FAA-E-2772B PC RVR-Revised.pdf

FAA-E-2772B, August 22, 2006

SUPERSEDING

FAA-E-2772A, October 22, 2002 FAA-E-2772, October 30, 1985

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

PERFORMANCE SPECIFICATION

PC BASED

RUNWAY VISUAL RANGE (RVR) SYSTEM

Navigation Services Lighting Systems Office RVR Product Team (AJW-46)

DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

FAA-E-2772B

CONTENTS

SECTION PAGE

1 SCOPE

1.1 Scope

1.2 System overview

2 APPLICABLE DOCUMENTS

2.1 General

2.2 Government documents

2.2.1 Specifications and handbooks

2.2.1.1 FAA specifications

2.2.1.2 FAA handbooks

2.2.2 Other Government documents, drawings, and publications

2.2.2.1 FAA drawings

2.2.2.2 Other FAA documents

2.2.3 Non-FAA Government documents

2.3 Non-Government documents

2.4 Order of precedence

3 REQUIREMENTS

3.1 System definition

3.1.1 Functional layouts

3.1.2 Major components

3.1.2.1 Data Processing Unit (DPU)

3.1.2.2 Visibility Sensor (VS)

3.1.2.3 Ambient Light Sensor (ALS)

3.1.2.4 Runway Light Intensity Monitor (RLIM)

3.1.2.5 Controller Displays (CD)

3.2 Performance

3.2.1 RVR product requirements

3.2.1.1 RVR product definition

3.2.1.2 RVR product reports

3.2.1.2.1 Report contents

3.2.1.2.2 Report update rate

3.2.1.2.3 Report format

3.2.1.2.4 Reporting increments

3.2.1.3 RVR product calculation

3.2.1.3.1 Data validation

3.2.1.3.2 Trend data

3.2.1.3.3 Koschmieder’s Law

3.2.1.3.4 Allard’s Law

3.2.1.4 RVR Product accuracy

3.2.1.5 RVR Product availability

3.2.2 System requirements

3.2.2.1 System components

3.2.2.1.1 Maintainability of electronic equipment

3.2.2.1.1.1 Reliability

3.2.2.1.1.2 Maintainability

ii

3.2.2.1.1.3 Self checks

3.2.2.1.1.4 Periodic maintenance

3.2.2.1.2 Recoverability

3.2.2.1.3 Expandability

3.2.2.1.3.1 Hardware

3.2.2.1.3.2 Software

3.2.2.1.3.3 Future capability

3.2.2.1.4 System certification

3.2.2.2 Data Processing Unit (DPU)

3.2.2.2.1 DPU computer hardware

3.2.2.2.2 DPU operating system software

3.2.2.2.2.1 System control

3.2.2.2.2.2 System access and security

3.2.2.2.2.3 Watchdog timer

3.2.2.2.2.4 Time source

3.2.2.2.3 DPU RVR data sets

3.2.2.2.3.1 Raw data

3.2.2.2.3.2 Product data

3.2.2.2.3.3 Maintenance data

3.2.2.2.3.4 Operational data

3.2.2.2.3.5 NG RVR data

3.2.2.2.4 DPU data management

3.2.2.2.4.1 Data acceptance

3.2.2.2.4.2 Data processing

3.2.2.2.4.3 Product dissemination

3.2.2.2.4.4 Data storage

3.2.2.2.4.5 Data access

3.2.2.2.5 DPU archiving

3.2.2.2.6 DPU interfaces

3.2.2.2.6.1 Internal (subsystem) interfaces

3.2.2.2.6.1.1 Primary subsystem interfaces

3.2.2.2.6.1.2 Alternative subsystem interface capability

3.2.2.2.6.2 External user interfaces

3.2.2.2.6.2.1 External display systems

3.2.2.2.6.2.2 Automated Surface Observing System (ASOS)

3.2.2.2.6.3 External controlling interfaces

3.2.2.2.6.3.1 Maintenance Data Terminal (MDT)

3.2.2.2.6.3.2 Remote Maintenance Monitoring System

3.2.2.2.6.3.3 External time source

3.2.2.2.6.3.4 NG RVR interface

3.2.2.2.7 DPU power

3.2.2.2.8 DPU installation

3.2.2.3 Visibility Sensor (VS)

3.2.2.3.1 VS measurement processing

iii

3.2.2.3.2 VS measurement range

3.2.2.3.3 VS calibration

3.2.2.3.3.1 Calibration device

3.2.2.3.3.2 Calibration process

3.2.2.3.4 VS alignment

3.2.2.3.5 VS accuracy

3.2.2.3.6 VS interfaces

3.2.2.3.7 VS power

3.2.2.3.8 VS installation

3.2.2.4 Ambient Light Sensor (ALS)

3.2.2.4.1 ALS measurement processing

3.2.2.4.2 ALS interfaces

3.2.2.4.3 ALS power

3.2.2.4.4 ALS installation

3.2.2.5 Runway Light Intensity Monitor (RLIM)

3.2.2.5.1 RLIM measurement processing

3.2.2.5.2 RLIM interfaces

3.2.2.5.3 RLIM power

3.2.2.5.4 RLIM installation

3.2.2.6 RVR Controller Display (CD)

3.2.2.6.1 CD readability

3.2.2.6.2 CD data display and presentation

3.2.2.6.2.1 Low visibility alarm threshold (LVAT) limits

3.2.2.6.3 CD control

3.2.2.6.3.1 Data entry/access

3.2.2.6.3.2 Keypad intensity

3.2.2.6.3.3 Controls

3.2.2.6.3.3.1 Display intensity

3.2.2.6.3.3.2 Keypad

3.2.2.6.3.3.3 Touchscreen

3.2.2.6.3.3.4 Volume

3.2.2.6.3.3.5 Power

3.2.2.6.4 CD alarm operation

3.2.2.6.4.1 Audio alarm operation

3.2.2.6.4.2 Visual alarm operation

3.2.2.6.5 CD self-test

3.2.2.6.6 CD interface

3.2.2.6.7 CD power

3.2.2.6.8 CD installation

3.2.2.6.8.1 Location

3.2.2.6.8.1.1 Local configuration

3.2.2.6.8.1.2 Remote configuration

3.2.2.6.8.2 Hardware size

3.2.3 Electronic equipment, general requirements

iv

3.2.3.1 Operating environmental conditions

3.2.3.2 Transportability

3.2.3.3 Materials, processes and parts

3.3 System characteristics

3.3.1 Safety

3.3.2 Security

3.3.2.1 Physical security

3.3.2.2 Information security

3.3.3 Human factors

4 VERIFICATION

4.1 Verification Requirements Traceability Matrix (VRTM)

4.1.1 Verification methods

4.1.1.1 Test

4.1.1.2 Demonstration

4.1.1.3 Analysis

4.1.1.4 Inspection

5 PACKAGING

6 NOTES

6.1 Intended use

6.1.1 Precision approach limits

6.1.2 RVR system

6.1.3 RVR system users

6.2 Acquisition requirements

6.3 Definitions

6.4 Abbreviations and acronyms

6.5 ICAO compliance

v

FIGURES

FIGURE PAGE

FIGURE 3-1 RVR System functional block diagram FIGURE 3-2 Controller display configurations

TABLES

TABLE PAGE

