NASA Scientific and Technical Aerospace Reports

mistuning identification technique was developed, and alternative designs featuring intentional mistuning were examined in
a series of simulations and experiments.
DTIC
Aircraft Maintenance; Jet Engines; Models; Tuning
20040112012 NASA Langley Research Center, Hampton, VA, USA
Graphical Analysis of B-737 Airplane Pathloss Data for GPS and Evaluation of Coupling Mitigation Techniques
Jafri, Madiha J.; Ely, Jay J.; Vahala, Linda; [2004]; 6 pp.; In English; IEEE International Symposium in Electromagnetic
Compatability, 9-13 Aug. 2004, Santa Clara, CA, USA; Original contains color illustrations
Contract(s)/Grant(s): 728-30-10; No Copyright; Avail: CASI; A02, Hardcopy
The use of Portable Electronic Devices (PEDs) onboard commercial airliners is considered to be desirable for many
passengers, However, the possibility of Electromagnetic Interference (EMI) caused by these devices may affect flight safety.
PEDs may act as transmitters, both intentional and unintentional, and their signals may be detected by the various navigation
and communication radios onboard the aircraft. Interference Pathloss (IPL) is defined as the measurement of the radiated field
coupling between passenger cabin locations and aircraft communication and navigation receivers, via their antennas. This
paper first focuses on IPL measurements for GPS, taken on an out-of-service United Airlines B-737-200. IPL pattern symmetry
is verified by analyzing data obtained on the windows of the Port as well as the Starboard side of the aircraft. Further graphical
analysis is performed with the door and exit seams sealed with conductive tape in order to better understand the effects of
shielding on IPL patterns. Shielding effects are analyzed from window data for VHF and LOC systems. In addition the
shielding benefit of applying electrically conductive film to aircraft windows is evaluated for GPS and TCAS systems.
Author
Boeing 737 Aircraft; Global Positioning System; Flight Paths; Electromagnetic Interference; Data Systems; Computer
Graphics; Coupling
20040112044 NASA Glenn Research Center, Cleveland, OH, USA
Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design
Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.; [2004]; 10 pp.;
In English; 45th AIAA/ASME/ASCE/AHS/ASC SDM Conference, 19-22 Apr. 2004, Palm Springs, CA, USA
Contract(s)/Grant(s): WBS 22-708-24-01
Report No.(s): AIAA Paper 2004-1836; No Copyright; Avail: CASI; A02, Hardcopy
The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and
propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the
use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core
material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The
resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of
17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A
vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for
different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.
Author
Fan Blades; High Strength; Propeller Blades; Sandwich Structures; Stiffness; Composite Materials; Aircraft Construction
Materials; Foams
20040120875 NASA Langley Research Center, Hampton, VA, USA
Detection of Fatigue Cracks at Rivets with Self-Nulling Probe
Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Namkung, Min; [1994]; 3 pp.; In English; No Copyright; Avail: CASI; A01,
Hardcopy
A new eddy current probe developed at NASA Langley Research Center has been used to detect small cracks at rivets
in aircraft lap splices [1]. The device has earlier been used to detect isolated fatigue cracks with a minimum detectable flaw
size of roughly 1/2 to 1/3 the diameter of the probe [2]. The present work shows that the detectable flaw size for cracks
originating at rivets can be greatly improved upon from that of isolated flaws. The use of a rotating probe method combined
with spatial filtering has been used to detect 0.18 cm EDM notches, as measured from the rivet shank, with a 1.27 cm diameter
probe and to detect flaws buried under the rivet head, down to a length of 0.076 cm, using a 0.32 cm diameter probe. The
Self-Nulling Electromagnetic Flaw Detector induces a high density eddy current ring in the sample under test. A ferromagnetic
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