A320 Managed versus Selected FG modes
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A320 Managed versus Selected FG modes
For the Airbus gurus amoung us.
The concept of Managed and Selected modes for the Airbus are quite straight forward however in relation to a ILS approach what would LOC and GS be classified as?.
The FCOM doesn't seem very clear. The reason for the question is if in the unlikely situation with NAV ACCUR LOW (and a negative nav accuracy check) is LOC and GS modes available or should the approach be flown with TRK and FPA.
Any references to confirm LOC and GS is a considered a managed or selected mode would be appreciated.
Thanks in advance.
The concept of Managed and Selected modes for the Airbus are quite straight forward however in relation to a ILS approach what would LOC and GS be classified as?.
The FCOM doesn't seem very clear. The reason for the question is if in the unlikely situation with NAV ACCUR LOW (and a negative nav accuracy check) is LOC and GS modes available or should the approach be flown with TRK and FPA.
Any references to confirm LOC and GS is a considered a managed or selected mode would be appreciated.
Thanks in advance.
One way to think about the difference is that a managed mode has a navigational feedback mechanism to ensure that the aircraft is following a navigational path to a particular target.
Whereas the only feedback mechanism with a selected mode is to ensure that the selected value is followed. The pilot sets a speed, V/S, FPA, HDG etc and the aircraft will follow, but does not use navigational feedback to adjust the values to achieve a navigational target - only the pilot can change them.
So a managed NPA will follow a navigational path, but HDG/FPA will only follow the values set on the FCU. These values might be incorrect, and without manual intervention you could end up in the wrong place.
For this reason, I would class an ILS as a managed mode, because it uses navigational feedback to adjust and guide the aircraft along a tightly defined path.
Magenta = Managed.
Cyan = Selected.
The ILS LOC and G/S scales are in Magenta, so this suggests to me that Airbus consider it to be a managed mode?
PS, NAV ACCY has no bearing on a conventional ILS because the guidance follows two specific navigational 'beams' physically transmitted from the runway in question, it is not navigating the ILS by reference to IRS or GPS etc.
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Whereas the only feedback mechanism with a selected mode is to ensure that the selected value is followed. The pilot sets a speed, V/S, FPA, HDG etc and the aircraft will follow, but does not use navigational feedback to adjust the values to achieve a navigational target - only the pilot can change them.
So a managed NPA will follow a navigational path, but HDG/FPA will only follow the values set on the FCU. These values might be incorrect, and without manual intervention you could end up in the wrong place.
For this reason, I would class an ILS as a managed mode, because it uses navigational feedback to adjust and guide the aircraft along a tightly defined path.
Magenta = Managed.
Cyan = Selected.
The ILS LOC and G/S scales are in Magenta, so this suggests to me that Airbus consider it to be a managed mode?
PS, NAV ACCY has no bearing on a conventional ILS because the guidance follows two specific navigational 'beams' physically transmitted from the runway in question, it is not navigating the ILS by reference to IRS or GPS etc.
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Last edited by Uplinker; 24th Jan 2017 at 09:14.
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The magenta is part of color-coding (CYAN / WHITE / YELLOW / MAGENTA), nothing to do with managed. The thumb rule is nice, but coincidental. See later MODs with green yo-yo.
ILS approach is a Precision Approach using ground-based NAVAID. The FD and AP are coupled to this signal. There is no guidance from the FMS and thus neither any managed nor selected guidance terminology or technique apply (that's for NPA approaches that cannot be coupled - which this is not).
@RumBear: On which type of aircraft did you fly ILS APCH before the Airbus?
ILS approach is a Precision Approach using ground-based NAVAID. The FD and AP are coupled to this signal. There is no guidance from the FMS and thus neither any managed nor selected guidance terminology or technique apply (that's for NPA approaches that cannot be coupled - which this is not).
@RumBear: On which type of aircraft did you fly ILS APCH before the Airbus?
Last edited by FlightDetent; 24th Jan 2017 at 10:59.
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Although logically I thought similarly to FD but the FCOM doesn't say so.
