Supplemental Analysis Regarding External Threats Below 30 MHz

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was also defined at wires exiting the FQIS

connector shielded box ("Area3"). Temperature

increases of about 5 º F were measured from within

the shielded box.

(a)

Testing at this level did not yield any evidence

of electrical discharge, except when intermittent

faults were introduced.

Fault Testing

In practice, it is feasible that conductive debris

may sometimes find its way into aircraft fuel tanks.

Because of this, it was decided that the laboratory

testing should also include an intermittent short

(b)

condition at the location of maximum voltage

enhancement.

A piece of brass wool was bonded to the

supporting structure and made to intermittently

contact a FQIS probe terminal (by applying forced

Figure 7. (a) AMT MO-32 Night Vision System.

air through a rotating plastic fan assembly). Two

(b) Inframetrics Model 600 Thermal Imaging

terminals on the compensator probe (TP-6) were

System.

determined to provide maximum voltage

enhancements. They were the HI Z terminal (with

LO Z-to-Chassis excitation), and the LO Z COMP

terminal (with LO Z Compto-Chassis excitation).

An intermittent short from one of these locations to

chassis could be expected to develop a break-spark

condition with the lowest applied RF power. A

photograph of the arrangement is shown in Figure

9a. Figure 9b shows a still-image of a videotaped

discharge event as viewed by the night vision

system.

Figure 10 shows each frequency and power

level at which a discharge event was detected for

both excitation modes, along with the worst-case

Figure 8. Inframetrics Thermal Imager Display

estimated coupled power from PEDs located within

the passenger cabin. The testing revealed that a

strategically placed, intermittent short circuit could

To simulate the condition of highest power

cause FQIS discharge events with as little as 1.5 W

PEDs with no path loss, a minimum of 10 W of RF

of applied RF power in the PED frequency range

power (from 1 MHz to 1 GHz) was applied to the

for Citizen's Band radio (27 MHz). However (also

three dominant excitation modes (LO Z-to Chassis,

as shown in Figure 10), 1.5 W was at least 10 times

LO Z Comp-to-Chassis, HI Z-to Chassis). Figure 8

greater than the maximum possible PED threat,

shows the thermal image display, when 24 to 65 W

when adjusted for path loss.

was applied across LO Z Comp-to-Chassis.

Temperature measurement windows were defined

at the peak current enhancement location (TP-2,

Supplemental Analysis Regarding

defined as "Area1"), and at the peak voltage

External Threats Below 30 MHz

enhancement location (TP-6, defined as "Area2").

From the fault testing, it was found that only

It can be seen that heating at these locations was

0.17 W of power was required for generating

negligible. A temperature measurement window