BACKGROUND
MANAGED APPROACH SELECTED APPROACH LOCALISER APPROACH INSTRUCTION
BACKGROUND
Non Precision Approaches can be broadly separated into two groups.
The first is the conventional VORDME, ADF and LOC approaches where ground based information is used as the primary source of information for lateral navigation and vertical navigation is controlled by the pilots inputs.
This is the case where the pilot adjusts the Heading of the aircraft to counter the effect of wind so that the aircraft flies along a path that is fixed in relation to the ground based aid. Vertical na vigation is performed by controlling the vertical speed, or Flight Path Angle, so that the aircraft is at a given height at a given distance from the ground based aid. If the ground based signals were removed there would be no information in the cockpit with which to continue the approach.
An enhancement of this first group of approaches is where the lateral and vertical parts of the approach are encoded so that the FMS can fly the same approach using the GPS to ensure the aircraft is in the correct position at all times. This is the “Managed Approach” that we demonstrate to our trainees and our progress must be confirmed by reference to the “Raw Data” which is the ground based information (inbound Radial – VOR, or Relative bearing – ADF, and DME). If we suspect an error we can always revert to a “Selected”
approach where we manoeuvre the aircraft (by hand, or AP) to follow the ground indications. It is possible to combine these two procedures so that our lateral navigation is Managed and our vertical
navigation is Selected.
An important technical point for a Managed Approach is that if the ground signals are removed there is no change in the aircrafts flight path down to the MDA as the aircraft is being guided by the information coded into the arrival as contained in the FMS. However, in this hypothetical case we would initiate an immediate go round as we would have no raw data with which to check our progress.
The second group of approaches do not use any ground based data but are solely based on GPS information and are called “RNAV GPS Approaches”. In this case the aircraft is guided by GPS to a point in space where a descent is commenced on a specific path to a minimum altitude from where a visual landing can be achieved or a missed approach carried out.
RNAV approaches are normally flown using lateral and vertical managed guidance (FINAL APP mode). However if altitude corrections are necessary due to large differences from the ISA temperature, or where an incorrect vertical coding has been identified in the navigation database, then vertical selected guidance (NAV / FPA), should be used.
The Airbus aircraft RNAV system is the FMGS. Flight crews are extensively trained to use this system during their type rating course so no specific training is required to use the FMGS for RNAV approaches.
For all Non Precision Approaches a stabilised approach is recommended (but is not mandatory). Configure to reach the FAF in CONF FULL and at VAPP.
As the Deceleration point is based on a decelerated approach you need to insert a speed constraint of VAPP at the FAF.
We aim to fly the NPA as much as possible like a stabilised ILS with similar procedures. The AP/FD guidance modes for a Managed approach are referred to the FMS FPLN and this is confirmed during the approach by reference to the raw data. This is why the crew must ensure that the FMS data is correct and accurate, with correct sequencing. An exception to this is a Localiser approach, where the ground generated LOC beam is captured Managed approaches (la teral and vertical or only lateral) are only available if they are in the FMGS database and the GPS is Primary or the NAV ACCY check is positive and the procedure has been validated by the Company concerned. A positive NAV ACCY check can be confirmed even if LOW accuracy is indicated on the PROG page. Otherwise an approach in selected mode is requied.
If for any reason GPS PRIMARY is LOST then a GPS defined approach cannot be performed and a VOR or NDB approach can only be continued by changing to a Selected Approach.
The ILS push button must be set to OFF in order to get VDEV information on the PFD (exception for LOC only approaches)
The Briefing for the Approach must specify the type of approach to be
performed and the intended guidance modes (FINAL APPR, NAV/FPA, TRK / FPA, or HDG V/S) and task sharing procedures and the importance of
crosschecking, During the briefing confirm the correct navigational aids and course settings are tuned (manually as applicable) for the approach.
ALL NPA’s
PRIOR TO APPROACH:
- Insertion of correct approach in MCDU - Set VAPP as a constraint at the FAF
- Check all constraints in FPLN match approach plates - Check Navigation accuracy
- Select and identify radio aids required for approach
- Conduct the Approach briefing and cross check the minima - Keep A/THR engaged to use managed speed
- Monitor the proper sequencing of the FPLN, particularly if HDG is selected.
(The NAV and APPR NAV modes are always guiding the A/C along the ACTIVE LEG of the FPLN, and the managed VERTICAL mode ensures VDEV = 0, VDEV being computed along the remaining FPLN to destination.) - Cleared for a Managed approach ?press the APPR P/B (the VDEV indication will now be visible, if not yet already there).
- Cleared for a Selected approach ?select an interception TRK on FCU.
- Cleared for a Laterally Managed, Vertically Selected approach remain in NAV
- The monitoring o f the interception must be achieved using the
applicable raw data depending upon the result of the NAV ACCY CHECK or whether GPS is PRIMARY.