According to DSC-22_30-10 P 1/6 FCOM A to C following are managed modes.
According to DSC-22_30-10 P 1/6 FCOM A to C following are managed modes.
GUIDANCE MANAGED modes
LATERAL NAV, APP NAV
LOC*, LOC
RWY
RWY TRK
GA TRK
ROLL OUT
VERTICAL SRS (TO and GA)
CLB, DES
ALT (magenta)
G/S*, G/S
FINAL
FLARE
LATERAL NAV, APP NAV
LOC*, LOC
RWY
RWY TRK
GA TRK
ROLL OUT
VERTICAL SRS (TO and GA)
CLB, DES
ALT (magenta)
G/S*, G/S
FINAL
FLARE
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Allright, that's actually easy logic.
AP/FD follow the guidance from within the "box" <-> managed
AP/FD follow the guidance entered manually via FCU knobs <-> selected
AP/FD follow the guidance from within the "box" <-> managed
AP/FD follow the guidance entered manually via FCU knobs <-> selected
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1. LOC and GS modes are available.
2. They are an external source tuned via the nav radio, whether automatically or manually, therefore do not require any level of nav accuracy in terms of GPS or FMGC to be followed.
3. This is not the case with external VOR/NDB approaches because the glideslope is a database function.
2. They are an external source tuned via the nav radio, whether automatically or manually, therefore do not require any level of nav accuracy in terms of GPS or FMGC to be followed.
3. This is not the case with external VOR/NDB approaches because the glideslope is a database function.
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I agree with Safelife.. FMA says Managed modes will come in Magenta and Selected will be in Blue.. And LOC and GS comes in Blue hence these should be Selected Guidance..
ILS (LOC + G/S or any combination thereof) is a selected mode. It's fully selected as in, it is not a managed mode.
It is completely dependent on ground based navaids, not the FMGS/GPS inputs.
If you've multiple Nav downgrades/electrical issues etc., you'll still have an ILS on 1 available. You'll fly to the LOC in HDG mode (under vectors or whatever) and it'll then follow the completely independent signal offered up from the airfield.
Think, say your aircraft is in perfect shape, it's locked on the LOC and GS and then the signal is interfered with etc on the ground. What'll the plane do? It'll follow the signal even though all GPS/FM position inputs are correct. The aircraft is not under the guidance/control of the flight management and guidance computers.
Likewise, if you're shooting an RNAV approach to a runway with an operating ILS signal and the ILS signal becomes erroneous, what'll the plane do? Continue tracking the RNAV correctly because it's using the GPS/FM inputs.
It is completely dependent on ground based navaids, not the FMGS/GPS inputs.
If you've multiple Nav downgrades/electrical issues etc., you'll still have an ILS on 1 available. You'll fly to the LOC in HDG mode (under vectors or whatever) and it'll then follow the completely independent signal offered up from the airfield.
Think, say your aircraft is in perfect shape, it's locked on the LOC and GS and then the signal is interfered with etc on the ground. What'll the plane do? It'll follow the signal even though all GPS/FM position inputs are correct. The aircraft is not under the guidance/control of the flight management and guidance computers.
Likewise, if you're shooting an RNAV approach to a runway with an operating ILS signal and the ILS signal becomes erroneous, what'll the plane do? Continue tracking the RNAV correctly because it's using the GPS/FM inputs.
DSC 22_30-10 Guidance modes show that it is managed! As Villas has already described above.
The A306 had localizer inertial smoothing to help the capture and tracking. It was an option which my airline didn't specify and it left the localizer susceptible to deviations .I would imagine that this function is incorporated into the fmgc in the A320 family and why there is a caveat about low accuracy.
The A306 had localizer inertial smoothing to help the capture and tracking. It was an option which my airline didn't specify and it left the localizer susceptible to deviations .I would imagine that this function is incorporated into the fmgc in the A320 family and why there is a caveat about low accuracy.
Last edited by tubby linton; 24th Jan 2017 at 21:21.
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Thanks for all the replies.
@Vilas and tubby - I was of similar opinion in that logically LOC and GS should be a selected mode however the FCOM did list LOC, GS, FLARE etc as managed.
