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APPENDIX TO INSTALLATION INSTRUCTIONS
POST INSTALLATION EMI TEST
PURPOSE
The purpose of this test is to identify any interference that the
TFM-556 may cause with existing
aircraft systems. As the TFM-556 installation may include the ATC-550 antenna tuner controller, this
test, as required, will also identify any interference caused by the ATC-550.
TEST CONDITIONS
The TFM-556 transceiver and any accessories (e.g., RC-550, ATC-550) should be installed and
function tested. The antenna VSWR should be checked. A forward/reverse power check with a in-line
wattmeter should show no more than 10% reflected power. For the following tests, insure that the
power switch is in the high position.
METHODOLOGY
Most of the EMI tests can be accomplished on the ground. In some cases flight testing is required or
is easier. If the aircraft is approved for IFR operations, then it is mandatory that interference between
the TFM-556 Airborne FM and the approach aids be checked in flight.
The GPS should be operational and navigating with at least the minimum compliment of satellites. The
VHF comm should be set to the frequencies indicated with the squelch open. VOR/DME receivers
should be set to the frequencies indicated and selected for display. If possible, set up a DME ramp test
set on the frequencies indicated and adjust the output until the flags are out of view. The transponder
and encoder should be monitored with ramp test equipment. Set the output of the transponder test
set to 3db above the output necessary to achieve 90% reply. If possible set the ADF to a nearby
navigation station.
Modulate the TFM-556 transmitter on the indicated frequencies for at least 20 seconds.
Observe the GPS for any degradation in satellite status or availability or flags. Listen for any noise or
detected audio signals on the VHF comm(s). Listen for any noise or detected audio signals on the
VOR/LOC receiver audio; look for any moment of flags or needles on the VOR/LOC/GS navigation
display(s). Observe the transponder for any loss of reply or spurious reply.
List the power plant, fuel and other electric instruments in the chart provided and note any anomalies
that occur while transmitting. Assess the results.
If the aircraft is equipped with an autopilot or a stability augmentation system, then test fly the aircraft
and verify that operation of the TFM-556 transceiver does not have adverse effects on these systems.
After checking for gross effects at a safe altitude, fly an approach with each of the different navigation
systems coupled to the autopilot (ILS, GPS ETC.) and look for any anomalies.
When the installation includes the ATC-550 antenna tuner controller, this test, where indicated by an
asterisk (*), will also identify any interference caused by the ATC-550. In these cases the ATC-550
must be turned on and off by means of its breaker as often as required while monitoring the victim
equipment.
