Breakout Boxes. The MLRS breakout boxes connect the cable assemblies with the electronic LRUs and bring individual data lines to test points for measurement of voltages, resistances, and continuity.
The MLRS has five breakout boxes: fire control panel, power distribution box, hoist, boom, and transducer. All of the breakout boxes are used on the system except the transducer breakout box, which is used as part of the bench setup in a GS shop.
Audio Oscillator. The audio oscillator is a power supply for the testing and repair of the elevation or azimuth transducers. It is connected to the transducer breakout box.
Synchro Angle Indicator. The synchro angle indicator is used strictly for the testing or repair of the elevation or azimuth transducers. It tells the repairer the degree at which the transducer is sitting (0° to 360°). The indicator is connected to the transducer breakout box.
Multimeter. The multimeter used by the repairer is a Fluke digital multimeter that can measure AC and DC voltage, resistance, and milliamps.
Oscilloscope. The MLRS uses a Tektronix 212 oscilloscope. It checks square waves for the position determining system and sine waves for the transducers.
Test Cables. There are two test cables the repairer uses. The limit switch test cable checks continuity of the limit switch connected to the test cable. The other test cable connects the transducer breakout box to the synchro angle indicator.
TRAINER LP/C
This is an MLRS-associated piece of training equipment. It is used to keep both the crew members and DS support personnel well trained. In your job, you have to know how to set up a training session for repairers.
Training is set up by the fault insertion panel (figure 2-8). The panel, in rocket tube number 4, allows the crew chief to insert a fault or faults into the LP/C for crew training during a simulated fire mission.
Figure 2-8. Trainer of LP/C.
The trainer can put six different faults into the fire control system through the LP/C simulator assembly. The position of switches on the fault insertion panel determines which fault is inserted. The following paragraphs explain how the switches cause the fault indications.
When the rocket-4 fuze switch is placed at dud, the fuze test circuit is opened. This causes the fire control system to sense a dud fuze. The FCP in the SPLL displays a D for rocket number 4 during a rocket status display.
When the rocket-4 status switch is placed in open, the rocket status signal is interrupted before it reaches the circuit card simulator. This simulates an empty rocket tube number 4.
Positioning the rocket-4 status switch to hangfire completes the number-4 igniter hi-circuit when the fire switch on the FCP is actuated. A path is complete through the normal side of the rocket-4 misfire switch, the hangfire
is sent through the normal side 4. A circuit path is complete for digital return, simulating a rocket still in tube number 4. The fire control system in the SPLL interprets this as a hangfire by sensing that a firing pulse was sent to the rocket and that a rocket is still in the tube.
Positioning the rocket-4 misfire switch to misfire interrupts the igniter high-firing pulse for tube number 4 before it reaches the simulator circuit card, simulating a firing pulse sent by the fire control system but not received by the rocket motor.
The rocket-2 misfire switch interrupts the igniter highfiring pulse for tube number 2 before it reaches the simulator circuit card, simulating a firing pulse sent by the fire control system but not received by the rocket motor.
When the rocket pod identification switch is open, it interrupts the identification signal. The fire control system senses and registers an improper umbilical cable connection.
REVIEW EXERCISES Circle the letter of the correct answer to each question.
1. From which menu is the start-up date selected?
a. Auxiliary menu.
b. Test menu.
c. Index menu.
d. Message menu.
2. Which two switches must be off before you perform fire control start-up procedures?
a. Arm and fire.
b. RFU and FCP.
c. Master power and interconnect.
d. Arm and RFU.
3. What is the first field you see when performing system start up?
a. Northing.
b. Altitude.
c. Grid.
d. Easting.
4. During communications start up, which fields are not used?
a. 24-32.
b. 26-32.
c. 25-32.
d. 23-32.
5. When you press the LCHR LAY key how many mils must the LLM elevate before traversing?
a. 302.
b. 240.
c. 360.
d. 180.
6. Which menu allows the crew to control manually the movement of the LLM?
a. Auxiliary menu.
b. Boom control menu.
c. Test menu.
d. Index menu.
7. Which of the following provides the interface between hydraulics and mechanical components?
a. Servomotors.
b. Speed reducer.
c. Actuator.
d. Angle drive.
8. The fire control system has how many batteries?
a. One.
b. Three.
c. Four.
d. Two.
9. What is the purpose of the travel lock actuator?
a. Secures the LP/Cs.
b. De-energizes the suspension lockout.
c. Secures cage for transport.
d. Keeps crew from moving SPLL.
10. Which limit switch sends a signal to lock the travel lock assembly?
a. 196°.
b. 27°.
c. Hoist up.
d. Cage down.
11. The spin rails initiate a spin rate of how many revolutions per second?
a. 4-6.
b. 10-12.
c. 7-10.
d. 15-18.
12. How many breakout boxes are used with the MLRS?
a. Eight.
b. Five.
c. Three.
d. Six.
13. The audio oscillator serves as a power supply for testing or repairs of what item below?
a. Breakout boxes.
b. All MLRS cables.
c. EL and AZ transducers.
d. All MLRS test equipment.
14. The synchro angle indicator is used for testing what item?
a. AZ and EL transducers.
b. Stabilization reference package.
c. Positioning determining system.
d. AZ and EL gyros.
15. How many MLRS test cables are there?
a. Three.
b. Four
c. Two.
d. Five.
16. The fault insertion panel is located in what tube of the LP/C?
a. Two.
17. If you received an improper umbilical cable connection prompt across the fire control panel, which switch on the fault insertion panel would cause this?
a. Fuze.
b. Rkt Status.
c. LP/C Ident.
d. Temp.
Recheck your answers to the Review Exercises. When you are satisfied that you have answered every question to the best of your ability, check your answers against the Exercise Solutions. If you missed five or more questions, you should retake the entire lesson, paying particular attention to the areas in which your answers were incorrect.
Lesson 3
PREVENTIVE MAINTENANCE CHECKS