FCTM All Weather Operations

Dear Readers, Important notice This guide is intended to provide general information regarding All Weather Operations. In no case it is intended to replace the operational and flight manuals for ATR aircraft. In all events, the information contained in the Aircraft Flight Manual shall prevail over the content of this guide.

Every effort has been made to ensure document quality. However please do not hesitate to share your comments and information with us by using the following address: [email protected] We would also like to thank ENAC (Ecole Nationale de l’Aviation Civile) for its involvement in the development of this guide. Yours faithfully,

Printed on 100% recycled paper using vegetable inks

Your ATR Training and Flight Operations support team.

© ATC June 2010 All reasonable care has been taken by ATC to ensure the accuracy of the present document. However this document does not constitute any contractual commitment from the part of ATC which will offer, on request, any further information on the content of this brochure. Information in this brochure is the property of ATC and will be treated as confidential. No use or reproduction or release to a third part may be made there of other than as expressely authorised by ATC.

7B$75B$:2BFRYHULQGGFRXY



Dear Readers, The ATR operational documentation chapters related to CAT II precision approaches are being revised (AFM 7-01-03 CATII Operation and FCOM 2-02-04 AFCS). The revision has been recently implemented for 42300/42-320 series and will be extended to the other aircraft types at their next documentation normal revision during the year 2010. The major evolution to notice is a change of the tasks management in the operational procedure, as described in Chapter E. Flight Crew Operating Procedures of this manual. Until the effective revision of the ATR operational documentation, the information contained in the Airplane Flight Manual shall prevail over the content of this manual. Your ATR Training and Flight Operations support team.

NoteTemporaire.indd 1

01/07/10 10:47

Introduction The purpose of this guide is to provide ATR aircraft pilots and operators with information and regulatory material relating to All Weather Operations. Training pilots for All Weather Operations is the operator’s responsibility. This guide aims to give pilots a good overview on low visibility operations and to help operators develop their own documentation and their flight crew training programmes in order to obtain the Low Visibility Operations approval from their national authority. Most stated recommendations are issued from ICAO annexes and from FAA and EASA regulations. Nevertheless, some national authorities may have additional requirements. The content of this guide is intentionally limited to operations for which ATR aircraft have a technical capability, that is to say: low visibility take-off, lower than standard Category I, Category II, other than standard Category II and Category IIIA approaches. The overall safety level of low visibility operations is achieved through the implementation of specific rules and requirements equally concerning: – the aircraft – the airfield – the flight crew – the operator All 4 fields are addressed in this guide but with an emphasis on the last two items being more widely developed. This guide incorporates features of the ATR -600 aircraft type due for entry into service by 2011. For the time being, low visibility approach certifications are still under progress and the guide will be amended to develop these points specifically related to the -600 in later revision.

Introduction 7B$75B$:2BLQWURLQGG

p. 1



Contents

Contents Chapter A. General 1. A brief history ........................................................................................................................................................................................................................................8 2. Economic aspects .........................................................................................................................................................................................................................8 3. Low Visibility Operations (LVO) concept...................................................................................................................................................9 3.1. General....................................................................................................................................................................................................................................................9 3.2. Low Visibility Take-Off (LVTO)..................................................................................................................................................................................9 3.3. Category II approaches................................................................................................................................................................................................10 3.4. Category IIIA approaches .........................................................................................................................................................................................10 3.5. Lower than standard Category I operation .......................................................................................................................................10 3.6. Other than Standard Category II operation ......................................................................................................................................10 4. Relevant regulations ..............................................................................................................................................................................................................10 4.1. Aeroplanes certification ..............................................................................................................................................................................................10 4.2. Airfield regulation .................................................................................................................................................................................................................10 4.3. Operational regulation ...................................................................................................................................................................................................11 5. Definitions ...............................................................................................................................................................................................................................................11 5.1. General................................................................................................................................................................................................................................................11 5.2. Categories of precision approach and landing operations ........................................................................................12 5.2.1. Category II (CAT II) .........................................................................................................................................................................................................12 5.2.2. Category IIIA (CAT IIIA) .............................................................................................................................................................................................13 5.2.3. Category IIIB (CAT IIIB) .............................................................................................................................................................................................13 5.2.4. Category IIIC (CAT IIIC).............................................................................................................................................................................................13 5.2.5. Lower than Standard Category I ....................................................................................................................................................................13 5.2 .6. Other than Standard Category II ....................................................................................................................................................................14 5.3. Summary ..........................................................................................................................................................................................................................................14

Chapter B. Revision of low visibility weather conditions 1. The characteristics of fog .............................................................................................................................................................................................16 1.1. Radiation fog ..............................................................................................................................................................................................................................16 1.2. Advection fog .............................................................................................................................................................................................................................17 1.3. Frontal / Precipitation fog .........................................................................................................................................................................................17 1.4. Upslope and valley fogs ..............................................................................................................................................................................................18 2. Effects of precipitation, wind and turbulences ..........................................................................................................................18 2.1. The effect of precipitation ........................................................................................................................................................................................18 2.2. The effect of wind and turbulences .............................................................................................................................................................19 3. Runway Visual Range (RVR)......................................................................................................................................................................................20 3.1. General................................................................................................................................................................................................................................................20 3.2. RVR measurements...........................................................................................................................................................................................................20 3.3. RVR use .............................................................................................................................................................................................................................................22 3.4. RVR practical limitation ...............................................................................................................................................................................................24 3.5. Conversion of reported meteorological visibility to RVR ...............................................................................................24

Contents 7B$75B$:2BLQWURLQGG

p. 2



4. Weather documentation ..................................................................................................................................................................................................25 4.1. Weather charts .........................................................................................................................................................................................................................25 4.2 TAF/METAR/SPECI ...............................................................................................................................................................................................................26 4.2.1. General .......................................................................................................................................................................................................................................26 4.2.2. TAF ..................................................................................................................................................................................................................................................26 4.2.3. METAR/SPECI .....................................................................................................................................................................................................................27

Chapter C. Aircraft requirements 1. Aircraft certification status .........................................................................................................................................................................................29 1.1. General................................................................................................................................................................................................................................................29 1.2. Guidance and landing systems .........................................................................................................................................................................29 1.2.1. CAT II approaches ..........................................................................................................................................................................................................29 1.2.2. CAT IIIA approaches with DH ≥50ft .............................................................................................................................................................30 1.2.3. Lower than standard CAT I and other than standard CAT II.............................................................................................30 1.2.4. Low visibility take-off ..................................................................................................................................................................................................30 1.3. System performances ....................................................................................................................................................................................................31 1.4. Aircraft Flight Manual content ............................................................................................................................................................................31 2. ATR automatic flight control system...........................................................................................................................................................31 2.1. AFCS on classic instruments ATR .................................................................................................................................................................31 2.2. AFCS on ATR -600 ...............................................................................................................................................................................................................33 3. Aircraft minimum equipment required .....................................................................................................................................................33 3.1. Classic instruments ATR ............................................................................................................................................................................................34 3.2. ATR -600 ............................................................................................................................................................................................................................................34 4. Aeroplane malfunctions ...................................................................................................................................................................................................34 4.1. ATR 72-500.....................................................................................................................................................................................................................................35 4.2. ATR -600 ............................................................................................................................................................................................................................................35 5. Maintenance ........................................................................................................................................................................................................................................36