TABLE 3-1 Standard runway light settings TABLE 3-2 Runway light intensity when edge and centerline settings match TABLE 3-3 Runway light intensity when centerline setting is zero (0) TABLE 3-4 RVR system interface summary TABLE 3-5 Characteristics of two-wire interfaces TABLE 3-6 DPU/Sensor data interface to the Radio Link TABLE 3-7 Runway light currents TABLE 3-8 CD data presentation TABLE 3-9 Audio alarm conditions TABLE 3-10 Displayed alarm conditions TABLE 3-11 Channel activation sequence TABLE 3-12 General Navigational Aid electronic equipment requirements TABLE 3-13 Environmental conditions TABLE 3-14 Fungi susceptibility of material TABLE 6-1 Precision approach limits and RVR sensor locations TABLE 6-2 RVR compliance with ICAO Annex 3

APPENDICES

APPENDIX PAGE

APPENDIX A. Verification Requirements Traceability Matrix (VRTM) vi

1 SCOPE

1.1 SCOPE

This performance specification establishes the performance, design and verification requirements for the forward-scatter meter PC-based Runway Visual Range (RVR) System.

1.2 SYSTEM OVERVIEW

The RVR is an essential system consisting of the hardware and software to calculate an estimate of how far down a runway a pilot can see. The objects viewed may be runway lights or runway markings. The RVR System provides reliable RVR measurements to various users including:

local Airport Traffic Control Tower (ATCT) cab and Terminal Radar Approach Control (TRACON) air traffic controllers; Enhanced Traffic Management System (ETMS)/Collaborative Decision Making (CDM) users (airline dispatchers); Automated Surface Observing System (ASOS) and Automated Weather Sensors System (AWSS) users; and Airport Operations Center personnel.

Currently two types of RVR Systems are deployed in the National Airspace System (NAS):

Tasker 500 Transmissometer Systems, deployed in the late 1960s; and the new generation-RVR (NGRVR), first deployed in 1994.

The performance requirements established in this specification are for a PC based-RVR System built on the systems requirements and component concepts that have proven successful with the NGRVR. Experience with current operational systems and the apparent availability of commercial systems indicate that forward-scatter meter technology is the current preferred type of visibility sensor for NAS RVR systems, therefore, the PC-based RVR System will also employ this technology. Through the use of modern commercial products and components, the PC-based RVR should exceed reliability, maintainability and availability objectives of this specification.

The PC-based RVR system may be collocated with an existing NG RVR system at airports within the NAS. In such instances, the PC-based RVR system must receive NG RVR system data and integrate it with similar data of the PC-based system for representation of RVR conditions over the relevant RVR airport configuration.

2 APPLICABLE DOCUMENTS

2.1 GENERAL

The documents listed in this section are specified in Sections 3 and 4 of this specification. This section does not include documents cited in other sections of this specification or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements in the documents cited in Sections 3 and 4 of this specification, whether or not they are cited specifically herein.

2.2 GOVERNMENT DOCUMENTS

2.2.1 Specifications and handbooks

The following specifications and handbooks form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those listed in the issue of the Department of Defense Index of Specifications and Standards (DoDISS) and supplement thereto, cited in the solicitation.

2.2.1.1 FAA specifications

FAA-E-2702A Low-Impact Resistant Structures.

FAA-G-2100G Electronic Equipment, General Requirements.

http://www.faa.gov/asd/standards/faa-g-2100g.pdf NAS-MD-793 Remote Maintenance Monitoring System Functional Requirements for the Remote Monitoring Subsystem (RMS).

2.2.1.2 FAA handbooks

FAA Order 6000.15C General Maintenance Handbook for Airway Facilities.

FAA TI-6560.17 Instructional Book-Runway Visual Range System On-site

Requirements.

[Copies of specifications and other applicable FAA documents may be obtained from the Contracting Officer (CO) in the office issuing the invitation-for-bids or request-for-proposals.

The request should fully identify material desired, i.e., standard, drawing and specification plus amendment numbers and dates. Requests should cite this specification or the related Screening Information Request (SIR) for the RVR or other use to be made of the requested material. A number of the documents may be obtained at Web site: http://isddc.dot.gov/.]

2.2.2 Other Government documents, drawings, and publications

The following other Government documents, drawings and publications form a part of this document to the extent specified herein. Unless otherwise specified, the issues are those cited in the solicitation.

2.2.2.1 FAA drawings

FAA- D-6155-21 ALSF-2 (6'-128') & MALSR (40'-128') LIR Structures, Assembly

Instructions for LIR Structures MG-20, MG-30, & MG-40.

FAA- D-6282-X New-Generation Runway Visual Range System.

2.2.2.2 Other FAA documents

DOT/FAA/CT-96/1 Human Factors Design Guide for Acquisition of Commercial Off

The Shelf Subsystems, Non-Developmental Items and Developmental Systems.

