Internal Analysis (Experimental)

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numerical modeling was used. The B-747-100

Beginning again with Equation 1, it was

fuselage was assumed to be a large rectangular

necessary to quantify the PED threat in terms of

cavity with rectangular windows on each side. The

power (A(f)), establish a "path factor" (B(f)) for the

cavity was assumed to be homogeneous and

lowest coupling loss between a passenger cabin

lossless, with no seats or other structures present. A

PED and the FQIS CWT connector, and determine

new, NASA-LaRC developed numerical simulation

the minimum RF stimulus required to cause an

technique, using a rectangular cavity Green's

ionization discharge or significant heating event

function and the integral equation method,

within the CWT (C(f)). It is important to note that

an "event" was taken to be the detection of any

estimated electromagnetic threats to the CWT due

to external electromagnetic sources. The

discharge event. In practice however, higher power

Modal/MoM (method of moments) code was

would likely be required for igniting fuel vapors.

validated through agreement with other analytical

NASA TM-2000-210077 [7] was completed in

techniques and measurements. The Modal/MoM

support of the investigation, and endeavors to

approach resulted in a lower number of unknowns

supplement the traditional understanding of

compared to other numerical methods, such as the

electrical breakdown, heating and combustion with

finite element method (FEM) and finite difference

currently available information regarding aircraft

time domain (FDTD) methods. Therefore, this new

fuel-vapor ignition by RF sources.

approach is able to solve the large-size problems up

to frequencies of 1-2 GHz. When applied to the

PED Emissions (A(f))

available energy from the 1.294 GHz emitter

In 1996, intentionally transmitting PEDs such

source, the Modal/MoM approach estimated that

as cellular phones, garage door openers, remote

CWT FQIS coupled energy levels were several

control toys, FM wireless microphones, handheld

orders of magnitude less than the maximum

radios (citizen's band, police, fire, business,

available energy. Details regarding the new

maritime, etc.), cordless phones and keyless entry

analysis tools and their application to this problem

transmitters could easily be found among the

may be found in [5] and [6].

traveling public. The FAA recommends prohibiting

operation of intentionally transmitting PEDs during

Internal Analysis (Experimental)

flight [8], however, adherence to the rules cannot be

guaranteed.

The threat from PEDs carried aboard the

aircraft did not lend itself to the same computational

For this effort, threat information was gathered

analysis as for external threats. First, virtually all

from three sources: typical device manufacturer's

PED sources transmit in a continuous or

specifications, ANSI C63.18-1997 (for typical

continuously modulated fashion. Thus, the threat

transmitters for radiated electromagnetic immunity

could not be evaluated in terms of energy. Most

testing of medical devices), and the Federal

widely known data regarding fuel-vapor ignition

Communication Commissions (FCC) regulations.

hazards are given in terms of energy, not RF power.

It was found that intentional radiators occupy

Second, there is the potential for near-field direct

numerous frequency bands from 27 MHz to 6 GHz,

illumination of FQIS wiring with sources internal to

and that virtually all "portable" devices radiate less

the aircraft. For the external source problem,

than 10 W. It was also found that the power

indirect illumination was the only option (via

radiated from typical PEDs drops significantly for

window. Direct illumination quickly becomes

frequencies higher than 1 GHz. Details of the

dominant for close proximity coupling, especially

analysis are given in [5] and [9].

in an electromagnetically lossy environment like an

aircraft passenger cabin. Direct coupling is highly

dependent upon very specific boundary conditions

Aircraft Measurements (B(f))

and will vary greatly with frequency, which makes

it exceedingly difficult to computationally model in

At the time of this investigation, several

an aircraft system.

Classic B-747-100 aircraft, about the same age as

TWA-800, were being retired from service. Such