SD3-60 AIRCRAFT MAINTENANCE MANUAL z AMM 55.0.0.0DME SYSTEM - DESCRIPTION AND OPERATION (POST-MOD A8062) 1. General A. The DME systems provides a visual indication of the distance, in nautical miles, the aircraft is from a selected ground station. In addition each system is capable of displaying the ground speed in knots or time-to-station (TTG) in minutes. The DME reading indicates the slant range between the aircraft and the ground station. The ground speed or TTG is thus only accurate if the aircraft is flying directly to the ground station at such a distance that the slant range and ground range are nearly equal. An audio output for station identification is also provided. The DME systems incorporate a 'hold' facility which enables the selected system to remember the last operating frequency selected on the associated NAV controller. This facility allows separate control of the DME and NAV receivers with a common control unit. The 'hold' facility is selected and indicated on the NAV controller. B. The first and second pilots installations are identical. Each installation comprises of the following:- - a DME transceiver - a NAV controller - an antenna - a DME volume control knob Refer to 34-31-20, pb1. The controllers form part of the VOR/ILS/MKR system. The antennae and DME VOL control are existing equipment (Pre-mod 8062) and are described. Refer to 34-52-10, pb1. 2. Component description A DME Transceiver, Collins type DME 42 (Part No. 622-6263-001). The No. 1 and No. 2 DME transceivers are installed to the left and right side of the aircraft in the No. 1 and No. 2 avionics compartments. The No. 1 and No. 2 transceivers measure the slant range (line-of-sight) from the aircraft to a ground station and displays that distance in nautical miles on the EHSI. Refer to 34-61-00, pb1. The transceiver can simultaneously track and provide complete information from any three of the 252 DME channels. 3. Operation A. General DME information is displayed on the Electronic Horizoal Situation Indicator (EHSI). Refer to 34-61-00, pb1. Details of system operation are described. Refer to 34-52-10, pb1. Page 1
z SD3-60 AIRCRAFT MAINTENANCE MANUAL B. Controls Control of the system is provided with the CTL-32 controller as follows. Refer to 34-31-20, pb1. (1) Active frequency display (upper window). On units operating on the left side, the active frequency is the frequency to which the DME-42 Channel 1 is tuned. In DME or NAV selftest, diagnostic messages are displayed in the upper window. On units operating on the right side, cross connected to the left side unit, the active frequency is the frequency to which the DME channel 2 is tuned. (2) Pre-set frequency display (lower window). On units operating on the right side with cross coupling to the left, the pre-set (inactive) frequency is the frequency to which the DME-42 channel 3 is tuned. In NAV self test, diagnostic messages are displayed in the lower window. On units operating on the right side with cross coupling to the left, the pre-set frequency is not used for DME-42 operation. (3) Compare annunciator ACT momentarily illuminates when frequncies are being changed. ATC Continues to flash if the frequency to which the radio is actually tuned is not identical to the frequency shown in the active frequency display. (4) Annunciators The controller displays MEM (memory) and HLD (hold) annunciators. (a) MEM The MEM annunciator illuminates when a stored frequency is being displayed in the lower window. (b) HLD The HLD annunciator indicates that the DME is in DME hold. In this mode it is normally tuned to the frequency that was displayed in the active window at the time of selection. After selecting hold, the upper window displays the NAV frequency and the lower window displays the DME hold frequency. (The frequency that was displayed on the pre-set window is stored in the pre-set memory and can be recalled to the active display with the XFR switch). Page 2
