MULTIPLE LAUNCH ROCKET SYSTEM AND DEEP ATTACK MISSILE SYSTEM
Subcourse Number MM4806 EDITION A
Missile and Munitions
United States Army Combined Arms Support Command Fort Lee, Virginia 23801-1809
7 Credit Hours Edition Date: October 1990 SUBCOURSE OVERVIEW
The Multiple Launch Rocket System (MLRS) is a free-flight rocket system that provides a high-volume fire supplement to tube artillery. The Deep Attack Missile System uses most of the same equipment as the MLRS, but substitutes Army Tactical Missile System (ATACMS) missiles for the MLRS rockets to achieve increased range and accuracy against the deep threat. Both systems have sophisticated hydraulic, mechanical, electrical, and electronics subsystems that must be maintained in order to keep them in operation on the battlefield. As a missile maintenance supervisor, MOS 27B40, you may have to supervise maintenance on the MLRS or the Deep Attack Missile System.
This seven-lesson subcourse has been developed for those who are new to the MLRS and the Deep Attack Missile System and for those who desire a refresher. Lesson 1 describes the general characteristics of the MLRS, its major components, and its communications net. Lesson 2 covers the fire control system menus; the hydraulic, mechanical, and electrical assemblies of the launcher loader module (LLM); and other MLRS components. Lesson 3 provides preventive maintenance checks and services for the system. Lesson 4 presents troubleshooting and repair background and procedures for the LLM. Lesson 5 presents troubleshooting and repair background and procedures for the fire control system (FCS). Lesson 6 identifies the major components of the MLRS carrier and describes maintenance. Lesson 7 identifies the major components, supporting equipment, and testing of the Deep Attack Missile System.
There are no prerequisites for this subcourse.
This subcourse reflects the doctrine that was current at the time the subcourse was prepared. In your own work situation, always refer to the latest publications.
The words “he,” “him,” “his,” and “men,” when used in this publication, represent both the masculine and feminine genders unless otherwise stated.
TERMINAL LEARNING OBJECTIVE
Task: You will learn how to supervise maintenance on the MLRS and the Deep Attack Missile System. Conditions: You will have this subcourse book and will work without supervision.
Standards: You must make a passing score of 70% on the end-of-subcourse examination to receive credit for this subcourse.
*** IMPORTANT NOTICE ***
THE PASSING SCORE FOR ALL ACCP MATERIAL IS NOW 70%. PLEASE DISREGARD ALL REFERENCES TO THE 75% REQUIREMENT.
TABLE OF CONTENTS SUBCOURSE OVERVIEW, i
TERMINAL LEARNING OBJECTIVE, ii
LESSON 1: TACTICAL USE, MAJOR COMPONENTS, AND COMMUNICATIONS NET (Task 093-436-4086), 1
Tactical Use, 1 SPLL Firing Limits, 2 LLM Travel Limits, 3
SPLL Reloading Balance Limits, 4 Nearby Firing Area Limits, 4 Major Components, 6 SPLL, 7
Fire Control System, 13 Primary Power System, 13 Electronics Unit, 16 C3 System Net, 16 TACFIRE, 17
SPLL Communications Equipment, 17 Platoon Leader's Digital Message Device, 19 Fire Direction System, 20
REVIEW EXERCISES, 21
LESSON 2: FIRE CONTROL SYSTEM MENUS, ASSEMBLIES, AND SUBASSEMBLIES; TEST EQUIPMENT; AND THE TRAINER LP/C (Task 093-436-4086), 23
Fire Control System Menus, 23 Firing Menus, 23
Administrative and Maintenance Menus, 32
Hydraulic and Mechanical Assemblies of the LLM, 34 Hydraulic Assembly, 34
Primary Power Assemblies, 35 LLM Subassemblies, 35 LP/C Hold-Down Latches, 35 Travel Lock Actuator, 36 Limit Switches, 36 Boom and Hoist, 36
MLRS Rocket Subassemblies, 37 Propulsion Section, 37 Warhead Section, 37 Test Equipment, 38 Trainer LP/C, 39 REVIEW EXERCISES, 41
LESSON 3: PREVENTIVE MAINTENANCE CHECKS AND SERVICES (Task 093-436-4086), 45 Crew Level, 45
Loading, 46
Organizational Level, 47
Using the Extract from TM 9-1425-646-20, 47 Checking Other Items, 47
Direct Support Level, 56 The 125-Percent Load Test, 56 Pretest Inspection, 56
Test, 57
Post-Test Inspection, 58 REVIEW EXERCISES, 59
LESSON 4: TROUBLESHOOTING AND REPAIR PROCEDURES FOR THE LLM (Task 093-436-4086), 60
Elevation and Azimuth Mechanical Drives, 60 LDS Electrical and Hydraulic System Parts, 60 LDS Electrical and Hydraulic System Operation, 61 Troubleshooting and Repair of Drives, 64
Boom and Hoist Mechanism, 66 Boom Control, 66
Hoist Control, 67
Troubleshooting and Repair of Mechanism, 68 REVIEW EXERCISES, 69
LESSON 5: TROUBLESHOOTING AND REPAIRING THE FIRE CONTROL SYSTEM (Task 093-436-4086), 71
Position Determining System, 71 Multimeter, 71
Oscilloscope, 72 Cables, 72
Line Replaceable Units, 73
Azimuth and Elevation Transducer, 73 Elevation Transducer Assembly, 73 Azimuth Transducer Assembly, 77 Resolver Test, 78
Rotary Limit Switch Adjustment, 81 Switch Deck A Adjustment, 82 Switch Deck B Adjustment, 84 Switch Deck C Adjustment, 86 Misoriented Switch Adjustment, 89 Fault Isolation of Binding Gear, 96 Fault Isolation of Resolver Test, 90 REVIEW EXERCISES, 91
LESSON 6: MAINTENANCE OF THE MLRS CARRIER, M993 (Task 093-436-4086), 93 Simplified Test Equipment/Internal Combustion Engine, 93
Maintenance Duties, 93 Maintainability, 93
Mechanics of the Suspension System, 94 Circuitry, 94
Driver's Controls and Indicators Familiarization, 95 Preventive Maintenance Checks and Services, 113
LESSON 7: THE DEEP ATTACK MISSILE SYSTEM: MAJOR COMPONENTS, SUPPORTING EQUIPMENT, AND TESTING, 152
Major Components, 152
Missile and Missile Launch Pod/Container, 152 M270 Launcher, 152
Supporting Equipment, 161
Trainer Missile/Launch Pod Assembly 161 Guided Missile System Test Set, 164 Surveillance and Verification Test, 170 Pretest Operations, 170
Test Procedures, 173 Missile Maintenance, 175 REVIEW EXERCISES, 176 EXERCISE SOLUTIONS, 184
Lesson 1
TACTICAL USE, MAJOR COMPONENTS, AND COMMUNICATIONS NET
Task. This lesson is based on the following task from STP 9-27B14-SM-TG: 093-436-4086, Direct Support Maintenance on the Multiple Launch Rocket System (MLRS) and Associated Test Equipment.
