Garmin GRA 5500 Installation Manual

Contents

Garmin GRA 5500 Installation Manual Manual pdf 19 page image

GRA 5500 Installation Manual 190-01277-00Page 2-4 Rev. A2.3.3 Antenna Location Planning GuidanceNOTEThe ability of any radar altimeter system to accurately and reliably detect and processradar altitude signals is highly dependent upon correct transmitter (TX) antenna andreceiver (RX) antenna placement on the airframe. Stated performance specifications forthe GRA 5500 can only be achieved when the system is installed in accordance with all theguidelines stipulated in this section and with all other instructions given in thisInstallation Manual.Careful planning for optimal antenna placement is extremely critical in any radar altimeter installationand requires a high level of attention to detail in order to achieve optimal system performance of theGRA 5500. The following guidelines must be followed in order to achieve acceptable performance of thesystem during all stages of normal operation. Failure to follow any of these guidelines will result indegradation of system performance.If there is any question as to whether a planned installation will meet all the guidelines given below or mayrequire special consideration, contact Garmin for further support.1. Location on Aircraft: Antennas must be mounted on a surface of the bottom of the aircraft near thecenter point of pitch and roll rotation (this reduces the effect of momentary pitch and roll altitudeoffsets/inaccuracies during approach and landing or while maneuvering the aircraft).2. Angle of Antennas to Ground: Antennas must be mounted such that the surface of each antenna iswithin +/- 6° of horizontal during level flight. If adapter plates are manufactured to ensure thisangle is met, the adapters must not recess the antenna surfaces within the skin of the aircraft. Theadapters must only extrude the antenna surfaces outside the skin of the aircraft.3. Mounting Surface: The antennas are normally mounted on a continuous metallic surface. Non-metallic surfaces or ones with discontinuities require special consideration. Contact Garmin formore information or clarification if needed.4. Minimum Height: Due to antenna spacing limits (described in following guideline 8.), theminimum antenna height possible above ground while parked, taxiing, or at aircraft touchdown is20 inches for any aircraft.5. Antenna Clearance Cones: The locations chosen for both antennas must be free of aircraftprojections (landing gear, flaps, drainage vents, etc…) within a 120° cone from each antennadownward to prevent locking onto false altitude returns. Consider all possible modes of aircraftoperation when establishing compliance with this guideline (e.g. – landing gear distances while intransition, flap distances while fully extended, etc.).6. Distance to Other Antennas: The radar altimeter antennas should be located no closer than 3 feetto any other aircraft antenna.7. Relative Location (Single System): The two radar altimeter antennas must be mounted either in astraight, nose-to-tail longitudinal line with both antenna arrows pointing forward, or in a straight,side-to-side, lateral line with both arrows pointing to one side of the aircraft or the other (they mayalternatively point toward each other or away from each other). The longitudinal installation ispreferred over the lateral installation to provide more roll than pitch angle coverage. Additionally,the angle between the antenna surface planes must not exceed 6° and the antennas must not betipped toward each other at any angle. In a single system, either antenna may be selected as thetransmitter (TX) or receiver (RX) antenna.DRAFT