1、-_ - - _- MIL-HDBK-V72 NOTICE L MN W 9799970 00283Li3 9 A 24-May 1886 MILITARY STANDARD1 ZATION HAUNDBOOK MA I N TA I NAB I LI TY PREDI C TI ON I FSC-M I SC 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. MIL-HDBK-Ll72 NOTICE 1 MN W 7797770 00283
2、LlLl O DEPARTMENT OF DEFENSE WASHINGTON D.C. 20360 MIL- HDBK- 472 MAINTAINABILITY PREDICTION 24 May 1966 1. This maintainability handbook was developed by the Department of Defense in accordance with established procedure. 2. This publication was approved on 24 May 1966 for printing and inclusion in
3、 the military standardization handbook series. 3. This document provides information on current maintainability prediction procedures. to personnel concerned with the design, development, and production of equipment and systems requiring a high order of maintainability. It will provide valuable info
4、rmation and guidance 4. Every effort has been made to reflect the latest information on maintainability prediction procedures. It is the intent to review this handbook periodically to insure its completeness and currency. Users of this document are encouraged to report any errors discovered and any
5、recom- mendations for changes or inclusions to the Commander, Naval Air Systems Command, Department of the Navy, Washington, D. C. 20360. i Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-LI72 NOTICE L MN 7799970 00283LI5 2 W MIL- HDBK-472 2
6、4 May 1966 FOREWORD The purpose of this Maintainability Prediction Handbook is to familiarize project managers and design engineers with current maintainability pre- diction procedures, To achieve this objective, particular care has been exercised in selecting and including only those procedures whi
7、ch are currently used in predicting the maintainability of equipment and systems, The high- lights of each maintainability prediction procedure are presented in a clear, lucid and intelligible manner and include useful supplementary information applicable to specific procedures, using the following
8、format. 1.0 GENERAL Philosophy, Assumptions and Summary Applicability Point of Application Basic Parameters of Measure Information Required Data Basis Correlation Between Predicted and Observed Values 2. O ANALYTIC FOUNDATION 3. O APPLICATION C This type of presentation facilitates reference to all
9、or to onIy those parts of a procedure which are of particular interest to the user. For example, the manager may be interested solely in the non-technical aspects, such as: Point of Application, or Applicability. Conversely, the engineer, may con- centrate on the kchnical aspects only, such as Analy
10、tic Foundation and Application. Thus, through the use of this handbook, maintainability engineers, working with a new development, can select the most applicable maintainability prediction procedure for a specific equipment or system. ii Provided by IHSNot for ResaleNo reproduction or networking per
11、mitted without license from IHS-,-,-Prediction facilitates an early asasesment of the maturity of the maintainability design and enables decisions concerning the compatibility of a proposed design with specified requirements or the choice of better al ternati ves. . The maintainability prediction pr
12、ocedures I and III are applicable solely to electronic systems and equipments. Procedures II and IV can be used for all systems and equipments. In applying procedure II to non-electronic equi pments the appropriate task times must be estimated. predict maintainability parameters of avionics, ground
13、and shipboard electronics at the organizational, intermediate and depot levels of mai ntenance. Procedure V can be used to In conclusion, the use of thls handbook facilitates the design, development, and production of equipment and systems requiring a high order of mai ntai nabi 1 i ty. iii -, 12 Ja
14、n 1984 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-472 NOTICE 1 12 January 1984 MILITARY HANDBOOK MAINTAINABILITY PREDICTION TO ALL HOLDERS OF MIL-HDBK-472: 1. THE FOLLOWING PAGES OF MIL-HDBK-472 HAVE BEEN REVISED AND SUPERSEDE THE PAGES
15、 LISTED: NEW PAGE 111 iv vi i vili ix 1 2 3- 4 : 6- 1 DATE 12 Jan 1984 24 May 1966 12 Jan 1984 12 Jan 1984 12 Jan 1984 12 Jan 1984 12 Jan 1984 24 May 1966 12 Jan 1984 12 Jan 1984 SUPERSEDED PAGE iii vi i vi ii i,x 1 (REPRINTED WITHOUT CHANGE). i 2 (REPRINTED WITHOUT CHANGE) 4 5- 1 PAGE X xi xi i xii
16、i xiv 5 2. THE FOLLOWING PAGES ARE TO BE ADDED: DATE 12 Jan 12 Jan 12 Jan 12 Jan 12 Jan 12 Jan V-1 bolru 1-33 12 Jan A-V-1 thru A-V-22 12 Jan 1984 B-V-1 thru B-V-27 12 Jan 1984 C-V-1 thru C-V-8 12 Jan 1984 D-V-1 thru D-V-9 12 Jan 1984 984 98% 989 984 984, 984 984 DATE 24 May 1966 24 May 1966 24 May
