The Safety Analysis and Risk Mitigation Process  Section 3  3.5.4.2.2  Using the NAS Equipment Worst Credible Severity Table  Weather  Table 3.4: NAS Equipment Worst Credible Severity Table 1 Service  Functionality  Failure  Condition/Hazard  Environment /  System State  Effect  Worst Credible  Severity/Rating  NAV  Instrument  approach  guidance  Loss of function  IMC, CAT III, critical  phase of flight (i.e.,  near or immediately  after touchdown)  Insufficient  reaction time  for pilot to  execute  missed  approach  Hazardous  Large reduction  in safety margin  IMC, CAT I/II  All, CAT III,  non-critical phase of  flight  Missed  approach  Minor  Increased flight  crew workload  VMC  Pilot has to  take over  manual control  Minimal  Flight crew  inconvenience  Malfunction  Day, VMC  Hazardously  Misleading  Information  (HMI), missed  approach  Minor  Increased flight  crew workload  44 3.5_SMSM_201904  Originally published April 2019  Uncontrolled copy when downloaded 1. Risk should be assessed and determined with regard to its operational impact on the provision of air traffic management, communication, navigation, or surveillance services. The severity levels in Table 3.4 are derived from the operational safety analyses and other  documentation produced during initial safety assessments completed as part of the AMS  processes that define severity based on the inherent functionality of systems. References to  high or low traffic are relative indications during a period of time at any given facility.  When assessing the severity of hazards related to NAS equipment, use the “NAS Equipment”  row in  Table 3.3 in conjunction with Table 3.4. Table 3.4, the NAS Equipment Worst Credible  Severity Table, is the starting point for severity assessments of NAS equipment. The severity of  hazards that result from specific equipment changes may be lower or higher than the worst case  presented in Table 3.4 due to the possible controls that limit exposure or the interactions and  dependencies that exist with other systems. Because effects of losses in equipment  functionality and equipment malfunctions may not necessarily be traceable to a loss in  separation, equipment safety effects may require separate assessment from operational effects  (i.e., assess the severity of equipment loss or malfunction irrespective of operational severity). • Automated Surface Observing System (ASOS), Automated Weather Observing System (AWOS), Low-Level Wind Shear Alert System, Flight Service automation system, Operations and Supportability Implementation System, NextGen Weather Radar, Terminal Doppler Weather Radar, Weather and Radar Processor, and Weather Messaging Switching Center Replacement