Chapter D. Airfield requirements 1. Aerodrome approval...............................................................................................................................................................................................................38 2. Runway and taxiway characteristics..........................................................................................................................................................38 2.1. Runway length ..........................................................................................................................................................................................................................38 2.2. Runway width ............................................................................................................................................................................................................................38 2.3. Runway slope ............................................................................................................................................................................................................................38 2.4 Runway-holding position .............................................................................................................................................................................................38 3. Effects of pre-threshold terrain profile....................................................................................................................................................39 4. Obstacles clearances requirements............................................................................................................................................................39 5. Navaids - Characteristics and limitations ..........................................................................................................................................41 5.1. General................................................................................................................................................................................................................................................41 5.2. ILS characteristics ..............................................................................................................................................................................................................41 5.3. ILS performances .................................................................................................................................................................................................................42 5.4. ILS classification ...................................................................................................................................................................................................................43 5.5. ILS protection ............................................................................................................................................................................................................................44 6. Characteristics of the visual aids .....................................................................................................................................................................44 6.1. Runway markings.................................................................................................................................................................................................................44

Contents

p. 3

Contents

6.2. CAT II/III Lighting systems .......................................................................................................................................................................................45 6.2.1 Taxiway lights........................................................................................................................................................................................................................46 6.2.2. Stop bars ..................................................................................................................................................................................................................................46 6.2.3. Runway guard lights ....................................................................................................................................................................................................46 6.2.4. Runway lights ......................................................................................................................................................................................................................47 6.2.5. The approach lighting system ...........................................................................................................................................................................47 6.2.6. Lighting system condition .....................................................................................................................................................................................49

6.3. Lighting systems for Lower than standard CAT I and other than standard CAT II approaches ...................................................................................................................................................................................................................................49

7. ATC Procedures.............................................................................................................................................................................................................................50

Chapter E. Flight crew operating procedures 1. General .........................................................................................................................................................................................................................................................52 2. Pre-flight procedures............................................................................................................................................................................................................52 3. On ground procedures and precautions...............................................................................................................................................53 3.1. General................................................................................................................................................................................................................................................53 3.2. Recommended procedures ....................................................................................................................................................................................53 3.2.1. Prior to taxiing ....................................................................................................................................................................................................................53 3.2.2. During taxi...............................................................................................................................................................................................................................53 3.2.3. Prior to approach phase ..........................................................................................................................................................................................54 3.3. Usual difficulties.....................................................................................................................................................................................................................54 3.4. Airport moving map...........................................................................................................................................................................................................55 3.4.1. Electronic Flight Bag (EFB)...................................................................................................................................................................................55 3.4.2. ATR -600 ....................................................................................................................................................................................................................................55 4. Low visibility take-off (LVTO) ...................................................................................................................................................................................55 4.1. General................................................................................................................................................................................................................................................55 4.2. Low Visibility Take-Off under European regulation (EU-OPS) .................................................................................56 5. Approach preparation..........................................................................................................................................................................................................57 5.1. Conditions at destination / at the alternate aerodrome ..................................................................................................57 5.2. Aircraft capability .................................................................................................................................................................................................................57 5.3. Fuel calculation .......................................................................................................................................................................................................................57 5.4. DH setting .......................................................................................................................................................................................................................................58 5.5. Approach briefing.................................................................................................................................................................................................................58 5.6. Cabin crew information................................................................................................................................................................................................58 5.7. Seat position ...............................................................................................................................................................................................................................59 6. Normal procedures for low visibility approaches ..................................................................................................................59 6.1. General................................................................................................................................................................................................................................................59 6.2. Approach ban / RVR controlling ......................................................................................................................................................................59 6.3. Task sharing .................................................................................................................................................................................................................................60 6.4. Normal procedures on classic instruments ATR for CAT II approaches ..................................................60 6.5. Normal procedures and task sharing for CAT III, other than standard CAT II and lower than standard CAT I approaches on ATR -600.......................................................................................................... 64 6.6.Visual segment at DH and minimum visual references......................................................................................................64 6.7. Loss of visual references below DH ...........................................................................................................................................................65

7. Abnormal procedures ..........................................................................................................................................................................................................65 7.1. General................................................................................................................................................................................................................................................65

Contents 7B$75B$:2BLQWURLQGG

p. 4



7.2. Failure treatment concept ........................................................................................................................................................................................66 7.3. Failure treatment on classic instruments ATR .............................................................................................................................66 7.4. Failure treatment on ATR -600 ............................................................................................................................................................................67 7.5. Maximum ILS deviation allowed ......................................................................................................................................................................67

8. Effects of failure of ground equipment....................................................................................................................................................68

Chapter F. Flight crew training and qualification 1. General .........................................................................................................................................................................................................................................................71 2. Ground training...............................................................................................................................................................................................................................71 3. Simulator training and checking ........................................................................................................................................................................72 3.1. Full training program .......................................................................................................................................................................................................72 3.2. Training for flight crew members with Category II or Category III experience................................74 3.3. Training for flight crew members flying on classic instruments ATR and on ATR -600 .......74 3.4. Flight crew qualification ..............................................................................................................................................................................................74 4. Line training..........................................................................................................................................................................................................................................74 5. Type and command experience ..........................................................................................................................................................................75 6. Recurrent training and checking.......................................................................................................................................................................75 7. The qualification process of flight crew under EASA regulation: overview ...............................76

Chapter G. Operator’s duties 1. Establishing operating minima .............................................................................................................................................................................78 1.1. General................................................................................................................................................................................................................................................78 1.2. EASA take-off minima ....................................................................................................................................................................................................79 1.3. EASA CAT II minima ..........................................................................................................................................................................................................79 1.4. EASA CAT III minima ........................................................................................................................................................................................................79 1.5. EASA Lower than standard CAT I minima ..........................................................................................................................................80 1.6. EASA other than standard CAT II minima ...........................................................................................................................................80 1.7. Operating minima publication.............................................................................................................................................................................81 2. Operations manual content .......................................................................................................................................................................................81 3. Operational demonstration.........................................................................................................................................................................................82 3.1. General................................................................................................................................................................................................................................................82 3.2. Operational demonstration under European regulation .................................................................................................83 3.3. Operational demonstration under FAA regulation ..................................................................................................................84 4. Eligible aerodromes and runways ...................................................................................................................................................................84 5. Continuous monitoring ......................................................................................................................................................................................................85 6. Operator approval process .........................................................................................................................................................................................85 6.1. Prerequisite / transitional period.....................................................................................................................................................................85 6.2. Operational approval file ............................................................................................................................................................................................86 6.3. Sequencing of action during the approval process ..............................................................................................................86

Abbreviations

...............................................................................................................................................................................................................