17、1966 24 May 1966 24 May 1966 24 May 1966 24 May 1966 24 May 1966 3. RETAIN THIS NOTICE AND INSERT BEFORE TABLE OF CONTENTS. 4. indicated herein have been entered. This notice will be retained as a check sheet. This issuance, together with appended pages, is a separate publication. Military Handbook
18、is completely revised or cancelled. Holders of MIL-HDBK-472 will verify that page changes and additions Each notice is to be retained by stocking points until the I MNTY - 79021 w Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NOTICE 1 Custodians: A
19、rmy - MI Navy - AS Air Force - 17 Preparing activity: (Project MNTY-7902) Navy - AS Revi ew act i vi ti es : Army - Navy - EC, OS, SH Air Force - 11, 13, 14 . ! L I 12 Jan 1984 I J . 2 - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Repair time req
20、uired at the maintenance level involved. There are many sources which record the failure rate of parts as a function of use and environment. This failure rate, is expressed as the number of failures per unit of time. A typical measure is “failures per lo6 hours.“ The major advantage of using the fai
21、lure rate in maintainablity prediction calculations is that it provides an estimate of the relative frequency of failure of those components which are utilized in the design. Similarly, the relative frequency of failure of components at other maintainable levels can be determined by employing standa
22、rd reliability prediction techniques using parts failure rates. regression equations for calculating the maintenance action time. Another use of the failure rates is to weight the repair times for various categories of repair activity, in order to provide an estimate of Its contribution, to the tota
23、l mai ntenance ti me. Failure rates can also be utilized in applicable 2 -. 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-472 24 XAY 1966 Repair times are determined from prior experience, simulation of repair tasks, or past data secured
24、 from similar applications. Most procedures break up the “maintenance action“, which is a more general expression than “repair actionff, into a number of basic maintenance tasks whose time of performance is summed to obtain the total time for the maintenance action. SUMMARY: It is emphasized that th
25、e selection and application of the proper maintainability technique resulta in many economies measured in terms of man-hours, materiel, and money. These savings are attributable to the fact that maintainability prediction is considered to be a tool for design enhancement because it provides for the
26、early recognition and elimination of areas of poor maintainability during the early stages of the design life cycle. Otherwise, areas of poor maintainability would only become apparent during demonstration testing or actual use, after which time, correction of design deficiencies would be costly and
27、 unduly delay schedules and missions. Maintainability prediction, therefore, is a most useful instrument to both manager and engineer because it provides for improved system effectiveness and reduces administrative and maintenance costs. The comparison matrix, Figure A, is included to provide a summ
28、ary of the signifi- cant attributes of each maintainability prediction procedure included in this hand- book. Additional details may be obtained by referring to specific maintainability prediction procedures of interest. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without
29、license from IHS-,-,-MIL-HDBK-UZ NOTICE L MN m 7777770 O2363 4 m MIL-HDBK-4 7 2 -4 H d n 12 Jan 1984 s- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A MIL-HDBK-472 NOTICE I UN I 7779770 0028361i b G O rl a U a I YI4 ou uu Crl rlrl OP “2 b a 4 2 rl
30、 d 4 rl p. - u o U na a 8 - CI Y Q n nn re Y b o U uu PG lo a GU.! Plso PU u h h “ 7) nn Ye 2 v c 12 Jan 1984 - 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- PROCEDURE I MIL-HDBK-472 NOTICE L MN 0 7779970 O028365 8 MILHDBK-472 24 May 1966 c * -
31、1.0 GENERAL This procedure is used to predict system downtime of airborne electronic and electro-mechanical systems involving modular replacement at the flight-line. Just as a masonry building,depends upon the brick as its basic building block, the procedure relies on the “Elemental Activity“ as the
32、 fundamental element of downtime from which other measures of downtime are developed through a process of synthesis of time distributions. The Elemental Activity is a simple maintenance action of short duration and relatively small variance which does not vary appreciably from one system to another.
