6. MAINTENANCE PROCEDURES 1 Introduction
6.2 Performance Check Procedures
Should abnormal performance occur during the performance check procedures, refer to Section 5.
6.2.1 System Frequency Performance Check
a. Assure the DME is operating in the NORMAL STATE.
b. Connect frequency counter to TX1 Low Power Amplifier (1A9) J1 TX LO connector. Measure and record the frequency.
c. For dual equipment, connect frequency counter to Low Power Amplifier (1A17) J1 TX LO connector.
Measure and record the frequency.
d. Connect frequency counter to Monitor Interrogator (1A11) INT LO connector. Measure and record the frequency.
e. For dual equipment, connect frequency counter to Monitor Interrogator (1A15) INT LO connector.
Measure and record the frequency.
f. Connect frequency counter to the Receiver Transmitter Controller (1A10) RX LO connector. This frequency is 125 MHz lower than the assigned receive frequency. Measure and record the frequency.
g. For dual equipment, connect frequency counter to the Receiver Transmitter Controller (1A16) RX LO connector. This frequency is 125 MHz lower than the assigned receive frequency. Measure and record the frequency.
6.2.2 Monitor Interrogator Signal Generator Test
a. Log on the PMDT. Place the DME into the BYPASS STATE.
b. Select Monitor 1 >> Test Results >> Interrogator.
c. Verify that all parameters are within the high and low limit as indicated by a green background.
d. For dual equipment, put repeat step b-c using monitor 2.
e. Restore the DME to the NORMAL STATE.
6.2.3 Transponder Performance Check
a. Log on the PMDT. Place the DME into the BYPASS STATE.
b. Select Monitor 1 >> Test Results >> Transponder.
c. Review the Date and Time to verify that current test results are displayed.
d. Verify that all parameters are within the high and low limit as indicated by a green background.
e. For dual equipment, put transmitter 2 on antenna and repeat step b - d.
f. Restore the DME to the NORMAL STATE.
6.2.4 Receiver and Decoder Performance Check
a. Log on the PMDT. Place the DME into the BYPASS STATE.
b. Select Tx1 on antenna. WARNING: System NOTAM warnings must be followed.
c. Select Monitors >> Special Tests. Select Decoder Tests, select Monitor 1 from the “Monitor Selection” menu then press the “Apply” button followed by the “Start” button.
d. Select Monitor 1 >> Test Results >> Decoder. Wait for all tests to complete.
e. Verify the receiver sensitivity, receiver bandwidth, and decoder aperture meet their performance as indicated by green backgrounds on all data parameters.
f. For dual equipment, repeat steps c. through e. for monitor 2.
g. For dual equipment, repeat steps c. through g. for transponder 2.
h. Restore the DME to the NORMAL STATE.
6.2.5 Transponder Reply Delay Performance Check
a. Log on the PMDT. Place the DME into the BYPASS STATE.
b. Connect channel 1 of an oscilloscope to 1A11 Monitor 1 DETECTED VIDEO (1A11, J5) c. Connect the Monitor 1 INT TRIG (1A11, J4) to the external trigger input of the oscilloscope.
d. Set the scope to trigger to external.
e. The scope should display both the interrogation and the reply pulse-pairs.
f. Verify the time from the leading edge of the first interrogation pulse to the leading edge of the first reply pulse matches Monitor 1 >> Data >> Integral >> Delay within ± 0.5µs. (If second pulse timing is selected then the measurements should be done using the second interrogation and reply pulses.)
g. For dual equipment, select Monitor 1 >> Trigger >> Standby Delay >> Normal.
h. Verify the time from the leading edge of the first interrogation pulse to the leading edge of the first reply pulse matches Monitor 1 >> Data >> Standby >> Delay within ± 0.5µs. (If second pulse timing is selected then the measurements should be done using the second interrogation and reply pulses.)
i. Repeat steps a through i for Monitor 2 (1A15).
j. Restore the DME to the NORMAL STATE.
