Structural Integrity of a Fighter Aircraft Undergoing Dynamic Combat Maneuvers

2004 ◽  
Author(s):  
George E. Karniadakis
Keyword(s):  
Structural Integrity ◽  
Fighter Aircraft

scholarly journals Windblast testing of an aircrew helmet: An approach to neck load analysis

2020 ◽  
Vol 63 ◽  
pp. 77-82
Author(s):  
NK Tripathy ◽  
N Divya ◽  
V Raghunandan
Keyword(s):  
Structural Integrity ◽  
Test Facility ◽  
Performance Limits ◽  
Fighter Aircraft ◽  
Injury Criteria ◽  
Test Conditions ◽  
Entire Duration ◽  
Hybrid Iii ◽  
Total Exposure Time ◽  
Structural Failures

Introduction: Modern generation fighter aircraft has expanded the escape envelope for a fighter aircrew. With the ejection occurring at very high airspeeds, windblast is a cause of major injuries and fatalities. Flying helmet, before its induction into operational usage, must be tested in simulated windblast conditions to ensure that they provide adequate safety. Material and Methods: Windblast tests were conducted on a newly designed/procured helmet in a standard windblast test facility as per Mil Std MIL-V-29591/1. A large instrumented Hybrid III male dummy was used for the tests. The test conditions were: Wind speed 600 ± 60 KEAS, rise time of 125 ± 20 ms, time at peak wind velocity of 300 ± 50 ms, and total exposure time of ≥3 s. Structural integrity, retention with the headform, and recorded neck loads were assessed for interpretation of test results. Results: Helmets could withstand the windblast conditions without any significant structural failures and were retained with the headform during the entire duration of test conditions. However, analysis of the neck loads resulted in a significant dilemma in aeromedical decision-making, there being no laid down criteria in the Mil Specification. The neck tension forces were more than the acceptable limits and found to have the potential for significant neck injuries as per the Injury Assessment Reference Values specified in AGARD-AR-330 specifically in the tests where blast was head on and outer visor in up configuration; however, these values were within the acceptable limits as per the other proposed criteria. Similarly, analysis of the neck tension extension combined effects revealed conflicting outcomes for Nij performance limits specified in various standards. This paper discusses the critical analysis of neck loads vis-à-vis the neck injury criteria to understand the neck loads generated during windblast conditions and its implication on aircrew safety. Conclusion: Neck loads assessment is critical in predicting aircrew safety during windblast testing. In the absence of a clearly defined criteria in the Mil Specification, critical ananlysis of neck loads vis-à-vis recommended standards in scientific literature be done to make meaningful conclusion.

Design and Experimental Validation of a Radial Air Turbine Wheel of an Air Starter for Fighter Aircraft Application

2013 ◽  
Author(s):  
Amar Singh ◽  
Joseph Shibu K. ◽  
R. K. Mishra
Keyword(s):  
Experimental Validation ◽  
Structural Integrity ◽  
Forced Response ◽  
Transient Effects ◽  
Fighter Aircraft ◽  
Turbine Wheel ◽  
Air Turbine ◽  
Starter Unit ◽  
Speed Range ◽  
Aircraft Application

A radial Air Turbine Wheel (ATW) designed to operate at 60000 rpm has been analysed for LCF and HCF life. Frequency and mode shape evaluation including blade disk coupling at different nodal diameters is carried out to obtain a speed range without undesirable resonance conditions. Harmonic analysis evaluated the effects of forced response during resonance. Structural integrity during transient has been analysed and found free from set in of any transient effects. The ATW has been fabricated through forging route and its structural integrity has been validated at its operating speed as well as 15% and 22% overspeeds. Satisfactory performance during these tests without any distress has demonstrated the adequacy of design and qualification of the turbine wheel for fitment in the air starter. The turbine wheel is fitted in an air starter unit which was then successfully performed consistently over 100 start cycles before cleared for aircraft application.