DOT/FAA/CT-01/08 Human Factors Design Guide Update (Report Number DOT/FAA/CT-96/01: A Revision to Chapter 8-Computer Human Interface Guidelines.

NAS-IC-51035101 Interface Control Document, Maintenance Processor Subsystem (MPS) to Remote Monitoring Subsystem (RMS) Using Simple Asynchronous Interface (SAI).

FAA-NAS-IR-33113106 Interface Requirements Document-PC based Runway Visual Range (RVR) System to Automated Surface Observing System (ASOS)-Draft.

FAA-NAS-IR-32063311 Interface Requirements Document-Facility Global Positioning System (GPS) Time Source to PC Based Runway Visual Range (RVR) System-Draft.

FAA-NAS-IR-33110001 Interface Requirements Document-PC Based Runway Visual Range (RVR) System to RVR CD Subsystem or External User- Draft.

2.2.3 Non-FAA Government documents

ASTM G21 Standard Practice for Determining Resistance of Synthetic

Polymeric Materials to Fungi.

L-P-516 Plastic Sheet & Plastic Rod, Thermosetting, Cast.

MIL-I-10 Insulating Compound, Electrical, Ceramic Class L.

MIL-I-23264 Insulators, Ceramic, Electrical and Electronic, General

Specification for.

MIL-S-22473 Sealing, Locking and Retaining Compounds: (Single-Component).

MIL-S-46163 Sealing. Lubricating, and Wicking Compounds: Thread-Locking, Anaerobic. Single Component.

MIL-STD-810 F Environmental Test Methods and Engineering Guidelines.

MIL-T-22361 Thread Compound; Antiseize, Zinc Dust-Pevolatum.

TT-S-1732 Sealing Compound, Pipe Joint and Thread, Lead Free General

Purpose.

NFPA-70 National Electrical Code.

29 CFR 1910 Occupational Safety and Health Standards.

29 CFR 1926 Safety and Health Regulations for Construction.

[Request for copies of: Military documents should be addressed to Defense Automated Printing Service, Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. Web site:

http://dodssp.daps.mil/; American Society for Testing Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959; National Fire Protection Association (NFPA), One Batterymarch Park, PO Box 9101, Quincy, MA 02269-9101.]

2.3 NON-GOVERNMENT DOCUMENTS

The following document(s) form a part of this document to the extent specified herein. Unless otherwise specified, the issues of the document, which are Department of Defense (DoD) adopted, are those listed in the issue of the DoDISS cited in the solicitation. Unless otherwise specified, the issues of documents not listed in the DoDISS are the issues of the documents cited in the solicitation.

EIA-STD-232F Interface Between Data Terminal Equipment and Data Circuit

Terminating Equipment Employing Serial Binary Data Interchange.

EIA-STD-485 Standard for Electrical Characteristics of Generators and Receivers for use in Balanced Digital Multipoint Systems.

2.4 ORDER OF PRECEDENCE

In the event of conflict between the text in this document and the references cited, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulation unless a specific exemption has been obtained.

3 REQUIREMENTS

Except where specifically noted, the RVR System shall meet the requirements stipulated herein while operating over the full range of the operating environment.

3.1 SYSTEM DEFINITION

3.1.1 Functional layouts

The RVR System functional block diagram, FIGURE 3-1, provides a functional block diagram of the RVR, its major components and external interfacing items.

RVR SYSTEM COMPONENTS

FIGURE 3-1 RVR System functional block diagram

3.1.2 Major components

3.1.2.1 Data Processing Unit (DPU)

The major functions of the DPU are data acceptance, data validation, data processing, product dissemination and data storage. The DPU accepts data inputs, performs various data validation functions, implements RVR algorithms and distributes RVR products. The DPU is also responsible for maintaining real time archiving, system control, system configuration and

Optional Redundant DPU

Ext. Time Source

Various Airport Airport Traffic Various Remote Control Tower LocationsLocations r

MDT

Controller Display

Data Processing Unit (DPU) (Includes Monitor/ Keyboard/Mouse)

Visibility S soen ACE-IDS

ASOS

(VS) VS SIE

ETMS

MPS

Controller Display

MDT

Ambient Light ALS SIE Sensor (ALS)

Current Loop Sensors RLIM SIE NGRVR maintenance diagnostic and reporting functions. The DPU will have a central processing unit (CPU), operating system software, sensor interfaces, communication interfaces, power supply, monitor, keyboard and a mouse.

The range of capacity, functionality and capability of the DPU is the same regardless of the size or location of the airport. The number of visibility sensors (VS), ambient light sensors (ALS) and runway light intensity monitors (RLIM) connecting to the DPU will vary with each airport's individual requirements. The VS, ALS and RLIM sensors may be located up to 5 nautical miles

(nm) from the DPU. The DPU will also accept input from the NG RVR DPU.

3.1.2.2 Visibility Sensor (VS)

The RVR VS is a forward-scatter meter that utilizes the most current sensor technology to measure the clarity of the atmosphere in terms of the visible extinction coefficient. The VS will typically be installed adjacent to a runway at up to three positions along the length of the runway: touchdown (TD), midpoint (MP) and rollout (RO).

Although VS measurements are made at a specific spatial location, their measurements are used to represent the extinction coefficient over large volumes of space. United States installation procedures permit a single sensor to provide RVR data for locations within 2,000 feet of the sensor.

3.1.2.3 Ambient Light Sensor (ALS)

The ALS provides the background light component for the RVR product. Normally two ALSs will be installed in central locations relative to the airfield environment. A single ALS is typically used at airports with only one visibility sensor.

3.1.2.4 Runway Light Intensity Monitor (RLIM)

The RLIM measures runway light settings, which establish the nominal intensities of a High Intensity Runway Lighting (HIRL) System. An RLIM will be capable of monitoring up to eight runway light current loops per runway. RLIMs will be installed within the airport power vault(s).

