1. Certified Professional Logistician
RELATIONSHIPS OF RELIABILITY, AVAILABILITY & MAINTAINABILITY (RAM) TO OPERATIONAL READINESS & SUPPORTABILITY
This topic covers the relationships of Reliability, Availability & Maintainability (RAM) to Operational Readiness & Supportability. Its content will contain some math to show some of the relationships. However, the mathematics being presented should hopefully be easy enough to follow. After the math, I will discuss the factors and metrics that influence Ao from the most impact to the lesser impact factors. I will finish this portion with a diagram of key factors impacting system effectiveness. This diagram will also show the importance of product support on system effectiveness.
Bernard Price
Certified Professional Logistician

2. Operational Availability
The Probability that the Equipment is Operating or in a Committable Condition to Operate at any Random Point in Time
Quantitative Expression of User Need Prior to Fielding
Operational Availability (Ao) is the probability that the equipment is operating or in a committable condition when not operating at any random point in calendar time. A specified equipment Ao is considered a quantitative expression of the User’s need. Ao is a macro metric used prior to fielding.

3. Operational Readiness
The Experienced Probability that Reported Weapon Systems are considered Up to Accomplish their Mission
Unit Commanders are Responsible for Readiness Rates of their Systems After Fielding
An Operational Readiness rate is the experienced probability that reported weapon systems at the unit level are considered up. This represents the percentage of days that the systems are available to accomplish their mission requirements.
Unit Commanders are responsible for the readiness rates of their systems. Readiness rates are a macro metric used after the systems are fielded. Readiness rates are also used in a monthly report card to judge how well field commanders perform in keeping their systems up. However, as will be discussed, readiness rates will also depend on the system design and its support, which are sometimes beyond the control of unit commanders.

4. Operational Availability & Readiness Rate Similarity
UP TIME
UP TIME / SYSTEM FAILURE
Ao = =
UP TIME + DOWN TIME
(UP TIME + DOWN TIME) / SYSTEM FAILURE
UP TIME
Readiness Rate =
UP TIME + DOWN TIME
This chart shows that Operational Availability & the Readiness Rate are mathematically similar. Both are represented as the percentage of Up Time divided by Total Time, which is the Up Time + Down Time. Ao is an expression typically used prior to fielding and readiness rates are experienced after fielding. If Ao is not attempted to be achieved during development, the readiness rate required may not be easily attained after development.
Operational Readiness rates are based on the number of days that systems are considered up divided by the total number of days that systems are either up or down. In theoretical terms, Operational Readiness is a sample of Ao. In the actual world, war fighters sometimes accomplish things differently to keep readiness rates up, which is not considered in achieving operational availability. For instance, a hanger queen may be used to get some extra equipment back up when more than one system would otherwise be down. A hanger queen is a system that has parts cannibalized from it to keep other systems up. Also, a Unit may borrow a spare from a nearby Unit to restore a system quicker. Possibly, war fighters may work extra hours to restore a system before considering it the end of the day, when the judgment is made as to whether the system is recorded as up or down.
NO. OF DAYS SYSTEM UP =
(NO. OF DAYS SYSTEM UP + NO. OF DAYS SYSTEM DOWN)

5. Derivation of Operational Availability
UP TIME
UP TIME / SYSTEM FAILURE
Ao = =
UP TIME + DOWN TIME
(UP TIME + DOWN TIME) / SYSTEM FAILURE
UP TIME / SYSTEM FAILURE =
MCTBF
SYSTEM
DOWN TIME / SYSTEM FAILURE =
Mean System Restoral Time per System Failure
Operational Availability (Ao) is the probability that the equipment is Up or operating or in a committable condition when not operating at any random point in calendar time. Ao can be shown to be dependent on the system’s reliability, maintainability and logistics support. For computing Ao, the percentage of Up time divided by Total Time is mathematically the same as the Up time per system failure divided by the Up Time plus Down Time per system failure.
The Up Time per system failure is equal to the system’s Mean Calendar Time Between Failure (MCTBF). MCTBF is a function of the product design reliability and the system operating tempo.
The Down Time per System Failure is equal to the Mean System Restoral Time (MSRT) per system failure. The MSRT is equal to the system’s Mean Time To Repair (MTTR) plus its Administrative and Logistics Down Time (ALDT). MTTR is a function of the product design maintainability. ALDT is a function of the support process efficiency for the system. =
MSRT
MTTR +
ALDT
SYSTEM
SYSTEM
SYSTEM

