Perform CAT II/III approaches (A320)[PDF]
- 1 INTRODUCTION
- 2 REVIEW OF IMPORTANT CONCEPTS
- 3 AIRBUS 320 RELATED CONCEPTS
- 4 PREPARATORY WORK
- 4.1 CAT II/III APPROACH PREPARATION
- 4.2 OPERATIONAL TASKS (TASK SHARING)
- 4.3 CHART READING
- 4.4 DESCENT PREPARATION
- 5 AIRCRAFT GUIDANCE MANAGEMENT
- 6 HANDLING OF ABNORMALS
- 7 SUPPLEMENTARY INFORMATION
- 8 Reference
- 9 Author
The purpose of this article is to provide general and standard operating concepts applicable to CAT II/III approaches, the main goal of which is to provide a higher level of safety when landing in low visibility conditions.
Despite the slight differences that may be found among ICAO, FAA or EASA regulations, all refer to the same principles for CAT II/III operations.
REVIEW OF IMPORTANT CONCEPTS
Refer to Marker Beacon (Beacon)
Refer to Aerodrome Lighting System
Refer to Aerodrome Marking Signs
RUNWAY VISUAL RANGE
Runway Visual Range (RVR) is the range over which a pilot of an aircraft on the centreline of the runway can see the runway surface markings or the lights delineating the runway or identifying its centreline (ICAO). RVR values are given for the three basic portions of the runway: TOUCH DOWN ZONE (TDZ), MID-RUNWAY PORTION (MID) and ROLL OUT PORTION.
RVR makes part of the ground equipment necessary for CAT II/III operations. This value is measured by a system of calibrated automatic visibility meters (previously known as transmissometer for earlier versions of this equipment), which consists of a transmitter and a receiver used to obtain a measurement of the visibility in terms of extinction coefficient of transmitted light. In other words, this will basically determine how far the light beam can go in space.
For CAT II operations, the TDZ measurement is required, but for CAT III, both the TDZ and MID are mandatory.
The Decision Height (DH) is a specified vertical point 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 (ICAO ANNEX 6).
Refer to IFR precision approach and minima for more information.
AIRBUS 320 RELATED CONCEPTS
The Flight Management Guidance System (F.M.G.S) contains the following:
- 2 Flight Augmentation Computers (FAC)
- 2 Flight Management Guidance Computers (FMGC)
- 2 Multipurpose Control and Display Units (MCDU)
- 1 Flight Control Unit (FCU) with two independent channels.
The Flight Management (FM) part controls the following functions:
- Navigation and management of navigation radios
- Management of flight planning
- Prediction and optimization of performance
- Display management
- Autopilot (AP) command
- Flight Director (FD) command
- Autothrust (A/THR) command
Each FMGS computes its own landing category : CAT1, CAT2, CAT3 Single and CAT3 Dual, which will be displayed on the FMA. Each category depends upon the availability of aircraft systems and functions. When the capability downgrades, a triple click aural warning will be triggered with the respective change on the FMA indication.
An Alert Height is a height above the runway, based on the characteristics of the aircraft and its fail-operational automatic landing system, above which a CATIII approach would be discontinued and a missed approach initiated if a failure occurred in one of the redundant parts of the automatic landing system, or in the relevant ground equipment (ICAO).
Note: Below Alert Height, the FMGS freezes the landing capability until LAND mode is disengaged or both APs are off, thus guaranteeing no degradation in the category of the system should a failure occur below this height (100ft Radio Altimeter).
CAT II/III APPROACH PREPARATION
In addition to the applicable standards, pilots should take special measures in preparation for CAT II/III approaches.
- Wind: 30kt HW, 20XW, 10TW (check your manual since it may differ)
- Elevation: Check your manual for autoland maximum altitude (typically 9200ft as the max value)
As soon as you arm the approach on the FCU, the system will display the Landing Capability (CAT1/2/3 SINGLE or DUAL). However, If any item is inoperative due to, for example, a computer fail during cruise, you should refer to QRH to verify the expected landing capability. Some failures are not monitored by the FMGC, so be prepared in advance.
Airport Facilities and Weather
- Check current NOTAMs applicable to airport facilities. Those NOTAMs in relation to ground equipment and facilities are often simulated in IVAO. So be prepared for possible CAT II/III restrictions.
- Check current METAR and TAF on destination and alternate airports (Alternates must be above minima). Be prepared for LVP operations. Visibility is the main character here. However, do not forget about wind components and runway conditions. Automatic Rollout has not been demonstrated on contaminated runways.
In IVAO, everybody is free to fly, following certain rules. We do not need approval nor a qualification. However, we encourage you to keep reading this article and practice these types of approaches in CAT I or better conditions.
In real life, this is a very important part. Set up your 3D cockpit view so that you can monitor your instruments and look outside. You may loose some visual references if you do not correctly set your cockpit views.
Normally NOT USED in CAT II/III weather conditions. Using landing lights during low visibility at night may have a negative impact, since the reflection can reduce the visibility even more.
Approach and Go around Strategies
Two important things in regards to this:
- In CAT II approaches, autoland is recommended, whereasIn CAT III approaches, AUTOLAND is absolutely MANDATORY.
Consider a possible course of actions in case of degradations in the aircraft capability (triple aural click) in order to assess all available options.