A Case of Structural Integrity of Ageing Fighter Aircraft Leveraging on Condition Maintenance Methodology

2012 ◽  
Vol 217-219 ◽  
pp. 2560-2565
Author(s):  
Bilal Younus ◽  
Bilal Farooq ◽  
Ahmed Jamal ◽  
Irfan Anjum Manarvi
Keyword(s):  
Structural Integrity ◽  
Aircraft Design ◽  
Extensive Study ◽  
Aviation Industry ◽  
Aircraft Maintenance ◽  
Fighter Aircraft ◽  
Engineering Technology ◽  
Design Philosophy ◽  
Manufacturing Techniques ◽  
Technology Advances

In recent years aircraft maintenance practices have been influenced by changes in aircraft design philosophy and improvements in engineering technology. Advances in manufacturing techniques and material specifications have made it less necessary to carry out frequent disassembly of aircraft and components to establish confidence. The need to be competitive and to reduce costs has meant that the aviation industry has sought to gain advantage from these improvements by moving from time consuming and cost extensive, invasive maintenance to a philosophy of on condition maintenance (OCM). The research is aimed at highlighting an OCM based maintenance methodology by carrying out an extensive study on structural integrity of various vintage Chinese fighter aircraft. The study finds that the structure of Chinese fighter aircraft is robust and is capable of flying for more hours/years than specified by OEM. The study will help air forces operating the ageing Chinese fighter aircraft in extending the lives of their respective fleets well beyond the OEM prescribed limits.

scholarly journals Structure Life Extension towards the Structural Integrity of Sukhoi Su-30MKM

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5562
Author(s):  
Arvinthan Venugopal ◽  
Roslina Mohammad ◽  
Md Fuad Shah Koslan ◽  
Ashaari Shafie ◽  
Alizarin Ali ◽  
...  
Keyword(s):  
Service Life ◽  
Structural Integrity ◽  
Simulation Analysis ◽  
Fatigue Loading ◽  
Operating Conditions ◽  
Life Assessment ◽  
Life Extension ◽  
Destructive Testing ◽  
Fighter Aircraft ◽  
Service Life Extension

The airframe structures of most fighter aircraft in the Royal Malaysian Airforce have been in service for 10 to 20 years. The effect of fatigue loading, operating conditions, and environmental degradation has led to the structural integrity of the airframe being assessed for its airworthiness. Various NDT methods were used to determine the current condition of the aircraft structure after operation of beyond 10 years, and their outcomes are summarized. In addition, although there are six critical locations, the wing root was chosen since it has the highest possibility of fatigue failure. It was further analyzed using simulation analysis for fatigue life. This contributes to the development of the maintenance task card and ultimately assists in extending the service life of the fighter aircraft. Using the concept of either safe life or damage tolerance as its fatigue design philosophy, the RMAF has adopted the Aircraft Structural Integrity Program (ASIP) to monitor the structural integrity of its fighter aircraft. With the current budget constraints and structural life extension requirements, the RMAF has embarked on the non-destructive testing method and engineering analysis. The research outcome will enhance the ASIP for other aircraft platforms in the RMAF fleet for its structure life assessment or service life extension program.

Electron Beam Damage of Biomolecules Assessed by Energy Loss Spectroscopy

1978 ◽  
Vol 36 (3) ◽  
pp. 61-69
Author(s):  
M. Isaacson ◽  
M.L. Collins ◽  
M. Listvan
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Structural Integrity ◽  
Analytical Electron Microscopy ◽  
High Dose ◽  
Dose Rates ◽  
Special Cases ◽  
Analytical Electron ◽  
Atom Migration ◽  
Beam Damage

Over the past five years it has become evident that radiation damage provides the fundamental limit to the study of blomolecular structure by electron microscopy. In some special cases structural determinations at very low doses can be achieved through superposition techniques to study periodic (Unwin & Henderson, 1975) and nonperiodic (Saxton & Frank, 1977) specimens. In addition, protection methods such as glucose embedding (Unwin & Henderson, 1975) and maintenance of specimen hydration at low temperatures (Taylor & Glaeser, 1976) have also shown promise. Despite these successes, the basic nature of radiation damage in the electron microscope is far from clear. In general we cannot predict exactly how different structures will behave during electron Irradiation at high dose rates. Moreover, with the rapid rise of analytical electron microscopy over the last few years, nvicroscopists are becoming concerned with questions of compositional as well as structural integrity. It is important to measure changes in elemental composition arising from atom migration in or loss from the specimen as a result of electron bombardment.

