## 3.5.4.2.1 Assessing Severity of NAS Equipment Hazard Effects 

NAS equipment is subjected to thorough safety analysis through the FAA Acquisition Management System (AMS). Refer to the Safety Risk Management Guidance for System Acquisitions, or go to the FAA Acquisition System Toolset website for more information on the AMS. As such, the inherent functional severity of certain NAS equipment hazard effects has been assessed and documented. 

When performing a safety analysis on NAS equipment that was previously assessed through the AMS, it is recommended to use the data, methodology, and results of the previous work as the starting point for the new safety analysis. If there are differences in functionality between the original, previously assessed system and the system undergoing analysis, the differences should be accounted for and documented in the new safety analysis. 

In general, NAS equipment can fail such that one of two effects is expected: 

• Loss of Function. The service is no longer provided. 

• Malfunction. The service is being provided inaccurately or with diminished integrity. 

When identifying functional failures that lead to hazards, the loss of function and the malfunction of constituent parts must be considered. The severity of malfunctions and losses of function from infrastructure systems, such as telecommunications and power systems, is dependent upon the services they support. 

Examples of the systems that provide services include, but are not limited to, the following: 

## Navigation (NAV) 

• Instrument approach systems : Localizer, glide slope (e.g., visual glide slope indicators, such as Precision Approach Path Indicator and Visual Approach Slope Indicator), Ground-Based Augmentation System, markers, approach lights, Distance Measuring Equipment, Localizer-Type Directional Aid, and Runway Visual Range 

• En Route guidance systems : Very-High Frequency Omnidirectional-Range Radio, Tactical Air Navigation, Distance Measuring Equipment, and Wide-Area Augmentation System 

## Communication (COMM) 

• Air-to-ground COMM : Headsets/microphones, speakers, voice switches, radio control equipment, and radios 

• Ground-to-ground COMM : Headsets/microphones, speakers, and voice switches 

## Surveillance 

• Automatic Dependent Surveillance – Broadcast (ADS-B), Airport Movement Area Safety System (AMASS), Automated Radar Terminal System (ARTS), Airport Surface Detection Equipment (ASDE), Air Route Surveillance Radar (ARSR), Air Traffic Control Radar Beacon System (ATCRBS), Mode Select Beacon System (MODES), Wide Area Multilateration (WAM), and Standard Terminal Automation Replacement System (STARS) 

