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~~~ *De*051 107 ARINC RESEARCH CORP AMIAPOLIS IV F/S 5/1

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EVAL UA TION CF THE RELIABIL ITY IPPACT OF ENGINEERING CHANGE PROP—ETCIUPSEP 76 G MEtTLER N00197 7* C 0311

LM CLASS IFI ED 1621-09 3 t537 M.

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• Piblicatisa 1621-U.I.1531

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EVALUATION OF THE RELIA BIliTY IMPACTOF ENGINEERING CHANGE PROPOSALS

September 1916

Prepar ed forLjJ NAVAL ORDNANCE STATION

Louisville, Kentucky 40214under Contract N00191-14-C•0314

C..3 Task Assitnnieet Mo. 9

I tñi~ tion ~~~jmited

RESEARCH CORPORATION

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DAI’E READ INSTRU CTIONSI~~& I ¶Jr% I U~~~~~UM f l ~~ I IlJI’~ U 1W

— BEFORE COMPLETING FORM

I. REPORT NUMBER GOVT ACCESSION NO 3. RECIPIENT S CATALOG NUMBER

1621—09—9— 1537 ______________________________4. TITLE (and Subtill.) S. TYPE OF REPORT S PERIOD COVERED

Evaluation of the Reliability Impact ofEngineering Change Proposals / • PERFORMING ORG. REPORT NUMBER

7. AUTHOR(.) —

S. CONTRACT OR GRANT NUUBER(a)

G. Mettler N00197_71~_ C_ O3114 ~~I. PERFORMING ORGANIZATION NAM E AND ADDRESS $0. PROGRAM ELEMENT. PRCJECT . TA SK

AREA & WORK UNIT NUMBERS

ABINC Research Corporation2551 Riva Road -

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September 1976I). NUMBER OF PAGES

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Unlimited -

Ii. DISTRIBUTION STATEMENT (of th. .batract .ntal.d In Block 20. II dllI.r.n t from R.pori)

IS. SUPPLEMENTARY NOTES

IS. KEY WORDS (Continu, on rover,. aid, if n.c.a.ary and id.ntity by block numb.r)

0. ABSTRACT (Continu. on r.v.r.. aid. II ,i.c...a,y and Id•nhIfr by block numb.r)

his report presents the results of ABINC Research Corporation’s efforts ‘toevaluate the reliability and availability impact of ECP 780—026 on the ~~/5hMod 0 Gun Mount, using a cc*nputer simulation modeling technique.

DD ~~ ~473 EDITION OF I NOV 65 IS OBSOLETE UnclassifiedSECUR ITY CLASSIF ICAT ION OF THIS PAGE (II?,.,, l).t. E,.t.

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Prepared f o r

Naval Ordnance StationLouisvil entucky 40214

under ~~~~~~~~~~~~~~~~~~~~~~~~~~~Task Assignment No. 9

ARINC Research Corporationa Subsidiary of Aeronautical Radio , Inc .

2551 Riva RoadAnnapolis, Maryland 21401 : . ‘ )

~Publication 1621—09—9—1537 - . -

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~~ ( (~ ): (•/ ~/ ~~~

( i .

ABSTRACT

This report presents the results of ARINC Research Corporation’sefforts to evaluate the reliability and availability impact of E~CP 780—026on the 5”/54 Mark 45 Mod 0 Gun Mount , using a compUter simulation modelingtechnique.

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CONTENTS

Page

ABSTRACT iii

CHAPTER ONE : INTRODUCTION 1

CHAPTER TWO : PROCEDURES 2

CHAPTER THREE: FINDINGS 3

CHAPTER FOUR: CONCLUSIONS AND RECOMMENDATIONS 6

APPENDIX: RELIABILITY BLOCK DIAGRAM FOR THE 5”/54 MX 45 MOD 0 GUNMOUNT A-l

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S •

CHAPTER ONE

INTRODUCTION

Under the terms of Specific Task Assignment No. 9 of Contract N00197—74-C-0314 with the Gun Systems Engineering Center (GSEC) at the Naval Ord-nance Station, Louisville (NOSL) , Kentucky, ARINC Research was tasked toevaluate the reliability impact of proposed changes to gun systems. Oneproposed change was forwarded for evaluation during the period of this taskassignment: Engineering Change Proposal (ECP) 780-026, involving the recoilpistons on the 5”/54 Mk 45 Mod 0 Gun Mount. The recoil pistons were changedfrom E4340 steel to a chrome-plated design to reduce the high failure rateof the “U” cup hydraulic seals in the piston assembly. This report describesthe analysis employed to assess the reliability impact of that change andidentifies the improvements expected to result from the change.