SD3-60 AIRCRAFT MAINTENANCE MANUAL z AMM 56.0.0.0DME SYSTEM - MAINTENANCE PRACTICES (POST-MOD A8062) 1. Adjustment/Test A. Bench Test The DME system is to be tested in accordance with the relevant Manufacturers Maintenance Manual. NOTE: An exception to this is the DME audio output the setting for which is defined in the audio test procedures. Refer to 23-51-00, pb201. B. Pre-installation checks Check that the units are free from signs of mechanical damage, corrosion or other defects. C. Post-installation tests (1) Function test Test equipment required. - Flight line DME test set - Two headsets 1 Ensure all avionic and electrical switches are at the off or neutral position. 2 Refer to 12-09-03, pb301. Connect external electrical power. 3 Set the ELECTRICAL MASTER switch to EXTERNAL, and set the AVIONIC MASTER switch at ON. 4 Set the DME 1 switch of both pilots audio controls panel to ON. 5 Plug headset into each pilots audio control panel. 6 Rotate mode select switch on the No. 1 NAV controller to the ON position. 7 On No. 1 HCP select HSI. 8 ow at least 60 seconds warm up time. 9 Select switch on the test set to SQTR. 10 Select X channel on the test set. 11 Select a velocity and distance on the test set. 12 Tune the No. 1 NAV controller to a frequency of 108 mhz. Page 201
z SD3-60 AIRCRAFT MAINTENANCE MANUAL 13 Check No. 1 EFD accuracy as follows: a b Distance: ± 1.0 nautical miles. Ground speed:± 2 knots or 2% whichever is greater. NOTE: If the ground speed is not displayed, press the HSI button on the HCP once and the ground speed (SPD) will appear on the bottom LH corner of the No. 1 EFD. To regain time-to-station (TTG) information, press the HSI button once again. c TTG: ± 1 minute or ± 4% whichever is greater. NOTE: The above accuracy checks must be performed at least 3 minutes after the system has "locked on" to the signal. This permits the system to compute the rate of change of distance to the station. 14 Repeat paragraph 13 for the distance and velocity range extremities on the test set. 15 Set the distance to greater than 256 nautical miles. 16 Check that no distance is displayed on the EFD. 17 Check that no ground speed is displayed and that there are three dashes below 'SPD'. 18 Select a distance of less than 256 natical miles and check that this distance (± 1 nautical mile) agrees with the test set. 19 Select a velocity of 50 knots. 20 Check that no ground speed is displayed and that there are 3 dashes below 'SPD'. 21 Select DME on audio panel. 22 Press and hold ident switch. 23 Check that a satisfactory audio output is obtained in the following units and that the DME volume control operates satisfactorily. a b c d First pilots headset First pilots loudspeaker Second pilots headset Second pilots loudspeaker Page 202
SD3-60 AIRCRAFT MAINTENANCE MANUAL z 24 Check DME HLD facility as follows: a On No. 1 NAV controller. - Rotate mode select switch to HLD. - Check that HLD annunciation appears in the lower display window. b c Change the frequency on the No. 1 NAV contoller and check that the DME range is unaffected. Change the velocity on the test set and check that the DME range changes. 25 Rotate mode selector switch on the No. 1 NAV controller to the OFF position. 26 Rotate the mode select switch on the No. 1 DME indicator to the OFF position. 27 Repeat paragraphs 6 to 26 reading No. 2 NAV controller for No. 1 NAV controller and No. 2 EFD for No. 1 EFD. 28 Switch off, disconnect and store test equipment. 29 Set the AVIONICS MASTER to OFF. 30 Check all avionic and electrical switches are at neutral or OFF position. 31 Set the ELECTRICAL MASTER switch to OFF. 32 Refer to 12-09-03, pb301. Disconnect external electrical power 12-09-03. (2) DME VSWR tests DME VSWR tests are identical to those pre mod A8062. Refer to 34-52-10, pb201. (3) DME self-test The self-test diagnostic routine for the DME transceiver is initiated with the TEST button on the CTL-32 NAV controller. A list of diagnostic codes is provided. Refer to Table 201. Refer to 34-31-20, pb201. CODE INTERPRETATION 01 Power supply 02 Synthesizer 03 Transmitter 04 Video processor 05 Receiver 06 Distance processor DME 42 SYSTEM DIAGNOSTIC CODES Table 201 Page 203
z SD3-60 AIRCRAFT MAINTENANCE MANUAL CODE INTERPRETATION 07 Microprocessor ROM 08 Microprocessor RAM DME 42 SYSTEM DIAGNOSTIC CODES Table 201 Page 204