. Researchers around the globe have been reporting significant scientific advancements in offshore wind turbines technology, addressing key issues, such as aerodynamic characteristics of turbine blades, dynamic response of the turbine, structural integrity of the turbine foundation, design of the mooring cables, ground scouring and cost modelling for commercial viability. These investigations range from component-level design and analysis to system-level response and optimization using a multitude of analytical, empirical and numerical techniques. With such wide-ranging studies available in the public domain, there is a need to carry out an extensive yet critical literature review on the recent advancements in offshore wind turbine technology. Offshore wind turbine blades’ aerodynamics and the structural integrity of offshore wind turbines are of particular importance, which can lead towards system’s optimal design and operation, leading to reduced maintenance costs. Thus, in this study, our focus is to highlight key knowledge gaps in the scientific investigations on offshore wind turbines’ aerodynamic and structural response. It is envisaged that this study will pave the way for future concentrated efforts in better understanding the complex behavior of these machines.

Analysis of Multiple Co-Planar Surface Breaking Flaws Loaded in Tension Under Cleavage Failure Conditions

2006 ◽  
Author(s):  
J. K. Sharples ◽  
M. A. Wilkes ◽  
S. F. Yellowlees ◽  
D. W. Beardsmore ◽  
G. T. Melvin ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Structural Integrity ◽  
Weakest Link ◽  
Early Results ◽  
Analytical Work ◽  
Failure Conditions ◽  
Constraint Effects ◽  
Crack Tip Constraint ◽  
Cleavage Failure

In procedures such as R6 and BS 7910 for assessing the structural integrity of structures, complex multiple flaws located in close proximity to each other are generally characterised as one, larger, single flaw. Recent studies have shown that the current characterisation rules may be non-conservative under some circumstances. Concurrent experimental and analytical programmes are being undertaken in order to further investigate this potential non-conservatism for situations where the possibility of cleavage failure has to be taken into account when assessing structures or components containing multiple flaws. The analytical work has involved inelastic finite element modelling in conjunction with numerical analysis based on the weakest link methodology for cleavage initiation to determine the probability of cleavage failure. This has allowed the probability of failure for the situation of multiple adjacent flaws to be compared with that for the single characterised flaw to determine whether the characterisation rules are conservative. Initial results from the cases studied so far indicate that: • For flaws that do not touch, the probability of cleavage failure for the single characterised flaw is higher than the original flaws, confirming that the characterisation process is conservative in this case (perhaps significantly so). • For low aspect ratio (depth/length ≪ 1.0) flaws in contact, the probability of cleavage failure for the single characterised is higher than the original flaws, confirming that the characterisation process is conservative in this case. • However, for high aspect ratio (depth/length ∼ 1.0) flaws in contact, the probability of cleavage failure for the single characterised flaw is lower than the original flaws, indicating that the characterisation process may be non-conservative in this case. This paper covers the initial stages of a much larger programme. The analyses presented in this paper are in the process of being extended to allow for crack-tip constraint effects. Early results from these further analyses indicate that the loss of constraint between interacting flaws may be a significant factor and could eliminate at least some of the perceived non-conservatism for the high aspect ratio flaw. Further work is also underway to examine the effect of any localised coalescence of defects (a re-entrant region); the current analyses consider defects that are only just in contact. Further papers are therefore expected.

scholarly journals Multibody dynamics analysis of the human upper body for rotorcraft–pilot interaction

2020 ◽  
Vol 102 (3) ◽  
pp. 1517-1539
Author(s):  
Andrea Zanoni ◽  
Alessandro Cocco ◽  
Pierangelo Masarati
Keyword(s):  
Aircraft Design ◽  
Upper Body ◽  
Support Design ◽  
Design Decisions ◽  
Detailed Model ◽  
Strong Base ◽  
Handling Qualities ◽  
Multibody Model ◽  
Scaling Procedure ◽  
Spine Model

