SC-226 MEETING MINUTES Working Group JANUARY 14 ... - RTCA

RTCA Paper No. 021-13/SC226-010
February 6, 2013
For Radiated Susceptibility: The level shall be 2 V/m at the frequency range
specified within the applicable category in DO-160x.
Note: DO-307 covers Radiated RF Interference considerations for
Transmitting Portable Electronic Devices (PEDs). RF Interference from PEDs
devices can interfere with functions of the audio system. Audio System
components are only exposed to PEDs RF Interference when the Audio System
component is located in an area of the aircraft near the PEDs devices and when
there is no metal shielding between the audio system component and the PEDs
devices. As a result, it is reasonable for only the exposed audio equipment to be
tested according to the requirements of DO-307. Additionally, when equipment
is mounted so that a portion of the equipment is shielded, it is reasonable for
only the exposed side(s) of the audio equipment to be exposed during the PEDs
RF Interference testing. An analysis should be used to describe the rationale
for the manner in which the equipment under test is exposed.
Discussion of problems experienced by members of the committee with regard to current test
requirements calling for the conducted RF frequency sweep to start at 10KHz.
Experience of the participants has found that even when the 10KHz RF signal is applied with no
modulation, it can often be heard over the audio system. 10KHz is very close to the audio frequency
band of interest for the audio system. The audio system is typically composed of a large number audio
inputs and outputs, all of which must be filtered to remove RF. However, with the RF starting
frequency so close to the audio frequency band, the filters must be more effective, more complex,
require more components, and occupy more space within the equipment enclosure in order to be
effective enough to remove 10 KHz RF noise. As a practical matter, such a design will be
mathematically less reliable, and the committee questions why the RF frequency should start at such a
low frequency when there are no sources of this type on board the aircraft. The consensus was that
the starting frequency should start at a frequency just beyond the maximum audio frequency band
discernible by human hearing (e.g. >20 KHz). 24 KHz was chosen as the new starting frequency. The
language in the standard was edited as follows for conducted RF susceptibility testing.
For Conducted Susceptibility: The level shall be 3 mA (2 V/m) from 500 kHz to
400 MHz, and from 500 kHz to 24 kHz shall fall at the rate of 6 dB per octave (20 dB per
decade).
Don Nault, Boeing took the action to check with his compliance personnel at Boeing to determine if the note is
acceptable.
Discussion on fire protection. TSO-C57a and TSO-C58a used to include a requirement similar to as follows from
DO-214 but no longer do and this sometimes causes problems for Boeing when equipment is not tested to Part 25
Appendix F.
2.1.4 Fire Protection
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