13_October_Industry_Questions.pdf

Answers to questions from 6 October 2015

The Current SRD (System Spec) for the AN/SPN-50(V)1 Radar (SATR) is PMA-213-0100/R2 dtd 2 Oct 2015. Note: some or all of these questions below may be referring to an outdated version of the SRD.

Question 1:

Reference: Systems Requirement Document (SRD):

Discussion: Within the System Requirements Document (SRD), the following

Reliability/Availability/Maintainability (RMA) parameters are listed within

“Explanation/Rationale” column and/or Section 1.1 Terminology; however, these RMA parameters are not indicated to be “requirements” within the Tables of Requirements:

• Operation Availability KPP of at least 98%

• KSA Mean Time Between Operational Mission Failure System

(MTBOMFsys) of at least 4400 hours

• Reliability KSA value of 80 hours

Is it correct to assume these RMA parameters are to be considered System-Level requirements? Additionally, please provide additional guidance with respect to how the

“Reliability KSA value of 80 hours” is to be interpreted and utilized to drive the system design.

Answer: In the current version of the SRD, PMA-213 0100/R2, the contractor is required to meet the T: Requirement of 21,120 MTBF, as per below. The Explanation/Rationale column is meant for informational purposes and is NOT a requirement for the contractor to meet. The requirements that the contractor will be held to are in the T: Requirement column.

Section 3.1 Terminology provides context and background used to interpret the requirements.

In the current version of the SRD, PMA-213 0100/R2, the contractor is required to meet the T:

Requirement of 600 MTBM, as per below. The Explanation/Rationale column is meant for informational purposes and is NOT a requirement for the contractor to meet. The requirements that the contractor will be held to are in the T: Requirement column.

Question 2:

Reference: REQ 8.2.1:

Discussion: REQ.8.2.1 specifies that MTBF exceed 21,120 hours, yet within the

“Explanation/Rationale” column, the MTBOMFsys at least 4,400 hours. The MTBF requirement is specified as a “predicted MTBF based on a MIL HDBK 217 prediction or an industrial standard alternative prediction”. MTBF (as specified) is classically a prediction based upon the total failure rate of all pieces of the system in a simple series model. MTBOMFsys is defined/based upon system-level failure events, and therefore includes contributions of system-level fault tolerance (e.g., excess capacity, fail-over, redundancy, etc.). Additionally, failure rate contributions due to non-mission critical equipment are not included within the MTBOMFsys computation. Based upon the above, it is not possible for the MTBF to be larger than the MTBOMF. Clarification / guidance is requested with respect to the perceived conflict of these RMA requirements / parameters.

Question: Please provide clarification and guidance with respect to the perceived conflict of the RMA requirements/parameters noted above.

Answer: In the current version of the SRD, PMA-213 0100/R2, the contractor is required to meet the T: Requirement of 21,120 MTBF, as per below. The Explanation/Rationale column is meant for informational purposes and is NOT a requirement for the contractor to meet. The requirements that the contractor will be held to are in the T: Requirement column.

Question 3:

Reference: REQ 8.2.1:

Discussion: REQ.8.2.1 specifies the MTBF exceed 21,120 hours and is specified as a

“predicted MTBF based on a MIL HDBK 217 prediction or an industrial standard alternative prediction”. MTBF (as specified) is classically a prediction based upon the total failure rate of all pieces of the system within a simple series model. This MTBF requirement appears to be quite high when compared to other radar systems. NRL

Memorandum Report 3867 lists the AN/SPN-43A MTBF as 83 hours (theoretical) and 77 hours (operational). Clarification / guidance is requested with respect to computation method / equation used to define the MTBF requirement.

Question: Please clarify the computation method/equation used to define the MTBF requirement.

Answer: The computation method used to define the MTBF requirement is MIL-HDBK-217F, Military Handbook, Reliability Prediction of Electronic Equipment, 2 December 1991, Department of Defense.

Question 4:

Reference: REQ 8.1:

Discussion: REQ.8.1 specifies the inherent availability (Ai) shall be at least 99.990%.

The definition for Inherent Availability (Ai) provides an equation as: “Ai =

MTBOMF/(MTBOMF + MCMTOMF)”. If the MTBOMF of 4,400 hours and the

MCMTOMF of 0.75 hours are used within the above equation, the resultant A is less than

99.983, which is less than the Ai requirement. As Ai is listed as a requirement (within the

Tables of Requirements) and MTBOMF is not, please provide clarification as to which parameter is considered the design driver.

Question: Which parameter is considered the design driver?

Answer: SRD PMA-213-0100/R2 includes the corrected Requirement 8.1 Ai of = 99.980%.

MTTRS is the design driver for this requirement.

