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B
Whenever checking the TAS bearing accuracy, the test antenna must be within
line-of-sight of the directional antenna under test. The accuracy to the top direc-
tional antenna should be checked while the test antenna is 50 to 75 feet distant,
and the landing gear logic is "DOWN". When measuring the accuracy of the bot-
tom antenna, the test antenna should not be within line-of sight of the Top Direc-
tional Antenna. Either use the fuselage to block the Top Directional Antenna and
position the test antenna 8 to 12 feet (if possible) from the bottom antenna or
shield the top antenna with echosorb or equivalent.
Bearing accuracy checks on the Bottom Directional Antenna can only be per-
formed accurately in the air with a target aircraft. If you choose to perform bear-
ing accuracy checks or boresight on the Bottom Directional Antenna while on
the ground, the Ramp Test Antenna and the KA 815 Antenna must have unob-
struted line-of sight to each other
The landing gear logic must simulate "RETRACTED" (UP) whenever checking
the bearing accuracy to the bottom antenna. TAs will appear as "No Bearing"
targets when the gear position logic is "EXTENDED" (DOWN) because the bot-
tom antenna is in omni directional mode.
To insure proper antenna selection, the relative altitude difference between
the simulated intruder and own aircraft altitude should be + 6,000 feet, i.e.
intruder at 56,000 ft. when checking the top antenna. The test antenna
should be elevated slightly above the height of the Top Directional Antenna.
When checking the bottom antenna bearing accuracy, the relative altitude
difference between the simulated intruder and own aircraft altitude should
be -6,000 feet, i.e. intruder at 44,000 ft.. The test antenna should be below
the mounting plane of the Bottom Directional Antenna.
When using the TT391 for bearing checks, the antenna not being tested should
be shielded from the Flightline Tester. This is needed since the intruder altitude
cannot be programmed on the TT391.
Position the aircraft outside away from hangers and other aircraft.
Rev 3, August/2002
NOTE
NOTE
NOTE
10609I03.CDL
KMH 880/KTA 870
Page 4-36
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