novice
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Final App (Flight Director Radio Modes/APD/FPD/AUU

Tue Oct 23, 2012 7:26 pm

ILS Approach

"When flying intercept heading the PM will call “Localiser alive” at the first movement of the course deviation bar. When Flight Director Radio modes are selected the APD/FPD annunciations must be monitored for correct indications.

Both pilots must be alert to false localiser indications and false captures by the Flight Directors. Tuning the ADF to the LOCATOR is invaluable in confirming the validity of the localiser indications. Heading bugs should be set to the runway heading. Descent below 1500ft AAL is not permitted until the localiser is captured. At the first movement of the glide slope pointers the PM will call “Glide slope alive”. Both pilots must be alert to false glide slope indications particularly when more than one dot from localiser centre line. In order to programme the Flight Directors correctly it is important that both localiser and glide slope are captured (APD.FPD, green/green) before descending below 1500ft AAL.

After glide slope capture the PM will confirm that the missed approach altitude has been selected in the AAU. Both pilots must be alert to the possibility of instrument and radio flags during the final approach phase."


"When Flight Director Radio modes are selected the APD/FPD annunciations must be monitored for correct indications."
What are the flight director radio modes LNAV/NAV etc?? and APD/FPD annunciation?

"Both pilots must be alert to false glide slope indications particularly when more than one dot from localiser centre line."

Why should the pilot be alert to false glide slope indications particularly when more than one dot from the localiser centre line when the glide slope and localiser measure two different dimensions?

"After glide slope capture the PM will confirm that the missed approach altitude has been selected in the AAU."

Could someone tell me what the AAU stands for i do remember seeing it a while back and i can't remember what it stands for
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novice
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Tue Oct 23, 2012 8:05 pm

Cleared up what the aau is; Altitude Alert Unit
 
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Starlionblue
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Tue Oct 23, 2012 9:47 pm

Quoting Novice (Thread starter):
"When Flight Director Radio modes are selected the APD/FPD annunciations must be monitored for correct indications."
What are the flight director radio modes LNAV/NAV etc?? and APD/FPD annunciation?

I'll just speculate based on radios used for approach. LNAV is a GPS approach with no ground based inputs, so I don't think it would be a radio mode. If we look at approach modes that use radio, I'm guessing the flight director can use LOC (localizer), ILS (localizer + glideslope), VOR, LDA (localizer type directional aid) and SDF (simplified directional facility). At least that's what the G1000 in a Cessna can do use as inputs for the CDI (course deviation indicator) when you've tuned the requisite source.

Quoting Novice (Thread starter):
"After glide slope capture the PM will confirm that the missed approach altitude has been selected in the AAU."

Could someone tell me what the AAU stands for i do remember seeing it a while back and i can't remember what it stands for

As you say "Altitude Alert Unit". Probably this results in a voice saying "minimums", plus a minimums bug on the altitude tape.

Quoting Novice (Thread starter):
"Both pilots must be alert to false glide slope indications particularly when more than one dot from localiser centre line."

Why should the pilot be alert to false glide slope indications particularly when more than one dot from the localiser centre line when the glide slope and localiser measure two different dimensions?

It has to do with the nature of the transmissions from the localizer and glide slope. If memory serves the likelihood of a false indication is higher when further from the centerline.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Fabo
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Wed Oct 24, 2012 12:48 am

Quoting Starlionblue (Reply 2):
As you say "Altitude Alert Unit". Probably this results in a voice saying "minimums", plus a minimums bug on the altitude tape.

Nope, as it has to be set for missed approach altitude, not minimums. This is so that you do not have to touch it after commencing a G/A on approach, and it will guide you precisely to where you should be (vertically)

Quoting Novice (Thread starter):
"When Flight Director Radio modes are selected the APD/FPD annunciations must be monitored for correct indications."
What are the flight director radio modes LNAV/NAV etc?? and APD/FPD annunciation?

As I understand it, FD Radio mode(s) means that your FD is set in APP mode or LOC mode, following radio signals. APD/FPD would mean approach path deviation/flight path deviation, and in practice this would mean that you will not just blindly follow the FD, but that you monitor your other indications, be it "diamonds" on side and under ADI, indications on HSI, or on Cessna-style indicator (OBI, OSI, something like that? CDI?)
LNAV/VNAV is something different.
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Starlionblue
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Wed Oct 24, 2012 1:27 am

Quoting Fabo (Reply 3):
Quoting Starlionblue (Reply 2):
As you say "Altitude Alert Unit". Probably this results in a voice saying "minimums", plus a minimums bug on the altitude tape.

