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Page Title:
Maximum Available Energy Inside Passenger Cabin |
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  Re-Distributed by http://www.tpub.com
Advisory Material Joint (20.1317 Final Draft 8,
Maximum Available Energy Inside Passenger
March 1998) were compared with the JSC-derived
TWA-800 environment. The results are shown in
Cabin
Figure 2. The draft AC/AMJ 20.1317 contains the
Using the maximum field strengths from signal
following definitions:
sources identified by the JSC as dominant emitters,
·
the maximum energy available inside the aircraft
"The Normal HIRF environment is an
passenger cabin for each source was estimated, and
estimate of the electromagnetic field
is summarized in Table 1. These dominant emitters
strength level in the airspace on and
were all pulsed sources, allowing the threat to be
about airports/heliports in which routine
quantified in terms of energy, instead of power.
departure and arrival operations take
place. This estimate considers the
Table 1: TWA-800 Environment Dominant
operational characteristics of the high
Emitters
peak power microwave transmitters,
which typically do not operate
Frequency 1.294
2.875
3.1
3.1 8.5 9.1
continuously at the maximum output
(GHz)
3.5
3.5
9.6
levels."
Description
Riverhead, Brook-
Shipboard Moores-
Airborne Calver-
·
NY Search haven, NY
Search
town,NJ
Search ton,NY
"The Fixed Wing Severe HIRF
RADAR Weather
RADAR Search
RADAR Tracking
environment is a worst case estimate of
RADAR
RADAR
RADAR
the electromagnetic field strength levels
EIRP (dBm)
128.0
134.8
136.0
139.8
117.4
128.0
Gain (dBi)
35
46
38
42
34
44
in the airspace in which fixed wing flight
Distance
13.1
15.7
156.3
112.0
2.93
17.0
operations are permitted."
(nmi)
Pulse Width
2.0
1.0,4.0
6.0,51.0
6.0,51.0 2.5
2.0
(µsec)
From Figure 2, it can be concluded that the
PRF
341
1300,320
1840,152 1840,
400
300
JSC-derived TWA-800 environment was far less
(Pulses/sec)
152
severe than that encountered in routine departure
Duty Cycle
0.00068
0.0013
0.011
0.011
0.001
0.0006
and arrival operations.
Polarization
HorV
V
V
V
Power Density
29.304
34.531
15.77
22.465
31.712
26.989
(dBm/m2)
(JSC data2.PGW)
Field Intensity
17.921
32.713
3.773
8.155
23.646
13.727
10000
(V/m)
Fixed Wing SEVERE PEAK Environment
Energy
1.704
11.355
1.933
9.031
3.708
1.00
NORMAL PEAK Environment
Density
(µJ/m2)
1000
NORMAL AVERAGE Environment
Energy
0.015
0.097
0.017 0.077 0.032 0.009
(mJ) *
100
* Assuming window surface area = 98 x 0.0875m2 = 8.575 m2
The total available energy inside the aircraft
10
cabin from RF pulses emitted by the maximum
TWA 800 Dominant Emitters
dominant emitter (f= 2.875 GHz) was found to be
less than 0.1 mJ. Even if this total energy could
1
0.01
0.1
1
10
100
1000
10000
have been focused into a single discharge event, it
Frequency, MHz
was still below the generally accepted estimate of
the minimum energy level (0.2 mJ) required to
Figure 2. JSC TWA-800 Environment vs.
achieve fuel vapor ignition [4]. Further details of
Proposed AC/AMJ 20.1317 HIRF Environments
the analysis may be found in [5].
Numerical Estimation of Coupling to FQIS
TWA-800 Electromagnetic Environment
Wiring
versus Standard HIRF Environments
To provide an estimate of how much energy
The "Normal" and "Fixed Wing Severe"
could actually be coupled to the FQIS wiring within
electromagnetic environments, defined in the soon-
the passenger cabin from external sources (ie. B(f)),
to-be released FAA Advisory Circular / JAA
3
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