(2)  
Ensure that following circuit breaker at P18 panel are closed:
DME-1 AC
DME-2 AC

B.  Test DME System Operation (No. 1 or No. 2 system)
(1)  
Adjust frequency tuning controls for 108.00 MHz.

(2)  
On appropriate VHF/NAV control panel, actuate DME self-test. Verify that within a few seconds, DME DISTANCE indicators display 000.0 miles.

3.  System Test - Using Collins 475D-1
A.  Equipment and Materials
(1) DME Ramp Test Set - Collins 475D-1 (modified for AUTO 5-180/270 feature).
B.  Prepare for Test
(1)  
Provide electrical power.

(2)  
Ensure that following circuit breakers on panel P18 are closed:
DME-1 AC
DME-2 AC
INTERPHONE

(3)  
Place DME test set approximately 40 feet from DME antenna. Ensure there are no obstructions between test set and DME antennas. (Run test on line-of-sight basis).

(4)  
Calibrate ramp test set as indicated in test set instructions book.

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C.  Test DME System
NOTE:  Prior to beginning test, ensure the other DME system VHF NAV control panel is tuned to a frequency other than test frequency.
(1)  
On test set, position controls as follows:

TR ATTEN DB - 15
Function Selector - AUTO 5-180/270
RANGE 180/270 - 270

(2)  
Position switches on VHF NAV control panel as follows:

(a)  On GJ ALL EXCEPT B-2504 and B-2505, 1) Function Selector - O'RIDE 2) Left frequency display - 108.00 MHz 3) Right frequency display -108.05 MHz 4) Position TFR switch -108.00: Verify DME indicators display 5 ±0.1 miles; after
approximately 18 seconds, display 270 ±5 miles and track inbound to 263 ±5 miles, then track outbound to 277 ±5 miles; and after approximately 18 seconds, display 5 ±0.1 miles.
NOTE:  The above test cycle will repeat as long as function selector switch is in O'RIDE position.
(b)  On GJ B-2504 and B-2505, 1) Function Selector - O'RIDE 2) Frequency display -108.00 MHz: Verify DME indicators display 5 ±0.1 miles;
after approximately 18 seconds, display 270 ±5 miles and track inbound to 263 ±5 miles, then track outbound to 277 ±5 miles; and after approximately 18 seconds, display 5 ±0.1 miles.
NOTE:  The above test cycle will repeat as long as function selector switch is in O'RIDE position.
(3)  
When DME is locked on, verify DME audio output is available at audio selector panel.

(4)  
While DME indicators are displaying 5-miles, position DME function selector on VHF NAV control panel to NORM or ON. Verify DME indicators display . 0.1 miles for approximately 18 seconds; then display dashes for approximately 18 seconds more; than again display 5 .0.1 miles.

(5)  
On test set, position RANGE switch to 180 and function selector to 180/270. Verify DME indicators display 180+9 miles, track inbound to 173+2 miles and outbound to 187+2 miles.

(6)  
Restore airplane and test set to original configuration and remove electrical power if no longer required.

NOTE:  The above test cycle will repeat as long as function selector switch is in DME position.
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4.  System Test - Using Instrument Flight Research ATC-600A
A.  Equipment and Materials
(1)  Transponder/DME Test Set - IFR Model ATC-600A
B.  Prepare for Test
(1)  
Position remote test set antenna approximately 21 inches from DME antenna for system under test. Test set antenna should be approximately same height as the airplane antenna.

CAUTION:  NEVER PLACE REMOTE TEST SET ANTENNA CLOSER THAN 15 INCHES TO AIRPLANE ANTENNA WITH TEST SET ON. DAMAGE TO TEST SET WILL RESULT.

(2)  
Route and connect coax from remote test set antenna to test set which should be located in cockpit.

(3)  
Set test set controls as follows:
PWR switch -AC or BAT (as appropriate)
Mode switch - DME Velocity Select switch – RANGE
Velocity HI/LO switch – HI
Squitter ON/OFF switch – ON
X/Y switch - X

C.  Test DME System
(1)  
On both VHF NAV control panels, select 109.00 MHz and position DME mode selector to NORM or ON. DME indicators should display dashes.

(2)  
Actuate DME self-test. Verify that in approximately 1.5 seconds, indicators DME display 000 +0.5 miles.
　
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