3.1.2.5 Controller Displays (CD)

Following calculation in the DPU, the content of each RVR product will be easily exportable via standard interface connections to displays such that it is associated with the TD, MP or RO position of a given runway. The DPU will easily interface with several different CDs to include:

the RVR Controller Display (see 3.2.2.6), hereafter referred to as “CD”; the existing CD Type FA-10268/6, hereafter referred to as CD Type FA-10268/6; and the existing ASOS Controller Equipment-Information Display System, hereafter referred to as ACE-IDS.

3.2 PERFORMANCE

3.2.1 RVR product requirements

3.2.1.1 RVR product definition

The RVR product is a calculated estimate of how far down a runway a pilot is expected to see. It is calculated using standardized equations from measurements of three parameters: extinction coefficient, ambient light level and the intensity of the runway lights. The RVR distance values shall be reported in feet.

3.2.1.2 RVR product reports

3.2.1.2.1 Report contents

The RVR products reports shall consist of: the runway identification (ID) and sub-ID; the most recently computed RVR product; RVR trends (increasing, decreasing or steady); and the associated intensity settings for the runway lights (edge and centerline).

3.2.1.2.2 Report update rate

The reported RVR products shall be updated at a minimum rate of once per 15 seconds, or at the rate specified in the applicable Interface Requirements Documents (IRD) identified in 2.2.2.2 and 3.2.2.2.6.

3.2.1.2.3 Report format

The reported RVR product formats shall be as specified in the applicable Interface Requirements Documents identified in 3.2.2.2.6.2 and 3.2.2.2.6.3.

3.2.1.2.4 Reporting increments

The RVR System shall report RVR values in: 100-foot increments from zero (0) feet through 800 feet; 200-foot increments from 800 through 3,000 feet; and, 500-foot increments from 3,000 through 6,500 feet.

A value of 6,500 feet shall be used to report RVR above 6,249 feet. An RVR value of zero (0) feet shall indicate runway visual range below 50 feet. The reported RVR shall be rounded off from the calculated value; therefore, the RVR values from 751 feet to 899 feet would be reported as 800 feet.

3.2.1.3 RVR product calculation

The validity of the VS and ALS measurements shall be checked. Valid values shall be used to calculate 60-second running averages. The RVR product shall be calculated from 60-second running averages of the readings of the VS and the ALS and the last valid reading of the RLIM.

The intensities of the runway edge and centerline lights shall be used, as appropriate for the calculated RVR value. Two RVR values shall be calculated: the first for seeing objects using Koschmieder’s Law (only VS is used); and the second for seeing lights using Allard’s Law (all three sensors are used). The larger calculated value shall be adopted and rounded off according to the reporting increments of 3.2.1.2.4. The RVR product sent to ASOS shall use RLIM light setting step five (5).

3.2.1.3.1 Data validation

All sensor data shall be validated to ensure there are no transmission errors or sensor failures.

The sensor measurement data shall pass reasonableness checks, including range limits or rate of change limits. If any sensor measurements are found to be invalid, the measurements shall be rejected. Invalid sensor data shall cause an appropriate alarm to be set. Invalid sensor data alarms shall be recorded in the RVR System maintenance data set (see 3.2.2.2.3.3).

3.2.1.3.2 Trend data

The RVR trend (increasing, decreasing or steady) shall be determined using a five (5) minute sampling window.

3.2.1.3.3 Koschmieder’s Law

Koschmieder’s Law states:

Ct = e-σR

Where: R = RVR σ = atmospheric extinction coefficient Ct = contrast threshold, which is taken as 0.05

Koschmieder’s Law shall give zero RVR whenever the ALS reading is below the night limit of 2 Foot-Lamberts (fL) (6.85 cd/m2).

3.2.1.3.4 Allard’s Law

In metric units, Allard’s Law states:

Et = (I/R2)e-σR

Where: Et = visual threshold in lux

R = RVR in meters (m) σ = atmospheric extinction coefficient in m-1

I = runway light intensity in candelas

The visual threshold Et is given by:

Log10 Et = -5.7 + 0.64 log B

Where: B = background luminance (ambient light) in cd/m2.

A lower threshold on Et is set at 6.8x10-6 lux, which corresponds to the night limit.

The standard runway light settings of a HIRL System, TABLE 3-1, shall be used.

TABLE 3-1 Standard runway light settings

Nominal Intensity (I) Candelas (cd) Light Setting

Edge Lights Centerline Lights

Step 0 (Off) Zero (0) Zero (0)

Step 1 15 7.5

Step 2 120 60

Step 3 500 250

Step 4 2,500 1,250

Step 5 10,000 5,000

The nominal intensity of the centerline lights for the same current is half that of the edge lights.

Because the centerline lights are located in the runway pavement and are hence more susceptible to contamination than the edge lights, their intensity is degraded by an additional factor of two in calculating the RVR in the following algorithms. Note that for high RVR values the edge lights are more visible because they are brighter than the centerline lights. For low RVR values the centerline lights are more visible than the edge lights because the pilot’s vision is within the main beam of the centerline lights but is in the weaker side lobes of the edge lights.

If both the edge light settings and the centerline light settings have values of 1, 2, 3, 4 or 5, then the value to be used for runway light intensity (I) in Allard's Law for certain values of RVR (in feet) shall be in accordance with TABLE 3-2, Runway light intensity when edge and centerline settings match. Note that the centerline light intensity and edge light intensity are taken from the light setting/candela table for the appropriate values of centerline light setting and edge light setting, respectively.

TABLE 3-2 Runway light intensity when edge and centerline settings match

No. Condition Action

1 RVR < 600 I = 50 % of Centerline Light Intensity

2 600 < RVR < 1,000 Interpolate linearly for "I" between a value of 50 % of Centerline Light Intensity at 600 feet and 100 % of Edge Light Intensity at 1,000 feet

3 RVR > 1,000 I = 100 % of Edge Light Intensity

If the edge light setting has a value of 1, 2, 3, 4 or 5 and the centerline light setting has a value of zero (0) then the value to be used for runway light intensity (I) in Allard's Law for certain values of RVR (in feet) shall be in accordance with TABLE 3-3, Runway light intensity when centerline setting is zero (0). Note that if the edge light setting is zero (0), then, regardless of the centerline light setting, a value of zero (0) shall be assigned to the Allard's Law solution.