Contents 7B$75B$:2BLQWURLQGG

88

p. 5



7B$75B$:2BLQWURLQGG



A. General

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 7



A. General

1. A brief history Landing in Low Visibility Conditions was made possible by huge improvements in aircraft automatic control systems over the last 40 years coupled with stringent requirements for airfield equipment and crew qualification. All modern aircraft are now certificated for CAT II operations and many for CAT III operations. CAT II approaches approval has been granted to ATR aircraft at the initial certification in 1985. The new series ATR 42-600 and ATR 72-600 will be certificated for CAT II and CAT IIIA approaches.

Figure A1: ATR aircraft in low visibility conditions at parking

2. Economic aspects There is an overall positive economic impact for the adoption of Low Visibility Operations. In certain regions of the world, the best way for an airline to maintain its schedule all year round without any diversion due to weather, is to be approved to perform Low Visibility Operations. There may initially be a cost implication to implement Low Visibility Operations (CAT II/III equipments, flight crew training...). However, it is the only way to keep in-line services operational throughout the whole year with a minimum number of diversions. Weather conditions mainly depend on the airfield location, nevertheless actual CAT II/III conditions may occur at any airfield depending on the periods of the year. Diversions and delayed flights are expensive for an airline, due not only to passenger compensation costs but also due to the resulting bad “image”. For these reasons, getting operational approval for CAT II/III approaches and Low Visibility Take-Off can be considered as a necessary step in the evolution of a modern airline. There may further be a slight positive environmental impact from a higher landing success rate at destination, plus a consequential reduction in fuel consumption.

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 8



3. Low Visibility Operations (LVO) concept 3.1. General When developing low visibility procedures, the airline objective is to achieve under low visibility conditions both a level of safety and a rate of reliability equivalent to those achieved during normal operating conditions. Take-off and taxing in low visibility conditions involves specific operating procedures and suitable airport installations (runway lighting system, RVR measurement system, ...) but does not require specific on board equipment. Landing in low visibility conditions is made possible using high performances ground ILS equipment together with the onboard receivers and the automatic flight control system of the aircraft. The decision to land is taken in very close proximity to the ground (between 200ft and 0 ft, depending on the category of the approach); pilots see the runway lights only a few seconds before touchdown, therefore there is no margin for error. The desired level of safety is achieved through: – Ground ILS facility, – Airborne equipment, – Visual aids (runway markings, lighting systems), – Flight crew training, – Flight crew procedures, – Air Traffic Control procedures, – Aircraft maintenance, – Airfield maintenance, – Criteria for obstacle clearance. The basic principles governing Low Visibility Operations are that: Q the

aerodrome satisfies the ICAO standards for LVO, including visual and non-visual aids, runway characteristics, obstacle clearance area, RVR measurements, ATC procedures… The aerodrome is approved for such operations by the State in which the aerodrome is located.

Q the

aeroplane is certificated for such operations. Limitations and conditions specified in the Aircraft Flight Manual are respected. The aeroplane and its equipments are maintained in accordance with the approved maintenance manual.

Q each

flight crew member has successfully completed the training and checking program approved by the operator’s Authority.

Q operating

procedures have been established and are applied by flight crew members. Those procedures cover task sharing during Low Visibility Take-Off and approaches and the actions to be taken in case of equipment failure.

Q the

operator has obtained from his national authority an operational approval to perform such operations.

3.2. Low Visibility Take-Off (LVTO) When visibility decreases the pilot must continue to be able to judge the aeroplane’s lateral position to keep it within acceptable limits relative to the runway centre line throughout the take-off roll and eventually during the aborted takeoff phase. The basic information required by the pilot is normally provided by external visual cues but these may be supplemented by instrument derived information. When take-off is performed using only external visual cues, the runway lighting system is essential.

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 9



A. General

3.3. Category II approaches In Category II operations, the ILS precision instrument approach is performed using the automatic flight control system down to below the Decision Height (typically 100ft). At the Decision Height, the visual references should be sufficient to allow the pilot to continue the approach and to perform a manual landing using only external visual cues.

3.4. Category IIIA approaches In Category III the Decision Height and the Runway Visual Range are lower than in CAT II operations. The time from the decision height to the start of the flare is shorter. To preserve the safety level it has been considered necessary that the ILS precision instrument approach be performed using the automatic flight control system right until the aircraft is on the ground. Approach, flare and landing are performed automatically. At the Decision Height, the visual references should be sufficient to allow the pilot to decide if the aircraft will land within the touchdown zone. The main difference between CAT II and CAT III operations is that in Category II conditions the pilot has enough time and sufficient visual references to permit a manual landing, whereas it is not the case when in Category III conditions and an automatic landing has to be performed.

3.5. Lower than Standard Category I operation On aerodromes only supporting Category I approach, the Decision Height can not be lower than 200ft. Nevertheless, depending on the ILS ground equipment performance, the required Runway Visual Range can be lower than the Standard CAT I RVR if the aircraft is equipped with an auto-land system approved for CAT III operations. In order to be authorised to use reduced RVR, the approach must be flown auto-coupled to an auto-land.

3.6. Other than Standard Category II operation Category II or III approach can not be published on aerodromes using limited facilities for approach lighting and runway lighting. On those aerodromes, aircraft able to perform an auto-land can consider the use of a Category II Decision Height (typically 100ft) with an RVR higher than the one of a Standard Category II approach. Such approaches are referred to as other than Standard Category II operation.

4. Relevant regulations 4.1. Aeroplanes certification FAA – Advisory circular AC 120-29A, Criteria for approval of Category I and Category II weather minima for approach – Advisory circular AC 120-28D, Criteria for approval of Category III weather minima for take-off, landing, and rollout – Advisory circular AC 20-57, Automatic Landing Systems

EASA – CS AWO, Certification Specifications for All Weather Operations

4.2. Airfield regulation ICAO – – – –

Annex 14 Volume 1, Aerodrome Design and Operations Annex 10 Volume 1, Radio navigation aids (ILS specifications) PANS-OPS (Doc 8168) Volume 2, Construction of visual and instrument flight procedures Doc 9328, Manual of Runway Visual Range Observing and Reporting Practices

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 10



Other Each State may have its own policy to approve its aerodromes for Low Visibility Operations. Those regulations are not supposed to be less restrictive than ICAO Annexes otherwise differences should be notified.

