RVSM AIRWORTHINESS PRESENTED BY COSCAP-SA

RVSM Airworthiness In the late 1950s it was recognized that as a result of the reduction of accuracy of pressure sensing of barometric Altimeters with increasing altitude,there was a need above a certain flight level to increase the prescribed vertical separation minimum of 300 m. In 1960 an increased separation of 600 m was established.

RVSM Airworthiness In the mid 1970s following the world fuel shortages and the escalation of fuel costs, allied to the growing demand for a more efficient utilization of the available airspace, ICAO encouraged states to conduct a detailed appraisal of the proposal to reduce the VSM above FL290.

RVSM Airworthiness In late 1988 the ICAO panel provided guidance to a specialist group tasked with translating the total vertical error distribution requirement into detailed specifications and procedures for controlling the height keeping standards of aircraft operating in RVSM airspace.

RVSM Airworthiness The detailed specification and procedures must be developed for use by Designers, Manufacturers, Operators and Approval Authorities and must be applicable for airworthiness approval to a Group of Aircraft as well as Individual Aircraft. When taken together this formed the Minimum Aircraft System Performance Specification ( MASPS )

RVSM Airworthiness The following characteristics were developed by the ICAO team to satisfy the distribution limit on T V E of the proportion of Height keeping errors beyond 90 m in magnitude is less than 2.0X10-3 beyond 150 m in magnitude is less than 3.5X 10 -6 beyond 200m in magnitude is less than 1.6X10 -7,and between 290 & 320 m in magnitude is less than 1.7 X 10 -9

RVSM Airworthiness These were intended to be the basis for development of the Minimum Aircraft System Performance Specification against which the Aircraft will be Approved.

RVSM Airworthiness The Mean Altimetry System Error of the Group of Aircraft shall not exceed ± 25 m( 80 ft) The sum of the absolute value of the mean ASE for the group and three standard Dev. Of ASE within the group shall not exceed 75 m The errors in altitude keeping shall be symmetrical about a mean of 0 and shall have a standard dev. Not more than 13 m and be such that the Error Frequency decreases with increasing Error magnitude at a rate which is at least exponential.

RVSM Airworthiness These characteristics were mainly to derive Type Approval standards for design capability ,but they primarily address the central part of the T V E distribution i.e the requirement of height keeping errors beyond 90 m magnitude is less than 2.0X 10 -3. In order to qualify the aircraft for other requirements it was felt necessary to develop detailed procedure and specification to cover production release and continued Airworthiness.

RVSM Airworthiness The Minimum Aircraft System Performance Specification ( MASPS ) was required to control three issues, Type Approval, Production Release, and Continued Airworthiness. Though it was necessary to meet all the requirements of MASPS for approval of operation in RVSM airspace it was also essential to change the structure of MASPS for existing aircraft,some of which may no longer be in production

RVSM Airworthiness On the basis of the ICAO studies, a recommendation was made that the margin between operational Performance and Design capability should be achieved as under: The mean uncorrected Residual position Error (Static Source Error ) of the group shall not exceed ±25 m The sum of the absolute value of the mean ASE within the group shall not exceed 60 m (This requirement has a narrower tolerance to allow for some degradation with increasing age)

RVSM Airworthiness Each individual aircraft in the group shall be built to have an ASE contained within ±60 m An automatic altitude-keeping device shall be required and will be capable of controlling altitude within a tolerance band of ±15m about commanded altitude when operated in the altitude hold mode in straight and level flight under non- turbulent, non-gust condition

RVSM Airworthiness Equipment and Functional requirements. Essential features for operation in RVSM airspace At least Two altitude measurement system Static source error correction /position error correction must be applied automatically

RVSM Airworthiness An SSR altitude reporting Transponder with the capability for switching to operate from either altitude measurement system. An altitude alert system that alerts the crew aurally and visually if displayed altitude deviates from the selected altitude by more than ± 60 m

RVSM Airworthiness An automatic Altitude keeping device to control altitude within a tolerance band of ± 15 m and designed such that the occurrence of any single failure in the device will not cause a displacement of the aircraft from its flight path greater than ± 90 m based on a 3 second delay in pilot intervention ± 90 M

RVSM Airworthiness An out-of-trim condition which can not easily be controlled by the Pilot. Any action of the flight control system that is not readily apparent to the pilot by movement of the flight controls,a flight instrument display ,or by display of an advisory note 1: Aircraft operating as on 1/1/90 with altitude keeping capability of ± 40 m need not be retrofitted future aircraft req. ± 15 m note 2: After 1/1/94 all RVSM airspace operating aircraft should meet the performance requirement of less than 45 m altitude overshoot

RVSM Airworthiness Continued Airworthiness: The Maintenance requirements and procedures should include periodic flight test demonstration of height-keeping accuracy. Independent TVE monitoring facility is acceptable provided errors can be measured consistent to the requirements and provided separate contributor to TVE I.e Airframe, Avionics or flight Technical Error can be assessed

RVSM Airworthiness IT is unlikely that many existing aircraft can be shown to have undergone the production release controls envisaged in the MASPS but Continued Airworthiness requirement should be developed so that the limits are met. Each such aircraft should undergo the appropriate check as well as meeting the type approval requirements. For young in-service aircraft there should be a requirement to reveal evidence of variation to normal production repeatability.

RVSM Airworthiness All Aircraft operating above FL 290 must be approved for such operation by the state of registry of the aircraft or of the aircraft operator. For Airworthiness, The Aircraft should be approved as meeting the requirements of the appropriate state airworthiness document derived from the height keeping capability requirements for operations in RVSM airspace. The aircraft altimetry and height keeping equipment must be maintained in accordance with approved procedures and servicing schedules END