AbstractThe study of the biodynamic response of helicopter passengers and pilots, when excited by rotorcraft vibrations that are transmitted through the seat and, for the latter, the control inceptors, is of great importance in different areas of aircraft design. Handling qualities are affected by the proneness of the aircraft to give rise to adverse interactions, an unwanted quality that can be captured by the so-called biodynamic feedthrough. On the other hand, the transmissibility of vibrations, especially from the seat to the head, affects the comfort of pilots and passengers during flight. Detailed and parametrised multibody modelling of the human upper body can provide a strong base to support design decisions justified by a first-principles approach. In this work, a multibody model of the upper body is formed by connecting a previously developed detailed model of the arms to a similarly detailed model of the spine. The whole model can be adapted to a specific subject, identified by age, gender, weight and height. The spine model and the scaling procedure have been validated using the experimental results for seat to head transmissibility. The coupled spine-arms model is used to evaluate the biodynamic response in terms of involuntary motion induced on the control inceptors, including the related nonlinearities.

An Engineering Basis for Establishing Radiographic Acceptance Standards for Porosity in Steel Weldments

1965 ◽  
Vol 87 (4) ◽  
pp. 887-893 ◽  
Author(s):  
H. Greenberg
Keyword(s):  
Stress Concentration ◽  
Nondestructive Testing ◽  
Pressure Vessel ◽  
Maximum Size ◽  
Theoretical Studies ◽  
Concentration Effects ◽  
Close Proximity ◽  
Testing Techniques ◽  
Steel Welds ◽  
Made In

Radiographic acceptance standards, such as those found in the ASME Unfired Pressure Vessel Code are critically reviewed. Limits on the size and distribution of porosity in steel welds are analyzed from the viewpoint of susceptibility to failure in service. In large part, present standards for porosity appear to have been established on a “good workmanship” basis rather than on setting sound conservative limits for the maximum size, and distribution of flaws which can be tolerated without decreasing the reliability of the product. Radiographic acceptance standards in use today do not reflect the significant advances being made in (1) the fracture mechanics approach to designing for prevention of failure; (2) theoretical studies of the stress-concentration effects of holes in close proximity to one another; and (3) the possible use of complementary nondestructive testing techniques. Considerable emphasis is placed on the proposition that radiographic acceptance standards for weldments must be designed specifically for each particular application. Considerations applicable to welds in the 120-in-dia rocket motor case are cited as an example of how standards for acceptable porosity and inclusions can be established.

The Heavy Assault Transport Helicopter

1966 ◽  
Vol 70 (670) ◽  
pp. 914-922
Author(s):  
R. B. Lightfoot
Keyword(s):  
Control System ◽  
Flight Control ◽  
Structural Integrity ◽  
Operating Cost ◽  
Maximum Level ◽  
Main Rotor ◽  
Handling Qualities ◽  
Level Flight ◽  
Integrity Tests ◽  
The Military

SummaryThe military tactics of vertical envelopment require the transport of 8000 pounds of payload to a radius of 100 nautical miles at a speed of 150 knots. The aircraft should be able to hover at 6000 feet on a standard day and with one engine inoperative maintain level flight in turbulent air. The helicopter should be readily convertible to carry cargo or troops.The CH-53A meets these requirements. Additional design constraints, including emergency water landing, rear loading, self-contained navigation system and weight and dimensions compatible with aircraft carriers have been imposed.With special attention having been given to the vibrational environment two General Electric T-64 engines have been installed. The 72-foot diameter main rotor is equipped with six blades with 26 inch chord and a NACA 0012 aerofoil modified to improve the characteristics at high Mach number. To achieve low drag and interference the fuselage and rotors have been developed in the wind tunnel. Tail surfaces have been especially developed to provide good handling qualities. An automatic stabilisation system was provided to relieve the pilot of various flight duties and to permit him to give more attention to the military situation.Special design procedures have been followed to control weight, drag, reliability and vibration. The final helicopter is within 3-7 per cent of the desired weight and the performance is in substantial accord with predictions. The vibration level is generally about ±0-10 g throughout the cockpit and cabin.During the flight development phase the control system was modified to provide appropriate coupling to relieve the pilot and automatic flight control system of any unnecessary compensating control motions. The structural integrity tests revealed the need for improvement of the main rotor blade attachment spindle. The engine-to-transmission shafting required a damped support.The finally developed version of the CH-53A meets the mission requirements already stated. The hovering ceiling on a standard day Is over 5000 feet. The maximum level flight speed is 170 kt. The handling qualities and vibration are superior to any helicopter previously built by Sikorsky Aircraft. The reliability and maintenance features have been demonstrated by extensive testing. The overhaul periods will be 1200 hours in early service operation; 5-5 direct maintenance man-hours per flight hour are required to accomplish all maintenance except overhaul of repairable components. The dynamic components have been developed to such a high degree of reliability that they will be overhauled “on condition” only and continued in service throughout the normal military usage.In terms of commercial service, the CH-53A (S-65) will have a direct operating cost of approximately 4c per seat mile.