4.3. Operational regulation ICAO – Annex 6, Operation of Aircraft – Doc 9365, Manual of All Weather Operations

FAA – Advisory circular AC 120-29A, Criteria for approval of Category I and Category II weather minima for approach – Advisory circular AC 120-28D, Criteria for approval of Category III weather minima for take-off, landing, and rollout

EASA – EU-OPS Subpart E, All Weather Operations

Other Each State may have its own operational regulation It is worth noting that harmonisation was conducted between EASA and FAA operational regulations for CAT II and CAT III operations which are now very similar.

5. Definitions 5.1. General All Weather Operations ICAO Doc 9365 – Foreword Any taxi, take-off and landing operations in conditions where visual reference is limited by weather conditions.

Aerodrome operating minima for take-off ICAO Annex 6 – Chapter 1: Definition The limits of usability of an aerodrome expressed in terms of runway visual range and/or visibility and, if necessary, cloud conditions.

Aerodrome operating minima for precision approach and landing operations ICAO Annex 6 – Chapter 1: Definition The limits of usability of an aerodrome expressed in terms of visibility and/or runway visual range and decision altitude/height (DA/H) as appropriate to the category of the operation.

Decision altitude (DA) or decision height (DH) ICAO Annex 6 – Chapter 1: Definition A specified altitude or height in the precision approach or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. Note: Decision altitude (DA) is referenced to mean sea level and decision height (DH) is referenced to the threshold elevation.

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 11



A. General

According to EASA, the Decision Height for Category II, Category III and other than Standard Category II operations is determined by means of radio-altimeter. For some specific Category II approaches, the FAA gives free choice on DH recognition (radio-altimeter, inner markers or barometric altimeter).

Low Visibility Operations (LVO) For this specific document, LVO includes Low Visibility Take-Off, Category II approaches, Category IIl approaches, other than Standard CAT II and lower than Standard CAT I approaches.

Low Visibility Procedures (LVP) - EASA definition EU-OPS 1.435 Terminology Procedures applied at an aerodrome for the purpose of ensuring safe operations during Lower than Standard Category I, Other than Standard Category II, Category II and III approaches and Low Visibility Take-Offs.

Low Visibility Take-Off (LVTO) - EASA definition EU-OPS 1.435 Terminology A Low Visibility Take-Off is a take off where the Runway Visual Range is less than 400m.

Runway visual range (RVR) ICAO Annex 6 – Chapter 1: Definition The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line. NOTE: Category II and Category III instrument approach and landing operations shall not be authorised unless RVR information is provided.

5.2. Categories of precision approach and landing operations 5.2.1. Category II (CAT II) ICAO and FAA ICAO Annex 6 – Chapter 1: Definition AC 120-29A - Appendix 1: Definitions and acronyms A Category II operation is a precision instrument approach and landing 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.

EASA EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (f) A Category II operation is a precision instrument approach and landing using ILS or MLS with a decision height below 200 ft but not lower than 100 ft; and a runway visual range of not less than 300 m. NOTE: For the minimum RVR requested, the EASA definition is slightly different from the ICAO and FAA definitions: not less than 350 m for ICAO and FAA but not less 300 m for EASA.

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 12



5.2.2. Category IIIA (CAT IIIA) ICAO and FAA ICAO Annex 6 – Chapter 1: Definition AC 120-29A - Appendix 1: Definitions and acronyms A Category IIIA operation is a precision instrument approach and landing with a decision height lower than 30 m (100 ft) or no decision height; and a runway visual range not less than 200 m.

EASA EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (g) A Category IIIA operation is a precision instrument approach and landing using ILS or MLS with a decision height lower than 100 ft; and a runway visual range not less than 200 m. NOTE: The ICAO and FAA regulations differ from EASA by considering CAT IIIA approaches with no DH. EASA systematically associates CAT IIIA approaches with a decision height.

5.2.3. Category IIIB (CAT IIIB) ICAO and FAA ICAO Annex 6 – Chapter 1: Definition AC 120-29A - Appendix 1: Definitions and acronyms A Category IIIB operation is a precision instrument approach and landing with a decision height lower than 15 m (50 ft) or no decision height; and a runway visual range less than 200m but not less than 50 m.

EASA EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (g) A Category IIIB operation is a precision instrument approach and landing using ILS or MLS with a decision height lower than 100 ft, or no decision height; and a runway visual range lower than 200 m but not less than 75 m. NOTE: The ICAO and FAA regulations differ from EASA on the minimum RVR associated with CAT III B approaches.

5.2.4. Category IIIC (CAT IIIC) ICAO and FAA ICAO Annex 6 – Chapter 1: Definition AC 120-29A - Appendix 1: Definitions and acronyms A Category IIIC operation is a precision instrument approach and landing with no decision height and no runway visual range limitations.

EASA CAT III C operations are not currently authorised so EASA does not make reference to this sub-category.

5.2.5. Lower than Standard Category I EASA EU-OPS 1.435 Terminology A Category I Instrument Approach and Landing Operation using Category I DH, with an RVR lower than would normally be associated with the applicable DH.

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 13



A. General

5.2.6. Other than Standard Category II EASA EU-OPS 1.435 Terminology A Category II Instrument Approach and Landing Operation to a runway where some or all of the elements of the ICAO Annex 14 Precision Approach Category II lighting system are not available.

5.3. Summary Definitions of Categories of precision approach give the lowest acceptable minima. During operations those values may be limited by aircraft capability, by airfield limitation, by crew individual qualification or by operator’s authorisation.

Lower than stand. CAT I

DH

ICAO

FAA

EASA

–

–

DH ≥200ft

RVR

–

–

400m≤RVR

DH

100ft ≤ DH < 200ft

100ft ≤ DH < 200ft

100ft ≤ DH < 200ft

CAT II

RVR

350m ≤ RVR 1200ft ≤ RVR

350m ≤ RVR < 800m 1200ft ≤ RVR < 2400ft

300m ≤ RVR 1000ft ≤ RVR

Other than stand. CAT II

DH

–

–

100ft ≤ DH < 200ft

RVR

–

–

350m ≤ RVR

DH

No DH or DH < 100ft

No DH or DH < 100ft

DH < 100ft

CAT IIIA

RVR

200m ≤ RVR 700ft ≤ RVR

200m ≤ RVR 700ft ≤ RVR

200m ≤ RVR 700ft ≤ RVR

DH

DH < 50ft or No DH

DH < 50ft or No DH

DH < 100ft or No DH

RVR

50m ≤ RVR < 200m 150ft ≤ RVR < 700ft

50m ≤ RVR < 200m 150ft ≤ RVR < 700ft

75m ≤ RVR < 200m 250ft ≤ RVR < 700ft

DH

No DH

No DH

–

RVR

No RVR limitation

No RVR limitation

–

CAT IIIB

CAT IIIC

Table A1: Summary of approach category definitions, in accordance with ICAO, FAA, and EASA Regulations

