Thursday, August 27, 2009
Airline travelers are used to being instructed to turn off
computers and cell phones during takeoffs and landings as a precaution against
interfering with the plane’s navigational equipment, but outside sources of
high-energy interference can be even more dangerous. Recent tests by
researchers at the National Institute of Standards and Technology (NIST) will
provide much needed, independent data on how electromagnetic radiation
penetrates aircraft, helping to ensure continued air travel safety.
click to enlarge
Testing equipment being used by NIST scientists in recent research mapping radio frequency penetration of airframes, in this case a Boeing 737-200. The data from the tests provided valuable independent data on how electromagnetic radiation penetrates commercial aircraft, thereby helping improve safety. Credit: NIST |
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The Federal Aviation Administration (FAA) requires aircraft
manufacturers to demonstrate that their aircraft have effective high intensity
radiated field (HIRF) protection. The manufacturers conduct tests on their
aircraft and provide those results to the FAA as part of the certification
process. The tests are designed to show where and to what extent
electromagnetic radiation, across a wide spectrum of frequencies, penetrates a
given craft’s airframe. This information is important in determining if and
where shielding is needed to protect vital electronic instrumentation from
malfunction or damage while flying through ground-based radar beams, for
example.
This effort was undertaken to assist the FAA with HIRF
measurement procedures and data processing methodologies. The FAA has struggled
with data sets provided by HIRF testers because they use a wide range of
measurement/data processing techniques that are not standardized.
For an independent analysis of the situation, a NIST team
recently performed HIRF tests on three representative aircraft to give FAA
officials a frame of reference for the procedures and data reduction techniques
used for typical low-level airframe HIRF attenuation/shielding tests. Having
this information will help the FAA ensure that commercial aircraft are indeed
meeting minimum shielding requirements and, ultimately, make the safety of
tested aircraft more transparent. “This will get everyone on the same page,”
says Chriss Grosvenor, a NIST electronics engineer. “The FAA and aircraft
manufacturers now have a lot of unbiased data they can look at, and our method
is just another method to obtain that information.”
The three aircraft chosen for the representative tests were
a Boeing 737-200 and a Bombardier Global 5000 business jet, both owned by the FAA,
and a Beechcraft Premier IA carbon-fiber composite business jet, owned by the
Hawker-Beechcraft company. By measuring all three aircraft and comparing the
results, NIST was able to provide a guide for the optimization of HIRF testing
standards for the EMC aircraft manufacturing community. The tests were
conducted over a two-year period using a commercial measurement system that
incorporates NIST-developed ultra-wideband antennas, a network analyzer and an
optical fiber link to obtain high-resolution measurements from the megahertz to
gigahertz range. NIST-developed special software extends the number of
frequencies to any desired value using a variable number of bands.
The findings of these tests were published last year and
were presented last week at the IEEE EMC Society Symposium on Electromagnetic
Compatibility in Austin, Texas.
Paper details: C. Grosvenor, D. Camell, G. Koepke, D.
Novotny and R.T. Johnk. Electromagnetic airframe penetration measurements.
Paper presented at the 2009 IEEE International Symposium on Electromagnetic
Compatibility, Austin, Texas, Aug. 17-21, 2009.
Original
article
SOURCE: NIST