Radaraltimetrar

Radaraltimetrar, eller radar altitude meters, are electronic devices that measure the distance between an aircraft (or another platform) and the terrain directly beneath it. They emit microwave radio pulses toward the ground and determine altitude from the time taken for the echoes to return, providing a vertical distance to the surface. Radaraltimetrar are used to support low-altitude flight operations, precision approaches, and landing, often complementing air data and terrain awareness systems.

The measuring principle can be implemented as pulsed radar or as frequency-modulated continuous-wave (FMCW) radar. In pulsed systems, a short radar pulse is sent and the round-trip travel time is converted into altitude, with corrections for atmospheric conditions and ground returns. FMCW systems compare the transmitted and received signals to derive range using beat frequency, enabling continuous measurements and improved clutter rejection.

In aviation, radaraltimeters contribute to automatic flight control during descent and landing, allow obstacle clearance at low altitude, and support autoland and autocoupled approaches. They are commonly integrated with cockpit instruments, flight management systems, and terrain awareness features. Some platforms use multiple channels or frequencies to reduce multipath errors and improve reliability.

Construction and placement typically involve a compact antenna mounted on the fuselage underside. Modern units may include multiple receivers, redundant channels, and filtering to cope with ground clutter, precipitation, and varying terrain. Operators must be aware of limitations, as readings can be affected by rough terrain, water surfaces, ice on the antenna, heavy rain, or steep slopes, and calibration and maintenance are important for accuracy.

Overall, radaraltimetrar provide critical altitude information at low levels, enhancing flight safety and precision in various aviation and aerospace applications.