6.2.6 Transmitter Power Output Performance Check 6.2.6.1 When Using a Wattmeter to Measure Power a. Turn OFF DME.
b. Connect the wattmeter directly to the RF OUT port (1J1) on the top of the cabinet. CAUTION: Use care to avoid excessive stress on the output connector 1J1. A short cable may be used between the output connector and wattmeter.
c. Connect the antenna feed cable to the output of the wattmeter.
d. Insert the 250 Watt (LPDME) or 2500 Watt (HPDME) element into the wattmeter with the direction arrow pointing away from the transmitter output. NOTE: The same element used for the reference reading should be used for power verification.
e. Turn ON DME.
f. Logon the PMDT. Place the DME is in the BYPASS STATE.
g. Place transmitter 1 ON ANTENNA.
h. Use the wattmeter to verify the transmitter power matches the reference reading taken during installation or the last flight check. NOTE: The ambient temperature in the shelter should be close to the temperature used when the reference reading was taken. This helps eliminate any wattmeter temperature variations.
i. If a change to output power is needed then refer to Section 3.6.10.3.1 to change the Power Output setting.
j. If dual equipment, put transmitter 2 on antenna and verify its power setting also matches the reference reading.
k. If a change to transmitter 2 power setting is required, the Tx2 Power Output Scale factor shown in Section 3.6.10.3.2 should be used.
l. On the Monitors >> Data >> Integral screen verify the Tx Power reading is 100W (LP) or 1000W (HP) ±10%.
m. If an integral monitor reading change is required then adjust the Integral Tx Power Offset shown in Section 3.6.9.4.2 for each monitor.
n. For dual equipment, on the Monitors >> Data >> Standby screen verify the Tx Power reading is 100W (LP) or 1000W (HP) ±10%.
o. If a standby monitor reading change is required then adjust the Standby Tx Power Scale shown in Section 3.6.9.4.1 for each monitor.
p. Save any changes made to the DME configuration, turn OFF DME, remove the wattmeter and reconnect the antenna cable to 1J1.
q. Restore the DME to the NORMAL STATE.
6.2.6.2 When Using a Digital Peak Power Meter to Measure Power a. Turn off the DME.
b. Connect a directional coupler (30 dB forward coupling factor) to the RF OUT port (1J1) on the top of the cabinet.
c. Connect the antenna feed cable to the output of the directional coupler.
d. Set the peak power meter offset to match the calibrated attenuation of the directional coupler and the 20dB attenuator. If calibrated results are unknown then enter the default setting of 50dB (30dB coupler + 20dB attenuator).
e. Set the peak power meter test frequency to the DME transmitter frequency then calibrate the meter.
f. Place an additional 20dB attenuator in line with the directional coupler forward output port. Connect the peak power sensor to the coupled port of the directional coupler.
g. Turn ON DME.
h. Log on the PMDT. Place the DME is in the BYPASS STATE.
i. Externally trigger the peak power meter (if necessary) with TX TRIG from RTC1 (1A10).
j. Use the power meter to verify the transmitter power is within the tolerance stated in Table 4-1, 2.1.4 Output Power.
k. If a change to output power is needed then refer to Section 3.6.10.3.1 to change the Power Output setting.
l. If dual equipment, put transmitter 2 on antenna and verify its performance meets Table 4-1, 2.1.4 Output Power.
m. If a change to transmitter 2 power setting is required, the Tx2 Power Output Scale factor shown in Section 3.6.10.3.2 should be used.
n. Select Monitors >> Data >> Integral verify the Tx Power readings match the external power readings within
±10%.
o. If an integral monitor reading change is required then adjust the Integral Tx Power Offset shown in Section 3.6.9.4.2 for each monitor.
p. For dual equipment, select Monitors >> Data >> Standby, verify the Tx Power readings match the external power readings within ±10%.
q. If a standby monitor reading change is required then adjust the Standby Tx Power Scale shown in Section 3.6.9.4.1 for each monitor.
r. Save any changes made to the DME configuration then turn off the DME, remove the directional coupler, and reconnect the antenna cable to 1J1.
s. Turn ON DME and restore the DME to the NORMAL STATE.
