Questions: What materials can the Altimeter RADAR see through.? What is the black cover on this unit made from.?. How would any extra cover affect the units operationg range..?
Answer: The black surface (“radome”) is made from fiber reinforced plastic.
Putting additional materials in front of the radar may cause three different issues:
– Attenuation of the radar signal, so the usable range is severely limited. This can be avoided by chosing the right material. Experience shows good success with Makrolon (polycarbonate), polypropylen and polyphenyl-terephthalamid. Any materials containing carbon or epoxy resin should not be used. The setup should be tested to make sure, the radar still operates well at the desired height above terrain. Worst-case: trees.
– Reflection of a certain fraction of the radar energy. Vibrating objects within the aircraft may reflect at the extra surface and be picked up by the radar. If there is any relative movement between the radar and the extra surface, even the extra surface itself may be detected. The solution is to put the radar as close to the extra surface as possible and to prevent any relative movements. The setup needs to be tested at high altitudes and high roll angles, as under normal circumstances the radar will favor the ground reflections, even if there are some unwanted reflections.
– Change of the antenna pattern. As the radar does not try to measure any angles, this is less critical. However, either the performance at high roll angles may be limited (less likely) or other disturbing echoes like propeller movements may be bent into the radar (more likely). This needs to be to tested.
Under ideal conditions, full range above “normal” terrain is acheived with no issues but a small decrease in detection range above trees/forest is possible.