ICAO Annex 6 – Chapter 1: Definition

Note: Where decision height (DH) and runway visual range (RVR) fall into different categories of operation, the instrument approach and landing operation would be conducted in accordance with the requirements of the most demanding category (e.g. an operation with a DH in the range of CAT IIIA but with an RVR in the range of CAT IIIB would be considered a CAT IIIB operation or an operation with a DH in the range of CAT II but with an RVR in the range of CAT I would be considered a CAT II operation). Acceptable operational correspondance meter/feet (according to ICAO) 15m = 50ft 30m = 100ft 50m = 150ft 100m = 300ft 150m = 500ft 175m = 600ft 300m = 1000ft 350m = 1200ft 500m = 1600ft 600m = 2000ft 800m = 2400ft 1000m = 3000ft 1600m = 5000ft

75m = 250ft 200m = 700ft 550m = 1800ft 1200m = 4000ft

A - General 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 14



B. Revision of low visibility weather conditions

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 15



B. Revision of low visibility weather conditions

1. The characteristics of fog Although visibility may be reduced by the presence in the air of solid particles such as smoke, dust or sand, most of the time low visibility conditions are caused by fog. There is fog if the visibility is less than 1000m and the obscuring agent is water droplets. Fog differs from rain or mist in that its water particles are more minute and suspended and do not fall earthward. The droplets of water suspended in the air near the earth’s surface act on scattering the light and thus reduce the visibility near the ground. The formation of a fog layer occurs when a moist air mass is cooled to its saturation point (dew point): the water vapor within the air mass condenses on small particles in the air to form liquid cloud droplets. This cooling can be the result of: – radiative processes (radiation fog), – advection of warm air over cold surfaces (advection fog), – evaporation of precipitation (precipitation or frontal fog), – movement of humid air up or down the hillside (upslope fog or valley fog).

1.1. Radiation fog Radiation fog is caused by the radiation cooling of earth’s surface. After sunset, earth receives no heat from the sun, but its surface continues to reradiate heat. The surface begins to cool because of this heat loss. As the Earth cools, the layer of air adjacent to the surface is cooled by conduction. This causes the layer near earth to be cooler than the air immediately above it, a condition called an inversion. If the air beneath the inversion layer is sufficiently moist and cools to its dew point, fog forms. In case of a calm wind and since air is a poor conductor of heat, this cooling by conduction affects only a very shallow layer i.e. a few inches deep. Wind of low speed (3 to 5 knots) causes slight, turbulent currents. Such turbulence is enough to spread the fog through deeper layers. As nocturnal cooling continues, the air temperature drops further, more moisture is condensed, and fog becomes deeper and denser. If wind speed is between 5 and 10 knots then the fog will usually thicken vertically. Winds greater than 10 knots usually result in the formation of low scud, stratus, or stratocumulus. At sunrise, the Earth is heated. Radiation from the warming surface heats the lower air, causing an evaporation of the lower part of fog, thereby giving the appearance of lifting fog. Before noon, the radiated heat from the warming of the earth surface destroys the inversion process, so then the fog evaporates into warmed air. Radiation fog appears over land, it never forms over a water surface and it may cover a wide area. The conditions giving rise to the formation of radiating fog are: – cloudless nights, allowing the earth to lose heat by radiation, – moist air that requires a little cooling to reach the dew point temperature, – light winds (5-7kts) to mix the lower layers of air, thereby thickening the fog layer. Such conditions are common in high-pressure areas during autumn and winter in temperate zones. Further radiational cooling at top of fog layer, deepens it.

Heat radiating from the surface at night, cools the bottom air until it reaches saturation.

Fog forms first at the surface, thickening as cooling continues. Figure B1: Radiation fog

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 16



1.2. Advection fog Advection fogs are formed when air moves either over a cooler surface or over a warmer moist surface and, as a result, the air mass reaches saturation. Most often this occurs when a moist air mass moves over a cold surface with a temperature lower than the dew point of the moving air. Cooling from below takes place and gradually builds up a fog layer. The cooling rate depends on the wind speed and the difference between the air temperature and the temperature of the surface over which the air travels. A low wind speed heightens the likelihood as the air remains in contact with the surface long enough to sufficiently cool the air layer. Advection fogs are often persistent since the weather situation that forms them can last a day or more. Usually, either a frontal passage with a change of air-mass or a major change in wind direction are needed for the dissipation of advection fog.

Fog forms

Colder surface

Warmer, moist air moves over a colder surface and its temperature drops Figure B2: Advection fog

1.3. Frontal / Precipitation fog This fog type is due to the evaporation of falling rain and occurs under the frontal surface in the cold air mass. Precipitation falls from the lifted warm air through the cold air. Evaporation from the rain continues as long as the raindrop temperature is higher than the temperature of the air, even though the cold air is already saturated. Naturally, the upper regions become saturated first because, at higher altitude, both the temperature and dew point are lower. As rain evaporation continues, a layer of clouds begins to build down from the frontal surface. Eventually, this cloud layer extends to the ground turning into fog. Cold fronts usually move so rapidly and have such narrow bands of precipitation and high wind speeds that a cold front fog is comparatively rare and short lived. A warm front fog, on the other hand, is fairly common. Warm-front fog may cover a wide area. Also this type of fog is deep because it extends from the ground to the frontal surface. precipitation falls through warm air rain cloud warm air

front cold air

fog evaporation leads to saturation

Figure B3: Frontal fog

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 17



B. Revision of low visibility weather conditions

1.4. Upslope and valley fogs Upslope fog is caused by adiabatic cooling of rising air. When moist, warm air is forced to move over a terrain obstacle, it cools to some degree as it rises, the degree of cooling depending on the amount of rise. During that cooling, if the air temperature falls below dew point, the resulting condensation will form a cloud. The air must be stable before it starts its motion, so that lifting does not cause convection, nor vertical currents, which would dissipate the fog. Wind speed is needed, of course, to cause upslope motion. This type of fog is deep and requires considerable time to dissipate.

Fog forms on slope.

Moist air flows toward slope.

As air rises with the terrain, it cools to condensation temperature. Figure B4: Upslope fog

Valley fog forms during the evening as a result of air being cooled by radiation on slopy topographical features. As this air becomes denser than its surroundings, it starts going down the slope. This results in the creation of a pool of cold air at valley floor level. If the air is cold enough to reach its dew point, fog formation occurs. Air cools at higher elevations. Fog forms in valley

Cold air drains downslope into valley.