TABLE 3-3 Runway light intensity when centerline setting is zero (0)

No. Condition Action

1 RVR < 1,000 Assign a value of zero (0) to the Allard's Law solution

2 RVR > 1,000 I = 100 % of Edge Light Intensity

Note: TABLES 3-2 and 3-3 light setting conditions assume that both edge and centerline lights are configured for a given runway. For those cases where centerline lights are not configured for a given runway (TABLE 3-3) the following action shall be taken: Allard's Law must be computed using a runway light intensity (I) corresponding to the edge light setting for all values of RVR; the RVR System must display a blank space in the associated CD centerline light setting data field; any attempt to configure a runway without edge lights must be treated as erroneous input and rejected by the RVR System.

3.2.1.4 RVR Product accuracy

Because of the complexity of Allard’s Law, an overall RVR accuracy is not specified. Rather, the accuracy of each individual sensor is specified (see 3.2.2.3 and 3.2.2.4). Note that the RVR value is much more sensitive to extinction coefficient errors than ambient light or runway light intensity errors.

3.2.1.5 RVR Product availability

RVR product availability is more important than strict RVR product accuracy. If the RVR system performance is degraded by environmental factors, such as excessive sensor window contamination, the RVR product shall continue to be output, provided that the reported RVR is not greater than the actual RVR.

3.2.2 System requirements

3.2.2.1 System components

The RVR System consists of the sensors necessary to produce required RVR products and a windows-based, industrial-grade DPU. The DPU shall contain the necessary hardware and software to meet the requirements of this specification. FIGURE 3-1 illustrates the typical interfaces that the DPU will have to meet the requirements of this specification. The sensor complement for each airport shall include a minimum of one ALS and as many VSs and RLIMs as are needed to provide coverage for the instrumented runways of the airport. The RVR System configuration shall be capable of being configured with two DPUs; two ALSs with sensor interface electronics (SIE); 30 VSs with SIEs; 10 RLIMs consisting of SIEs with 8 current loop sensors each; and 32 CDs on each of the local and remote communications lines.

3.2.2.1.1 Maintainability of electronic equipment

The RVR System shall provide for a site and depot concept of maintenance. This concept assumes the use of modular equipment that enables maintenance specialists to correct a majority of equipment failures by replacing the faulty lowest replaceable unit (LRU).

3.2.2.1.1.1 Reliability

A core RVR System, consisting of one DPU, one ALS with SIE and connecting cable, one VS with SIE and connecting cable, two CDs, and one RLIM SIE with four current loop sensors, shall have a Mean-Time-Between-Failure (MTBF) of 5,000 hours, not including communications failures external to the RVR System components.

3.2.2.1.1.2 Maintainability

The RVR System components shall be transportable by one Maintenance Specialist, contain a minimum number of subsystems to meet the RVR System requirements, and be easy to install.

The Mean-Time-To-Repair (MTTR) a single point failure of a core RVR System, consisting of one DPU, one ALS with SIE and connecting cable, one VS with SIE and connecting cable, two CDs, and one RLIM SIE with four current loop sensors, shall be 30 minutes or less exclusive of time required to travel to the affected location.

3.2.2.1.1.3 Self checks

The RVR System shall incorporate self-checks to verify proper operation of all major subsystems. Self-checks shall be used to validate the system measurements and to determine when maintenance is required. Examples of typical functions include power supply voltages, out-of range performance and window contamination signals. Hard alarms shall be generated whenever a parameter is found to be outside acceptable operation limits. A soft alarm shall be generated whenever a parameter is approaching the limit for acceptable operation. The RVR System shall include software that determines whether all RVR processes are operating properly.

The system shall be capable of detecting at least 90 % of all faults. In addition, as a minimum, 90 % of all detected faults shall be isolated to one LRU using automatically initiated diagnostics.

Automatically initiated diagnostics shall occur when a hard alarm occurs. Automatically initiated diagnostics shall be designed to identify the faulty LRU. Additional manually initiated diagnostics shall be provided to offer more detailed information on the status of LRUs to aid the maintenance process. All built-in diagnostics shall be capable of initiation from the MPS or a portable MDT. Complete results of the built in diagnostics shall be available to the Maintenance Specialist.

If a failure cannot be isolated to a single LRU, a list of the suspected LRUs shall be generated in order of probability (highest to lowest). Any built-in diagnostics contained in on-line system hardware shall be functionally independent of the rest of the on-line system.

Sensor and DPU self check data, including alarm information, shall be stored in the maintenance data set (3.2.2.2.3.3) for output to the MDT and MPS interfaces, as appropriate.

3.2.2.1.1.4 Periodic maintenance

The RVR System shall be designed such that periodic maintenance of the DPU is not required for the system more often than biweekly. Periodic maintenance on the RVR sensors, at the sensor(s) location, shall not be required more often than once every 90 days. The mean periodic maintenance time (MPMT) shall not exceed 4 hours over a 90 day period for the following system configuration: one DPU, one ALS with SIE and connecting cable, one VS with SIE and connecting cable, two CDs, and one RLIM SIE with four current loop sensors. The periodic maintenance tasks for the sensors shall require the services of only one person. During the periodic maintenance visits, the calibration and operation of each sensor and the system shall be verified. The procedures and the required frequency of calibration shall be defined by the contractor, keeping in mind that sensor drift outside of the required specification limits constitutes a failure of the system.

The RVR DPU hardware/software configuration shall be designed such that scheduled periodic maintenance is minimized. The RVR System operations shall not be interrupted for routine DPU periodic maintenance.

3.2.2.1.2 Recoverability

All system components of an operationally capable system shall recover automatically from the loss of power, the loss of an interface, loss of critical processes (any RVR System process) and processor lock up.

3.2.2.1.3 Expandability

3.2.2.1.3.1 Hardware

The RVR System shall be capable of a 50 % growth in the size of the system (additional VSs, ALSs, RLIMs, CPU time, DPU memory, displays and communications ports).

3.2.2.1.3.2 Software

The RVR System shall be capable of having the software/firmware expanded by up to 50 % of the total lines of code initially implemented.

