Downloaded from https://www.everyspec.com ADS-79D-HDBK P(H|+): Probability of having a healthy component given the system indicates an alarm P(H|-): Probability of having a healthy component given the system indicates a healthy component P(+|F): Probability of a system indicating an alarm given there is an unhealthy component requiring maintenance. P(+|F) is also called ―Probability of Detection‖ (POD) or ―Probability of Detecting a Fault‖ (PODF) which is specified in this document to equal or exceed 90% or 0.9 for critical components. POD is complementary to ―Probability of False Negative‖ (PFN). Therefore, POD + PFN = 1 and PODF = 1 – PFN. P(-|F):
Probability of a system not indicating an alarm given there is an unhealthy component requiring maintenance. P(-|F) is also called ―Probability of False Negative‖ (PFN) and is complementary to the Probability of Detection (POD). Therefore, PFN = 1-PODF and 1-POD. If POD is specified as 90% or greater, then PFN is less than or equal to 10% or 0.1. P(+|H): Probability of a system indicating an alarm for a healthy component = 1-PODH. P(+|H) is also called ―Probability of False Positive‖ (PFP) which is specified in this document to be equal to or less than 10% or 0.1 for critical components. PFP is complementary to ―Probability of True Negative‖ (PODH).
Therefore, PFP + PODH = 1 and PFP = 1 - PODH. Also, PFP = Significance level = (1 – Confidence). P(-|H): Probability of a system not indicating an alarm for a healthy component. P(-|H) is also called ―Probability of True Negative‖ or ―Probability of Detecting Healthy‖ components (PODH) which is specified in this document to be equal or greater than 90% or 0.9 for critical components. PODH is complementary to ―Probability of False Positive‖ (PFP). Therefore, PODH + PFP = 1 and PODH = 1 – PFP. 4. GENERAL GUIDANCE 4.1 Background.
Department of Defense (DoD) policy on maintenance of aviation equipment has employed Reliability Centered Maintenance (RCM) analysis and methods (Ref DOD CBM+ Guidebook, SAE JA1011, & SAE JA1012) to avoid the consequences of material failure. The structured processes of RCM have been part of army aviation for decades. RCM analysis provides a basis for developing requirements for CBM through a process known as ―Gap Analysis.‖ 1 The purpose of Condition Based Maintenance is to take maintenance action on equipment where there is evidence of need.
Maintenance guidance is based on the condition or status of the equipment instead of specified calendar or time based limits while preserving the system baseline risk. The key to implementing CBM is to ‗right size‘ CBM for the targeted platform. This is achieved by defining what is practical to implement vs. attempting to implement condition based maintenance on all possible equipment. This Design Handbook describes the elements that enable the issuance of CBM Credits, or 1 Felker, Douglas, ―PM/FM Matrix & CBM Gap Analysis in Reliability Centered Maintenance,‖ presented to the 2006 DoD Maintenance Symposium. 14