Objective. When you have completed this lesson, you should be able to describe the major components of the MLRS, its general characteristics, and its communications net.
Conditions. You will have this subcourse book and work without supervision.
Standard. You must score at least 70 on the end-of-subcourse examination that covers this lesson and lessons 2, 3, 4, 5, 6, and 7.
TACTICAL USE
The MLRS is a highly mobile rocket launching system that can deliver a high volume of indirect fire against critical, time-sensitive targets in a short time. It is designed to supplement conventional artillery in the general support (GS) role by engaging medium-range targets. (Targets beyond the range of MLRS are to be engaged by tactical surface-to-surface missile systems; tactical aircraft; and, in some cases, off-shore conventional or missile fire.) One MLRS vehicle firing its on-board load of 12 rockets delivers 7,728 submunitions on the target. This is equivalent to three 8-inch guns in six batteries of a battalion firing three volleys.
When being used, the MLRS is in one of three areas of operation (figure 1-1), the firing area (or point), the reload area, and the hide area. The firing area is the location from which a mission will be fired. It can be a hasty position or one chosen in advance. The reload area is used to resupply the self-propelled launcher loader (SPLL) with ammunition. In figure 1-1, it is shown in the open. However, in use, it would be covered and concealed. The hide area is used for cover and concealment while the SPLL awaits a fire mission. It is generally close (50-100 meters) to a firing point.
When a fire mission is received over a digital radio link, the SPLL moves out of the hide area and travels to a firing site. The SPLL pulls into the firing site, parks, fires 1 to 12 rockets, and moves out within a matter of minutes. If all the rockets are used, the SPLL moves to a reload area for more ammunition. After reloading, the SPLL moves to a new hide area or to a second firing area, and the cycle is repeated. The SPLL is versatile and mobile, but it and the MLRS in general have certain operating limits that are discussed below.
Figure 1-1. MLRS in Action, Showing Areas of Operation. SPLL Firing Limits
The carrier cab, engine housing, and rocket blast all limit firing angles of the launcher loader module (LLM), and the fire control system (FCS) computes safe firing angles within these limits. Firing angles for the LLM make up a zone through which rockets can be fired safely (figure 1-2). Firing into a no-fire zone is prevented by a safety feature in the FCS.
LLM Travel Limits
The carrier bed, the engine housing, and the interconnecting cables limit LLM moment for safety. The FCS has programmed limits to control the LLM movement. In addition, the system has mechanical limit switches to shut off the launcher drive system (LDS) if the FCS limits (figure 1-3) fail. Thus, if an FCS limit is reached when the boom controller (BC) is used, reversing the control will move the LLM out of the limit. However, if a mechanical limit is reached, the LLM must be moved out of the limit manually.
SPLL Reloading Balance Limits
When loading or unloading full launch pod/containers (LP/C), SPLL balance is critical. There are particular LLM positions where the full LP/Cs must be loaded or unloaded one at a time (figure 1-4).
Figure 1-4. Balance Limits. Nearby Firing Area Limits
When a rocket fires, it produces flying debris, loud noise, and toxic gas from rocket propellant. There are areas near the SPLL where unprotected personnel could be injured (figure 1-5). Personnel, in these areas must be aware of safety limits.
The actual location of toxic propellant gas is determined by weather conditions at the firing site. Generally, unprotected personnel should be upwind of the SPLL. If downwind, personnel must wear nuclear, biological, and chemical (NBC) masks for maximum protection. In addition, the normal SPLL firing configuration is with two LP/Cs loaded in the LLM. The front of the LLM is designed so that the LP/C helps to keep rocket blast out of the LLM. For this reason, rockets can be fired only with two LP/Cs loaded in the LLM. If only one LP/C with live rounds is to be loaded and fired, a second, empty LP/C must be loaded in the opposite bay. See figure 1-6.
MAJOR COMPONENTS
The MLRS is made up of the SPLL, M270, which includes the LLM (M269) and the full-tracked carrier (M993) (figure 1-7); a command, control, and communications (C3) net that includes the fire direction system (FDS) in the
SPLL and the battery and battalion fire direction centers (FDC); and the platoon leader's vehicle (PLV) with the platoon leader's digital message device (PLDMD) (AN/ PGS-4) (X0-1). This subcourse is concerned with systems and components in the SPLL and some of those in the FDC and the PLV.
The ammunition resupply vehicle (RS), which is the heavy expanded mobility tactical truck (HEMTT) and the heavy expanded mobility ammunition trailer (HEMAT), are associated with the system but are not really a part of it. RSVs will not be covered in this subcourse.
SPLL
The SPLL has two assemblies, an LLM and a carrier.
LLM. There are three parts to the LLM, the cage, the turret, and the base. Loaded in the LLM are the LP/Cs with rockets.
The cage (figure 1-8) is a welded aluminum assembly with 14-mm aluminum armor plate on the top and sides. The cage aligns, holds, and protects the LP/Cs during all operations. It also supports the boom and hoist assemblies that make the MLRS self-loading.
The turret (figure 1-9) is an aluminum weldment that supports the cage assembly and attaches to the azimuth-drive, geared-bearing outer race. The turret houses the components of the elevation drive system.
Figure 1-9. SPLL Turret.
The base (figure 1-10) is a welded aluminum structure with a rectangular lower flange that provides the structural interface with the carrier. An upper circular flange bolts to the azimuth-drive geared bearing providing the interface to the turret. The base houses the major components of the hydraulic system and the azimuth drive
Figure 1-10. SPLL Base. Launch Pod/Container. The LP/C (figure 1-11) is made of six, filament-wound E-glass fiber launch tubes supported and accurately aligned by four cast-aluminum bulkheads. The support framework is a combination of aluminum angles and channels. As a result of logistics supply studies, the LP/C was designed as a low-cost throw-away item.
MLRS Rocket. The MLRS rocket (figure 1-12) is a tube-launched, fin stabilized, free-flight rocket. The rocket is 3.94 m (155 in) long, 227 mm (8.93 in) in diameter, and weighs 310 kg (682 lb). The complete rocket is assembled, checked out, and packaged in a dual-purpose launch/storage tube at the factory. This “wooden round” design provides for tactical load and fire of the rocket without troop assembly or check out.
Figure 1-12. Rocket.
MLRS Carrier. The carrier provides a highly mobile, fully tracked, lightly armored stable platform for the LLM. A pressurized cab is provided for a three-man crew (driver, gunner, and section chief). The cab design makes it possible for the crew safely and effectively to complete a fire mission from inside. The cab is protected by armor, has adjustable heating and ventilation, and attenuates noise. It hinges from the front, making maintenance easy. There is a cab-mounted fire extinguisher with one interior and one exterior release handle.