Nope, as it has to be set for missed approach altitude, not minimums. This is so that you do not have to touch it after commencing a G/A on approach, and it will guide you precisely to where you should be (vertically)


Do you mean that the AAU will be set to the initial climb altitude for the missed approach? Maybe I'm being sloppy with the terminology. I meant "minimums" as either MDA or DA/DH depending on approach type.

On a non-precision approach, missed approach altitude would be known as "Minimum Descent Altitude" right?

On a precision approach, you would have a decision height or decision altitude. Wouldn't this AAU then tell you when you reached it so you would initiate a missed approach.

How would the AAU guide you vertically?

[Edited 2012-10-23 18:29:26]

[Edited 2012-10-23 18:32:36]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Fabo
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Wed Oct 24, 2012 11:28 am

Quoting Starlionblue (Reply 4):
Do you mean that the AAU will be set to the initial climb altitude for the missed approach? Maybe I'm being sloppy with the terminology. I meant "minimums" as either MDA or DA/DH depending on approach type.

Yes. I am just using the original terminology as shown by OP.

Quoting Starlionblue (Reply 4):
On a non-precision approach, missed approach altitude would be known as "Minimum Descent Altitude" right?

Not in the meaning I intended. in a non-precision approach, you would descend to MDA, then continue to Mapt, and continue via missed approach procedure, including (at least generally) a climb to missed approach altitude.

Quoting Starlionblue (Reply 4):
On a precision approach, you would have a decision height or decision altitude. Wouldn't this AAU then tell you when you reached it so you would initiate a missed approach.

You could use AAU for this, but,
a) it might not be precise enough,
b) it is put to better use for GA situation

Many airplanes have a different device for announcing minimums, ranging from a bell coupled to radio altimeter, to a complex system fully selectable and settable for BARO/RADIO from negative to thousands of feet.

Quoting Starlionblue (Reply 4):
How would the AAU guide you vertically?

Not the AAU itself, but other systems in cooperation with AAU. A flight director or autopilot might have a mode for selected altitude capture, that would possibly read its selection from AAU.
Or at the very least the AAU will let you know you are approaching your level off altitude, and you cease your ascent manually.
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Pihero
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Wed Oct 24, 2012 12:52 pm

First, you're still not on final approach. You will be when - in this case - descending the ILS.
1/- You're on the final approach interception phase : Basically your AP and FD will be showing the lateral and vertical modes for that : HDG or LNAV - or the equivalents thereof - and VS or DES (It's open descent or FL change ).The altitude window will show the interception altitude and the ALT is blue until you level off.
So in this last part of the the intermediate approach your readings will be
Laterally : HDG or LNAV green, LOC armed
Vertically : VS or DES or ALT green, GS armed.

2/-The call outs for the ILS interception are , depending on one's SOPs :
Localizer alive... LOC green... Glide slope alive... Glide slope green... Go-around altitude set in the ALT selection window ( to calml it AAU is, IMO a vast exaggeration of its capabilities as the alerting bit is dependent on the value selected in the window )

Quoting Fabo (Reply 3):

Nope, as it has to be set for missed approach altitude, not minimums. This is so that you do not have to touch it after commencing a G/A on approach,

Correct

Quoting Starlionblue (Reply 4):

On a non-precision approach, missed approach altitude would be known as "Minimum Descent Altitude" right?

The MDA is the altitude you woudn't go under unlerss you can visually identify the features of your landing.
In a non-FMC-equipped airlplane, there is no way of setting it aside altimeter bugs. There won't be any auto call out ( i.e "Minimums" )
The altitude window is, here used for setting the missed approach altitude.

Quoting Starlionblue (Reply 4):


Do you mean that the AAU will be set to the initial climb altitude for the missed approach?

Correct

Quoting Starlionblue (Reply 4):

On a precision approach, you would have a decision height or decision altitude.

The main difference between precision and non-precision approaches is the radio-altimeter use : Decision height is based on the RadAlt, and all the auto call-outs too.

Quoting Starlionblue (Reply 4):
Wouldn't this AAU then tell you when you reached it so you would initiate a missed approach.

The dangers of using the AAU in this way are documented on the AF 744 Papeete incident. Very good reading, especially for a fan like you.

Regards
Contrail designer
 
Mir
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Wed Oct 24, 2012 2:14 pm

Quoting Starlionblue (Reply 4):
On a non-precision approach, missed approach altitude would be known as "Minimum Descent Altitude" right?