6. Equipment Levels of Indenture
Other Terminology
SYSTEM
TOTAL WEAPON SYSTEM WITH ITS GFE
READINESS REPORTED EQUIPMENT
END ITEMS
PRIMARY ITEMS BEING DEVELOPED/ACQUIRED
SYSTEM WITHOUT GFE OR GFE ITEMS
LINE REPLACEABLE
UNITS (LRUs)
SECONDARY ITEMS REPLACED FORWARD
ITEMS IMPACTING MAINTAINABILITY
This chart shows equipment levels of indentures to promote a better understanding of the influence of equipment indenture levels on RAM and supportability.
The SYSTEM is the total weapon system where readiness rates are measured. It is the system with all its furnished equipment.
The END ITEM is a major item being developed or being acquired. It is either the system without any Government Furnished Equipment (GFE) or the the equipment procured separately and furnished to the system.
A Line Replaceable Unit (LRU) is a secondary item removed and replaced forward to restore the end item after it fails. The LRU is an item directly impacting maintainability. Sometimes an LRU is referred to as a Weapon Replaceable Assembly (WRA).
A Shop Replaceable Unit (SRU) is a secondary item used to repair the LRU or possibly repair some higher indentured level SRU. Sometimes an SRU is referred to as a Shop Replaceable Assembly (SRA).
SHOP REPLACEABLE
UNITS (SRUs)
SECONDARY ITEMS USED TO REPAIR LRU
OR HIGHER LEVEL SRU

7. Serially Configured Ao
AoSYSTEM =
Ao1 x
Ao2 x x
AoN
AoSYSTEM
Ao1 =
A serially configured system is where end item failures always brings the system down. A serially configured end item is where the failure of its critical LRUs always causes the end item to fail. The top formula shown on this chart assumes that the end items within the system are serially configured. The Operational Availability (Ao) of the System is equal to the product of the Availabilities of each End Item.
If a redundant end item exists or a float spare end item exist, the Ao of the end item increases because the redundant end item or available float will cause the system to only be down for just the switch over time to the other end item. Therefore, redundancy or floats increases the effective Ao of that end item and the system.
If the system being acquired from a contractor includes serially configured Government Furnished Equipment (GFE) that counts in the System Operational Readiness Rate being reported, then the system being acquired will need a higher Ao goal than the system Ao or readiness rate requirement. In the bottom formula, Ao of the 1st end item represents the end item being developed or acquired from the contractor. Since the Ao of the other end items cannot exceed 100%, the product of their Availabilities will be less than 1 making the Ao of the end item being acquired be a larger number than the system Ao.
Ao2 x x
AoN .

8. Serially Configured Reliability1 1 1 1 = + + +
MCTBFSYSTEM
MCTBF1
MCTBF2
MCTBFN
The reliability formula shown on this chart assumes the end items within the system are serially configured. The reciprocal of MCTBF is 1 divided by MCTBF. This represents the calendar time failure rate of the item. In a series configuration, the failure rates of each end item add up to yield the system failure rate.
Equipment that is not serially configured may contain redundant components or more than one of the same item performing the same function. In a redundant configuration, the effective MCTBF computation is very complex. Suppose 2 items perform the same function and only one of them is needed to be up for the equipment to be up. If one of the items fail, the system continues to perform its mission. If the second item fails before restoring the first item, then a system failure occurs. The longer it takes to restore the first item, the greater the probability that the second item will fail before the first item is restored. Therefore, the computation of the effective MCTBF for a redundant configuration depends on both the equipment’s support and the item’s reliability. .