The driver's controls, such as gauges and warning lights, are grouped according to function and importance. They include warning lights that indicate a fire anywhere in the engine compartment.
Windows. A MLRS carrier crew has excellent forward and side vision through shatterproof windows. For added safety during launches, the front windows are fitted with exterior louvered covers, and the side windows have fold-down covers. During rocket firing and for nuclear survivability, each set of louvers can be opened or closed individually by actuator levers inside the cab. During a nontactical situation, the louvers may be stowed so the crew can see better and can clean the windshield. The overhead hatch, above the commander's seat, can be opened and used as a window for added visibility and crew ventilation.
Personnel Ventilation and Heating Systems. The personnel ventilation system is located in the left rear corner of the cab. It has a 5-micron dust filter, a 1-micron particulate filter, a charcoal filter, a bypass valve, and a fan. The bypass valve passes air through all three filters or through just the dust filter.
During normal operation the bypass valve is open, and the fan delivers 450 cfm of air through the dust filter. During rocket firing, the bypass valve is closed, and air passes through all three filters to remove toxic products from the rocket exhaust (except carbon monoxide, which is present at low concentrations). With the bypass valve closed, the system develops an overpressure of 1.2 inches of water and a flow of 150 cfm.
The cab also is equipped with M13A1 chemical, biological, and radiological (CBR) heater units and a dual-air personnel heater that recirculates cabin air.
Fire Control Unit. The FCU (figure 1-13) is at the aft end of the cage between the two LP/C bays. The area is covered by a hinged armor plate. The FCU is the main connecting link between the electronics of the FCS and the drive and monitoring equipment of the LLM. The FCU is the interface device that converts the information (such as switch position and resolver pick off) from the peripheral devices into information the electronics unit (EU) can use. Likewise, the EU computer words are converted by the FCU to information the peripheral devices can use.
Figure 1-13. Fire Control Unit. Functions performed by the FCU are: synchronizing digital data transfer to and from the stabilization reference package (SRP); providing azimuth and elevation drive signals to the servo motors; monitoring hydraulic “fluid over temp,” low fluid level, pump pressure, “motor over temperature,” and filter status; controlling LDS power through launcher drive contactors; communicating with the remote settable fuze (RSF) during fuze setting; and communicating with the boom controller (BC) when the BC is enabled.
Stabilization Reference Package/Position Determining System. The SRP/PDS (figure 1-14) is located at the rear of the cage between the LP/C bays, beneath the FCU. The SRP part of the system is an electrically driven device that orients itself on true North and makes a level platform for reference in computing fire mission data. The SRP is mounted on an accurately machined surface of the LLM cage that acts as the reference foundation for computing firing angles. To achieve SRP orientation, power is applied by the FCS during system start up procedures. During fire mission operations, signals from the SRP allow for launcher azimuth and elevation position corrections.
Figure 1-14. Stabilization Reference Package/Position Determining System.
Short/No-Voltage Tester. The SNVT (figure 1-15) is a built-in tester used during loading operations to test the umbilical cables to the LP/Cs. The test makes sure the cables are safe to connect to loaded LP/Cs. The SNVT is in the LLM and is protected by a cover that swings to one side when the SNVT is used.
Boom Controller. The BC in the LLM permits remote control of loading and off-loading. Fire Control System
The FCS is the heart of the MLRS operation. It is the interface between the crew, the fire direction center, and the on-board weapon system. It is the means by which the crew operates and controls the SPLL. The FCS enables the crew to execute fire missions accurately, easily, and safely. It is an electronic system of the SPLL, designed specifically to give the Army field commander easy access to, and control of, the SPLLs fire power.
The FCS is simple to operate under high-stress combat conditions. It accepts tactical fire mission assignments from the battery FDS, computes firing data, aims the launcher, and prompts the crew to fire the rocket, all automatically and in real time.
The fire control panel (FCP) (figure 1-16) in the carrier provides the crew with a visual display and push-button and switch control of the FCS; it also provides line replaceable unit (LRU) bit display and built-in test equipment (BITE) status via the plasma display.
Figure 1-16. Fire Control Panel. Primary Power System
The primary power system (PPS) (figure 1-17) is the source of electrical power for SPLL equipment. The system consists of the battery box, electronics box, power distribution box (PDB), and connecting power cables.
The Battery Box. The battery box contains six military standard, lead-acid 12-V batteries. Four of the batteries are connected in series/parallel to provide ±24 V power to the high-current launcher drive system (LDS) electric motor. The remaining two batteries, connected in series and electronically isolated from the four LDS batteries, provide power to the low-current electronic equipment.
Electronics Box. The electronics box (EB) is attached to the battery box. The carrier's batteries and generator are connected to the SPLL batteries in the EB. This interconnection permits the use of the carrier batteries to operate the SPLL and the use of the SPLL batteries to be charged by the vehicle's alternator. The interconnection is controlled by the carrier's launcher interconnect switch in the carrier cab. The carrier and SPLL electrical power systems are protected to prevent a fault in one system from affecting the other system. From the EB, the output of the two-battery hook-up is supplied to the FCS and to some of the communication equipment. The output of the four-battery hook-up is supplied to the PDB and the launcher drive system (LDS) contactor. The LDS contactor is a relay with contacts large enough to carry the high current needed to operate the hydraulic power supply motor. The contactor is actuated by a signal from the FCS.
Power Distribution Box. The power distribution box (PDB) (figure 1-18), mounted on the right rear of the LLM, is the main distribution point for electrical power to the SPLL systems. The PDB also distributes command signals to some of the SPLL systems.
Electronics Unit
The EU is the forward end of the carrier bed and is mounted under the cage assembly (figure 1-19). It receives and processes mission data and performs the computer function of the FCS. Input to the EU is made by either the FDC through the communication equipment or by the crew using the FCP keyboard.
The EU performs all the mathematical operations required for the solution of the ballistic equations. It stores, processes, controls, and displays the coding format, and it transmits digital data on the data link.
The EU, along with the communications system, receives messages from the FDS digital RF communication link. Types of messages received include: tactical fire control data, rocket fuze setting data, meteorological data, firing point location, warhead type, number of rounds, time to fire, and target location data.
The EU has a 128 K memory. This memory is divided into three units. Memory 1 contains 96 K words of programmable read-only memory (PROM), memory 2 is made up of 16 K words of random access memory (RAM), and memory 3 contains 16 K words of nonvolatile RAM.
