Parameter  Measurement Uncertainty 
Accuracy  1.0. (2143) 
Field Strength  3dB (2144) 

13  Records and Graphs
13.1  Where chart recordings are used for parameter evaluation, they shall have sufficient resolution for this purpose (2145).
13.2  Records and graphs must be annotated to show the position of the aircraft at the time of making the measurement (2146).
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NAV 01  Engineering Requirements for Instrumented Runway Visual Range (IRVR) Systems
Part 1 Preliminary Information
1  Introduction
Under the terms of the Air Navigation Order, all air traffic service equipment  at civil facilities within the United Kingdom require approval by the CAA. IRVR is considered to be an item of air traffic service equipment.
2  Scope
2.1  This document details the performance criteria and safeguarding requirements for IRVR equipment installed in the UK and intended for use in the provision of an air traffic service.
2.2  The purpose of this document is to ensure that consideration has been taken of those aspects that affect the safety of services provided and supported by an IRVR facility.
Part 2 Requirements
3  Safety Objective
The equipment shall enable the provision of an accurate indication of the runway visual range to be available to the pilot during the take-off and landing phases of flight (1641).
4  Technical Requirements
4.1  Instrumented Runway Visual Range (IRVR) shall be measured, over the range appropriate for the approach categorisation, to a minimum accuracy of (1642): ±10 Metres from 50 metres to 400 metres.
±25 Metres from 400 metres to 800 metres.
±10 per cent above 800 metres.

4.2  All systems shall meet these accuracy requirements over background luminance levels in the range 5 to 30,000 Cd.m-2 (1643).
4.3  For calculating the IRVR value, 20 per cent of the peak beam on axis intensity of the runway light (rounded to the nearest 100 cd) shall be assumed (1644).
4.4  The sensor output shall be sampled at a minimum rate of once per second (1645).
4.5  The equipment shall average the recorded extinction coefficient over a period of 1 minute, to effect smoothing of short-term atmospheric variations in ATS reports (1646).
4.6  The IRVR value presented to the user shall be rounded down to the nearest increment specified in paragraph 8.5 (1647).
4.7  When RVR is increasing, a hysteresis of 1.5 increments shall be used to prevent unnecessary fluctuations in the displayed IRVR (1648).
4.8  The equipment integrity and reliability shall be such that the number of safety-related failures shall be no more than 10-5 per operating hour, unless otherwise indicated by a formal and documented hazard analysis (1756).
4.9  For METAR, a 10-minute averaging period shall be used for obtaining mean value(s), except when the 10-minute period immediately preceding the observation includes a marked discontinuity in RVR values (2306). Only those values occurring after the discontinuity shall be used for obtaining mean values (2307).
NOTE:  A marked discontinuity occurs when there is an abrupt and sustained change in RVR lasting at least 2 minutes.
5  Equipment Calibration
The maintenance and calibration policy, and facilities necessary to maintain performance within the parameters stated in this document, shall be documented and implemented (1757).
6  Equipment Interfaces
6.1  Technical justification that the safe operation of the equipment is not compromised by any non-passive interfaces installed in or connected to other equipment shall be provided (1651).
NOTE:  The connection of the IRVR system to any existing approved equipment may require the reassessment of that other equipment.
　
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本文鏈接地址：CAP 670 Air Traffic Services Safety Requirements 2(63)