INTERMEDIATE APPROACH:
- Check deceleration occurs at the decel point, or activate approach phase 10 NM prior to FAF
- Select FPD
- Ensure raw data is correctly displayed
- Verify accuracy is HIGH on PROG page or NAV ACCY positive - Complete approach checks when cleared for APP
- Crosscheck FPD approach track with approach plates - Ensure raw data is correctly displayed
FINAL APPROACH:
- Ensure landing configuration achieved prior to FAF - Start CHRONO at FAF
- Crosscheck altitudes and distances with those published on approach plate
- Set go around altitude
- Monitor raw data and FMA, calling mode changes AT MDA:
- If visual, disconnect autopilot and both Flight Directors and continue visually or perform a go around if there is insufficient visual references.
MANAGED APPROACH
Monitor the engagement of FINAL APP mode; use start of descent blue symbol on the ND, VDEV and FMA on the PFD.
Use A/THR and Managed speed.
With GPS PRIMARY, monitor VDEV / XTK / FPLN on ND and confirm by needles on ND and DME versus altitude.
Set Go Around Altitude when you have passed below that altitude.
If for any reason, FINAL APPR does not engage at start of descent, select a Flight Path Angle to recapture the Final Descent Path and so fly towards DEV 0. Once VDEV = 0, you may try to re-engage APPR.
If during the final approach the message NAV ACCY DNGRADED appears, immediately refer to raw data. If the check is OK, you may continue, however if the check is NEGATIVE, select TRK / FPA and fly according to your raw data.
If during the final approach, the message GPS PRIMARY LOST appears while flying a GPS approach immediately INTERRUPT the approach by going round.
Non precision approaches must be properly coded in the Navigation Data Base so as to be satisfactorily flown with the APPR NAV / FINAL managed modes. The coding of the vertical part of the approach must be verified by the airline. Should there be any doubt on the vertical F.PLN, or an Airline has not validated the procedure the crew may elect to fly the approach with NAV / FPA modes, provided the NAV ACCY CHECK is OK.
You are not allowed to modify the Final Approach F.PLN data (clear
waypoints or modify altitude constraints), and you must not insert DIR TO an intermediate waypoint of the final approach segment in Managed Mode.
NOTE : At the earlier of MDA -50 ft or MAP the autopilot will disconnect if in FINAL APP mode. Airbus does not recommend levelling off at MDA.
SELECTED APPROACH
The Selected non precision approach procedure is necessary when the NAV ACCURACY check is negative (or the approach is not in the database) and Raw data must be used for cross check throughout the approach.
Track to the FAF having intercepted the inbound track and select TRK / FPA.
Pre-select FPA –3.0º (ensure you remain in ALT) and approaching the FAF pull the FPA knob to activate the descent. (the pre-selection will remain for 40 seconds when it automatically returns to dashes. If you are concerned about
the possibility of your setting disappearing just before activation cycle the setting up or down by 0.1º and a new 40 seconds commences). With your TRK corresponding to the Final Approach Course, initiate your FPA descent momentarily before the FAF so as to establish your descent on the profile given by the chart, using A/THR and Managed speed.
Monitor Raw data for accuracy both Laterally and Vertically.
The Minimum Descent Altitude is not a decision altitude (as is the case with an ILS). Be aware that some companies add an amount (say 50ft) to a published MDA in order to treat it like a Decision Altitude.
If you have a horizontal distance scale you will reach the MDA in position to continue on the same profile to touchdown. If you are not visual at MDA you must go around immediately as there will be no possibility of achieving a safe landing if you subsequently get visual at the MDA altitude, but closer to the threshold.
However, if there is no distance scale on the profile you may level off at MDA until the MAP which in this case will usually be station passage of the relevant Navigation Aid.
LOCALISER APPROACH
As for all Non Precision Approaches, the recommended flying reference is the Flight Path Vector and the recommended FG modes for the final approach are LOC / FPA with A/THR and managed speed.
When cleared to intercept the LOC press the LOC P/B on the FCU to arm LOC mode and monitor LOC*.
On final approach, coming to the FAF prepare the FPA selection and at the FAF activate the descent by activating the FPA mode by pulling the knob.
Monitor the final approach using the LOC deviation scale and cross check the descent with the DME data.
INSTRUCTION
Watch out for the following potential errors
Raw data information not monitored closely throughout approach.
Confusion between managed and selected.
NAV accuracy not confirmed or checked.
TO waypoint validity not checked on ND
Navigation aids not manually tuned and course not inserted.
VAPP not stabilized at FAF.
Incomplete or rushed briefing.
TRACK / FPA selected late.
Aircraft descent preparation late.
Go around altitude set incorrectly.
Going below MDA.
You are not allowed (from a legal point of view) to teach initiating the descent 0.3nm before the FAF during a vertically selected approach. A technique such as this is part of the Initial Operating Experience training given by a TRE and only in accordance with specific National Regulations.