TRIP TRIM MOD RECEIVER TRANSMITTER
LRRA 1 OR 2 System Schematic Figure 3 (Sheet 1)
EFFECTIVITY
CONFIG 2 AF ALL; SN351-399; MD ALL;
799 Page 8 GN ALL; AT ALL; VM ALL Apr 25/88
34-33-00
LRRA 1 OR 2 System Schematic
Figure 3 (Sheet 2)
EFFECTIVITY
CONFIG 2 AF ALL; SN351-399; MD ALL;
799 Page 9 GN ALL; AT ALL; VM ALL Sep 25/94
34-33-00
TRIP TRIM RECEIVER TRANSMITTER MODULE
LRRA-3 System Schematic
Figure 3 (Sheet 3)
EFFECTIVITY
CONFIG 2
SN 351-399
799 Page 10
34-33-00
Apr 25/88
LRRA 3 System Schematic
Figure 3 (Sheet 4)
EFFECTIVITY
CONFIG 2
SN 351-399
799 Page 11
34-33-00
Apr 25/88
(b)
The saw-tooth generator signal is applied to the transmitter to produce a frequency modulated output signal. The modulating frequency is a function of saw-tooth time duration. The transmitter signal is applied through the transmit circulator to the transmit antenna and radiated to the earth beneath the airplane. This signal is reflected back to the receive antenna and applied through the receive circulator to the mixer.
(c)
The mixer also accepts a small amount of the transmitted signal. The mixer output is a beat frequency which is applied through an amplifier to the track and contrast discriminators. The contrast discriminator output controls the search/track switch.
(d)
In the track discriminator, the beat frequency is compared to the 25-kHz center frequency of the discriminator to produce an error voltage when the frequencies are not equal. The error voltage is applied through the search/track switch to an integrator.
(e)
The output from the integrator is applied to the saw-tooth generator to control the saw-tooth time duration which subsequently eliminates the error voltage in the tracking discriminator. This keeps the beat frequency constant which establishes a linear relationship between the saw-tooth time duration and airplane altitude.
(f)
The time-to-voltage converters measure the variable saw-tooth time duration and convert the data to dc altitude voltages which are applied to output conditioning amplifiers. The dual amplifiers provide the dc altitude signals used to drive the height indicator and to provide altitude data to other systems on the airplane. The autopilot/flight director system uses the altitude signal to facilitate gain programming of the glide slope and localizer deviation signals during approach modes. The auto throttle system uses the altitude signal to enable speed control during the low altitude flare maneuver.
(g)
The dc altitude signals are also applied to the receiver-transmitter altitude trip circuits. Each altitude trip circuit consists of an adjustment potentiometer, altitude detector, dc amplifier, and a switch which drives a relay. The potentiometer for each trip circuit is located in the trip trim module. All other circuit components are located in the receiver-transmitter. Each altitude trip circuit is adjusted (preset) to provide a closed circuit output at a precise dc altitude voltage. When a trip circuit actuates to provide the closed circuit, a ground signal is supplied to external using equipment.
EFFECTIVITY
AF ALL; SN351-399; MD ALL; CONFIG GN ALL; AT ALL; VM ALL 05 Page 12 Apr 25/88
34-33-00
(h)
The dc altitude signal supplied to the height indicator is applied to the pointer drive comparator. A second input to the comparator is obtained from the servo potentiometer which is mechanically coupled to the pointer drive motor. The output from the comparator is zero when the two input signals are equal. When the two signals are not equal, an output from the comparator is applied to the servo-amplifier which drives the motor. The motor turns both the altitude pointer and potentiometer until the comparator output is again zero. Thus, the closed servo loop moves the altitude pointer to a position determined by the dc altitude input.
(i)
The dc altitude signal supplied to the height indicator is also applied to the DH comparator. A second input to the DH comparator is obtained from the DH potentiometer which is mechanically coupled to the DH index and control knob. When the dc altitude signal is equal to or less than the signal from the DH potentiometer, the comparator produces an output which is used to actuate a switch. When the switch is actuated, a ground is applied to the DH relay coil causing the relay to energize and turn on the DH light on the associated ADI. The DH light can be turned off (reset) by pushing in on the DH control knob. This will cause the reset relay to energize which will de-energize the DH relay.
(j)
A dc altitude signal from receiver-transmitter 1 and 2 is applied to the captain's and first officer's ADI, respectively. The altitude signal controls the vertical movement of the rising runway symbol. The 200-foot altitude trip signal will initiate the vertical movement of the symbol provided the required valid signals are supplied to the ADI logic circuits to retract the runway flag from view. The LRRA system flag alarm signal is provided as one of the required valid signals. Additional signals are required from the VOR/ILS system (Ref 34-31-00).
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(63)
