Figure 3. a) Retired B-747-100 aircraft in Roswell, New Mexico

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an aircraft was located in Roswell, New Mexico,

frequencies below 2 GHz. Details can be found in

and was employed for the following four

[5] and [9].

objectives:

Even if filled with fuel, the aluminum aircraft

fuel tank was expected to exhibit a high degree of

Measure input impedance characteristics

electromagnetic reverberation. This was a concern

of the FQIS at the CWT connector, for

for comparing aircraft vs. laboratory FQIS

comparison to laboratory installation.

installations. The laboratory chamber was made of

Measure peak radiated/conducted

steel, not aluminum. While its overall volume was

coupling from passenger cabin to CWT

similar to the CWT, the overall dimensions were

FQIS wiring (B(f)).

different, and the interior was not divided into sub-

Measure reverberation characteristics of

cavities (fuel bays). An actual CWT also has

empty CWT for comparison with the

penetrations for fuel and vent lines that are not

laboratory reverberation chamber.

necessarily secure from electromagnetic leakage.

Recovery of actual FQIS components for

Because of these concerns, detailed measurements

installation into NASA Langley's HIRF

of fuel bay cavity coupling factor, and fuel bay-to-

laboratory.

fuel bay coupling factors were measured on the

aircraft. This data was subsequently used to scale

NASA LaRC researchers developed a custom

laboratory radiated field measurements to that

instrumentation package to comprehensively

which would be observed in the actual aircraft.

measure CWT FQIS RF input impedance. The

Details regarding these measurements may be found

FQIS connection consisted of 4 copper paths.

in [5] and [9].

Impedance data for differential combinations of

these terminals, plus each to chassis were measured.

Based upon the PED emission data and the limited

high frequency transmission line performance of

FQIS type wiring, a frequency range of 300 kHz to

1 GHz was selected. The instrumentation included

a vector network analyzer, specialized calibration

adapters and software for rapid, automated

measurements of each terminal combination.

Details regarding the instrumentation, as well as

(a)

standard DC resistance and capacitance

measurements can be found in [5] and [10].

A particularly unique set of measurements was

obtained for the maximum possible path factor

(B(f)) between the passenger cabin and FQIS CWT

connection, from 25 MHz to 1 GHz. For this, a

laboratory RF signal generator was swept

continuously while transmitting through a

(b)

broadband antenna positioned at numerous

locations throughout the passenger cabin, directly

and indirectly illuminating FQIS wiring under the

(c)

floor and along the walls. A RF spectrum analyzer

was used to measure maximum voltages induced

upon the FQIS CWT conductors. In addition,

Figure 3. a) Retired B-747-100 aircraft in

radiated field measurements resulting from the

Roswell, New Mexico. b) Fuel quantity probe

passenger cabin source were also taken inside the

within CWT of retired aircraft. c) Path Factor

fuel tank, using an antenna. These measurements

measurements in B-747 passenger cabin.

were useful in establishing FQIS wiring as the

dominant coupling path into the CWT for