The radar altimeter AN/APN-209 is a short pulse, terrain tracking and
altitude sensing radar system that measures and visually indicates by pointer and digital
display actual clearance in feet between the helicopter and terrain over a range from zero
to 1500 feet. The indicator contains all the electronic components necessary for the
generation, reception, and tracking of the radar pulses. The indicator provides precise
altitude indications with a manually set low-level and high-level warning flag to warn
when a predetermined low or high altitude limit has been reached.
| Control/Indicator |
Function |
| 1. LO SET control knob |
Turns facility on and off, and sets low limits index. |
| 2. LO level warning flag |
Indicates LO when altitude pointer indicates below low limit index. |
| 3. Low limit index. |
Indicates low altitude limit index setting. Actuates LO level warning flag
when limit reached. |
| 4. HI level warning flag |
Indicates HI when altitude pointer indicates above high limit index. |
| 5. High limit index |
Indicates high altitude limit index. Actuates HI level warning flag when
limit reached. |
| 6. Altitude pointer |
Indicates actual altitude in feet from helicopter to terrain (zero to 1500
feet). |
| 7. HI SET control knob |
Sets high altitude limit index and actuates self-test mode. |