9. Mean System Restoral Time Breakdown in Models
MSRTSYSTEM = MTRSYSTEM + CWTSYSTEM
MTR - Mean Time to Restore with 100% Stock Availability Forward
CWT- Mean Customer Wait Time at Forward Level per System Failure
MTRSYSTEM = MTTRSYSTEM + MRDTSYSTEM
MRDT - Mean Restoral Delay Time with Spares Available Forward
This slide shows how the Mean System Restoral Time (MSRT) is broken down in models. The MSRT is equal to the system’s Mean Time to Restore (MTR) when spares are available at the forward supply level plus the Customer Wait Time (CWT) per failure that occurs because Line Replaceable Unit (LRU) spares are not always available forward in stock 100% of the time to restore the system.
The Mean Time to Restore a system when spares are available is equal to the system’s Mean Time To Repair (MTTR) plus those support efficiency factors that contribute to a Mean Restoral Delay Time (MRDT) when spares are available at the forward supply level.

10. Restoral Delay Time Contributors
Spares are Not Collocated with Equipment
Spares are Delivered Forward to Restore
Contact Maintenance Team Restores Equipment
Equipment is Evacuated to Restore
Some ILS Elements May Not Be Satisfactory
Personnel Lacking Appropriate Skills
Personnel Not Available
Non-Functioning TMDE Forward
Forward Repair Documentation Insufficient
Non-design contributors to the restoral delay time are shown on this chart. When spares stocked forward are not collocated with the equipment, additional time is needed to get the appropriate spare to the equipment. This may happen by having the spares shipped or delivered forward to restore the equipment, or have a contact maintenance team come out to restore the equipment, or have the equipment evacuated so that it can be restored and returned to service.
Since some Integrated Logistics Support (ILS) elements may not always be performed satisfactorily, they also contribute to the delay time. Lack of appropriate training leads to personnel lacking appropriate skills. Possibly, the personnel doing system repair are not available immediately. Another delay time factor may be inadequate or non-functioning test measurement and diagnostic equipment (TMDE) at the forward support location. If the forward repair manual documentation is insufficient, it will contribute to the restoral delay time.

11. Operational Availability Restated
MCTBFSYSTEM
AoSYSTEM =
MCTBFSYSTEM +
MTTRSYSTEM +
ALDTSYSTEM
MCTBFSYSTEM
AoSYSTEM =
MCTBFSYSTEM +
MTRSYSTEM +
CWTSYSTEM
As previously mentioned, Operational Availability (Ao) can be computed as the system Mean Calendar Time Between Failure (MCTBF) divided by the quantity of the system MCTBF plus the Mean Time To Repair (MTTR) plus the Administrative and Logistics Down Time (ALDT).
Since the MSRT is based on the system Mean Time to Restore (MTR) when spares are available and the Customer Wait Time (CWT) per failure, the equation describing Ao can be restated. For logistics models, the system Ao is computed as the system MCTBF divided by the quantity of the system’s MCTBF plus its MTR plus its CWT per system failure.

12. Relationship of Customer Wait Time to LRU Logistics Response Time
CWT = FILL1 x 0 + (1 - FILL1) x MTTO1
CWT = (1 - FILL1 ) x MTTO1
FILL1 - Probability of Filling an Order from Forward Level Stock
MTTO1 - Mean Time to Obtain a LRU at Forward Level Support
The relationship of the Customer Wait Time (CWT) per system failure to the LRU logistics response time is shown on this chart. If a failure occurs and the appropriate LRU is stocked forward, there is no customer wait time associated with that failure to restore the system. However, when a failure occurs and the appropriate LRU is not stocked forward, the LRU has to be obtained through the logistics chain. Therefore, CWT per system failure is equal to 1 minus the probability of filling an order from the forward level LRU stock times the Mean Time to Obtain (MTTO) a good LRU at the forward support level. 1 minus the order fill rate is the same as the probability of not filling an order at the forward supply level.