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CHAPTER TWO

PROCEDURE

We were asked to evaluate the effect of the proposed change (to chrome—plated recoil pistons) in the 5”/54 Mk 45 Mod 0 Gun Mount by using baselineReliability, Maintainability, and Availability (RM&A) data established underSpecific Task Assignment No. 7 of Contract NOO197—76—C—03l4. In that taskwe provided a baseline RM&A for the Mk 45 Gun Mount, using a computer simu-lation model. The details of the model and the baseline are presented inthe Final Report for Specific Task Assignment No. 7*~

Information supplied by GSEC personnel indicated that an MRBF of 618rounds for the recoil—piston assemblies had been established on the basis offiring 2115 rounds with an unmodified system. Following installation of theECP, an MRBF of 1835 was measured after 1835 rounds were expended, with onefailure occurring at 1402 rounds. The recoil pistons are contained withinthe gun barrel housing assembly. That assembly contains elements thatcould fail during both cycling and firing (rounds) operations. By thenature of gun operations , a mount will be cycled many more times than it isfi red. A cycles-to-rounds ratio of 10:1 is reasonable.

A review of simulation—model parameters revealed that the recoil pistonswere properly treated as part of the Gun Barrel Housing, model block l2a ofthe block diagram presented in the Appendix (block number 33 for computersimulation). The failure mode for this block was based on system cycles,and a predicted value of 5000 cycles had been assigned as the MCBF for theblock. For use in the simulation model to project the improvement in theRM&A of the mount with the new chrome-plated pistons, the expected MCBF ofblock l2a was assumed to be 15,000 cycles -— three times the original value .

*See ARINC Research Publication 1621-07—06—1523 , September 1976.2

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CHAPTER THREE

FINDINGS

The new MCBF of 15,000 cycles was used to modify the input parameterfor block l2a of the simulation model. Tables 1, 2 , and 3 list the RM&Aparameters for the modified system, as established by simulation of systemoperation for periods of varying lengths (after discounting of the firstfive years to allow the model outputs to stabilize). For purposes of compar-isons, these tables also contain the RM &A parameters for the unmodifiedsystem values .

Table 1 gives the system parameters that were observed through 219 ,000hours of simulated system operation under the four—year—cycle scenario. Inthis scenario, mount operational intervals varied between 0.2 and 8.0 hours,the average interval being four hours. Table 2 shows the results obtainedby simulating system operation over 350,400 hours of the two-year-cyclescenario with the same operational—interval range and average. In Table 3the data shown for the unmodified system represent 166,400 hours of simulatedsystem operation, and the data for the unmodified system were observed over50,000 hours of simulated system operation. These Table 3 data resultedfrom simulating system operation under continuous combat conditions wherecontinuous operational intervals ranged from 0.2 to 21 hours in length andhad a 11.5-hour average duration.

Each table gives the parameters MTBF, MTEBF, MCBF, MRBF, Availability ,and Reliability. These parameters are defined as:

MTBF = Calendar Time (in Hours)Number of Failures

~~ BF = Energize Time (in Hours)

E Number of Failures while Energized

MCBF Number of Cycles— Number of Failures while Cycling

MRBF = Number of Rounds FiredNumber of Failures while Firing

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Table 1. 5”/54 MX 45 MOD 0 RM&APARAMETERS , FOUR-YE ARSCENARIO

Unmodified ModifiedParameter System Mean System Mean

MTBF 629.3 590.3

t.TrEBF 54.7 51.1

MCBF 67.1 67.5

MRBF 15.6 17.0

Availability 0.980 0.977

Reliability 0.931 0.927

Table 2. 5”/54 MX 45 MOD 0 RM&APARAMETERS , TWO-YEARSCENARIO

Unmod ified ModifiedParameter System Mean System Mean

MTBF 518.3 534.1

MTEBF 54 .4 56.4

MCBF 70.4 69.6

MRBF 18.1 19.0

Availability 0.977 0.977

Reliability 0.931 0.933

Table 3. 5”/54 MX 45 MOD 0 RM&APARAMETERS, COMBATSCENARIO

Unmodified ModifiedParameters System Mean System Mean

MTBF 93.2 90.4

MTEBF 72.0 70.3

MCBF 69.5 72.3

MRBF 13.9 13.8

Availability 0.857 0.861

Reliability 0.867 0.8634

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(Hours of System Operation)-(Active Repair Hours)Availability =Hours of System Operation

(Number of Times Turned On)—(Numb er of Failures)Reliability = Number of Times Turned On

As shown in Tables 1, 2, and 3, the modified—system mean values areclose to the mean values of the unmodified system. The conclusion to bedrawn from this analysis is that the Gun Barrel Housing Assembly has onlya minor effect on total system reliability and availability. The 3—to—lincrease in the MCBF of block l2a has a negligible effect on system opera-tion because the mission length in cycles (approximately 40 to 50 cycles)is relatively small compared with the mean values of 5,000 and 15,000 usedfor block 12a. The fact that the modified—system parameters increase insome cases and decreare in others is accounted for by the random variationof the simulation—modeling technique.

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CHAPTER FOUR

CONCLUSIONS ANt) RECOMMEND ATIONS

The change to chrome—plated recoil piston rods should improve thereliability of the hydraulic seals , as demonstrated by the test results.However, the improvement to the overall gun system reliability from thischange is minor. It is recommended that future proposed gun systemimprovements be evaluated for their effect on total gun system RM&A byusing this simulation modeling technique.

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APPENDIX

RELIABILITY BLOCK DIAGRAMFOR THE 5”/54 MK 45 MOD 0 GUN MOUNT

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