33、 An example of a basic elemental activity would be the opening and shutting of a door, or opening and closing of a radome on an aircraft. It should be obvious that the performance time does not depend upon the construction of the house or aircraft provided that the door or radome are similar. Theref
34、ore if one should record the times required over many trials, to open and close a door, he should be able to calculate the mean tims,/L, and the standard deviation, U, of this Elemental Activity. This is precisely what has been done .in this prediction procedure for various Elemental Activities whic
35、h in total comprise the basic Categories of Active Repair Time. These activities are listed in Table 1-1 and the corresponding recommended values ofpand C for the Elemental Activities of each category are shown in Table 1-2. The technique of using the basic building block, namely the Elemental Activ
36、ity, and building the structure step by step to include other measures of downtime is explained in 2. O “Analytic Foundation“ and detailed in 3. O “Application“. 1.1 Philosophy, Assumptions and Summary Figure 1-7 entitled Wtructure of Time Elements in ffFixtl of Malfunction“ illustrates the “buildin
37、g block“ principle. An examination of this figure shows how elemental activity times are synthesized to produce maintenance categories and that these in turn combine to produce Malfunction Active Repair Time, The remainder of this chart showing the complete buildup to total system downtime is self e
38、vident. There are two exceptions to be noted. The first is that the category entitled “Distribution of Final Test Time“ is not derived from other Elemental Activities since it has constant parameters and is shown in Table 1-8. The second exception is that this procedure does not include the techniqu
39、es for calculating Total System - c -. .- - r. . . - - 1- 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL HDBK- 47 2 24 May1966 Downtime but rather concludes with the determination of System Downtime. The reason is that Total System Downtime is
40、 the result of combining the distributions of System Downtime with Initial Delay. The methods of determining Initial Delay require some further refinement before they will be considered for inclusion. In summary, the philosophy of the entire prediction procedure is based on the principles of synthes
41、is and transferability. As already discussed the synthesis principle involves a buildup of downtimes, step by step, progressing from the distribution of downtimes of Elemental Activities through various stages culminat- ing finally with the Distribution of System Downtime. The transferability princi
42、ple embodies the concept that data applicable to one type of system can be applied to similar systems under like conditions of use and environment to predict system maintainability. 1.2 Applicability This maintainability prediction procedure is applicable to predict flight-line maintenance of airbor
43、ne electronic and electro-mechanical systems involving modular replacement at the flight-line. The procedure may also be used for maintainability prediction in echelons of maintenance other than flight-line such as field or depot by extension of formulae through further developmental work, as requir
44、ed, to include other elemental activities. 1.3 Point of Application The technique can be applied at any time after the design concept has been established, provided the essential data enumerated in 1. 5 entitled “Information Required“ is available. 1.4 Basic Parameters of Measure The ultimate measur
45、e of maintainability is the distribution of System Downtime. Intermediate measures include the distribution of times for the various Elemental Activities, Maintenance Categories, Malfunction Active Repair Time, Malfunction Repair Time, System Repair Time and System Downtime. (See Figure 1-7.) 1.5 In
46、formation Required in order to perform a maintainability prediction the following information must be available. 1-2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-flIL-HDBK-LI72 NOTICE I MN = 9779770 0028367 L -. 24 May 1966 I (a) Location and fail
47、ure rate of each component of the system. (b) Number of flight-line replaceable components of each type. (c) List of flight-line replaceable components containing adjustments or flight-line replaceable parts. (d) Number and character of readouts (Monitoring devices for portions of the system). (e) N
48、umber of types of spares carried. (f) Number of pressure-retaining connectors. (g) Number of test points. (h) Nature of special test equipment (designed specifically for the system). (i) Number of magnetrons. u) Estimates of durations of average mission. (k) Manning schedules for operations and main
49、tenance personnel including all shifts and all breaks for lunch, coffee, etc. 0) Estimates for intervals occupied by unscheduled activities such as debriefing. 1.6 Data Basis In the original development of the prediction procedure, data were employed from malfunction repairs on the AN/ASB-4 Bombing and Navigation System(used in
