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时间:2011-03-26 00:16来源:蓝天飞行翻译 作者:admin
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R  A. Principle 
R  The principle of the radio altimeter is to : 
R  - transmit a frequency modulated signal from the aircraft to the ground 
R  - receive the ground reflected signal after a certain delay. 
R  The time between the transmitted frequency and the received frequency is 
R  proportional to the aircraft height. 
R  B. System Architecture 
R  (Ref. Fig. 002) 
R  The radio altimeter comprises two independent systems. Each system 
R  consists of : 
R  - one transceiver 2SA1 (2SA2) 
R  - one transmission antenna 6SA1 (6SA2) 
R  - one reception antenna 5SA1 (5SA2) 
R  - one fan 3SA1 (3SA2). 
R  In addition, the Centralized Fault-Display Interface-Unit (CFDIU) 1TW 
R  controls the system through the Multipurpose Control and Display Unit 1 
R  (2) (MCDU) 3CA1 (3CA2) for test causes. 
R  (Ref. Fig. 003) 
R  The radio height data is shown on the Primary Flight Display (PFD). In 
R  normal operation, system 1 provides information to the CAPT PFD and 
R  system 2 to the F/O PFD. 
R  C. Utilization Technical Data 
R  (Ref. Fig. 004) 
R  (1) Height data display (Item 3) 
R  The aircraft height data with respect to the ground is shown in the 
R  sector 2 of the PFD. This indication is at the bottom of the attitude 
R  sphere, for height less than or equal to 2500 ft. 
R  The dimension and color of the digits change in relation to the 
R  height (H) and decision height (DH) as follows : 
R  H more than or equal to 400 ft. : 3 mm green digits 
R  400 ft. > H > DH + 100 ft. : 4 mm green digits 
R  H < DH + 100 ft. : 4 mm amber digits. 
R  The sensitivity of the digits is also a function of the height : 
R  H > 50 ft. : 10 ft. increments 
R  50 ft > or = to H and H > or = to 5 ft : 5 ft. increments 
R  H < 5 ft. : 1 ft. increments. 
R  With failure of both radio altimeters, a red RA warning message is 
R  shown in place of the radio height information (Item 4) in slats 
R  extented configuration only. The message flashes during 3 seconds 
R  then remains on.

 1EFF : ALL 1 34-42-00Page 5 1 1 Aug 01/04 1 1 1CES 1


 Radio Altimeter - Block Diagram Figure 002
 1EFF : 1 1R 1CES  ALL  1 11 1 34-42-00 Page 6 May 01/04

 

 Radio Altimeter - Control and Indicating Figure 003
 1EFF : 1 1R 1CES  ALL  1 11 1 34-42-00 Page 7 May 01/04

 

 Radio Altimeter - Data and Warning Displays Figure 004
 1EFF : 1 1R 1CES  ALL  1 11 1 34-42-00 Page 8 May 01/04

 

R R  When the aircraft is below 500 ft. height above the terrain : a red ribbon comes into view on the bottom of the altitude scale and moves 
R R R  up with this scale as the aircraft is in the descent phase (Item 2). When the aircraft has touched down the ground : the top of this ribbon is at the middle of the altitude window. 
R R R  With failure of both radio altimeters, the ribbon goes out of view. Below 300 ft., the height is shown by the distance between the horizon line and the limit of the sector 2. The limit of the sector 2 
R R R R R  moves up as the aircraft is in the descent phase. The distance between these two lines is proportional to the ground height (sensitivity 5 ft./mm). As it moves up, the limit line erases the graduations on the pitch scale. 
R R  With failure of both radio altimeters, this indication goes out of view. 
R R R R R R  (2) Decision height display (DH) (Item 1) The pilot sets the DH on the MCDU. The DH data are shown on the R top corner of the PFD (3 mm high digits) as soon as the radio altimeter operates. When the height is lower than the DH, a DH amber warning message comes into view at the bottom of the attitude sphere (Item 5). 
R R R R R R R  D. Warnings (Ref. Fig. 003, 004) The warnings related to the radio altimeter are : - local warning on the instruments that use the radio altimeter data - MASTER CAUT lights on the CAPT and F/O glareshield panels - aural warning : single chime - warning message shown on the upper ECAM display unit.
 4. Power Supply____________ (Ref. Fig. 002) Energization of each system is through 115VAC, 400 Hz normal buses : - 115VAC BUS1 101XP via circuit breaker 1SA1 for system 1 - 115VAC BUS2 202XP via circuit breaker 1SA2 for system 2.
 
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