Figure 1-19. Electronics Unit. C3 SYSTEM NET
The three principle elements of the MLRS communications net are the SPLL, the PLDMD in the PLV, and the battery FDC's computer. The MLRS C3 net interfaces with its higher command level C3 network through either a
battalion-level tactical fire direction system (TACFIRE) or a battalion-level FDS. The system used depends upon the MLRS unit of assignment, which is either a composite artillery battalion or a pure MLRS battalion. Tactical fire control for an MLRS battalion is provided by the battalion fire direction center (FDC), which is equipped with an FDS and interfaces with a field artillery brigade.
TACFIRE
Tactical fire control for an MLRS battery assigned to a composite artillery battalion is provided by the organic battalion-level TACFIRE, which interfaces with the division artillery TACFIRE. Technical fire control for all MLRS firing sections is provided by the SPLL onboard fire control system computer interfacing with the battery level FDS.
SPLL Communications Equipment
The SPLL uses a military standard AN/VRC-47 radio set. Three tactical vehicle intercom units are connected to the system through an AM-1780 audio amplifier. These are mounted in the vehicle crew compartment (figure 1-20). Digital messages are received by the RT-524 and sent to the FCS through a communications processor. The processor converts incoming frequency shift key (FSK) audio-pair signals to digital bit data and transmits them to the SPLL FCS; it receives data as well.
Figure 1-20. SPLL Communications Equipment. Mission input information to the FCS can be both automatic and manual (figure 1-21). Automatic inputs are received over the SPLL radio. Manual inputs can be voice instructions received over the radio or written information on the FCP. The SPLL radio system is equipped with a communications processing unit
Figure 1-22. Communications Processor. Platoon Leader's Digital Message Device
The PLDMD is a compact, portable, two-channel digital terminal (figure 1-23). When linked by standard radio or wire, this terminal receives, composes, displays, stores, and transmits digital messages. The PLDMD can act as a relay between FDC and SPLLs, can link with TACFIRE on a limited basis, and can act as a degraded FDC if the FDC fails. The PLDMD is used primarily by the MLRS platoon leader to monitor transmissions to and from the three SPLLs in the command. The PLDMD weighs less than 10 lbs and measures 11 x 8 x 4 in.
Fire Direction System
The MLRS uses a battery computer unit (BCU), which is called the FDS in the MLRS, for fire direction at the battery level and at the battalion level for the MLRS (27-launcher) battalion. The FDC is made up of FDS with MLRS-peculiar software, COMSEC equipment, and standard military radio equipment mounted in an M577 vehicle (figure 1-24).
The FDS provides tactical fire control and is linked with the SPLL on-board computer, TACFIRE, and the PLDMDs. The FDS accepts fire mission requests from higher headquarters, selects the battery/SPLL to fire (dependent upon battery or battalion FDC use), and transmits necessary data, such as meteorological data (MET) and target (TGT).
REVIEW EXERCISES Circle the letter of the correct answer to each question.
1. Which assembly of the MLRS houses the major components of the hydraulic system? a. Turret assembly.
b. Base assembly. c. Cage assembly. d. Boom assembly.
2. Which box of the MLRS provides the interface between the carrier electrical system and the primary power system (PPS)?
a. Battery box.
b. Power distribution box. c. Electronics box. d. LDS contactor box.
3. Which of the following positions is within tolerable limits for loading one full LPC at a time into the cage?
a. 1,600 mils. b. 3,200 mils. c. 90 mils. d. 400 mils.
4. Which radio set does the SPLL use? a. AN/VRC-47.
b. AN/VRC-46. c. AN/VRC-13. d. AN/VRC-22.
5. Which component of the MLRS receives and processes mission data? a. Electronics box.
b. Electronics unit. c. Fire control panel. d. Fire control unit.
6. The short/no-voltage tester (SNVT) is a built-in tester used during what operation? a. Loading.
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 two or more questions, you should retake the entire lesson, paying particular attention to the areas in which your answers were incorrect.
Lesson 2
FIRE CONTROL SYSTEM MENUS, ASSEMBLIES, AND SUBASSEMBLIES; TEST EQUIPMENT;
AND THE TRAINER LP/C
Task. This lesson is based on the following task from STP 9-27B14-SM-TG: 093-436-4086, Direct Support Maintenance on the Multiple Launch Rocket System (MLRS) and Associated Test Equipment.
Objective. When you have completed this lesson, you should be able to describe the operation of the FCS and MLRS assemblies, subassemblies, trainer LP/C, and ancillary equipment.
Conditions. You will have this subcourse book and work without supervision.
Standard. You must score at least 70 on the end-of-subcourse examination that covers this lesson and lessons 1, 3, 4, 5, 6, and 7.
FIRE CONTROL SYSTEM MENUS
You need to know the detailed operation of the system's menus because you and your repairers use them for calibration, repair, and verification of repair. Running these menus is the only self-test the system has.
Firing Menus
Starting Up. Ensure that communication equipment and arm and fire switches are off. Set master power switch on. Set launcher interconnect switch on. Turn on fire control panel system power. When ensure language prompt appears on the display screen, select appropriate language prompt, and press execute.
Inputting Start-Up Data. The next prompt that will appear after execute is pressed will be the index menu. From this menu, select option zero (0), which is the start-up data menu. The start-up data selection field is displayed. Select the system start up, option number zero (0), and press store.
The first field in the system start-up routine is the easting field (part of determining position). The location coordinates entered for this field are the present location of the SPLL at the time of start up. Enter the easting numbers written on your SPLL start-up data card (figure 2-1) and press store.
The northing, altitude and grid zone are all inputted the way the easting was. Once all the inputs are stored, the next prompts will appear. They are giving you the status of the rocket.
The last field requires time input. Once this is complete, the next prompt tells you the SRP is aligning and how long it will take. The displayed time counts down until the SRP is aligned. The maximum time you can have is 8 minutes.
During SRP alignment, press index and select start up data. When the start up data menu appears, select the communications start up option, which is 1, and press store. Once store has been pressed, the prompt on the display screen changes.
There are 32 fields in the communications start up. The only fields used are fields 1 through 25. All information to be inputted is taken off of the MLRS SPLL start-up data card. For each field, enter the appropriate number and press store. All fields are entered in the same manner. Upon completion of the communications start up, the next prompt will be either SRP aligning--time-to-go or SRP ready.
Inputting PDS Data. In order to gain access to the PDS, start up from the last prompt with the index key. This displays the index menu again. Select start up data, option zero (0). On the new display, notice that PDS start up is option 2. Press number 2 and store keys.
The first field to be seen is the odometer scale factor. The numbers for input are found on the MLRS SPLL start-up data card. Entries for azimuth crab angle and elevation crab angle are inputted the same.
