Telephonics Corporation
R ADAR SYSTEMS D IVISION
TM113806 (3/10) 2-29
2.5.1.2.3 Orientation
The mounting position of the antenna drive unit must satisfy the following conditions:
1
Centerline of antenna must be aligned with aircraft horizontal centerline.
2
Azimuth scan axis of antenna must parallel spin axis of the stabilizing vertical gyro.
3
Tilt axis of antenna must parallel pitch axis of aircraft. This should result in the azimuth spin axis
of the antenna lying mutually perpendicular to the roll and pitch axes of the aircraft.
4
To ensure that targets are displayed in their proper relative positions with respect to the aircraft, the
radar beam must radiate forward, perpendicular to the pitch axis of the aircraft, and in the plane of
flight path when the antenna is positioned at zero degrees in both azimuth and tilt. The antenna
stabilization system will function properly only when the azimuth spin axis of the antenna parallels
the spin axis of the stabilizing vertical gyro. Should an ambiguity exist between the two spin axes,
an inherent error is developed in the system. The error is evidenced by uneven azimuth
illumination of terrain as the antenna scans. This condition is undesirable and may cause some
confusion when interpreting the radar display. Therefore, it is important that the antenna and gyro
spin axes be in coincidence (both pitch and roll planes) when the antenna is being mounted. THE
SAME REFERENCE CRITERION FOR MOUNTING THE GYRO SHOULD BE EMPLOYED
FOR LEVELING AND MOUNTING THE ANTENNA.
2.5.1.2.4 Radome
The radome used with the radar system should meet or exceed the following characteristics.
1
Transmissivity
The average one-way transmission should not be less than 90% for any continuous scan of the
antenna relative to the radome.
The minimum transmissibility at any point should not be less than 85% throughout the window
area of the basic radome, including any installed rain erosion protection, but not including the
lightning protection devices. Trim finishes should not degrade the transmission efficiency by more
than 3%. The window area is that portion of the radome which is illuminated by the antenna as the
antenna is tilted and rotated over its entire elevation and azimuth scan limits.
2
Incident Reflection
Power reflected back into the radar system by the radome should be less than 0.5% of the
impinging energy throughout those portions of the window area at all positions of the system
antenna within its mechanical limits.
3
Side Lobe Levels
The side lobe levels should exhibit the following characteristics when measured with an
appropriate system antenna and the fully finished radome, including the installation of lightning
protection, all trim finish materials, and the associated nacelle structure.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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