AMOSSG/5-SN No. 19

21/3/05

AERODROME METEOROLOGICAL OBSERVING SYSTEMS STUDY GROUP (AMOSSG)

FIFTH MEETING

Montreal, 11 to 14 April 2005

Agenda Item	5:	Aerodrome observation requirements
5.2:	Capability of automatic observing equipment to meet aeronautical requirements and the use of automated equipment during operational hours

APPROPRIATE LOCATIONS FOR FULLY AUTOMATED WEATHER SYSTEMS

(Presented by Bill Maynard)

SUMMARY
This paper considers criteria for where fully automated weather stations are appropriate during operational hours. It concludes that a simple matrix approach is likely to be inadequate and that an inclusive approach addressing a wide range of factors should be taken into account to make such a determination.

1.	INTRODUCTION

1.1	The Aerodrome Meteorological Observing Systems Study Group (AMOSSG) was created to support the International Civil Aviation Organization (ICAO) secretariat in reviewing and updating the international standards and recommended practices for meteorological observations and reports.

1.2	During the fourth meeting of the AMOSSG, it was agreed that there is a need to establish a framework for the use of fully automatic observing systems during operational hours based on criteria such as the runway categories and aerodrome operational categories. It was also agreed that any criteria for defining aerodrome categories must be agreed internationally.

2.	DISCUSSION

Background

2.1	For the purposes of this paper, a fully automated weather station refers to a system for which human intervention is not possible. Therefore, any application of automation during operational hours must be considered to be inclusive of systems that do not provide for augmentation.

2.2	Amendment 73 to Annex 3 introduced new recommendations specific to automated weather observations and reporting. Of particular note is the text of 4.7 which states:

Recommendation. — METAR and SPECI from automatic observing systems should only be used during non-operational hours of the aerodrome. These METAR and SPECI should be identified with the word "AUTO".

2.3	At least 5 States permit the operation of fully automated weather stations, during operational hours, based on their own domestic criteria.

2.4	It is the conclusion of the author that these States will be joined by others, and that the use of fully automated systems during operational hours will continue to expand regardless of whether the international standards permit their use or not.

Need for international standard

2.5	It is imperative that the international standard provide a common basis for the use of automated systems at the earliest possible opportunity. Undue delay may result in:

a)	significant increased costs for many States and international users;

b)	uncertainty among international users regarding the use, limitations and characteristics of automated systems used in various States;

c)	delays in the development of automated technologies;

d)	the probability that technological developments will move ahead of the standard rather than respond to it resulting in further reductions in the commonality in the operation of automated systems among States; and

e)	observational network inadequacy by the elimination of some weather observation sites due to the lack of any cost-effective alternative.

2.6	Amendment 74 to Annex 3 is expected to introduce provisions that will allow the use of automation during operational hours at some airports. However, the criteria for the determination of which airports would be suitable for the use of automation during operational hours has not been developed.

Criteria for Use of Automated Weather Stations

2.7

It has been suggested that a new concept of "required levels of meteorological service" be linked to the categories of available runways at a particular airport (as detailed in Appendix A) and/or to the international usage made of the airport (as detailed in Appendix B).

2.8	In the opinion of the author, neither the airport runway categories nor the international usage categories are adequate criteria for determining whether a given aerodrome is an appropriate location for the operational use of automated weather stations. Moreover, they provide an inflexible basis for such a determination.

2.9	With the arguable exception of the "smallest" of airports and the busiest international hubs, additional criteria should be considered for determining where automation is appropriate.

2.10	The available runways and approach aids for a given aerodrome may change over time, with both increases and decreases in availability being possible. Furthermore, the categories may not reflect what is operationally available at a given time due to maintenance, unscheduled outages, periodic changes in operational hours or as a result of weather limitations (i.e. the wind may not permit use of the preferred runway).

2.11	The approach of considering only runway and international use categories does not address a range of important considerations, such as:

a)	the expected air traffic mix and density and variations thereof through the day;

b)	the possibility that automation may be appropriate during a subset of operational hours;

c)	whether the only practicable alternative to automation is to provide no weather service at all;

d)	whether the local climate is such that the known characteristics and limitations of current automated systems could occur with an unacceptably high frequency thereby making them less suitable even for some less busy airports;

e)	whether the local climate is such that the known characteristics and limitations of current automated systems could occur with a very low frequency thereby making automation suitable at even some very busy airports;

f)	whether the airport proposed for automation is in a "data rich" area for weather information and/or located in close proximity to suitable alternate airports; and

g)	the ability, availability, affordability and reliability of human staff to be able to provide the weather observations.

Proposed alternative

2.12	The key prerequisite for the use of automation during operational hours should be the completion of a risk assessment that demonstrates that an equivalent level of safety, in comparison with a human observation program, is maintained.

2.13	It is proposed that the text in section 4.7 of Part I of Annex 3, be revised in a subsequent amendment to read as follows.

4.7.1 Recommendation. — METAR and SPECI based on automatic systems should, during the operational hours of an aerodrome, be provided in accordance with the regional air navigation plan and local agreements between the meteorological authority, the appropriate ATS authority and operators concerned.

4.7.2 METAR and SPECI from automatic observing systems shall be identified with the word "AUTO".

2.14	A possible modification may be to specifically recommend that fully automated systems not be used during the operational hours at the RS category airports for efficiency reasons.

3.	ACTION BY THE GROUP

3.1	The working group is invited to:

a)	comment on the conclusion that multiple States will proceed to implement fully automated weather station during operational hours, regardless of whether the international standard will permit this or not;

b)	review and comment on the alternative text proposed for a future amendment to Annex 3 regarding the criteria for the appropriateness of using automated weather stations during operational hours.

— — — — — — — —

Excerpted from section 3.5.7 of the summary of discussion of AMOSSG 4.

Non-instrument runway. A runway intended for the operation of aircraft using visual approach procedures.

Instrument runway. One of the following types of runways intended for the operation of aircraft using instrument approach procedures:

a)	non-precision approach runway. An instrument runway served by visual aids and a non-visual aid providing at least directional guidance adequate for a straight-in approach.

b)	precision approach runway, category I. An instrument runway served by ILS and/or MLS and visual aids intended for operations with a decision height no lower than 60 m (200 ft) and either a visibility not less than 800 m or a runway visual range not less than 550 m.

c)	precision approach runway, category II. An instrument runway served by ILS and/or MLS and visual aids intended for operations with a decision height lower than 60 m (200 ft) but not lower than 30 m (100 ft) and a runway visual range not less than 350 m.

d)	precision approach runway, category III. An instrument runway served by ILS and/or MLS to and along the surface of the runway and:

1)	intended for operations with a decision height lower than 30 m (100 ft), or no decision height and a runway visual range not less than 200 m.

2)	intended for operations with a decision height lower than 15 m (50 ft), or no decision height and a runway visual range less than 200 m but not less than 50 m.

3)	intended for operations with no decision height and no runway visual range limitations.

— — — — — — — —

Excerpted from section 3.5.7 of the summary of discussion of AMOSSG 4.

The five categories of aerodromes available for each of the regional plans which are allotted to all international aerodromes are:

a)	RS — international scheduled air transport, regular use;

b)	RSN — international non-scheduled air transport, regular use;

c)	RG — international general aviation, regular use;

d)	AS— international scheduled air transport, alternate use; and

e)	ANS — international non-scheduled air transport, alternate use.

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