Inputting Fire Mission Data. Press the index key for the index menu to be displayed. From the index menu, select the auxiliary menu, option number 8. Press execute. The auxiliary menu will be displayed, and, from it, select the fire-mission routine, option number 4. Press execute key. The first field in the fire mission routine will be displayed. The target number is for editing only. There is no input for this field. To get the next prompt, press next field. (This also pertains to move easting, move northing, and move grid zone.) Once next field is pressed, the first prompt seen is warhead. All
information needed for input of fire mission data is obtained from the SPLL tactical fire mission data card (figure 2-2). Each field is self explanatory and all information is inputted the same way.
Following Firing Sequence. The entries for manual fire mission have now all been inputted, and the first prompt in the fire mission routine is displayed.
Press initiate when the crew has parked the vehicle at the appropriate heading. The next prompt appears at the same time the fire control system calculates all fire mission data.
When LCHR LAY (launcher lay) is pressed, the fire control system recalculates fire mission data, then unlocks the travel locks. The LLM elevates to 302 mils, then traverses left or right to the first firing point. When movement stops in azimuth, the LLM elevates or depresses to the first firing point. When the degrees of both azimuth and elevation are correct, after a few seconds, the display adds one line, arm rockets. The operator flips the toggle that arms the rocket. The system sets the fuze of the rocket, and the display adds another line, fire rockets. The operator now flips the toggle switch that fires the rocket.
Closing Down. When the fire mission is complete, the next prompt tells the crew to stow LLM. When LLM stow is pressed, the LLM starts to move to the stow position. When the LLM is stowed, the LLM stowed prompt appears. The fire mission is complete, and the crew moves the system to the reload area.
Administrative and Maintenance Menus
Index. The index menu initially has five menus that are functional when power is first applied. After SRP has aligned, the index menu increases its memory to 10 functional menus (adds five).
Rocket Status. When this menu is called up, it shows the status of all rockets.
D = Dud = Good
Blank Space = Fired H = Hangfire
Update PDS. This menu is called up when the PDS is to be updated or calibrated by the crew
HYDRAULIC AND MECHANICAL ASSEMBLIES OF THE LLM Hydraulic Assembly
The hydraulic system assembly is a power supply that is in three sections as follows (figure 2-3): Reservoir. This is the container for the hydraulic fluid supply.
Hydraulic Pump. The MLRS system uses a Vickers radial piston pump with nine pistons. The pump also has two, 5-micron filters.
Electric Motor. The MLRS hydraulic motor is a constant displacement, seven-radial piston motor controlled by electrical servo motors.
Figure 2-3. Hydraulic Assembly. Mechanical Assembly
Azimuth and Elevation Servomotors. The azimuth (AZ) and elevation (EL) servomotors are the same, but they are not interchangeable because they are bolted to their transmissions. The motor is a seven-piston, constant-displacement, electrical-valve-controlled motor. The servomotors provide the interface between the hydraulic and mechanical components.
Elevation Angle Drive. The elevation angle drive is a fixed-displacement, bidirectional, radial-piston motor. Incorporated in the motor are a series of relief and check valves to control internal hydraulic fluid flow during
Azimuth Drive. The azimuth drive is the same as elevation angle drive except that it is not interchangeable. Elevation Actuators. The elevation actuators are mechanical devices that raise or lower the cage. They are connected to the elevation angle drive by drive shafts.
Speed Reducer. The speed reducer is geared for a low traversing ratio. It can be operated hydraulically or manually by a flex cable. The speed reducer allows for smooth operation of the cage assembly when traversing left or right.
PRIMARY POWER ASSEMBLIES
Battery Box. The MLRS battery box (BB) houses six lead acid batteries. The fire control system uses two batteries connected in series to provide ±24 V of low amperage. The launcher drive system uses four batteries connected in series and parallel combined to provide continuous -24 VDC high amperage. The batteries are charged by the vehicle charging system.
Electronics Box. The electronics box (EB) is attached to the BB. It relays voltage to the rest of the system. Power Distribution Box. The power distribution box (PDB) distributes the high amperage to the left and right booms, the left and right hoists, and the hydraulic system.
LLM SUBASSEMBLIES LP/C Hold-Down Latches
The two LP/C hold-down latches are hand-operated and hold the LP/Cs in place inside the LLM cage. The LP/C hold-down latches are operated from the rear of the LLM (figure 2-4). The MLRS repairer is responsible for adjusting the latches.
Travel Lock Actuator
The travel lock actuator (figure 2-5) is the mechanism that locks or unlocks the transport locking system. If there's an electrical failure, the actuator can be manually locked or unlocked. Its main purpose is to secure the cage while in transport so damage does not occur to the LLM and its assemblies.
Figure 2-5. Travel Lock Actuator. Limit Switches
The limit switches (figure 2-6) prevent the system from overtravel, which could cause damage. The 1.25°, 15°, 27°, 62.2°, 73°, 106°, and 196° limit switches prevent damage to the SPLL while it is in elevation or azimuth movement. The boom-out limit switch keeps the booms from extending beyond their limits.
The boom-in limit switch keeps the boom from damaging other components in the cage when the boom is retracted. The hoist limit switches keep the hoist motor from winding the cable too tightly or from letting all the cable out of the hoist drum. The cage down limit switch sends a signal through the FCS to lock the cage.
Boom and Hoist
The boom-and-hoist assembly is a telescoping beam, hoist carriage, and a hoist. Each boom has two outer fixed beams and two telescoping beams. The booms are extended and retracted by a pair of ball screw actuators attached to the telescoping beams and driven by an electric motor. Note: Remember that the hoist carriage assembly moves twice as fast as the telescoping beam. The hoist carriage is made up of the hoist control box and the hoist motor/drum assembly. Manual drive inputs are provided for both the booms and hoists in case there's an electrical failure.
Figure 2-6. Limit Switches. MLRS ROCKET SUBASSEMBLIES
Propulsion Section
The MLRS rocket propulsion section is a solid-propellant rocket motor. The rocket motor uses hydroxyl terminated polybutadine (HTPB) solid propellant, which is molded to the inner wall of the motor skin. Two spin lugs and two rider buttons interface the aft end of the rocket motor with spin rails on the launch tube interior wall. The spin rails initiate a 10-12-revolutions-per-second, counterclockwise spin for the missile's flight stability. Warhead Section
There are two warheads that can be used. One delivers M77 submunitions and the other delivers German-developed AT-2 mines (figure 2-7).
M77 Submunitions. Six hundred forty-four individual M77 munitions are packaged end-to-end in a honeycomb matrix around a centered, lead-lined, warhead burst charge. Four V-shaped grooves help split the warhead's aluminum shell. These grooves are cut along the entire length of the warhead's outer surface.
Figure 2-7. Contents of Warhead. TEST EQUIPMENT
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.
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. b. Four c. Six. d. One. e. Three. f. Five.
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 AND SERVICES
Task. This lesson is based on the following task from STP 9-27B14-SM-TG: 093-436-4086, Direct Support Maintenance on the Multiple Launch Rocket System (MLRS) and Associated Test Equipment.