Structural integrity after cold storage of human epidermal model in hypothermosol: A correlative ultrastructural and fluorescent assay

1994 ◽  
Vol 52 ◽  
pp. 270-271
Author(s):  
Henry H. Eichelberger ◽  
John G. Baust ◽  
Robert G. Van Buskirk
Keyword(s):  
Cold Storage ◽  
Structural Integrity ◽  
Culture Media ◽  
Cell Structure ◽  
Natural State ◽  
Sodium Cacodylate ◽  
Ruthenium Tetroxide ◽  
Cacodylate Buffer ◽  
Before And After

For research in cell differentiation and in vitro toxicology it is essential to provide a natural state of cell structure as a benchmark for interpreting results. Hypothermosol (Cryomedical Sciences, Rockville, MD) has proven useful in insuring the viability of synthetic human epidermis during cold-storage and in maintaining the epidermis’ ability to continue to differentiate following warming.Human epidermal equivalent, EpiDerm (MatTek Corporation, Ashland, MA) consisting of fully differentiated stratified human epidermal cells were grown on a microporous membrane. EpiDerm samples were fixed before and after cold-storage (4°C) for 5 days in Hypothermosol or skin culture media (MatTek Corporation) and allowed to recover for 7 days at 37°C. EpiDerm samples were fixed 1 hour in 2.5% glutaraldehyde in sodium cacodylate buffer (pH 7.2). A secondary fixation with 0.2% ruthenium tetroxide (Polysciences, Inc., Warrington, PA) in sodium cacodylate was carried out for 3 hours at 4°C. Other samples were similarly fixed, but with 1% Osmium tetroxide in place of ruthenium tetroxide. Samples were dehydrated through a graded acetone series, infiltrated with Spurrs resin (Polysciences Inc.) and polymerized at 70°C.

High-Resolution electron crystallography of the light-harvesting chlorophyll-a/b protein complex from chloroplast membranes

1990 ◽  
Vol 48 (1) ◽  
pp. 610-610
Author(s):  
Werner Kühlbrandt ◽  
Da Neng Wang ◽  
K.H. Downing
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Chlorophyll A ◽  
Protein Complex ◽  
Structural Integrity ◽  
Light Harvesting ◽  
Lhc Ii ◽  
Diffraction Patterns ◽  
Difference Fourier ◽  
2D Crystals

The light-harvesting chlorophyll-a/b protein complex (LHC-II) is the most abundant membrane protein in the chloroplasts of green plants where it functions as a molecular antenna of solar energy for photosynthesis. We have grown two-dimensional (2d) crystals of the purified, detergent-solubilized LHC-II . The crystals which measured 5 to 10 μm in diameter were stabilized for electron microscopy by washing with a 0.5% solution of tannin. Electron diffraction patterns of untilted 2d crystals cooled to 130 K showed sharp spots to 3.1 Å resolution. Spot-scan images of 2d crystals were recorded at 160 K with the Berkeley microscope . Images of untilted crystals were processed, using the unbending procedure by Henderson et al . A projection map of the complex at 3.7Å resolution was generated from electron diffraction amplitudes and high-resolution phases obtained by image processing .A difference Fourier analysis with the same image phases and electron diffraction amplitudes recorded of frozen, hydrated specimens showed no significant differences in the 3.7Å projection map. Our tannin treatment therefore does not affect the structural integrity of the complex.

Effects of Fatigue on Cognitive Performance in Long-Duration Simulated Flight Missions

2020 ◽  
Vol 10 (2) ◽  
pp. 82-93
Author(s):  
Eduardo Rosa ◽  
Ola Eiken ◽  
Mikael Grönkvist ◽  
Roger Kölegård ◽  
Nicklas Dahlström ◽  
...  
Keyword(s):  
Executive Functions ◽  
Task Performance ◽  
Cognitive Performance ◽  
Cognitive Tasks ◽  
Fatigue Index ◽  
Fighter Aircraft ◽  
Long Duration ◽  
Metacognitive Accuracy

Abstract. Fighter pilots may be exposed to extended flight missions. Consequently, there is increasing concern about fatigue. We investigated the effects of fatigue and cognitive performance in a simulated 11-hr mission in the 39 Gripen fighter aircraft. Five cognitive tasks were used to assess cognitive performance. Fatigue was measured with the Samn–Perelli Fatigue Index. Results showed that performance in the non-executive task degraded after approximately 7 hr. Fatigue ratings showed a matching trend to the performance in this task. Performance in tasks taxing executive functions did not decline. We interpreted that fatigue can be overridden by increased attentional effort for executive tasks but not for non-executive components of cognition. Participants underestimated their performance and metacognitive accuracy was not influenced by fatigue.

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