Cold air drainage reduces air temperature in valley to condensation point. Figure B5: Valley fog

2. Effects of precipitation, wind and turbulences 2.1. The effect of precipitation Precipitation includes drizzle, rain, snow, ice crystals and hail. Although liquid precipitation on windshields can be a serious irritation for pilots, it does not seriously limit visibility, except when rain or drizzle is associated with fog. Even heavy rain does not usually limit visibility to less than 1 km.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 18



Figure B6: View from windshield during precipitation

Snow fall is a different matter; a very light snowfall alone can reduce visibility considerably. As snowfall becomes heavy, visibility may drop to only a few meters. Blowing snow is to be expected when loose snow is raised by the wind. The limited visibility may extend to a considerable height. This problem is quite significant in cold climates. Snow also affects approach and runway lighting intensity, thus reducing the chances of acquiring visual cues at Decision Height. Furthermore, the actual visibility may be less than the horizontally measured visibility because of the lack of contrast between the approach lighting and the snow-covered ground.

Figure B7: Snowy environment

2.2. The effect of wind and turbulences Low visibility conditions are usually due to the presence of fog which often appears in anticyclones. Therefore most of the time CAT II and CAT III approaches are performed with light or moderate wind, except on a limited number of airports where specific conditions may associate fog and strong wind. For CAT II operations, the ATR flight manual states the maximum “demonstrated wind”. It corresponds to the worth wind conditions encountered during certification flight tests. Therefore it should not be considered as a limitation. It is the operator’s responsibility to set the limit as per his national operational regulations. CAT III operations are constrained in respect of the wind component. Unlike the demonstrated wind for manual landings, the autoland wind capabilities are always limiting. The maximum crosswind values for auto-land operations are often less than the manually demonstrated crosswind landings.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 19



effect of tailwind: in some airports, not all runways are equipped for cat II/III operations. Therefore in low visibility conditions, a runway may be in use in spite of a light tail wind. The main consequence is a higher ground speed, reducing the time between DH and touchdown. During CAT II approaches, the pilot has less time to take control of the aircraft after the auto pilot disconnection.

Q The

effect of crosswind: At decision height the pilot may have more difficulties to acquire the visual references which are not located on the aircraft axis. Before Decision Height, according to the drift resulting from the crosswind, the pilot has to anticipate where to search visual cues. In CAT III operations the ATR autoland system performs the de-crab but does not follow the runway axis when the aircraft is on ground (no roll out function).

Q The

effect of turbulences: turbulences will increase the pilot’s workload to maintain the approach speed within acceptable limits. In case of severe turbulences, there is also a risk of autopilot disconnection, leading to a missed approach.

3. Runway Visual Range (RVR) 3.1. General The Runway Visual Range (RVR) is an instrumentally derived value that represents the horizontal distance a pilot may see down the runway. It is the maximum distance at which the runway markings or the runway lights can be seen by the pilot of a lined up aircraft. The purpose of RVR is to provide pilots and air traffic services with information on runway visibility conditions during periods of low visibility. ICAO Doc 9328 Chapter 11, Transmission and reporting practices, states the following practices for RVR reporting: – RVR must be assessed on all runways intended for Categories II and III approaches. – Where RVR assessments are required, they should be made and reported throughout periods when either the visibility or the RVR is observed to be less than 1500m. – The lower limit of the reporting range should be 50 m and the upper limit should be 2000 m. – The reporting increments should be 25 m up to 400 m RVR, 50 m between 400 and 800 m RVR, 100 m for values of RVR above 800 m. – The measurements should be averaged over a period of one minute.

3.2. RVR measurements The RVR value is determined by calibrated instruments (i.e. transmissometer or forward scatter meter) located alongside and higher than the centre line of the runway. A transmissometer measures the transmittance of the atmosphere between two points in space, over a specified path length or baseline. It consists essentially of a transmitter that directs a beam of light at a photo detector in a receiver unit. receiver

transmitter optical axis

height mini: 1.50 m maxi: 1.00 m

B. Revision of low visibility weather conditions

Q The

measurement reference = 30.00 m

electronic box frangible post data concentrator optical fibres link

Figure B8: Transmissometer principle

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 20



A scatter meter estimates the extinction coefficient by measuring the flux scattered from a light beam by particles present in the atmosphere. It consists of a transmitter and a receiver spaced by about one meter.

Transmitter

Receiver

Figure B9: Forward scatter meter principle

RVR is calculated taking into account the measured quantity (i.e. transmittance or extinction coefficient), the characteristics of the lights and the expected detection sensitivity of the pilot’s eye under prevailing conditions of background luminance.

Figure B10: Transmissometer

Figure B11: Forward scatter meter

The RVR measurement system includes: – instruments (transmissometers or scatter meters), – background luminance sensor: it measures the brightness of the background, against which the pilot would view the runway lights, – a runway light intensity monitor: it provides information on runway light setting, – RVR computer (dedicated or part of the integrated observing system), – digital displays of RVR in the appropriate Air Traffic Services unit, – a recorder to archive data over a given period of time.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 21



B. Revision of low visibility weather conditions

Figure B12: RVR measurement

The visibility sensors are strategically located along the runway to provide RVR measurements associated with three basic portions of a runway: – the touchdown zone (TDZ), located about 300m from the threshold – the mid-runway portion (MID), located at a distance of 1000 m to 1 500 m from the threshold – the rollout portion or stop end located at a distance of about 300 m from the end of the runway NOTE: For runways less than 2400m, RVR is normally provided for TDZ and Rollout only. The lateral position of the sensors should be within 120m of the runway centreline and the height above runway should be approximately 2.5 m. In certain conditions the RVR may be measured by the pilot or other weather observers. Typically the RVR may be evaluated by the pilot at take-off position, by counting the number of either the runway edge lights or the centreline lights that are visible.

3.3. RVR use Operating minima are expressed in terms of DH and RVR for approach and landing but exclusively in terms of RVR for take-off (please refer to Paragraph G.1, Establishing operating minima). Before commencing a take-off or an approach to land, the crew must satisfy itself that the RVR reported by air traffic services is equal to, or better than, its operating minima.

Take-off The minimum RVR required for a take-off should provide the pilot with sufficient visual references to control the aeroplane until it is airborne, or until the end of an abandoned take-off. This minimum RVR value is to be compared to the reported RVR which represents the visual segment available at the take-off position.

Approach and landing For approach and landing, the minimum RVR associated to a Decision Height is intended to provide a high probability that the required visual references will be available at that decision height. The visual references required (please refer to Paragraph E.6.6, Visual segment at DH and minimum visual references) at and below DH depend on the nature of the task the pilot has to carry out (manual landing or monitoring of an autoland). The reported RVR is an horizontal measure made on the ground while the pilot will normally be looking along a slant path at approach Iights. It is probable that the fog will be less dense at ground level than it is above ground level and slant visibility will probably be Iess than the horizontal visibility at ground level too. Thus, the most relevant information for the pilot is the slant visual range (SVR); however, as practical methods of measuring SVR have not yet been developed, only the RVR measurement is made available.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 22



9=9

3PTP[VM ]PZPVU

3PTP[VM ]PZPVU

:=9

Figure B13: RVR and SVR

A geometrical relation can be used to compute the SVR required for the pilot to visually acquire the specified visual segment in relation to the obscured segment. There exist a number of models to convert required SVR into required RVR. They take into account the increase of fog density with the height and they provide SVR/RVR ratios as a function of eyes height. It is then possible to compute a minimum RVR as a function of the DH and of the required visual segment.