13. Traditional Supply Flow
DECENTRALIZED
LOCATION
DECENTRALIZED
LOCATION
DECENTRALIZED
LOCATION
DECENTRALIZED
LOCATION
INTERMEDIATE
SUPPORT
INTERMEDIATE
SUPPORT
When a spare LRU is to be obtained from stock, the Customer Wait Time to obtain the spare becomes more dependent on the supply chain flow. In a traditional 3 level supply chain, the decentralized, forward location will obtain its spare from an intermediate support location. The intermediate support location in turn is resupplied by the centralized location. In a traditional 2 level supply chain, the centralized stockage location will supply the decentralized, forward location directly.
A non-traditional supply chain with total asset visibility management may sometimes have one decentralized location supply another decentralized location if there are no spares in stock at its supporting higher echelon of supply.
CENTRALIZED
LOCATION

14. Inventory Distribution
STOCKAGE LOCATION
COMMERCIAL
GOVERNMENT
CENTRALIZED LOCATION
INTERMEDIATE SUPPORTS
DECENTRALIZED LOCATION
MANUFACTURER OR
PLANT WAREHOUSE
DISTRIBUTION CENTER OR
REGIONAL WAREHOUSE
RETAIL STORE
DEPOT SUPPORT OR
WHOLESALE LEVEL
GENERAL SUPPORT
DIRECT SUPPORT
(AUTH STOCKAGE LIST)
ORGANIZATIONAL SUPPORT
OR SITE
(PRESCRIBED LOAD LIST)
Traditional inventory distribution in Government or commercial industry follows the same supply flow.
For a 3 level supply chain related to commercial industry, the original equipment manufacturer or its plant warehouse supplies the distribution center or regional warehouse. This intermediate supplier ships to the retail store or customer.
For a 3 level supply chain related to Government, the depot level supplies the general support or direct support level. This intermediate supplier ships to the organizational support level or unit operating the equipment.
In Government, the Prescribed Load List or PLL contains all the spares initially provisioned at the forward, decentralized location. The Authorized Stockage List or ASL contains the spares initially provisioned at the Direct Support or General Support level. The depot level is referred to being the wholesale level of supply.

15. Maintenance Flow ECHELON (J) LOCATION 1 2 3 M P(1) P(2) P(3) 3
DECENTRALIZED
LOCATION
Repair at
Organizational
or Unit Level 1
THROW AWAY
P(1)
Ship Out
for Repair
Ship Out
for Repair
INTERMEDIATE
SUPPORT
Repair at
Direct or Regional
Support(s) 2
THROW AWAY
P(2)
Ship Out
for Repair
The Maintenance Flow is another contributor to the customer wait time per system failure. In maintenance support, the failed end item and system are typically repaired forward at the decentralized forward location. When a failed LRU is removed, the failed LRU will either be repaired and returned to bring the equipment back up or a spare LRU will be used to bring the equipment back up. If the item is repaired and returned, the Customer Wait Time becomes more dependent on the maintenance chain. However, if a spare is used to restore the system, the removed LRU will either be thrown away or be sent back to the intermediate support level or centralized support level to be repaired and placed back into stockage there.
The Maintenance Task Distribution of an item shows the percentage of repairs made at each support level and the percentage thrown away. The sum of the repair percentages at each maintenance support level plus the washout rate of throwaways needing replenishment rather than repair total to 100%.
CENTRALIZED
LOCATION
Repair at
Depot or
Contractor 3
THROW AWAY
P(3)
WASHOUT
RATE 3
NOTE: P(J) is percentage of repairs made at echelon J P(J) + Washout Rate = 1 M
J=1