- Be Go-around minded during the approach. Should a failure occur above 1000ft Radio Altimeter, all ECAMs and DH amendments must be completed before reaching 1000ft. Otherwise, perform a missed approach.
- Make an AUTOLAND system test by depressing the AUTOLAND push button on the glareshield (Check your flight sim features for this).
- Set Autobreaks to LOW/MED. Assess runway conditions, landing distance and possible taxi-out route.
- Set DHs according to the charted values. For CATIII approaches with no DH, "NO" should be entered in the DH field of the MCDU to avoid false "HUNDRED ABOVE" or "MINIMUM" auto callouts which would not be applicable.
- Consider flaps setting accordingly. Most A320s series are approved for autoland in Flaps 3 or Full. Check your manual for limitations.
OPERATIONAL TASKS (TASK SHARING)
According to A320 SOPs, pilots should review in advance all those operational tasks required for CAT II/III approaches. This is well known as Task Sharing, since these tasks are shared between Pilot Flying (PF) and Pilot Monitoring (PM).
- At 350 ft RA: CHECK “LAND” on FMA
- CHECK ILS course.
- Between 50 and 40 ft RA: CHECK that “FLARE” is displayed on the FMA
- At approximately 30 ft RA: CHECK that “IDLE” is displayed on the FMA
- Autothrust starts to reduce thrust toward IDLE.
- At 10 ft: CHECK “RETARD” auto-callout comes up
- MOVE the thrust levers to IDLE. Autothrust disconnects.
- At touchdown: CHECK “ROLL OUT” on the FMA.
- With the autopilots ON, it should keep the aircraft along the runway centerline.
- At the end of the Rollout: Disconnect the autopilot.
CAT II/III APPROACH 13R
Final Approach Course: 134o
GS Interception: 5NM from IADO at 10000ft
Glide path: 3.0o
DH: No DH for CAT III, 137ft RA for CAT II
Use the “TOP HAT” method as per AIRBUS SOP for descent preparation. Follow the flow from left to right. Here you’ll find some of the most important setups.
- Pay particular attention to the F-PLN sequence. Select the appropriate ILS approach (CAT II/III). Make a vertical revision and check altitude and speed constraints for each point along the approach. Press key R2:
2. On RAD NAV page, select the most appropriate radio NAV aids for the procedure.
3. On PERF, set the approach page with the most current weather data.
AIRCRAFT GUIDANCE MANAGEMENT
|CONDITIONS||CAT I||CAT II||CAT III WITH DH||CAT III WITHOUT DH|
|TECHNIQUE||Manual Flight or AP, FD, A/THR||AP, FD, A/THR down to DH||AP, FD, A/THR AUTOLAND||AP, FD, A/THR AUTOLAND|
|MINIMA AND WEATHER||Baro DA and Visibility||DH with RA / RVR minima||DH with RA / RVR minima||RVR minima|
|AUTOLAND||Optional with precautions||Recommended||Mandatory||Mandatory|
- Clearance for the approach has been received.
- Aircraft is on the intercepting trajectory for the final approach course.
- LOC deviation scale is available on PFD.
Note: According to ICAO, the normal glide slope envelope is within 10 NM, ±8o off the centerline of the ILS glide path and up to 1.75 θ and down to 0.3 θ (θ = nominal glide path angle)
COMMON PARAMETERS FOR STABILIZATION DURING THE APPROACH
- Speed: between VAPP -5kt // +10kt
- V/S: Max -1000ft/min in descent
- Bank: Max 7o
- Pitch: Max -2.5o // +10o
- LOC: deviation not greater than 1/2 dot
- GS: deviation not greater than 1/2 dot
HANDLING OF ABNORMALS
ECAM actions will guide through the different affected systems to the STATUS page in order for pilots to assess, among other relevant issues, possible degradations of the automatic landing system.
In this example, IR unit #2 has failed.
The image above shows the current aircraft status, as well as the updates made for the APPR PERF page on the MCDU according to the situation. The CAT II/III approach chart indicates that in case of FAIL PASSIVE (CAT 3 SINGLE) capability, a DH of 50ft RA should be used. (See Chart Reading section).
When the APPR push button is pressed, the approach arms the LOC/GS mode in blue (as when in normal conditions). However, due to the failure affecting the autoland capability, the FMGS shows on the FMA the expected capability CAT 3 SINGLE with both autopilots ON.
This failure can be also verified by looking at some specific indications on the copilot ND displaying MAP NOT AVAIL and SET OFFSIDE RNG/MODE and the MCDU.
According to ICAO Annex 6, there is a very important concept that pilots should be familiar with, and it refers to the “Commencement and Continuation of the Approach”. (Some similar concepts may apply to EASA and FAA regulations)
This policy limits aircraft from proceeding beyond a point on an IAP, which is 300 m (1000ft) AFE or the beginning of the final approach segment, unless weather conditions satisfy the required minima for the approach. If weather deteriorates after having passed the approach ban point, the pilot may decide to continue down to DA/H or MDA.
Note: “Relevant” in this context refers to that part of the RWY used during the high-speed phase of the landing down to a speed of approximately 60KIAS.)
- A320 FCOM/FCTM
- Getting to grips with CAT II/III
- All weather operations manual
- VID 109661 - Creation
DATE OF SUBMISSION
- 06:58, 14 May 2021
- This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.
- The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.