7PSV[L`LZM[

‡WP[JO /VYPaVU[HSYLMLYLUJL ‡*\[VMM HUNSL

M[T

:=9 ‡ :LNTLU[VIZJ\YLK M[T

=PZ\HSZLNTLU[

Figure B14: Visual and Obscured segment

SVR / RVR

1 0,9 0,8 0,7 0,6 0,5 0,4 0

25

50

75

100

125

150

175

Pilot’s eyes height (ft) Figure B15: Evolution of SVR/RVR ratio depending on height

Even if such methods enable to deal with the DH/RVR relationship in respect of Category II and III operations, the minimum RVR values set in most current operational regulations have been established by also taking into account various real-life operating experiences which have given satisfactory results over a long period. However it is worth noting that these RVR values, published in tables of operating minima, on their own, have no intrinsic meaning; they have significance only in conjunction with a set of operating policies and procedures.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 23



B. Revision of low visibility weather conditions

3.4. RVR practical limitation The reported RVR is an instrumentally derived value that has significant limitations. It can be greater than, or less than, the actual visibility available to a pilot’s eye. None of the values measured on the ground can accurately indicate whether or not the pilot will have the required visual reference when at decision height. Main error conditions are as follows: – RVR is measured horizontally while the pilot is looking along a slant path, – unusual daylight, such as when a runway is aligned with a sunrise or sunset conditions in shallow or patchy fog, – spatial variations in the weather phenomenon between the pilot‘s view and the location where the RVR is measured (e.g. patchy fog or obscuration varying rapidly in time), – measurement errors from the sensor measuring the extinction coefficient or the transmittance, – angular and temporal variations in light intensity, – differences between the actual and assumed runway light intensity, – differences in background luminance between the pilot‘s view and the direction where the background luminance is measured, or errors in background luminance measurements.

Figure B16: Distorted vision through the windshield

Figure B17: Shallow or patchy fog

Furthermore, when assessing RVR, no account is taken of the effects on the pilot‘s vision of factors such as: – the transmittance of the windshield of the aircraft, – rain on the windscreen, – the level of cockpit lighting, – the illumination to which the pilot has been exposed prior to take-off or landing such as apron floodlighting, very bright fog and flying over bright approach lights, – physical and psychological conditions, e.g. tiredness or stress.

3.5. Conversion of reported meteorological visibility to RVR On aerodromes where there is no instrument to measure the RVR, the only information transmitted to the pilot by Air traffic services is the meteorological visibility. To compare the transmitted value to his operating minima (expressed in terms of RVR), the pilot needs to convert the reported meteorological visibility into RVR. This conversion is prohibited for CAT II and CATIII operations. For other types of operations, the regulatory Authorities usually specify the rules for such conversion.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 24



For example the European regulation states that: EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (l) Conversion of reported meteorological visibility to RVR/CMV. An operator must ensure that a meteorological visibility to RVR/CMV conversion is not used for take-off, for calculating any other required RVR minimum less than 800m, or when reported RVR is available. (…) In all other circumstances an operator must ensure that the following Table is used: Lighting elements in operation

RVR/CMV= Report Met Visibility x Day

Night

Hi approach and runway lighting

1.5

2

Any type of lighting installation other than above

1.5

1.5

1

Not applicable

No Lighting

Note: If the RVR is reported as being above the maximum value assessed by the aerodrome operator, e.g. “RVR more than 1 500 meters”, it is not considered to be a reported RVR in this context and the Conversion Table may be used. Amongst the Low Visibility Operations covered by this document, only lower than Standard CAT I is concerned by this conversion.

4. Weather documentation During flight preparation the weather document analysis should enable the flight crew to identify or assess the risk of encountering low visibility conditions.

4.1. Weather charts Weather charts cover a large area and are not intended for detection of low visibility condition on a specific airport, nevertheless significant weather symbols inform where visibility reducing weather phenomena are likely to appear. Such information allows the crew to anticipate weather degradation and to be prepared to face low visibility conditions. 'UL]]OH +DLO 5DLQ 6HYHUHVDQGRUGXVWKD]H 6KRZHU 6QRZ :LGHVSUHDGEORZLQJVQRZ :LGHVSUHDGIRJ :LGHVSUHDGKD]H :LGHVSUHDGPLVW :LGHVSUHDGVDQGVWRUPRUGXVWVWRUP :LGHVSUHDGVPRNH Figure B18: Symbol of weather phenomena affecting visibility

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 25



B. Revision of low visibility weather conditions

4.2 TAF/METAR/ SPECI The Information provided in the following paragraphs is voluntarily limited to elements affecting visibility.

4.2.1. General A METAR states the weather observed on an aerodrome during the last 10 minutes prior to the observation time. It is issued twice every hour. At some airports it may be issued only once an hour. If the weather changes significantly from the last METAR a special observation report (SPECI) is issued. The TAFs are meteorological forecasting at airport. It is worth noting that RVRs are never forecasted and thus never included in TAF messages. Only the horizontal meteorological visibility is provided. Range and resolution of visibility in TAF, METAR and SPECI: Horizontal visibility range

Resolution

Vertical visibility

Resolution

0000 m – 0800 m

50 m

VV000 – VV020

100ft (e.g. 160ft → VV001; 2000ft → VV020)

0800 m – 5000 m

100 m

VV ///

No vertical vis at all

5000 m – 10000 m

1000 m

Weather phenomena affecting visibility are reported into TAF METAR and SPECI using the following information.

