MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.cycle cost.Although the SEM has been applied to the Navy’selectronic equipment, the circuit modules could be appliedadvantageously to new Army equipment design.This would provide initial cost savings and possibleimprovement in the availability of repair parts for theNorth Atlantic Treaty Organization.SEM documentation can be found in1. MIL-STD-l378, Requirements for EmployingStandard Electronic Modules2. MIL-STD-1389, Design Requirements for StandardElectronic Modules3. Navy Pub 0101-073, Module Design Handbook4. Navy Pub 0101-051, Program Manager's Handbook.5-6.2 MISSILES AND ROCKETSTo facilitate the handling, transportation, and storage,large missiles and rockets should be divided into functionallypackaged modules or sections i.e., warhead,adaption kit, guidance, and motor—that are adaptable torapid field assembly. This division allows for the separationof the explosive or other hazardous materials frominert components.The Army’s HELLFIRE missile system contains amodular guidance package that permits the missile to beused in three different modes. Although this is not modularizationprimarily for ease of maintenance, the HELL-FIRE demonstrates the application of modularization ofa component to permit the use of the basic system indifferent operational modes.5-6.3 TANK-AUTOMOTIVE EQUIPMENTModularization as it applies to the tank-automotivearea is already well-developed and present in vehicles.Consider the ancilliary equipment related to the engine—plug, distributor, wiring harness, alternator, starter, oilfilter, etc. which are good examples of modularization.Room for improvement exists. Examples of fuel injection,cylinder packages, and total vehicle modularization—discussed in the paragraphs that follow are examples ofhow the design can be improved to facilitate maintenance.5-6.3.1 Fuel InjectionIn many diesel engines the fuel injection pump can befactory timed and calibrated; thus it requires no adjustmentswhen replacing an unserviceable system. The fuelinjection system can be simply removed and replaced as aself-contained module and, when installed, is ready foroperation. other assemblies that lend themselves to thiskind of no-calibration or -adjustment are prime candidatesfor exploitation.5-6.3.2 Engine ModulesFig. 5-4 shows the three major modules–-gearbox,DOD-HDBK-791(AM)forward engine, and rear engine—of the M1 turbine tankengine. Each module is a packaged assembly ready forinstallation. These modules significantly reduce the overhaultime previously required to disassemble, clean,inspect, recondition, and reinstall individual components.Special fittings and rigging are provided to remove themodules from their shipping containers for assembly intothe tank as illustrated for the rear engine module in Fig.5-5.5-6.3.3 Total VehicleA study was undertaken to determine whether a conceptof modular design for an automotive vehicle wouldeffect a significant reduction in the maintenance load andimprove the strategic posture of the field Army (Ref. 3).The significant results of this study indicated1. Maintenance man-hours reduced 27%2. Active maintenance downtime reduced 25%3. Ratio of inactive to active downtime reduced 44%4. Unavailability of trucks reduced 54%.The modular units designed for quick disconnect andease of replacement were1. Engine Assembly. (See 1, Fig. 5-6.) Quick-disconnectfuel line, ignition wiring, starter cable, generatorcable, and throttle controls2. Transmission. (See 2, Fig. 5-6.) Quick-disconnectcontrols, features to permit ease of separation fromengine by rail guides or lifting device3. Transfer Assembly. (See 3, Fig. 5-6.)4. Differential and Axle Assembly. (See 4, Fig. 5-6.)5. Propeller Shaft Assemblies. (See 5 and 6, Fig.5-6.)6. Rear Wheels (Hub and Brake) With Tires. (See 7,Fig. 5-6.) Quick disconnect on brakes7. Front Wheels (Hub and Brake) With Tires. (See7, Fig. 5-6.) Quick disconnect on brakes8. Steering Gear Assembly. Quick disconnect.Real data on fielded trucks were used in a Monte Carlosimulation to compare parameters of a standard vehicleto a modular vehicle. Fig. 5-7 summarizes the results,which indicate1. Reduction in occupational specialists2. Considerable savings in training costs3. Substantial savings in special tools and testequipment4. Improvement in the availability status.5-6.4 MODULARIZATION IN ARMAMENTThis subparagraph describes examples of modularizationin armament equipment, e.g., small arms and cannons.The first example is the modularization of a functionalgroup in a gun; the second example is the modularizationof a complete gun.5-9