Objective. When you have completed this lesson, you should be able to describe the proper preventive maintenance checks and services (PMCS) for the MLRS at the crew, organizational, and direct support levels. Conditions. You will have this subcourse book and work without supervision.
Standard. You must score at least 70 on the end-of-subcourse examination that covers this lesson and lessons 1, 2, 4, 5, 6, and 7.
CREW LEVEL
For each check or service, you will find what indicates the fire control system or launcher loader module is NOT ready to be used. The list is taken from TM 9-1425-646-10. Make sure all cautions, warnings, and other safety measures are followed.
Travel Lock Hooks. Travel lock hooks are not fully under rollers, and actuator is extended.
Hydraulic Lines and LDS Components. Any hydraulic line or component has a class III leak. For a definition of a class III leak, look ahead to Checking Other Items in this lesson. The definition is under the heading: Hoses and Fluid Lines.
System Start Up. SRP aligning, timing-to-go prompt, or start-up complete, SRP ready prompt is not displayed. Communications processor does not accept overhead message and inconsistent communications data error prompt is displayed.
Communications Check. Messages cannot be sent. Communications processor sends a communications processor message back to the FCS and causes a no response or an invalid serial number prompt to be displayed when you try to send a message.
Loading.
The LDS does not come on and move LLM to loading position selected. Any fault prompt is displayed.
There are broken, bulging, or kinked strands (will foul hoist pulleys and interfere with hoist operation). SPLL is not able to load or unload LP/Cs from either bay.
SNVT light or either the left or right umbilical test no go light comes on. LP/C in either bay cannot be latched in place.
PDS Update. Any SPLL location data (easting, northing, or altitude) is in error by more than 85 meters after traveling 6-8 kilometers with loaded LP/Cs. PDS data bad prompt is displayed while SRP/PDS is turned on. Radio Antennas. Antenna or antenna mounting base is damaged. Antennas have heavy rocket motor exhaust deposits that stop or interfere with the ability to send or receive messages.
Umbilical Cables. Cable connector adapter has broken or damaged pins. Cable connector adapter key or guides are badly worn and can keep cable from making proper connection.
Hoist Assembly. Neither hoist assembly is able to load or unload LP/Cs. Hoist pulley assembly cannot be positioned to M26 position.
Hydraulic Fluid Level. Fluid level indicator red band is at or below the refill mark.
Heat Exchanger. There is something stopping or interfering with the air flow, and it cannot be removed.
Azimuth Drive and Elevation Angle Drive. Any component has a class III leak. For a definition of a class III leak look ahead to Hoses and Fluid Lines.
Elevation Actuator Gear Housing. Actuator gear housing has a class III leak with a leak rate more than three drops per minute.
Batteries. Batteries are cracked or broken, or terminals are loose. Hoist Cables. A cable has a broken strand, bulge, or kink.
Limit Switches. The limit switch on the plunger does not operate properly. ORGANIZATIONAL LEVEL
Using the Extract from TM 9-1425-646-20
The order of your repairers inspection and checks are numbered in the item column in the following extract, figure 3-1. Do them in the order shown. This is the same number that you will enter in the TM manual column of DA Form 2404.
Each item to be inspected includes instructions for correcting problems you may find. These instructions might refer you to the next higher maintenance level or refer you to a maintenance or troubleshooting paragraph in the TM. Sometimes the instructions are how you can correct the problem yourself. You must record on a DA Form 2404 all the deficiencies that you find during PMCS.
If you correct the deficiency, record your corrective action on DA Form 2404. Any deficiency that you cannot correct you must report to next higher maintenance level on a DA Form 2407. For complete instructions on filling out forms, refer to DA Pam 738-750 (not necessary for this subcourse).
Checking Other Items
The following are common items that are not shown on the PMCS table. They do need to be checked ahead of time, however, because they are basic and essential to the continuing operation of the MLRS.
Bolts, Nuts, Screws, Clamps. If any are loose, tighten them.
Welds. Look for chipped paint, rust, or gaps where parts were welded together. Touch up chipped paint. Clean rust and repaint. Notify next higher maintenance level of broken welds.
Electrical Cables and Connectors. Look for cracked or broken insulation, bare wires, and loose or broken connectors. Tighten loose connectors. Notify next higher maintenance level of damaged wiring or connectors.
continue to check the hydraulic fluid level in the reservoir. You can expect some leakage from certain seals and weep holes in LDS components. The azimuth and elevation drive motors and the hydraulic power supply will have class III leaks at their seals, which drain into their scavenge reservoirs. No other class III leak is permitted. Check for leaks and bent or damaged lines. Tighten loose connectors. Notify next higher maintenance level of broken or damaged lines or of connectors that continue to leak after being tightened. The definitions of class I, II, and III leaks are as follows:
Class I - Seepage of hydraulic fluid (as indicated by wetness or discoloration) not great enough to form drops.
Class II - Leakage of hydraulic fluid great enough to form drops but not enough to cause drops to drip from item being checked or inspected.
Class III - Leakage of hydraulic fluid great enough to form drops that fall from the item being checked or inspected.
Paint. Check for chipped paint. Touch up paint where it's required.
In the following extract from TM 9-1425-646-20, figure 3-1, there may be other TMs or appendixes referred to. Since you do not need them to complete this subcourse, they have not been included.
DIRECT SUPPORT LEVEL
At the DS level, the MLRS repairer uses both TM 9-1425-646-10 and -20 manuals to perform PMCS on operational readiness float equipment.
THE 125-PERCENT LOAD TEST
At organizational and DS levels, the repairer also performs an annual PMCS test that is particularly important, especially after repair of the hoist or boom assemblies: the 125-percent load test.
Pretest Inspection
Perform SPLL start-up procedures, and drive the SPLL to the place where the test loads have been prepositioned. Place the SPLL so the loads may be picked up from 1,600 mils (90°) azimuth position. Using the fire control panel, position the LLM to 1,600 mils. Engage the suspension lockout and enable the boom controller. Go to the rear of the LLM, and remove the BC from the storage compartment at the left rear of LLM as follows:
Release both latches on BC storage compartment door, and swing door open. Unfasten strap holding BC in holder inside the door, and carefully remove BC from the holder on the door. Remove and uncoil the BC cable.
On the BC, select “both position” on the boom/hoist selection switch, then extend both booms. Traverse the LLM until the hook-and-pulley assemblies, when lowered, will clear test loads. Lower both hook-and-pulley assemblies while making sure the cable is operating smoothly and without slack.
Inspect both cables by lifting the cable off the pulleys in the hoist carriage and the hook-and-pulley assemblies. Examine pulleys for rim nicks that might cut the cable and for other damage. Spin pulleys to verify that they turn freely. Examine the hook lock mechanism for damage and proper operation. Using the BC, raise both hook-and-pulley assemblies until they clear the test loads. Traverse the LLM until the hook-and-pulley assembly for one boom is directly above test-load lifting bar.
