What are the radar altimeter limits?

What are the radar altimeter limits?

• A. Above 5,200 AGL, 45 deg of pitch or bank
• B. Below 1,000 ft AGL only
• C. In excess of 60 degrees bank only
• D. At sea level, any attitude

Answer: (A)

Radar altimeters have a limited operating envelope: they measure height above the ground but only reliably within a certain altitude and within safe attitude limits. The instrument is generally reliable up to about 5,200 feet above ground level, and it requires the aircraft to stay within roughly 45 degrees of pitch or bank. If you go higher than about 5,200 feet AGL or tilt more than 45 degrees in either axis, the radar path to the ground changes geometry and the reading can become inaccurate or unavailable. That combination of altitude and attitude limits is what the option conveys. The other choices miss this dual constraint or misstate the conditions under which the radar altimeter can be trusted.

Radar altimeters have a limited operating envelope: they measure height above the ground but only reliably within a certain altitude and within safe attitude limits. The instrument is generally reliable up to about 5,200 feet above ground level, and it requires the aircraft to stay within roughly 45 degrees of pitch or bank. If you go higher than about 5,200 feet AGL or tilt more than 45 degrees in either axis, the radar path to the ground changes geometry and the reading can become inaccurate or unavailable. That combination of altitude and attitude limits is what the option conveys. The other choices miss this dual constraint or misstate the conditions under which the radar altimeter can be trusted.