16. Determining Mean Time To Obtain Spares Values
MTTO1 = RCT1 x PCTREP1 + (1-PCTREP1) x (OST (1-FILL2) x MTTO2)
FOR LRU THROWAWAY OR REPAIR AT CENTRALIZED LOCATION
FOR LRU REPAIR AT THE INTERMEDIATE LOCATION
OST - ORDER & SHIP TIME
FILL - ORDER FILL RATE (STOCK AVAILABILITY)
PCTREP - PERCENTAGE OF LRUs REPAIRED
RCT - REPAIR CYCLE TIME
MTTO2 = OST (1- FILL3) x MTTO3
MTTO2 = RCT2 x PCTREP2 + (1-PCTREP2) x (OST (1-FILL3) x MTTO3)
Logistics response times are critical to the efficiency of product support. Both Order and Ship Times (OST) associated with supply support and Repair Cycle Times (RCT) associated with the maintenance support are instrumental in determining the Mean Time To Obtain (MTTO) spares.
On this chart, the subscript 1 represents the forward support level, 2 is the intermediate level, and 3 is the centralized support level. The time for the forward, decentralized support to obtain a spare depends on the percentage of LRUs repaired and returned there times its RCT. When a spare is used for removal and replacement, the MTTO a spare at the forward support level depends on its OST from the next higher support level and its Stock Availability there.
The mean time for the intermediated support level to obtain a spare depends on whether the stock is primarily refilled by the supply chain flow or by the maintenance chain flow. For LRU throw away or repair at the centralized location, the OST from the centralized stockage location and its stock availability there is more critical than the maintenance flow. For LRU repair at the intermediate maintenance level or a repair and return to the intermediate support level, the RCT times the percentage repaired tends to be more critical than the supply flow. The MTTO spares at the centralized support level depends on the average amount of time it takes to fill back orders times the percentage of time that the wholesale level or depot cannot fill an order because it is out of stock.

17. Ao Adjustment Possibility
Periodic Maintenance Actions that may cause Down Time:
Preventive Maintenance
Tear Down and Set up
Software Change Actions
Servicing Prior to and/or After Missions
MCTBMA – Maintenance Action Time
AoADJUSTMENT =
MCTBMA
Operational Availability (Ao) in supportability optimization models only cover the Ao impacted by supply and maintenance to correct a hardware failure. However, there are other actions that may cause the system down time. If these periodic maintenance actions apply to the system Ao, the system Ao goal for the acquisition being modeled for supportability optimization may need to be adjusted to account for the extra down time not being covered in the modeling.
The periodic maintenance actions that may be counted as causing system down time are scheduled preventive maintenance; the tear down, movement and set up of the system, switch over to a new version of software, and servicing actions that occur prior to and/or after a mission. However, since many of these actions may be accomplished in less than a day, they typically do not impact the Operational Readiness Rate being reported, unless the scheduled maintenance is a system overhaul.
If periodic maintenance actions are being counted in the acquisition, but is not covered in the Ao model being used in the acquisition, then the system Ao requirement or goal will need to be adjusted. The Ao adjustment factor is the quantity of the Mean Calendar Time Between Maintenance Actions (MCTBMA) minus the average Maintenance Action Time divided by the MCTBMA. This adjustment factor will effectively raise the system Ao goal needed to be modeled in the acquisition.
Adjusted
AoSYSTEM =
AoSYSTEM /
AoADJUSTMENT
MCTBMA - Mean Calendar Time Between Maintenance Action .

18. Primary Impacters of Operation Availability
Critical Items Within Serial Configurations
Critical Items that are Line Replaceable Units
Demand Frequency of Critical Items (Reliability and False Pull Rate)
Mean Time to Restore (Maintainability & Restoral Delay Time Forward with 100% Stock Availability)
Stock Availability at Most Forward Retail Supply Level
Order and Ship Time to Most Forward Retail Supply Level
Equipment operational readiness or operational availability (Ao) is influenced by reliability, maintainability and supportability. Based on modeling relationships, some supportability factors will influence Ao more significantly than other factors. The primary impacters of Ao or operational readiness are listed on this slide.
The most important factors are the critical items within serial configurations and the critical items that are Line Replaceable Units (LRUs). The demand frequency of these critical items based on the product’s design reliability and equipment false pull rate significantly impacts operational readiness. The mean time to restore based on the product’s design maintainability and the restoral delay time when spares are available forward are also very important factors. The stock availability at most forward, retail supply level and the order and ship time to the most forward, retail supply level also drive Ao and readiness rates.

