High Intensity Radio Transmission Area

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• High Intensity Radio Transmission Area
• Definition Electro-Magnetic Interference (EMI)
  produced by high power antennas such as radio and
  television transmitters and microwave stations.
• ALL Army aircraft are affected.

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Effects of EMI

• Unexplained illumination of segment / warning
  lights

• Unusual instrument readings (Navaid Signals /
  CIS)

• Unexplained flight control movements

• Departure from normal flight

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Electromagnetic Interference (EMI) and
Electromagnetic Variation (EMV) affect certain
aircraft more than others.
In order to minimize the effects of EMI/EMV, the
Department of Defense (DOD) has established a
classified list of HIRTA sites, available at S-2
and Flt Ops, which provides locations and
standoff distances for those sites.
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For high power transmitters not listed in the
HIRTA message standard avoidance and standoff
distances have been established to aid the
aviator in avoiding these sites.
The new standard avoidance distances are listed
in the current HIRTA message (May 01).
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• EMI can affect aircraft with Electronic
  Environmental Effects (E3) hardening installed.
• Standoff distances are given for A/C with and
  without E3 hardening.
• If any E3 measures are removed - the standard
  standoff distance is significantly increased.
• Maintaining standoff does not preclude anomalies
  from occurring.

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Frequently affected systems
Transponder Radar Altimeter Doppler
Gyromagnetic Compass ADF UHF ICS Blade
De-ice CIS
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All incidents that cannot be confirmed as
material or mechanical failure or malfunction
through maintenance troubleshooting procedures
should be reported as Electromagnetic
Interference (EMI)
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Symptoms
Deviations in readings Un-Commanded Control
Movements Disengagement of selected mode
Unexplained Departure From Regular Flight
Unexplained illumination of Caution, Warning,
or Advisory lights with/without degradation
Excessive radio noise
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• Actions on entering HIRTA
• Maintain Aircraft Control Execute the
• Appropriate Emergency Procedure
• Exit area
• Recover system
• Notify S-2

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• AVIATORS RESPONSIBILITIES
• Ensure incidents concerning HIRTA are reported
• Check for HIRTA sites when planning routes in
  unfamiliar areas
• Ensure briefings address information on HIRTA
  sites
• Be familiar with HIRTA Messages

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