The FCTM (SI-030) describes FG strategies in the event NAV ACCUR is LOW (and NAV ACCUR check is negative). In this situation we should display ROSE LS and use selected modes. This was primarily my question. (i.e. use APPR mode or TRK/FPA)
So Lookleft I can assure you i am not worried as to whether LOC and GS is defined as managed or selected while conducting an ILS approach with an FMS operating in HIGH accuracy. Merely a question of "What if" and interested in other opinions.
@Vilas and tubby - I was of similar opinion in that logically LOC and GS should be a selected mode however the FCOM did list LOC, GS, FLARE etc as managed.
The FCTM (SI-030) describes FG strategies in the event NAV ACCUR is LOW (and NAV ACCUR check is negative). In this situation we should display ROSE LS and use selected modes. This was primarily my question. (i.e. use APPR mode or TRK/FPA)
So Lookleft I can assure you i am not worried as to whether LOC and GS is defined as managed or selected while conducting an ILS approach with an FMS operating in HIGH accuracy. Merely a question of "What if" and interested in other opinions.
Only half a speed-brake
I think they advise not to use ND map modes with negative ACCUR check, that's all there is to it. Kind of make sense.
The strategy you describe seem to have a definition problem because they logically say do not use FMGS generated (using the word "managed") guidance and at the same time ILS to which there are no restricitons also falls into this category (=provided by FMGS) as per quote by Villas.
You'll run into discrepancies like this with FCTM which evolved from a book aptly named Instructor Support. For instance it reads that for predictive WINDSHEAR AHEAD - GO AROUND you should immediately commence the manouevre, wheras FCOM-ABN explains how to ignore spurious warnings.
The strategy you describe seem to have a definition problem because they logically say do not use FMGS generated (using the word "managed") guidance and at the same time ILS to which there are no restricitons also falls into this category (=provided by FMGS) as per quote by Villas.
You'll run into discrepancies like this with FCTM which evolved from a book aptly named Instructor Support. For instance it reads that for predictive WINDSHEAR AHEAD - GO AROUND you should immediately commence the manouevre, wheras FCOM-ABN explains how to ignore spurious warnings.
The magenta is part of color-coding (CYAN / WHITE / YELLOW / MAGENTA), nothing to do with managed. The thumb rule is nice, but coincidental.
FCOM DSC-31-40: Airspeed
(3)Target Airspeed (magenta or blue)
This symbol gives the target airspeed or the airspeed corresponding to the target Mach number.
The target airspeed is the airspeed computed by FMGC in managed speed mode (magenta) or entered manually on the FCU for selected speed mode (blue).
(3)Target Airspeed (magenta or blue)
This symbol gives the target airspeed or the airspeed corresponding to the target Mach number.
The target airspeed is the airspeed computed by FMGC in managed speed mode (magenta) or entered manually on the FCU for selected speed mode (blue).
The FCOM doesn't seem very clear. The reason for the question is if in the unlikely situation with NAV ACCUR LOW (and a negative nav accuracy check) is LOC and GS modes available or should the approach be flown with TRK and FPA.
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I think LOC and GS are considered managed modes as per definition because the ILS is selected in the MCDU and FMGC uses it through that. If there was no ILS selected and was flown by tuning the frequency in RAD NAV it will be considered as selected. Also for managed descent lateral managed includes LOC* and LOC along with NAV. That is why appears confusing. Further in airbus there are two functions that help prevent overshoot of localiser i.e.
LOC convergence function: this requires NAV mode and it keeps converging track of 20 degrees from LOC axis.
Enhanced LOC capture: This requires GPS primary it starts the capture using FMS data by turning with 15 degrees convergence before LOC becomes alive.
Obviously with NAV accuracy low these functions will be lost.
LOC convergence function: this requires NAV mode and it keeps converging track of 20 degrees from LOC axis.
Enhanced LOC capture: This requires GPS primary it starts the capture using FMS data by turning with 15 degrees convergence before LOC becomes alive.
Obviously with NAV accuracy low these functions will be lost.