AN/ARN 126 VHF NAV

Glideslope antenna

Mounted below the RADAR antenna in the radome A semi-circular stub antenna that receives signals from ILS G/S stations and sends these signals to the #1 and #2 ARN-126 receivers

G/S stations

Provides G/S vertical deviation and signal validity during an ILS approach

LOC stations

Provides LOC lateral deviation, signal validity and station identification during an ILS approach

Purpose

Provides reception of VHF Omnirange (VOR), localizer (LOC), marker beacon, and glideslope (G/S) (instrument landing systems) The number 1 system is used primarily by the pilot, the number 2 system is used primarily by the copilot system. Either system can be selected through navigation instrument switching (NIS)

MB stations

Provides the pilots with audio and visual indication when flying over the Marker Beacon

Tuning operation

The VOR 1 and 2 are tuned to a valid frequency via the CDNU NAV page When VOR/ILS is selected via the NAV select switch, the VOR deviation to/from indication and system validity are provided to the ADI/HSI

Receiver purpose

The receiver contains three separate receivers • VOR and LOC receiver • Glideslope receiver • Marker beacon receiver They are all automatically tuned when a frequency is selected. Both receivers are identical but the marker beacon is only active in the number 1 receiver.

Receiver location

The receivers for the ARN-126 are both located in the LH underdeck rack

Marker beacon purpose

Illuminates marker beacon lights and initiates a tone when passing through the outer, intermediate and inner ground stations Receives the RF from the marker beacon antenna Only the number one receiver provides marker beacon information

VOR operation

Receives the VHF frequency from the VOR/LOC antenna Provides audio to the ICS if selected Provides VOR bearing to • Pilot and Co-pilot NAV select switches • Pilot and Co-pilot BDHI pointer select switches • TSO Right hand BDHI pointer select switches • NIS (Navigation instrument switching system)

Localizer operation

Receives the VHF frequency from the VOR/LOC antenna Vertical deviation is displayed on the ADI and HSI Provides audio to the ICS if selected.

Power source

Each VHF NAV system requires 28 VDC and 26 VAC 400 HZ for operation 28 volts ESS DC power Copilot upper CB panel #1 VOR/ILS #2 VOR/ILS 26 volts AC Supplied the compass transformers #1 VOR/ILS #2 VOR/ILS

Marker beacon antenna

Flush mounted in the bottom of the left wheel well fairing, forward section Functions only with the #1 receiver

Directional Antennas

VHF NAV antennas protrude horizontally from either side of the vertical stabilizer Receives RF signals from the tuned ground station

Glideslope purpose

Vertical deviation is displayed on the ADI and HSI The glideslope interface interacts with the GPWS. Audio and visual warning can be supplied when deviation from glideslope is detected when at and below 200ft AGL