Test
Using the BC, lower one hook-and-pulley assembly and attach it to the test load.
After making sure all personnel are clear of the test load, raise the test load about 1 ft (1/3 m) off the ground. Hold the test load in this position for 30 sec while observing the cable for evidence of slippage. Using the BC,
Reposition the SPLL to a position to load the test loads from 3,200 mils (180°) azimuth. Position LLM to 3,200 mils. Engage the suspension lockout.
Using the BC, extend both booms. Lower the hook-and-pulley assemblies, one at a time, while making sure the cable runs smoothly. Attach the hook-and-pulley assemblies to the test loads, and clear all personnel from the test area. Raise both test loads together until the hoist-up limit switch stops the operation. Hold both of the test loads in this position for 30 sec while observing the cables for any evidence of slippage and the cage-to-turret gap.
With one hand placed on the side of the cage, use the BC to rotate the cage in either direction about 36 mils (2°), and make sure that the cage stops moving promptly when you release the BC switch.
Using the BC, lower the LLM to the horizontal position. Then lower the test loads and disconnect the hook-and-pulley assemblies from the test loads.
Post-Test Inspection
Using the BC, raise both hook-and-pulley assemblies enough to clear the test loads. Traverse the LLM until the hook-and-pulley assemblies clear the test loads, then lower the hook-and-pulley assemblies. Inspect the hoist cables and pulleys and the boom structures for warped or bent beams. Using the BC, raise the hook-and-pulley assemblies, retract both booms, and stow the cage. If the SPLL has passed, stencil the date of the test on the upper left forward side of the cage.
REVIEW EXERCISES Circle the letter of the correct answer to each question.
1. What is the class and leakage of hydraulic fluid that is great enough to form drops but not great enough to drip from item being checked or inspected?
a. IV. b. II.
c. I.
d. III.
2. The order of the inspection and checks should be according to which of the following? a. The DA Form 2404.
b. What you first find wrong. c. The order in the TM.
d. The first interval given in the TM.
3. Replace the EU if the azimuth resolver indication on the FCP is not between which figures in item V? a. -1325 and -1334.
b. -1335 and -1345. c. -1324 and -1334. d. -1334 and -1345.
4. The test load has been raised 1 foot off the ground. How many seconds must the test load be held in this position?
a. 15.
b. 25.
c. 20.
d. 30.
5. Before starting travel limit switch checks, make sure that, with the LLM in stow, the elevation resolver indication on the FCP is how many mils?
a. -1 to +1. b. -3 to +3. c. -4 to +4. d. -2 to +2.
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 two or more questions, you should retake the entire lesson, paying particular attention to the areas in which your answers were incorrect.
Lesson 4
TROUBLESHOOTING AND REPAIR PROCEDURES FOR THE LLM
Task. This lesson is based on the following task from STP 9-27B14-SM-TG: 093-436-4086, Direct Support Maintenance on the Multiple Launch Rocket System (MLRS) and Associated Test Equipment.
Objective. When you have completed this lesson, you should be able to describe the proper troubleshooting and repair procedures for the elevation and azimuth mechanical drives and for the boom and hoist mechanisms in the LLM.
Conditions. You will have this subcourse book and work without supervision.
Standard. You must score at least 70 on the end-of-subcourse examination that covers this lesson and lessons 1, 2, 3, 5, 6, and 7.
ELEVATION AND AZIMUTH MECHANICAL DRIVES
The elevation and azimuth mechanical drives are part of the launcher drive system (LDS) and are run electrically and hydraulically. Other parts include the hydraulic power supply, the servomotor, valve assemblies, and related electronics components. The related electronics components, the LDS contactors, give the LLM movement. The azimuth mechanical drive includes the speed reducer and the geared bearing. The elevation mechanical drive includes the transmission/brake angle drive unit, propshafts, and actuators.
If the drive systems fail, the crew will not be able to position the cage manually to fire the rockets. The MLRS repairers you supervise are responsible for isolating malfunctions in the system in forward areas as members of direct support contact teams.
LDS Electrical and Hydraulic System Parts
LDS Electric Motor. The LDS motor is a 12.1 hp, ±18-28 VDC motor, rated 4,000 rpm at ±21 VDC. Steady-state power consumption is 12 kW. The motor drives the hydraulic pump to provide pressure to the azimuth and elevation servo valves. The motor is controlled by the LDS contactor and limit switch system.
LDS Contactor. The contactor is a large power relay with contacts that can carry the high-current demands of the LDS electric motor (1,650-amp surges). The contactor is actuated by the FCS-generated command, LDS ON CMD, from the FCU. The limit switch system can interrupt current to the contactor.
Limit Switch System. The LDS limit switch system is made up of single-pole switches connected in series with the LDS contactor circuit. They interrupt LDS power if the FCS fails to control LLM movement. The switches can be actuated mechanically if the LLM moves into positions that would cause damage to any MLRS system mechanical or electrical component.
Azimuth and Elevation Servo Valves. These are electrically operated valves controlled by command signs from the FCS. They direct hydraulic pressure to the azimuth and elevation servo motors.
Elevation Pressure Regulator. This is a solenoid-operated valve that reduces pressure to the elevation servo valve during the last 35 mils of down movement during stow. It prevents damage to mechanical actuators and is controlled by FCS command signals.
Azimuth Freewheel Solenoid. This is another solenoid-operated valve that removes hydraulic operating pressure from the azimuth servo valve for the last 35 mils of down movement during stow to prevent damage to the cage centering probe. It is also controlled by FCS commands.
Azimuth and Elevation Resolvers. The azimuth and elevation resolver are position indicator devices used during stow and reload to provide servo loop closure to the FCS. The resolver shafts are coupled by gear train to the LLM's azimuth and elevation mechanical axes. They are adjusted when they are installed on the carrier cab and bed and are 0 mils when the LLM is stowed. The FCS supplies an AC, 400-Hz, 18-V signal on the resolver S1 and S3 terminals. This voltage is induced on the R1 to R4 windings and is determinate in phase and amplitude to the direction and amount of movement of the resolver shaft. The resolver position output from R1 to R4 windings is convened to digital position data by an R/D converter and is supplied to the FCS as servo loop feedback. The resolvers are also used to back up the SRP/PDS position signals to the FCS during firing. The two position signals are compared and, if they do not match within ±5 mils, generate a fault message.
Cage Transport Latch Actuator. This is an electric motor-driven screw jack used to lock and unlock the transport latch, which secures the cage for travel. It is controlled by command signals from the FCS.
Boom Controller. This is a hand-held remote switch box used to control LLM and boom and hoist movement during reloading and maintenance.
