TM 1-1520-240-102-14-52-14-13. Controls and Function, Radar Altime-ter(AN/APN-209(V)) (AVWS).CONTROLS/INDICATOR FUNCTIONLO SET knobThe LO Set knob appliespower to altimeter system. LOset index on both pilot’s altim-eters can be set independent-ly. Both LO set indexes mustbe masked to turn the set off.HI SET knobSets position of HI set indexwhen turned. Adjusts thewarning message volume lev-el and tests altimeter systemwhen pressed.LO set indexIndicates altitude trip point forLO caution light.HI set indexIndicates altitude trip point forHI caution light.Indicator pointerIndicates absolute altitudefrom 0 to 1,500 feet.Digital indicatorProvides direct reading fourdigit indication of absolute alti-tude from 0 to 1,500 feet.LO caution lightComes on when helicopterdescends below altitude onLO set index.HI caution lightLight comes on when helicop-ter rises above altitude on HIset Index.OFF flagFlag is displayed when poweris removed from set, when in-dications are unreliable, orwhen altitude exceedsapproximately 1,500 feet.RAD ALT dimmingcontrolsOn right side of both instru-ment panels. Controls light in-tensity of digital display and HIand LO caution light.2-14-14. Normal Operation - Radar Altimeter(AN/APN-209(V)) (AVWS).a.Starting.NOTEConnect monitor headset to the aircraft ICS.(1)Rotate the LO SET knob on the altimeteruntil the LO index is at 100 feet. Rotate the HI set knobuntil HI index is at 800 feet. Allow 1 minute for warmup.(2)Check for the following indications:(a)The pointers indicate between –5 and 5feet.(b)The digital displays indicate between0and 3 feet.(c)LO caution light is on.(d)Low altitude warning (”ALTITUDE LOW,TOO LOW”) is heard in the headset.(e)HI caution light is off.(f)Off flag not in view.b.Testing.(1)Press and hold the PUSH-TO-TEST knob toactuate the PUSH-TO-TEST condition. Verify the follow-ing:(a)OFF flags not in view.(b)Pointers indicate between 900 feet and1,100feet.(c)Digital displays read between 900 feetand 1,100 feet.(d)LO caution light is off(e)HI caution light is on.(f)The high altitude warning “ALTITUDEHIGH, CHECK ALTITUDE”, is audible (Full volume) at 10seconds intervals throughout the test. Verify that thevoice warning audio is discernable by all active crewmembers.(2)Release the PUSH-TO-TEST knob. Checkthat all indications return to those specified in step a. (2).(a)Momentarily press the PUSH-TO-TESTknob once and verify the message is at 1/2 volume.(b)Momentarily press the PUSH-TO-TESTa second time and verify the warning message is OFF.(c)Pointers indicate between 900 feet and1,100feet.NOTEThe LO caution light may appear to go out.However, the light will be visible with nightvision goggles. In bright daylight, it may benecessary to shade the indicator to verify op-eration of the dimming control.(3)Rotate the RAD ALT dimming control fromBRT to DIM. Check that the digital display dims and goesout. Check that the LO caution light dims but does not goout completely.c.Inflight operation.
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