19. Conditional Primary Impacters of Operational Availability
Additional Mean Time to Restore (when forward level supply is not co-located with the system)
Frequency of Scheduled/Periodic Actions to System or Serially Configured End Items (when servicing, preventive maintenance, etc. applies)
Time to Perform Scheduled/Periodic Actions
End Item Redundancy or Float Stock Availability (when failed end items are sent back for repair or thrown away)
Number of Serially Configured Common End Items or LRUs in System
There are also conditional primary impacters of operational availability (Ao). The additional mean time to restore when the forward supply level is not co-located with the weapon system is a conditional impacter.
Preventive maintenance and servicing actions periodically conducted to the system or its serially configured end items, impacts both system Ao and manpower needs. The frequency of scheduled or periodic actions that cause system down time and the time associated with performing each of these actions significantly impact Ao. Periodic or scheduled actions may include preventive maintenance, set up or tear down, software change actions, or servicing prior to and after missions.
End item redundancy or float stock availability when end items are used in lieu of LRUs to bring the system back up after an end item failure is another conditional primary impacter of Ao and readiness.
Commonality occurs when there are multiple quantities of the same item, which may be serially or redundantly configured. Serially configured common end items or LRUs adds to the system failure rate making them a more critical impacter of Ao. Commonality increases demands to cause a faster depletion rate of stocked LRUs, but is more economically advantageous since more quantities of the same item can be bought at discounted prices and less different items will be needed for support.

20. Secondary Impacters of Operational Availability
Stock Availability of Critical Item LRUs at Intermediate Retail Supply Levels
Order and Ship Time to Intermediate Retail Supply Levels
Centralized Support Level Mean Time to Obtain Backorders of Critical Item LRUs
The secondary impacters of Ao or operational readiness are listed on this slide. One of these secondary impacters are the stock availability of critical item LRUs at the intermediate retail supply levels and the order and ship time (OST) to the intermediate supply level.
The back order duration time of the critical LRUs at the centralized support level is another secondary impacter. A back order occurs when an item is ordered, but not available in stock to ship forward. Since the mean time to fill back orders are typically in terms of weeks or months, it can significantly add to the average OST to the intermediate supply level.
In fact, when stock availabilities are low at all retail supply levels, the order and shipment time from the wholesale supply level and its mean time to obtain a back order may start to become conditional primary impacters of Ao.

21. Conditional Secondary Impacters of Operational Availability
IF LRU IS NOT STOCKED OR REPAIRED AT INTERMEDIATE SUPPORT:
Stock Availability of Critical Item LRUs at Centralized Supply Level
Turn Around Time to Diagnose False Pulls if Performed
IF LRU IS REPAIRED AT INTERMEDIATE SUPPORT OR CONTRACTOR REPAIR & RETURN APPLIES INSTEAD OF USING DEPOT LEVEL SUPPLY:
Percentage Repaired at Intermediate Repair Level(s)/Contractor
Retrograde Shipping Time to Intermediate Repair Level(s)/Contractor
Turn Around Time for Intermediate Repair Level(s) Repairs/Contractor
Stock Availability of Critical Item Shop Replaceable Units (SRUs) at Intermediate Retail Supply Level(s)
There are also conditional secondary impacters of Ao or operational readiness based on Line Replaceable Unit (LRU) maintenance and supply concepts. If LRUs are not stocked or repaired at Intermediate support levels as in 2 level support, the stock availability of critical item LRUs at the centralized, wholesale supply level becomes more important. Also, the turn around time to diagnose false pulls and put them back into stock becomes a secondary impacter.
If LRUs are repaired at the intermediate support level or the contractor performs repair and return maintenance instead of ordering from depot level supply, different factors become more important. The percentage repaired at the intermediate maintenance level or the contractor and their Repair Cycle Time (RCT) become a secondary impacter. The RCT is based on the retrograde shipping time back to the intermediate maintenance level or the contractor and their corresponding turn around time to repair the failed LRU and return it to intermediate level stock. When LRU repair and return to the intermediate support level occurs, the stock availability of critical item Shop Replaceable Units (SRUs) needed to repair the LRU becomes more significant.