Forecast weather abbreviations DZ RA SN SG IC PL GR

drizzle rain snow snow grains ice crystals (diamond dust) ice pellets hail

GS small hail and/or snow pellets BR mist FG fog FU smoke VA volcanic ash DU widespread dust

SA HZ PO SQ FC SS DS

sand haze dust/sand whirls (dust devils) squall funnel cloud(s) (tornado and waterspout) sandstorm duststorm

Examples + SHRA FZDZ + TSSNGR

heavy shower of rain moderate freezing drizzle thunderstorm with heavy snow and hail

TSSN SNRA

thunderstorm with moderate snow moderate snow and rain

4.2.2. TAF Below is a TAF message typical of CAT II conditions forecasting:

LFBO

150500Z

Airport identification

Day of issue 15 at 05TU

150615

36003KT

0500

Validity: the 15th between 06 and 15 TU

Wind 360° 03kt

Visibility: 500m

FZFG

Cloud layout 200ft

Weather: freezing fog

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

OVC002

p. 26



4.2.3. METAR / SPECI Below is a METAR typical of CAT III conditions:

LFBO

191050Z

Airport identification

01002KT

0200

Wind: 010°, 02kt

Day of issue 19 at 10h50 z

FZFG

R14R0250D

OVC001

Weather: RVR RWY Freezing fog 14R = 250m downgrading

Visibility 200m

M02/M02

Q1025

AOT= –2°C Dew point= –2°C

Cloud layout: 100ft

QNH

Other information on reported RVR in METAR (cf. ICAO Annex 3): – the RVR reported in a METAR is a value averaged over a period of 10 minutes, – only the representative value of the touchdown zone is reported in METAR, – in METAR, the runway visual range should be based on the maximum light intensity available on the runway, – whenever RVR changes and passes through 150, 350, 600 or 800m a report of special observations (SPECI) is issued. R16L/0350

R for RVR Runway 16 Left (C: center R right) RVR 350 meters

R16C/M0050

M means RVR is below the minimum value that can be determined by the system in use (i.e 50m)

R14L/P2000

P means RVR is above the maximum value that can be determined by the system in use (i.e.2000m)

R20/0400V0800

V means that during the averaging period of 10 minutes RVR has varied between 400m and 800m

R12/0550N R20/800D

“U” or “D” are used when during the averaging period of 10 minutes the variation of the RVR shows an Upward or Downward tendency. The abbreviation “N” indicates there is no distinct tendency Table B1: Description of the RVR in METAR

In a METAR, the present weather phenomena (i.e. FG or SN) may be associated with the following information: MIFG

Shallow – less than 2m above ground level.

BCFG

Patches – fog patches randomly covering the aerodrome.

PRFG

Partial – a substantial part of the aerodrome covered by fog while the remainder is clear.

DRSN

Low drifting – snow raised by the wind to less than 2 m above ground level.

BLSN

Blowing – snow raised by the wind to a height of 2 m or more above the ground.

VCFG

Vicinity – Fog reported between approximately 8 and 16 km of the aerodrome reference point.

The OAT / dew point is an interesting indicator: fog usually forms when the dew point and the air temperature are within a few degrees of each other, with the air temperature being lowered to the dew point, or when the dew point being increased to the air temperature causes fog formation. Contrarily, fog would be lifting when the temperature-dew point spread begins increasing.

B - Revision of low visibility weather conditions 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 27



C. Aircraft requirements

C - Aircraft requirements 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 28



1. Aircraft certification status 1.1. General The basic rule for an aeroplane is to be operated under a current certificate of airworthiness and to be maintained in a serviceable condition, in accordance with an approved maintenance program. Instruments and equipment for Category II and Category III operations have to comply with specific airworthiness requirements. It is assumed that the aircraft has a basic airworthiness approval for IFR operations. The supplementary airworthiness requirements for CAT II operations are described in appendix 3 of AC 120-29A (FAA regulation) and in subpart 2 of CS-AWO (European regulation). For CAT IIIA operations the relevant regulations are Appendix 3 of AC 120-28D (FAA) and subpart 3 of CS AWO (European regulation). To perform lower than Standard CAT I approaches under European regulation, the aeroplane has to be certificated in accordance with CS-AWO to conduct Category II operations and the auto-land system shall be approved for Category IIIA operations. For other than Standard Category II operations under European regulation, the aircraft has to be certificated in accordance with CS-AWO for operations with a decision height below 200ft. The certification process is to demonstrate that a high safety level and an acceptable rate of missed approaches are achieved during low visibility approaches. Such demonstration can be done examining: – airborne system accuracy, – airborne system availability and integrity, – reliability of the airborne equipment, – degree of redundancy, – probability of airborne system failure and consequences. The safety level must not be less than the average safety level achieved in Category I precision approaches. The rate of approaches terminating in a go-around below 500ft, due to the approach and landing system performance or reliability, may not be greater than 5%.

1.2. Guidance and landing systems Aircraft equipped with head up guidance landing system (HUDLS) or enhanced/synthetic vision systems or hybrid system (e.g.; autoland system in combination with head up display system) can be certificated to perform CAT II, CAT IIIA, lower than Standard CAT I and other than Standard CAT II approaches. As ATR aircraft are not equipped with HUDLS the following paragraphs do not deal with those systems.

1.2.1. CAT II approaches An aircraft cannot be approved to perform CAT II approaches without being fitted with an approach guidance system, composed of the following equipment and functions: – two ILS and/or two MLS receivers, – an automatic approach coupler with an audible warning of automatic pilot failure or a flight director system, – one radio altimeter with display at each pilot’s station of radio altitude and the selected decision height, – an indication, at each pilot’s station, of when the aeroplane reaches the pre-selected decision height appropriate to the approach (e.g. an alert light), – an automatic or flight director go-around system, – an appropriate equipment failure warning system, – an alert, at each pilot’s station, on excess deviation from the required approach path. NOTE: FAA regulation authorises flight director CAT II approaches. For EU operational regulation, only auto-coupled CAT II approaches are considered. Classic instruments ATR aircraft are certificated for CAT II approaches providing MOD (1112) is applied. MOD (0069) allows the use of the auto-pilot down to 50ft (MOD 0069 is not available for ATR 42-500).

C - Aircraft requirements 7B$75B$:2FKDSWHU$WR*PD\LQGG

p. 29



C. Aircraft requirements

AIRCRAFT

MOD

NAME

SB

42-300 72

0069

AUTOFLIGHT – AFCS: USE A CAT II APPROVED AP/FD DOWN TO 50 FT

42-22-0017 72-22-1006

All

1112

AUTOFLIGHT – RETROFIT CAT II CAPABILITY TO A/C DELIVERED WITH CAT I CAPABILITY

42-22-0001 72-22-1007

Basically, ATR -600s are CAT II certified.

1.2.2. CAT IIIA approaches with DH ≥50ft An aircraft approved to perform automatic CAT IIIA approaches (with DH ≥ 50ft) is basically fitted with an automatic approach and landing system including the equipment and functions listed above for CAT II approaches plus: – an automatic voice system, which calls when the aeroplane is approaching the decision height and when it reaches the decision height, – a fail-passive or fail-operational automatic landing system, – an acceptable speed control device or an automatic throttle control. An automatic landing system is fail-passive if, in the event of a failure, there is no significant out-of-trim condition or deviation of flight path or attitude but the landing is not completed automatically. For a fail-passive automatic landing system the pilot assumes control of the aircraft after a failure (cf. CS-AWO 300 Applicability and Terminology (b)(3)). Fail-passive landing system can support CAT IIIA approaches with DH ≥ 50ft, but cannot support CAT IIIB approaches nor CAT IIIA approaches with DH