Fatigue in aerostructures—where structural health monitoring can contribute to a complex subject

2006 ◽  
Vol 365 (1851) ◽  
pp. 561-587 ◽  
Author(s):  
Christian Boller ◽  
Matthias Buderath
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Structural Integrity ◽  
Aircraft Design ◽  
Jet Engines ◽  
Structural Health ◽  
Fatigue Design ◽  
The Impact ◽  
Maintenance Process ◽  
Complex Subject

An overview of the aircraft design and maintenance process is given with specific emphasis on the fatigue design as well as the phenomenon of the ageing aircraft observed over the life cycle. The different measures taken to guarantee structural integrity along the maintenance process are addressed. The impact of structural health monitoring as a means of possibly revolutionizing the current aircraft structural monitoring and design process is emphasized and comparison is made to jet engines and helicopters, where health monitoring has already found the respective breakthrough.

Information Exchange Patterns in Digital Engineering: An Observational Study Using Web-Based Virtual Design Studio

2021 ◽  
Vol 21 (4) ◽  
Author(s):  
Joseph Thekinen ◽  
Paul T. Grogan
Keyword(s):  
Information Exchange ◽  
Negative Relationship ◽  
Aircraft Design ◽  
System Level ◽  
Design Parameters ◽  
Design Studio ◽  
Functional Requirements ◽  
Virtual Design ◽  
Design Task ◽  
Outcome Performance

Abstract This paper performs an observational human subjects study to investigate how design teams use an information system to exchange, store, and synthesize information in an engineering design task. Framed through the lens of decision-based design, a surrogate design task models an aircraft design problem with 12 design parameters across four roles and six system-level functional requirements. A virtual design studio provides a browser-based interface for four participants in a 30-min design session. Data collected across 10 design sessions provide process factors about communication patterns and outcome factors about the resulting design. Correlation analysis shows a positive relationship between design iteration and outcome performance but a negative relationship between chat messages and outcome performance. Discussion explains how advances in information exchange, storage, and synthesis can support future design activities.

Material Control and Fracture Control Planning for the Space Shuttle Orbiter Program

1980 ◽  
Vol 102 (1) ◽  
pp. 40-44 ◽  
Author(s):  
R. M. Ehret
Keyword(s):  
Structural Integrity ◽  
Space Shuttle ◽  
Detailed Examination ◽  
Material Control ◽  
Design Environments ◽  
Control Programs ◽  
Analysis Methods ◽  
Direct Demonstration ◽  
Fracture Control ◽  
Certification Requirements

Structural integrity of the Space Shuttle orbiter vehicle is assured primarily through analysis. The analysis is supplemented by tests intended to validate analysis methods or, in some cases, to provide direct demonstration of structural capability to withstand the design environments. The paper summarizes the Shuttle’s structural certification requirements and the major test efforts supporting this certification. A more detailed examination of the orbiter material control land fracture control programs is presented as efficient and constructive components of a viable structural integrity plane.

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