# Presentation: 916955

## A BRIEF HISTORY OF THE REDUCED VERTICAL SEPARATION MINIMUM (RVSM)

**A BRIEF HISTORY OF THE REDUCED VERTICAL SEPARATION MINIMUM (RVSM)**

- Presentation 14

## OVERVIEW

**OVERVIEW**

- Early Vertical Separation Practices
- ICAO Vertical Separation Panel
- Early Regional Air Navigation (RAN) Meetings
- Review of the General Concept of Separation Panel (RGCSP)
- Implementation History

## EARLY VERTICAL SEPARATION PRACTICES

**EARLY VERTICAL SEPARATION PRACTICES**

- See and avoid for enroute traffic above well defined top of cloud if frequent weather reports indicate unlimited ceiling and flight visibility of at least 3 miles.
- 1,000 foot vertical spacing used in 1940s in all cases except 500 feet used in see and avoid conditions:

## ICAO VERTICAL SEPARATION PANEL

**ICAO VERTICAL SEPARATION PANEL**

- Advent of commercial turbojet aircraft operating at high levels necessitated reevaluation of the vertical separation minimum.
- 1954:	ICAO Vertical Separation Panel formed
- Panel identified factors likely to contribute to loss of vertical separation;   proposed steps to reduce or eliminate their influence

## BASIS FOR THE CHANGE IN THE VERTICAL SEPARATION MINIMUM AT FL290

**BASIS FOR THE CHANGE IN THE VERTICAL SEPARATION MINIMUM AT FL290**

**The 1958 ICAO RAC/SAR Divisional Meeting: **
- Vertical separation a nominal 1000 ft. below an altitude of 29000 ft. or flight level 290
- 2000 ft. at or above this level, except where, on the basis of regional air navigation agreements, a lower level is prescribed

##  Early 60’s ICAO Meetings

- Encouraged pursuit of developments necessary to extend 1000 ft. standard upward from FL290
- Encouraged operators to enhance altimetry systems and maintenance practices to allow RVSM implementation

## DEVELOPMENT OF THE REDUCED VERTICAL SEPARATION MINIMUM (RVSM) - WHY SO MUCH INTEREST?

**DEVELOPMENT OF THE REDUCED VERTICAL SEPARATION MINIMUM (RVSM) - WHY SO MUCH INTEREST?**

- Late 70s:   Oceanic Area System Improvement Study (OASIS)    study concluded that RVSM was single best enhancement to pursue:
- Theoretical doubling of capacity in same airspace
- Approx 1% fuel burn enhancement
- RVSM thought achievable without major change to aircraft or ATC system

## REVIEW OF THE GENERAL CONCEPT OF SEPARATION PANEL

**REVIEW OF THE GENERAL CONCEPT OF SEPARATION PANEL**

- 1982:    ICAO Review of the General Concept of Separation Panel (RGCSP) agreed to begin task to determine RVSM technical feasibility
- State programs coordinated with RGCSP:   Canada, Eurocontrol (France, Germany, Netherlands, United Kingdom), Japan, the former USSR and the United States

## REVIEW OF THE GENERAL CONCEPT OF SEPARATION PANEL II

**REVIEW OF THE GENERAL CONCEPT OF SEPARATION PANEL II**

- RGCSP/6 (1988):  Concluded that the RVSM was technically feasible without placing undue burden on equipment
- RGCSP/7 (1990): produced draft RVSM guidance material - Doc 9574
- ICAO Air Navigation Commission (1990): approved draft guidance material and draft Standards and Recommended Practices (SARPS) - Annex 2

## WHY DID IT TAKE SO LONG FOR RGCSP TO FINALIZE GUIDANCE MATERIAL?

**WHY DID IT TAKE SO LONG FOR RGCSP TO FINALIZE GUIDANCE MATERIAL?**

- Aircraft maintain assigned flight level by sensing and measuring pressure and converting pressure to feet via ICAO Standard Atmosphere
- Errors in the sensing and conversion process not easily estimated
- Difference called altimetry system error (ASE)

## WHY SO LONG?

**WHY SO LONG?**

- Flight levels (constant pressure) defined by constant-pressure surfaces in atmosphere
- Constant-pressure surface over a geographic region is not at constant geometric (tape measure) height
- To determine errors in altimetry system:
- need information about geometric height of FL and geometric height of aircraft - neither of which is readily available

## DEVELOPMENT OF THE RVSM -THE MAJOR PROBLEM 

*FL 350  Geometric Height*

*FL 350  = Constant Pressure Altitude*

**DEVELOPMENT OF THE RVSM -****THE MAJOR PROBLEM **

## HEIGHT KEEPING PERFORMANCE ERRORS

*FL 350  Geometric Height*

**HEIGHT KEEPING PERFORMANCE ERRORS**

*Aircraft geometric height*

*            **Total Vertical Error  (TVE)*
*            **=  Altimetry System Error +*
*           **Assigned Altitude Deviation    *
*            **= ASE +AAD *

## IMPLEMENTATION HISTORY IN THE NORTH ATLANTIC REGION

**IMPLEMENTATION HISTORY IN THE NORTH ATLANTIC REGION**

- 1990:   NAT Systems Planning Group (NAT SPG)  formed RVSM study group in 1990
- 1992:   Limited NAT Regional Air Navigation Meeting   agreed on an implementation plan
- Operational trial 1 January 1997

## IMPLEMENTATION HISTORY IN THE NORTH ATLANTIC REGION

**IMPLEMENTATION HISTORY IN THE NORTH ATLANTIC REGION**

- March 1997:  RVSM implemented between FL 330 and 370
- October 1998: expanded to FL 310 - 390
- January 2002:    FL 290 - FL 410 to coincide with  European RVSM implementation

## Oceanic Experience

- Same-direction track problems:
- Wake Turbulence  - generally moderate or less
- Repetitive TCAS II Version 6.04a Traffic Alerts
- Tactical offset procedure mitigated both problems
- Aircraft population performance significantly better than minimum requirements
- Human errors most significant contributor to risk estimation

## Areas Where Implemented

- North Atlantic FIRs
- Pacific Oceanic FIRs
- Western Pacific and South China Sea FIRs
- West Atlantic Route System
- Australia
- Designated South Atlantic routes
- Europe

## WAS IT WORTH IT?

**WAS IT WORTH IT?**

- Operators have found benefits greater and costs less than predicted
- Most major oceanic operators have recovered equipment costs within first year of RVSM implementation based on fuel savings alone
- ATC units report little difficulty with RVSM procedures or RVSM/conventional VSM transitions
- ATC units able to offer more desirable routings
- ATC units report RVSM provides more operational flexibility