3.2.2.1.3.3 Future capability

The RVR System shall be capable of accepting different visibility sensor types, and of upgrading with newer, improved sensors without requiring hardware redesign or major software changes which require use of more than 50 % of addressable memory.

3.2.2.1.4 System certification

The RVR System shall be certifiable, that is, capable of validating that the system is providing the advertised service to the user in compliance with Chapter 5 of FAA Order 6000.15C.

3.2.2.2 Data Processing Unit (DPU)

The DPU shall use open architecture, standard multitasking Windows-based operating system and object-oriented application software. The computer/server components shall employ current technology that must be sustainable with replacement hardware and software that are both forward and backward compatible.

To assure RVR System availability at critical airports, the option shall be provided for using dual DPUs. Both DPUs shall receive all inputs. The outputs shall be provided by only one DPU (normally the primary DPU). The proper functioning of both DPUs shall be monitored and any failures in either DPU logged to the maintenance files and maintenance interfaces of both. If the primary DPU fails to provide valid RVR products because of a DPU software or hardware failure, RVR functionality shall automatically be switched to the backup DPU.

3.2.2.2.1 DPU computer hardware

The RVR DPU shall contain the necessary processors, memory, disk storage and input/output (I/O) cards/capabilities to, at a minimum, implement the required RVR functionalities. The DPU shall consist of a high-reliability industrial grade server/computer with Redundant Array of Independent Disks (RAID) – two protected redundant hot-swappable hard drive storage and compact disc-rewritable (CD-RW) drive, display, keyboard, mouse and I/O interfaces.

3.2.2.2.2 DPU operating system software

All RVR application software shall be run under a standard Microsoft Windows-based operating system. The application software shall include the functions for system configuration, data validation, system monitoring, diagnostics, communication control and other appropriate routines for execution of the various system functions.

Without making code changes, the DPU shall be locally capable, with restricted access, of configuring: selected system parameters (including configuration, measurements and maintenance parameters) with flexible data formats and locations, including alarms for limits on varying parameters; and output products by specifying parameters to be included, formats, output frequency, output port (or file name and location) and port parameters.

3.2.2.2.2.1 System control

The RVR system shall be controlled by a single entity at any given time as prioritized in the following list: locally through the DPU’s keyboard, mouse and display, locally through the MDT, and remotely through the MPS.

An “on-site operator” is an operator using a local DPU console or a local MDT interface.

If a system control session is initiated using the local DPU console, the local MDT interface shall immediately abort any existing MDT system control sessions and prevent any other MDT system control sessions as long as the local DPU console has an active system control session.

If there is an active system control session on either the local DPU console or a local MDT interface, the MPS interface shall ignore all incoming Equipment Command Messages and Status Command Messages as specified in Section 3.4.3 of NAS-MD-793.

System control shall include the ability to: (a) display the current output of the RVR System including the RVR products and sensor output data; (b) retrieve and display historical RVR data/products from archived files; and (c) allow an on-site operator to initially configure or reconfigure the RVR System airport configuration that includes the ability to independently configure primary and alternate runways, sensor configuration, and system security.

3.2.2.2.2.2 System access and security

Users shall be able to log into the RVR System on-site using the DPU keyboard and display or MDT. User identification shall be via password. User capabilities shall be limited by general network considerations such as read or write access to specific directories and by specific RVR System functions such as viewing raw data, current products, maintenance data, operational data, archived data, and changing configurations.

3.2.2.2.2.3 Watchdog timer

The DPU shall include a Watchdog Timer to detect a processor lock-up and to verify that all RVR System processes are correctly performing their functions. In the event the Watchdog Timer detects a processor failure, it shall initiate a reboot. In the event the Watchdog Timer detects a processor failure in the active DPU of a dual DPU RVR System configuration, a reboot is initiated in the active DPU, and the inactive DPU shall switch to active status. Reboots shall be logged to a daily reboot file. The reason for the reboot shall be logged.

3.2.2.2.2.4 Time source

The RVR System shall use an external time source for synchronization of data with other NAS systems as specified in 3.2.2.2.6.3.3. All RVR System functions requiring the use of date and/or time shall utilize the date and time from a DPU system clock synchronized to the external source.

3.2.2.2.3 DPU RVR data sets

3.2.2.2.3.1 Raw data

The raw data shall consist of: date time stamp; extinction coefficient; ALS background luminance; associated runway light settings (edge and centerline); current status of sensors, communications and DPU status. Status shall be classified valid or invalid.

3.2.2.2.3.2 Product data

The product data shall consist of: date time stamp; runway ID and sub-ID; most recently computed RVR product; and RVR trends (increasing, decreasing, or steady).

3.2.2.2.3.3 Maintenance data

The maintenance data shall consist of: date time stamp; hard and soft alarms, warnings and diagnostics; and system failures.

3.2.2.2.3.4 Operational data

The operational data shall consist of: date time stamp; current and previous system configurations with user name; and system calibrations.

3.2.2.2.3.5 NG RVR data

The NG RVR data shall consist of: date time stamp; VS SIE number, extinction coefficient, window contamination values, sensor temperature, and all maintenance bytes for all configured NG RVR VSs; NG RVR ALS measurement, window contamination value, sensor temperature, and all maintenance bytes; RLIM SIE number, light step measurements for each of the current loop sensors, and all maintenance bytes for all configured NG RVR RLIMs; and the maintenance parameter bytes for the NG RVR Product Processing Unit.

3.2.2.2.4 DPU data management

3.2.2.2.4.1 Data acceptance

The DPU shall have the capability to receive RVR sensor data as well as system diagnostics information directly from the RVR sensors. The DPU shall have the capability of receiving all the NG RVR data identified in 3.2.2.2.3.5.

3.2.2.2.4.2 Data processing

The DPU shall implement the product algorithms. The DPU shall prepare the processed data as RVR products in a digital format.

3.2.2.2.4.3 Product dissemination

The DPU shall provide RVR products to the interfaces identified in 3.2.2.2.6 as defined by the applicable IRD.