Question 5:

Reference: REQ 8.2.2:

Discussion: REQ. 8.2.2 specifies Mean Time Between Maintenance (MTBM) shall be at least 600 hours. REQ.8.2.3 specifies Mean Time Between Scheduled Maintenance shall be at least 6570 hours. If it is assumed that “all maintenance” is comprised of “Scheduled

Maintenance” and “Unscheduled Maintenance”, then the Mean Time Between

Unscheduled Maintenance is computed to be ~660 hours. “Unscheduled Maintenance” can be assumed to be the same as “Corrective Maintenance”. However, the MTBOMFsys is defined as at least 4400 hours. Clarification /guidance is requested with respect to the perceived conflict of these RMA requirements / parameters.

Question: Please clarify the perceived conflict of the requirements/parameters above

Answer: This question appears to be referencing an outdated SRD. The current SRD for the

AN/SPN-50(V)1 Radar (SATR) is PMA-213-0100/R2 dtd 2 Oct 2015, provided in Amendment

4. The question also appears to be highlighting a perceived conflict between corrective maintenance and MTBOMFsys. There is no conflict because unscheduled/corrective maintenance does not necessarily result in Operational Mission Failure.

Question 6:

Discussion: With respect to Mean Corrective Maintenance Time for Scheduled

Maintenance Actions (MCMTSMA), Mean Corrective Maintenance Time for Operational

Mission Failures (MCMTOMF), and Mean Corrective Maintenance Time for Unscheduled

Maintenance Actions (MCMTUMA), the definition uses the phrase “during a stated period of time.” It recommended that the wording be modified to “during the defined system lifetime’. These statistical RMA parameters are classically computed as averages

(means) over the life of the system and not as an instantaneous parameter.

Question: Please clarify the duration.

Answer: This question appears to be referencing an outdated SRD. The Current SRD (System

Spec) for the AN/SPN-50(V)1 Radar (SATR) is PMA-213-0100/R2 dtd 2 Oct 2015, provided in

Amendment 4.

Question 7:

Discussion: With respect to definition for Operational Availability (Ao), there are a few inconsistencies / contradictions:

• The Ao equation provided within the definition is “Ao= MTBF / (MTBF +

MTTR + MLDT)”

• The MTTR parameter is not defined within the SRD

• The MLDT parameter is not defined within the SRD (however, Mean Off

Board Logistics Delay Time (MOBLDT) is defined as 24 hours)

Clarification / guidance is requested with respect to the non-defined parameters.

The Ao equation provided within the definition is “Ao= MTBF / (MTBF +

MTTR + MLDT)”. This equation only encompasses downtimes associated with Failure events, yet other text in this Ao definition includes downtime contributions due to “planned maintenance” (i.e., preventive maintenance).

Clarification/guidance is requested with respect the required method to compute Ao.

Should all downtime be included or should the provided equation be used.

• Within the definition, the term “test duration time” is used.

Clarification / guidance is requested with respect to the definition of this parameter.

• Within the definition, the text “Planned maintenance time that is of periodicity greater than the test duration time is considered neutral time and is not included in the availability calculation” is used.

• This indicates that there is time within “total time” that is not either “uptime” or “downtime”, and is excluded from the Ao calculation.

Clarification / guidance is requested with respect this excluded time, as it could represent a statistically significant driver to the Ao calculation.

Question: Please clarify and provide guidance on the above points.

Answer: This question appears to be referencing an outdated SRD. The Current SRD (System

Spec) for the AN/SPN-50(V)1 Radar (SATR) is PMA-213-0100/R2 dtd 2 Oct 2015, provided in

Amendment 4.

Question 8:

Discussion: The reader is accustomed to a RMA requirement within fault tolerant systems that defines a time period that the system could recover from a system fault and return to compliant operational performance and not have the fault event considered a system failure/downing event. Is such a system-level fault-recovery time-period requirement considered applicable to the AN/SPN-50 system requirements?

Question: Please clarify and provide guidance

Answer: No, there is no system-level fault-recovery time-period allowed for the AN/SPN-

50(V)1 System.

Question 9:

Reference: REQ 2.5.8:

Discussion: REQ. 2.5.8 specifies that a 2D radar is adequate to meet AN/SPN-50(V)1 requirements. Section M of the RFP cites Lowest Evaluated Price of Proposals to be a selection criterion. Since a 3D radar provides elevation information of detected targets and therefore would improve safety of flight for aircraft in the pattern monitored by the

Shipboard Air Traffic Radar, it would seem that a 3D would add more value and therefore be given an accordingly higher degree of value in the selection criterion. Clarification / guidance is requested whether a 3D radar will be evaluated as adding value that a 2D radar does not add.

Question: Please clarify and provide guidance

Answer: Sections L&M of the RFP, inclusive of all amendments, identify the evaluation criteria.