NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
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Aviation related applications that rely upon datalink for information exchange are increasingly being developed <strong>and</strong><br />
deployed. The increase in the quantity of applications <strong>and</strong> associated data communications will expose problems <strong>and</strong> issues<br />
to resolve. <strong>NASA</strong> Glenn Research Center has prepared to study the communications issues that will arise as datalink<br />
applications are employed within the National Airspace System (NAS) by developing a aviation communications emulation<br />
testbed. The Testbed is evolving <strong>and</strong> currently provides the hardware <strong>and</strong> software needed to study the communications impact<br />
of Air Traffic Control (ATC) <strong>and</strong> surveillance applications in a densely populated environment. The communications load<br />
associated with up to 160 aircraft transmitting <strong>and</strong> receiving ATC <strong>and</strong> surveillance data can be generated in real time in a<br />
sequence similar to what would occur in the NAS.<br />
Derived from text<br />
Air Traffıc Control; Computer Programs; Aircraft Communication; Ground-Air-Ground Communication; Test St<strong>and</strong>s<br />
20040112054 Analex Corp., Brook Park, OH, USA<br />
Erlang B/C Link Availability/Blockage for Data <strong>and</strong> Voice over VDL Mode 3<br />
Shamma, Mohammed A.; [2004]; 10 pp.; In English; ICNS 2004, 27-29 Apr. 2004, Fairfax, VA, USA<br />
Contract(s)/Grant(s): NAS3-00145; WBS 22-727-01-01; No Copyright; Avail: CASI; A02, Hardcopy<br />
This study looks into the blockage <strong>and</strong> availability of Digital VHF Mode 3 link. Using future predicted voice <strong>and</strong> CPDLC<br />
data traffic loads, the Erlang B <strong>and</strong> Erlang C formulas were utilized to measure the availability/blockage of the two<br />
applications over VDL mode 3. The results here, along with previous cell capacity calculations on the number of frequency<br />
channels available done as a part of a separate study, can give a measure of the overall system capacity. This study shows<br />
sufficient availability (for acceptable blockage levels for worst case traffic loads. It is found that overall the voice<br />
communications will reduce the system availability the most, followed by Management accessing portion of the data which<br />
turns limits the CPDLC capability.<br />
Derived from text<br />
Blocking; Traffıc; Voice Communication; Ground-Air-Ground Communication; Data Links<br />
05<br />
AIRCRAFT DESIGN, TESTING AND PERFORMANCE<br />
Includes all stages of design of aircraft <strong>and</strong> aircraft structures <strong>and</strong> systems. Also includes aircraft testing, performance, <strong>and</strong> evaluation,<br />
<strong>and</strong> aircraft <strong>and</strong> flight simulation technology. For related information see also 18 Spacecraft Design, Testing <strong>and</strong> Performance; <strong>and</strong> 39<br />
Structural Mechanics. For l<strong>and</strong> transportation vehicles see 85 Technology Utilization <strong>and</strong> Surface Transportation.<br />
20040111160 California Univ., Irvine, CA, USA<br />
Assessment, Development, <strong>and</strong> Validation of Computational Fracture Mechanics Methodologies <strong>and</strong> Tools for<br />
Shot-Peened Materials Used in Rotorcraft Principal Structural Elements<br />
Jul. 2004; In English<br />
Report No.(s): PB2004-106665; No Copyright; Avail: National <strong>Technical</strong> Information Service (NTIS)<br />
This report describes an analytical model that simulates the shot-peening process <strong>and</strong> estimates the residual stress field<br />
in the surface layer. A numerical approach for the prediction of crack growth rates for cracks in compressive stress fields was<br />
implemented in AGILE 3D. AGILE 3D is an accurate <strong>and</strong> efficient tool for predicting nonplanar three-dimensional (3D)<br />
fatigue crack growth in structural components. The results of validation of AGILE 3D for predicting 3D fatigue growth,<br />
compared to the University of Washington test data, were very good. The effect of shot peening on crack growth rates of<br />
various materials is investigated numerically by means of AGILE 3D. Various fatigue crack growth models, including plastic<br />
strip model <strong>and</strong> plastic zone model in the presence of residual stresses <strong>and</strong> plasticity, are discussed.<br />
NTIS<br />
Compression Loads; Crack Propagation; Mathematical Models<br />
20040111162 Florida State Univ., Tallahassee, FL, USA<br />
Detection of Stress Buildup in Airframes<br />
Aug. 2004; In English<br />
Report No.(s): PB2004-106664; No Copyright; Avail: National <strong>Technical</strong> Information Service (NTIS)<br />
This exploratory study investigates the role of texture development during fatigue cycling on crack initiation in airframes.<br />
The presence of texture in metals is known to relate to fatigue <strong>and</strong> the initiation of cracks. It has not been conclusively<br />
demonstrated, however, that texture will develop in a material simply due to cyclic fatigue. In this study, the development of<br />
9
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