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threegreen

F/D disappearing on final

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Hello,

 

I usually fly the NGX as a F/O and noticed that my F/D disappeares on final approach, upon capturing the localizer the vertical component disappears before the horizontal one does as well when G/S's alive. I also lose my G/S and localizer indicators around the ADI. Following this I kind of execute a visual landing because there's no more indication on my PFD. However, this happens only at specific airports e.g. Toronto and Vancouver. The captain's F/D is still operating normally.

 

I looked up the FMC settings for displays but couldn't find anything related. Any ideas?

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Please note forum rules ask that we sign all posts with full names.

 

I am not familiar with the acronym ADI..., you referring to an outer maker locator beacon?

 

Left PFD and right PFD having different indications could be because you have NAV 1 and 2 different? Not sure, never flown right seat but I have used the right outboard DU 2D popup as a replacement for the left outboard DU. Only happens at certain airports? Are you sure you have identified exactly what you are seeing?  For example, you're not confusing the VNAV/LNAV indicators for the ILS?

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I am not familiar with the acronym ADI..., you referring to an outer maker locator beacon?

 

I think he means the raw data LOC and GS pointers around the PFD attitude display.

 

Surely you haven't forgotten the Attitude Director Indicator? ;)

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I am not familiar with the acronym ADI..., you referring to an outer maker locator beacon?

 

Just the Attitude Director Indicator like Kevin said, the artificial horizon without speed, altitude indicators etc. Underneath that is the localizer indicator and to the right the glideslope indicator. These are what keeps disappearing plus the F/D once localizer and G/S are captured. No idea why...

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Yeah, it's been a long time since I've flown the old attitude indicator. Got used to the HSI in real world and the correct term for the attitude/airspeed/altitude indicator is PFD.  I'm not flying the NGX right now, but you said the left PFD is normal while the right PFD looses LOC/GS indicators?? That is odd and not something I've ever seen, and you added that it only happens at certain airports. My gut says you are missing something, perhaps I do no understand but what about the FMA? Is it announcing LOC and GS in green or white?

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FMA first shows LOC/VOR and G/S in white while armed and upon capturing in normal green, just how it should be.

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Check to see if any failures are active? Who is the Master? The MA light on the MCP should be on the Pilot Flying side.

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Haven't yet been able to get into the sim but how do I control the MA light? Via the navigation transfer/display switches?

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Hello Dan,  I think you owe Ryan an apology, as  he did have his name on the original Post. I know we all make mistakes.

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Nope, just turn the FD off on the FO side, the MA light will switch to your side if not already there and then re-enable the FO FD on. 

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Nope, just turn the FD off on the FO side, the MA light will switch to your side if not already there and then re-enable the FO FD on.

 

I've tried switching it off already, didn't work. Switched off the Captain's too, then switched them off separately, nothing.

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This is not confusing.  It's really simple, with both FD off the first one turned on is the master.  If you want the right side to be master turn it on first.

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If you want the right side to be master turn it on first.

 

When I turn the F/Ds on before the flight I always select the right one first.

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You turn on right FD first but the left MA light is on even before you turn on left FD?  Something is getting lost here, I think we are pretty far off track of original problem that only happens at certain airports.

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I haven't had time yet to get into P3D and I can't remember what the MA light was doing on my last flights. However, I do know that I switch on the right one first every flight but it just keeps disappearing while on approach.

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Which AP is selected will also affect which side is master. If AP A becomes master for some reason then the Capt FD becomes master too. If only AP B is engaged the F/O FD will definitely be master and should stay that way.

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Thanks I will try that. But it seems a bit odd to me that the F/O's F/D disappeares on approach just because the other one is master or because AP A is engaged. Can't believe this is the case in reality.

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You are right, it shouldn't happen and I've use the right PFD 2D popup for approaches before when flying the left seat (to prevent a CTD in P3D by using the left PFD popup), I've never seen the FD bars disappear.

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You are right, it shouldn't happen and I've use the right PFD 2D popup for approaches before when flying the left seat (to prevent a CTD in P3D by using the left PFD popup), I've never seen the FD bars disappear.

 

Ive never heard of this happening, I use the Left PFD all the time. This causes CTDs??

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Different subject, it's a problem that only appears after hours and only to a few.  Most the time I don't use a PFD popup in the NGX because I've gotten used to and favor the HUD.

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Doesn't cause CTDs, all fine. Like I said, first the vertical part disappears and as soon as the glideslope is captured the horizontal one leaves me as well.

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Thanks I will try that. But it seems a bit odd to me that the F/O's F/D disappeares on approach just because the other one is master or because AP A is engaged. Can't believe this is the case in reality.

Both master F/D and autopilot must be choosen for PF's side. Because when you select autopilot it sets the FD on a corresponding side as a master. So if flying as FO - you use FD B and AP B.

Two FCCs are calculating flight path differently using their own sensors and flight computers, thus their data might mismatch sometimes. And you don't want captain and FO FDs to show different things, so master-slave logic is used, where slave just "copies" the master FD guidance. However, on approach, probably due to safety reasons, slave FD requires its own nav radio to be set for ILS frequency, otherwise it will not show GS. That is because on automatic approach both FDs become masters and the GS data is compared between them and only if tolerances on and between both the FDs are met, autoland would be available.

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Both master F/D and autopilot must be choosen for PF's side. Because when you select autopilot it sets the FD on a corresponding side as a master. So if flying as FO - you use FD B and AP B.

Two FCCs are calculating flight path differently using their own sensors and flight computers, thus their data might mismatch sometimes. And you don't want captain and FO FDs to show different things, so master-slave logic is used, where slave just "copies" the master FD guidance. However, on approach, probably due to safety reasons, slave FD requires its own nav radio to be set for ILS frequency, otherwise it will not show GS. That is because on automatic approach both FDs become masters and the GS data is compared between them and only if tolerances on and between both the FDs are met, autoland would be available.

 

SPOT ON!!! GREAT THREAD!!

 

I want to thank both the OP and Rostyslav for enriching my knowledge today. I had never flown an ILS from the F/O side. With only the NAV1 frequency tuned into the ILS, VORLOC and GS arm in the FMA's, because the airplane is still flying other roll and pitch modes. Notice however that during this time the VORLOC and GS triangles in the PFD are not shown in the F/O side PFD.

 

As soon as CMD A goes into approach mode however, the FD and FMA's in the F/O side disappear. Now tune the ILS frequency in NAV2 radio, everything back to normal. Except that now channel B is providing FD clues for the F/O side.

 

Learn something every day.

 

 

EDIT: I want to ADD to this post instead of correcting what might be a wrong last sentence. This for knowledge base reasons. It appears I am still a bit confused and would like further enrichment. So now that we have the ILS freq. tuned in NAV2 radio, is the FD on the F/O side now receiving clues from channel B ? or from the MASTER channel ?

Then, what happens during DUAL CHANNEL AUTOLAND with both CMD A and CMD B engaged ? is each one independent and the aircraft flying from which FCC ?

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