3.2.2.2.4.4 Data storage

The current product plus raw, maintenance and operational data shall be stored. Every minute the current product and raw and maintenance data shall be archived in three separate daily data files:

product data, raw data and maintenance data. Operational data shall be stored quarterly in data files to include the system configuration and calibration data. Data storage shall use an American Standard Code for Information Interchange (ASCII) format to facilitate readability.

3.2.2.2.4.5 Data access

The stored data shall be accessible to programs running on the DPU and to authorized users, located either locally or at a remote site.

3.2.2.2.5 DPU archiving

The DPU shall automatically archive RVR product data, raw data, maintenance data, operational data and data received from the NG RVR EU port and have the capacity to store all such data for more than 1.3 years.

The archiving software shall provide the capability for easily extractible and protected retrieval and verification of the stored data by date time stamp to the display and CD-RW drive. The archiving software shall only allow manual deletion of obsolete (older than 1-year) archived data files that have been confirmed as being previously successfully transferred to a CD for permanent archiving.

The accessing, viewing, and downloading of archive data shall be capable without interruption to RVR System operation, including the real time archiving of data.

3.2.2.2.6 DPU interfaces

3.2.2.2.6.1 Internal (subsystem) interfaces

TABLE 3-4 provides a summary of the RVR System interfaces. Each RVR sensor type shall be capable of communicating with the DPU across three communication media: copper landline, fiber network or radio link. The primary subsystem interface will utilize copper landlines or fiber-optic network communications utilizing a two-wire modem interface. Alternative means of communications shall be provided on the DPU and sensors to allow data communications across a digital radio link. The following paragraphs identify the requirements for the subsystem interfaces.

TABLE 3-4 RVR system interface summary

Interface Name/IRD Number Quantity of Interfaces Comments

DPU to:

VS TBD* 30 See 3.2.2.2.6.1

ALS TBD* 2 See 3.2.2.2.6.1

RLIM TBD* 10 See 3.2.2.2.6.1

NG RVR

FAA Technical Instruction Book

6560.17, Section 3.7 and Table 3-5

1 RS-232 Interface, See 3.2.2.2.6.3.4

Local External Display Systems NAS-IR-33110001 6 RS-485 Interface

(EIA Standard 485) Remote External Display Systems NAS-IR-33110001 6 RS-232 Interface

ASOS NAS-IR-33113106 1 See 3.2.2.2.6.2.2

MPS NAS-IC-51035101 1 RS-232 Interface, See 3.2.2.2.6.3.2

MDT TBD* 1 RS-232 Interface External Time

Source NAS-IR-32063311 1 BNC Coaxial

VS to:

DPU TBD* 2 See 3.2.2.2.6.1

MDT TBD* 1 RS-232 Interface

ALS to:

DPU TBD* 2 See 3.2.2.2.6.1

MDT TBD* 1 RS-232 Interface

RLIM to:

DPU TBD* 2 See 3.2.2.2.6.1

MDT TBD* 1 RS-232 Interface

Note: (*) denotes interface documents that are part of RVR contract deliverables.

3.2.2.2.6.1.1 Primary subsystem interfaces

Many airports within the NAS provide “voice grade” AWG 19, shielded twisted pair landlines or fiber optic networks between the ATCT facility and the RVR sensor locations. The RVR System shall provide integrated modems for data communications between the VS, ALS and RLIM SIEs and the DPU across these Government-furnished media. The RVR System shall operate across two-wire interfaces with the characteristics described in TABLE 3-5, Characteristics of two-wire interfaces.

TABLE 3-5 Characteristics of two-wire interfaces

No. Characteristic Type A Best Case Type B Worst Case

1 Frequency Response

1.a 1,004 Hz Net Loss 0 dB 22 dB

1.b 404 Hz Net Loss 0 dB 20 dB

1.c 2,750 Hz Net Loss 0 dB 24 dB

1.d 3,000 Hz Net Loss 0 dB 26 dB

2 DC Loop Resistance N/A 520 Ω

3 Conductor to Conductor Resistance 50 MΩ 20 KΩ

4 Conductor to Ground Resistance 50 MΩ 10 KΩ

5 Signal to Noise 24 dB 24 dB

6 Peak-to-Average Ratio N/A 66

3.2.2.2.6.1.2 Alternative subsystem interface capability

Radio frequency data link communication is required for airports where it is prohibitively expensive to run data wiring between a sensor and the DPU. The radio link will provide an asynchronous RS-232 interface for data communications between the DPU and a sensor. The DPU and VS, ALS and RLIM SIEs shall be configured as Data Transmission Equipment (DTE).

The DPU and SIEs for the VS, ALS, and RLIM sensors shall provide the data interface to the radio link as directed in TABLE 3-6, DPU/Sensor data interface to the Radio Link.

TABLE 3-6 DPU/Sensor data interface to the Radio Link

No. Characteristic Interface

1 Data Rate Less than or equal to 9,600 baud

2 Data Format Asynchronous, Half Duplex RS-232

3 Required Interchange Circuits TD, RD, SG, RTS, CTS, DCD, DSR, DTR (These terms are defined in EIA Standard 232F)

3.2.2.2.6.2 External user interfaces

The RVR System shall use open systems interface architecture to support RVR product user interfaces. The external user interfaces are defined as those components interfacing with the

RVR DPU after the internal RVR sensor data is received and processed. The external user interfaces disseminate RVR product data as well as system status and alarm information.

3.2.2.2.6.2.1 External display systems

The RVR DPU shall interface to the following external display systems via three sets of dual, redundant RS-232 and RS-485 interfaces: the existing CD Type FA-10268/6 and the PC based- RVR CD as specified in 3.2.2.6; the ACE-IDS Control Cabinet or workstation; and the ETMS.

The interfaces shall comply with the requirements of FAA-NAS-IR-33110001.

3.2.2.2.6.2.2 Automated Surface Observing System (ASOS)

In the RVR to ASOS interface, data from up to 20 RVR touchdown sensors shall be sent from the RVR DPU to the ASOS or AWSS processor. Sensor and runway selection shall be configurable. The runway light setting for computation of the reported RVR shall always be step five (5). The RVR System reports a value that is the average of sensor measurements over a period of 1 minute. Detail of this interface can be found in FAA-NAS-IR-33113106.