22. Tertiary Impacters of Operational Availability
Critical LRUs Within Redundant Configurations
Stock Availability of Critical Items at Centralized Supply Level
Administrative & Production Lead Times of Replacements (washouts, losses or non-returns)
Percentage of Critical Item LRUs Repaired at Depot or Contractor Repair Facility
Depot Level Repair Cycle Time
Back Order Duration Time of Critical Item SRUs
The factors that influence Operational Readiness to a lesser extent than the other factors previously discussed are listed as tertiary impacters of Ao. One of these factors are typically the critical LRUs within redundant configurations.
The stock availability of critical items at the wholesale or depot supply level is often a tertiary factor unless there are only 2 levels of maintenance and supply support. The Procurement Lead Times to replenish washouts, which includes both the Administrative Lead Time and Production Lead Time, are factors influencing the stock availability at the centralized support location.
The percentage of critical item LRUs repaired at depot or at the contractor repair facility and their repair cycle times (RCT) are often tertiary factors influencing stock availability at the centralized support location. The backorder duration time of critical item SRUs influences the RCT at the depot level. As previously mentioned, the RCT is equal to the Retrograde Ship Time plus the Turn Around Time to put the repaired LRU into wholesale level stock.

23. System Effectiveness
Probability System Performs Appropriately In Mission
System
Performance
Product
Effectiveness
Probability System Lasts Mission Without Failing
Mission
Reliability
System
Effectiveness
Probability System is Available to Accomplish Mission
Support
Effectiveness
This diagram provides a macro-level breakdown of system effectiveness. The product’s technical performance impacts the probability that the system performs appropriately in a mission, which is a system performance metric. The probability that the system lasts the mission duration without aborting or reducing mission capability is its mission reliability. Similar to system performance, mission reliability also influences mission success. Product effectiveness is the measure of mission success given that the system is used in a mission. Product effectiveness is basically the responsibility of the development contractor.
The probability that the system will be available to accomplish missions depends on the effectiveness of support. Operational Availability is a support effectiveness metric used prior to fielding and an operational readiness rate is a support effectiveness measure applied after fielding. Sortie rates apply to the availability of aircraft to perform planned missions. Support effectiveness is typically a mixture of Government and system contractor responsibility, unless Contractor Logistics Support is applied forward with the system. System effectiveness is impacted by both product effectiveness and support effectiveness because an unavailable system cannot perform a mission. The probability of mission success when intending to accomplish missions is a metric associated with system effectiveness.
e.g. Operational Availability
Readiness Rate
Sortie Rate
Basically Contractor Responsibility
Typically Government and Contractor Responsibility

24. Relationship of RMS & Availability to System Effectiveness
Capabilities
System
Functions
Performance
Priorities
Product
Mission Use
Effectiveness
Reliability
System
Maintainability
Effectiveness
Design for Supportability
Support
Operations/Uses
Effectiveness
Maintenance Concept
Support
e.g. Operational Availability
Readiness Rate
Sortie Rate
This diagram provides an expanded view showing the relationship of reliability, maintainability, supportability (RMS) and operational availability or readiness to system effectiveness. The product’s capabilities, functions and priorities are technical performance factors that impact system performance. Reliability, maintainability and design for supportability are product design factors that can influence both product effectiveness and support effectiveness. Mission reliability is based on the system’s reliability to not critically fail during mission duration use. Logistics reliability, which impacts the demand rate of items requiring support, is based on frequency of demands caused by the product’s reliability and the system’s operating usage rate. Other design for supportability factors, such as servicing, preventive maintenance, durability, transportability, etc. can also influence the frequency of the system going down and the logistics footprint.
Support effectiveness is impacted by the frequency of the equipment being down and its associated downtime that prevents the system from performing in a mission. The amount of downtime, which includes maintainability, is influenced by the timeliness of support to restore equipment or support efficiency. Support process times are functions of supply chain and maintenance chain response times and the influence of Integrated Logistics Support (ILS) elements on process efficiency. The maintenance concept and supply sparing mix determines which logistics chain response times will apply more frequently to impact support process efficiency. Supportability encompasses all the design and support process efficiency factors that influence support effectiveness.
Supply Spares Mix
Efficiency
Support Process Times
e.g. Logistics Response Times
Impact of ILS Elements
Supportability
Basically Contractor Responsibility
Typically Government and Contractor Responsibility