Hydraulic Heat Exchanger. This is a simple oil-cooler device that uses a fan-cooled radiator through which the return hydraulic fluid is routed. The heat exchanger fan circuit is connected with the LDS electric motor in parallel and runs whenever the LDS motor is on.
LDS Electrical and Hydraulic System Operation
Prefire. During tactical fire mission operations, after the crew has moved the SPLL to the designated firing point and has parked within the proper azimuth and slope limits, the fire control panel displays a prompt, when parked press INIT. After INIT is pressed, the prompt, to continue mission press LCHR lay, is displayed. When the launcher lay key is pressed, the fire control system initiates the necessary commands to unlock the LLM cage and move it to the firing azimuth and elevation.
The fire control unit issues a cage unlock command to the PDB. This command provides a return for the cage unlock (K4) relay in the PDB. The +24 VDC goes from the positive bus of the PDB to the transport latch actuator retract circuit via PDB connector J3, pins R and J. Return is via PDB connector J3, pins T and H. When the actuator completes its travel, a limit switch in the actuator opens the retract circuit and closes the LDS relay +24 VDC connection from the actuator limit switch to the LDS on relay X1 pole via pin N of the PDB J3 connector The cage unlock signal is also routed to the FCS via PDB connector J1, pin 72, to the FCU as a signal that the cage is unlocked.
The FCU then issues an LDS on command to the PDB to provide a return for the LDS on relay K2. When PDB K2 closes, +24 VDC is provided to the X2 anode pole of the LDS contactor relay via PDB connector J4, pin 23, and the limit switch circuitry.
The LDS limit switches are connected in a series-parallel combination, with the +24 VDC routed to the LDS contactor relay from the PDB K2 relay. The limit switch system interrupts LDS power if the LLM moves into azimuth or elevation angles that would damage the SPLL mechanical components. Movement of the LLM is controlled by software in the FCS. The limit switch system functions only if the FCS fails to control the LLM. There are four azimuth limit switches. Three of these are in the azimuth position transducer assembly (they have limits of 73°, 106°, and 196°). The remaining azimuth limit switch (1.25°) is on the turret and is actuated by a cam on the base assembly.
There are also four elevation limit switches. Two, 15° and 27°, are mounted on the right rear hinge point of the turret and are operated by cams on the cage. The other two are right and left 62.2° switches and are inside the elevation (ballscrew actuators).
From the stowed position, the 1.25° azimuth limit switch limits azimuth movement until the cage has been elevated to at least 15°. This is to allow clearance between the front of the cage and the carrier cab and engine components. When the cage has been traversed to 73°, the 15° minimum elevation limit is bypassed. After 106°
in azimuth has been reached, elevation is limited to a maximum of 27° to prevent interference between the rear of the cage and the carrier's components. The 196° azimuth switch prevents azimuth movement past that point to protect the electrical cables that interface the base with the turret and cage. The ballscrew actuator 62.2° limit switches keep the actuators from extending to the mechanical limits that damage the actuator.
The return for the K2 relay is by the PDB connector J4, pin 24. When the contactor relay closes, +24 VDC from the batteries pass through the resistor contacts to the LDS motor for 50 msec only, because there's a time delay device in the relay. This delay allows the rest of the circuit to initiate. The resistor circuit is necessary to limit surge current to 1,650 amp. When the time delay is over, the battery-direct contacts route battery current directly to the motor through the M terminal. The LDS motor then runs, driving the hydraulic pump that, in turn, creates operating pressure levels after about 1 sec. Afterwards, the FCS reviews the built-in test (BIT) for LDS.
The LDS built-in test equipment (BITE) is six sensor switches installed in the hydraulic power supply components. They monitor: hydraulic pump
pressure, reservoir fluid level, hydraulic fluid temperature, hydraulic fluid filter cleanliness, and the electric motor brush temperature. The sixth sensor is installed in the elevation valve module to monitor elevation hydraulic pressure when the LLM is stowed.
Abnormal LDS conditions actuate the sensor switches and provide a malfunction display on the gunner's fire control panel. All prefire activity stops until the malfunction is fixed.
If the BIT finds nothing wrong, the FCS will issue an elevation signal from the FCU to the elevation servo valve through the PDB connector J1; pins 46, 47, 48, and 56; and through PDB connector J4; pins 3, 4, 25, and 26. The signal will be software controlled to elevate the LLM to 310 mils (±8 mils). During this initial elevation, the LLM reference angle comes from the azimuth and elevation resolvers, and the azimuth position is maintained at 0 mils (±2.5 mils). Once elevation has been achieved, the FCS commands azimuth movement of the LLM to the firing azimuth through PDB connector J1; pins 49, 50, 51, and 52; and connector J4; pins 27, 28, 29, and 30; to the azimuth servo valve. The FCS then commands the LLM to the firing elevation through a reiteration if it has not already been achieved. During the final firing alignment, the LLM angle reference is supplied by the SRP/PDS. If an arm command is not issued to the crew and acted upon within 10 sec after the aim point has been reached, the FCS shuts the LDS down by removing the LDS on command. When an arm command is issued and the arm switch set to arm, the LDS is powered up and remains active until all selected rockets are fired.
Fire. During firing the FCS monitors the LLM's position, using SRP reference signals. It also issues appropriate azimuth and elevation commands to the servo valves in order to maintain the aim point.
Postfire. After firing is completed, the FCP prompts the operator to stow the LLM. When the stow button is pressed, the FCS issues the appropriate servo valve signals to, first, position the LLM to 310 mils (±8 mils) in elevation and, second, to 0 mils azimuth (±2.5 mils). This angle reference comes from the azimuth and elevation resolvers during stow, and it is backed up by the SRP. After it gets to the proper azimuth, the FCS lowers the LLM with commands to the elevation servo valve.
When the LLM reaches 35 mils (±5 mils), the FCS issues a hydraulic regulator and bypass command from the FCU to PDB connector J1, pin 54. This closes the PDB relay K1, supplying +24 V to the freewheel solenoid and +24 V to the elevation regulator solenoid on PDB J4 connector, pins 1 and 14. Return is by J4, pins 2 and 15. When the azimuth freewheel solenoid energizes, hydraulic pressure to the azimuth motor through the servo valve is removed, allowing the LLM to freewheel in azimuth as the LLM centering probe enters the centering socket. When the elevation pressure regulator solenoid energizes, hydraulic pressure to the elevation servo motor slows the rate of depression and reduces mechanical load on the cage ball screw actuators.
When the cage is fully down, a cage down switch on the probe completes a signal circuit to the FCS by PDB connector J1, pins 70 and 71, telling the FCS that the cage is down. The FCS releases the unlock command on PDB connector J1, pin 53, to the PDB K4 relay and supplies ±24 VDC to the transport latch actuator extend circuit engaging the transport latch. When