3.2.2.2.6.3 External controlling interfaces

3.2.2.2.6.3.1 Maintenance Data Terminal (MDT)

A MDT is a windows-based laptop computer, loaded with appropriate software to permit it to interface with the DPU and SIE. An MDT port using EIA Standard 232f interface(s) shall be installed on the RVR DPU. The DPU MDT serial port shall enable local access and communication for the purposes of real-time diagnostics, calibration, monitoring and/or control of the VS, ALS and RLIM sensors and the RVR System.

The RVR to MDT interface shall provide, at a minimum, the following functionality or data:

help function; immediate response; security through operator sign-on; configurable operator access based on predetermined user needs; terminal timeout; formatted facility data readout showing available parameters, limits and current values of selected parameter(s) along with a log of failures; and selection of a local function MDT or remote MPS function (see 3.2.2.2.6.3.2).

3.2.2.2.6.3.2 Remote Maintenance Monitoring System

The purpose of the Remote Maintenance Monitoring System is to provide automation support services for the management of the NAS infrastructure.

The RVR System shall implement a Remote Monitoring Subsystem (RMS). RMS system administration and performance shall be in accordance with NAS-MD-793, Section 3.5 and all subsections.

The RMS shall implement functional requirements related to data acquisition, data processing, communication processing, and command processing. RMS data acquisition shall be in accordance with NAS-MD-793, Section 3.1 and all subsections.

RMS data processing shall be in accordance with NAS-MD-793, Sections 3.2 through 3.2.3.2 with the following exceptions. Internal addressing, command codes, and message generation shall follow applicable requirements in NAS-IC-51035101.

RMS communication processing shall be in accordance with NAS-IC-51035101.

RMS command processing shall be in accordance with NAS-MD-793, Sections 3.4 through 3.4.4 with the following exceptions: Command Acceptance and Verification and Command Results Reporting follow applicable requirements in NAS-IC-51035101.

System control via the MPS shall be limited to the following actions: Master reset and Startup/Recovery Equipment Command Messages as defined in NAS-IC-51035101, Section

3.1.2.2.1.11 and RVR system unique Equipment Command Messages. RVR system unique Equipment Command Messages shall include the following functionality: Online/Offline control for each RVR subsystem component; control of alarm (hard alarm) and alert (soft alarm) limits and data quality check limits/parameters, as appropriate; control of RVR system and subsystem component fault diagnostics; and individual RVR subsystem component resets.

The interface between the RVR RMS and the MPS shall be designed in accordance with NAS- IC-51035101 using a dedicated leased line. All communication shall be initiated by the MPS in accordance with NAS-IC-51035101.

The communication link between the MPS and RVR RMS shall be considered inoperable if no MPS poll has been received by the RVR RMS within a configurable time period. The communication link between the MPS and RVR RMS shall also be considered inoperable if the RVR RMS has to send a configurable number of repeated messages to the MPS because of a MPS NAK (not acknowledged) response or timeout. The link shall be considered inoperable until a valid MPS poll is received by the RVR RMS, a message is sent by the RMS to the MPS and the MPS sends an ACK (acknowledged) to the RVR RMS.

Upon re-establishment of the link, the RVR RMS shall send appropriate messages for each Logical Unit to assure that the data available at the MPS reflects the latest configuration and data associated with the RVR system.

3.2.2.2.6.3.3 External time source

An external time source will provide a coded date/time input to the RVR DPU. The DPU shall interface to the external time source and synchronize its internal system clock in accordance with the requirements identified in FAA-NAS-IR-32063311. The purpose of this coded input is to provide clock synchronization with other NAS systems.

3.2.2.2.6.3.4 NG RVR interface

The PC-based RVR system may be collocated with an existing NG RVR system at airports within the NAS. In such instances, the PC-based RVR system shall receive NG RVR system data and integrate it with similar data of the PC-based system for representation of RVR conditions over the relevant RVR airport configuration. The PC-based RVR DPU shall interface with the NGRVR system via the latter’s “Engineering User 1” (EU1) port in accordance with the engineering test data details given in FAA Technical Instruction Book 6560.17, Section 3.7 and Table 3-5. The PC-based RVR DPU shall: receive the simplex data stream from the NG RVR DPU; verify that the NG RVR sensors are operating correctly; process the NG RVR ALS measurement in accordance with paragraph 3.2.2.4; recalculate RVR products associated with NG RVR sensors; and format the RVR products for transmission across the external user interfaces described in paragraph 3.2.2.2.6.2. The PC-based RVR DPU shall verify that the NG RVRs VSs, ALS, and RLIMs are operating properly through analysis of maintenance parameter bytes provided for each configured NG RVR sensor in the EU1 data stream. The default values for the NG RVR EU-1 port shall be used.

3.2.2.2.7 DPU power

The DPU shall use standard alternating-current (AC) commercial power, single phase, rated at 115 volts (V), (+ 15 %), 60 Hertz (Hz) (+ 3 Hz). DPU power may be commercial, essential or critical, depending on the particular facility power source availability and definition. All power conditioning systems shall be equipped with input and output fuses and/or circuit breakers and semiconductor protection devices. Battery backup is not required for the DPU.

The DPU shall have an 8-foot long power cable that plugs into a standard 3-prong convenience outlet that provides no more than 10 Amperes (A) (circuit breaker protected).

3.2.2.2.8 DPU installation

The DPU shall be installed in a standard 19” electronics rack, typically located in the equipment room at the ATCT, as shown on FAA Standard Drawings D-6282-3, -7 and -9.

3.2.2.3 Visibility Sensor (VS)

The VS shall utilize forward-scatter meter technology that measures the clarity of the atmosphere and produces a signal proportional to the visible extinction coefficient. It is one of three components used in the determination of the RVR product for a particular location along a runway. The VS has stringent accuracy requirements because its measurement has the greatest influence on the accuracy of the final RVR product.