(2)
The distance indicators will show flags and the system will remain in standby mode even afte the warmup period since no interrogation can take place until the system is airborne.
EFFECTIVITY
SN 301-350 CONFIG 2 06 Page 9 Apr 25/8634-55-00
DME SYSTEM - DESCRIPTION AND OPERATION
______________________________________
1. General (Fig. 1)
_______
A. The DME (distance measuring equipment) system automatically measures the distance (in nautical miles) between the airplane and a selected ground station. The system measures the airplane-to-station slant-range distance (line-of-sight) and the information is displayed on a digital readout indicator as miles-to-go. The method of measuring this distance is primarily a function of an interrogator (receiver-transmitter) unit, operating in the 960- to 1215-MHz range. The DME frequency is automatically selected when a VOR frequency is selected.
B. The interrogator unit transmits a pulse-coded interrogation signal which actuates a corresponding ground station reply. This reply signal is received and processed by the interrogator. The time interval between the interrogation signal transmitted from the airplane and the ground station reply signal received by the airplane is measured, converted into distance, and displayed on the indicator.
C. AF 121-122, 157, 161, 183-184; the system is designed to indicate a maximum range of 390 nautical miles.
D. Two complete DME systems are installed in the airplane. Each system consists of an interrogator (transmitter-receiver) unit, an antenna, two distance indicators, and a remote tuning control panel (Fig. 1).
E. The 115-volt ac, 400-Hz power is applied to the DME systems No. 1 and 2 from the essential radio bus and radio bus No. 2, respectively. An internally mounted power supply converts the 115 volts ac to 26 volts ac and 20 volts dc for required operating power.
F. The DME system interface is shown in Fig. 2. The output of each interrogator is applied to the appropriate digital readout of both DME indicators. A sample pulse is taken from each interrogator and coupled to the ATC system, which operates in the same general frequency range. This pulse acts as a suppression pulse. An audio signal from the DME interrogator is applied to the flight interphone system. On IB 411-499; AF 121-122, 157, 161, 183-184; an analog pulse pair and the DME valid outputs from the interrogators are provided for DME updating the inertial navigation or the performance management systems.
2. Control Panel (Fig. 1 and 2)
_____________
A. Each ground station installation is assigned a specific VOR frequency and associated DME frequency. Since the DME system operates in conjunction with the VOR navigation system, controls for both are located on the same control panel and consist of a VOR/DME frequency selector and on XA ALL EXCEPT LH 011-030, 051-070, 082-099, a DME mode selector switch, and a DME test switch. DME system No. 1 is controlled from the captain's control panel and DME system No. 2 from the first officer's control panel. Both panels are located as shown in Fig. 1.
EFFECTIVITY
LH 011-099;
AF 121-122, 152-199; AZ 221-299; IB 406-499; CONFIG 3 SN 351-399; AT, GN, MD, 01 Page 1 AND VM ALL Apr 25/95
34-55-00
SEE A
DME ANTENNA NO. 1
DME ANTENNA NO. 2
SEE B
DME INTERROGATORS
VHF NAV
VHF NAV
3 108.00
108.00
VOR
ILS
VOR/DME UP/LT
TEST OFF DME
MODE SWITCH TEST TEST
4
FREQUENCYTEST BUTTON
VHF NAV CONTROL PANEL
SELECTOR A2
VHF NAV CONTROL PANEL
A1
INS
DISPLAY TEST APRCH AUTO
1 LH 011-013,015-030,051-060,082,083; AZ 221-299; IB 406-499; AF 121,122,152-199; NORM MAN SN 301-350; AT,GN,MD,VM ALL VHF NAV
2 LH 014,061-069,084-099 UP/LT STBY
DME 3
SN 351-399 DN/RT TEST VOR
4
MODE SWITCH NOT INSTALLED ON
LH 011-099
5
AT ALL VHF NAV CONTROL PANEL
6 XA ALL EXCEPT AT; AF 121,122,157,161,183,184
A3
DME System Component Location Figure 1 (Sheet 1)
EFFECTIVITY
LH 011-099; AF 121,122,152-199;CONFIG 3 AZ 221-299; IB 406-499;
799 Page 2
34-55-00SN 351-399; AT,GN,MD AND VM ALL Apr 25/95
DME INDICATOR
DME-1 DME-2
RADIO MAGNETIC INDICATOR
(VOR/DME DISPLAY)
DME System Component Location
Figure 1 (Sheet 2)
EFFECTIVITY LH 011-099; AF 121,122,152-199;
CONFIG 3AZ 221-299; IB 406-499; 799 Page 3
34-55-00
SN 351-399; AT,GN,MD AND VM ALL Apr 25/95
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115V AC NO. 2 RADIO BUS 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航4(92)