6.2.6.3 When Using a Lady Bug® Power Sensor a. Ensure the DME is operating normally.
b. Place the DME is in the BYPASS STATE.
c. Place Tx1 on the antenna, place TX2 on standby.
d. Activate the Lady Bug® Power Meter program. Connect sensor to computer USB port.
e. Lady Bug® setup:
1. Select Pulse Power measurement.
2. Set measurement frequency to station transmit frequency.
3. Set measurement averaging to “3000”.
4. Set Display Power Units to “Watts”.
5. Set Offset value. The offset value is the sum of the following:
a. Coupling loss indicated on the DME RF Panel. This is the sum of the coupling factor of 1DC1 and 1HY1. Note: Single transmitter systems have no 1HY1.
b. Total external attenuation. WARNING: At least approximately 30 db of external attenuation should be used to protect the power sensor.
c. Adapter cable loss [.6db] (SMA male to N female cable provided with Lady Bug®).
6. Enable the offset function.
f. Remove the cable at J3 of 1HY1 (1HY1 is located on the left side of the RF panel facing the back of the cabinet). For single transmitter systems, remove the cable from J2 of 1DC1.
g. Connect the adapter cable to J3 of 1HY1, to a 30db attenuator, then to the Lady Bug® sensor. Note: Rest the measurement setup in a manner that will not place stress on cables. Record the peak power (Pk) reference indication. For single transmitter systems, connect the measurement setup directly to J2 of 1DC1.
h. Remove measurement cable from J3, replace original cable to J3. For single transmitter systems, replace original cable to J2 of 1DC1.
i. Place Tx2 on the antenna, place Tx1 in standby. Remove the cable at J2 of 1HY1. Connect the measurement setup to J2 of 1HY1, Record power indication.
j. Replace the original cable to J2 of 1HY1.
k. Return the system to normal.
6.2.7 Monitor Shutdown/Transfer Control Performance Check a. Assure the DME is in the NORMAL STATE.
b. Remove the monitor antenna input cable at 1J2 (ANT MON 1) on top of the DME cabinet to create a transponder alarm condition.
c. Verify transmitter 1 is shutdown in less than 10 seconds.
d. For dual equipment, verify transmitter 2 is transferred to the antenna before it is shutdown.
e. Reconnect the monitor antenna input cable f. Restore the DME to the NORMAL STATE.
6.2.8 Monitor Alarm Integrity/Certification Performance Check
a. Log on the PMDT. Select Monitors >> Data >> Integral, verify all integral monitor parameters are within tolerance as indicated by a green background color.
b. For dual, hot standby equipment select Monitors >> Data >> Standby. Verify all standby monitor parameters are within tolerance as indicated by a green background color.
c. Select: Monitor 1 >> Test Results >> Alarm Limits.
d. Verify the monitor passes all Low Limit and High Limit certification tests as indicated by green backgrounds on all parameters.
e. For dual equipment, view Monitor 2 >> Test Results >> Alarm Limits and repeat step c.
f. Restore the DME to the NORMAL STATE.
6.2.9 Power Supply and Battery Performance Check
a. Log on the PMDT. Place the DME into the BYPASS STATE.
b. Select RMS >> Data >> Power Supply Data.
c. Verify “Tx1 48V PS”, “Volts” indicates 48±2V and “Battery 1”, “Volts” indicates 52 to 56V when in trickle charge mode.
d. For dual equipment verify “Tx2 48V PS”, “Volts” indicates 48±2V and “Battery 2”, “Volts” indicates 52 to 56V when in trickle charge mode.
e. Turn off AC breaker 1 and verify transponder 1 remains operational for at least 5 minutes.
f. For dual equipment, Turn off AC breaker 1 and 2, verify the system remains operational for at least 5 minutes.
g. Restore the DME to the NORMAL STATE.
6.3 Other Maintenance Procedures