No, MDA is the minimum altitude you can descend to on the approach (a few hundred feet above the airport, usually). Missed approach altitude is the altitude you'd be climbing to if you didn't see the runway at MDA and had to do a missed approach.

We set the altitude selector to the MDA on a non-precision approach so that the FD (and AP, if engaged) will stop descent at that altitude. After the level-off, it gets reset to missed approach altitude.

-Mir
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Starlionblue
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Wed Oct 24, 2012 7:56 pm

Thx to Fabo, Pihero and Mir for much good info.

Quoting Pihero (Reply 6):
Quoting Starlionblue (Reply 4):

On a precision approach, you would have a decision height or decision altitude.

The main difference between precision and non-precision approaches is the radio-altimeter use : Decision height is based on the RadAlt, and all the auto call-outs too.

Well, in the plane I fly we don't have a radar altimeter so in our case the DA/DH is based on the barometric altimeter.  
Quoting Mir (Reply 7):
Quoting Starlionblue (Reply 4):
On a non-precision approach, missed approach altitude would be known as "Minimum Descent Altitude" right?

No, MDA is the minimum altitude you can descend to on the approach (a few hundred feet above the airport, usually). Missed approach altitude is the altitude you'd be climbing to if you didn't see the runway at MDA and had to do a missed approach.

Sorry, yes. I knew that. I was just being sloppy with terminology again.

Quoting Pihero (Reply 6):
Quoting Starlionblue (Reply 4):
Wouldn't this AAU then tell you when you reached it so you would initiate a missed approach.

The dangers of using the AAU in this way are documented on the AF 744 Papeete incident. Very good reading, especially for a fan like you.

Very interesting reading thanks.

[Edited 2012-10-24 13:02:32]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Mir
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Thu Oct 25, 2012 2:54 am

Quoting Starlionblue (Reply 8):
Well, in the plane I fly we don't have a radar altimeter so in our case the DA/DH is based on the barometric altimeter.

To be technical, if you don't have a radar altimeter, you can't use a DH (which is calculated in altitude above the ground). You have to use the DA (which is calculated in MSL altitude).

We do have a radar altimeter in our plane, but always use a DA since CatI minimums are in feet MSL, and we're not approved for the approaches that use DH (CatII and CatIII).

-Mir
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Fabo
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Thu Oct 25, 2012 7:48 am

Quoting Pihero (Reply 6):
The main difference between precision and non-precision approaches is the radio-altimeter use : Decision height is based on the RadAlt, and all the auto call-outs too.

Incorrect. Compare CAT I ILS landing - precission approach, but baro reference, RAlt commonly unreliable at this distance from landing point. (for referencing AAL)
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zeke
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Thu Oct 25, 2012 8:18 am

Quoting Mir (Reply 9):

Cold Wx ops and QFE approaches would not reference MSL, some places in the wold you have both at the same time.

Quoting Fabo (Reply 10):

Rad alts are reliable under 2500 ft, I am not aware of an approach where the rad lt I unreliable. Maybe you are talking about he terrain/water on approach ? E.g. A raising sea floor towards the runway ?
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Pihero
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Thu Oct 25, 2012 11:39 am

Quoting Fabo (Reply 10):
Incorrect. Compare CAT I ILS landing - precission approach, but baro reference, RAlt commonly unreliable at this distance from landing point.

That was written with a broad brush as the discussion wasn't on AWOps.
The broad brush was ok as there are more differences - including on scale - between Cat III and Cat I approaches than there are between a Cat I ILS and a ADF let-down.
*Secondly, the brush wasn't even mentioning the FAA acceptance of baro altimeter readings - or even an inner marker - for positioning a CAT II decision.
*Thirdly, CAT I decicion height is linked to the OCH on the runway... and OCHs are heights above thr runway reference point, hence baro-ref'd... and that's the reason why we use baro altimeters for CAT I.

You're right : there are lots more than my ballpark sentence.

Regards
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Fabo
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Thu Oct 25, 2012 2:26 pm

Quoting zeke (Reply 11):
Rad alts are reliable under 2500 ft, I am not aware of an approach where the rad lt I unreliable. Maybe you are talking about he terrain/water on approach ? E.g. A raising sea floor towards the runway ?

Yes, that is what I meant with

Quoting Fabo (Reply 10):
(for referencing AAL)

Especially if terrain slopes down from runway end, it would give you an illusion of being higher than you really are relative to the runway. (just to further elaborate on the point - I see I did not explain myself as well as I should have)

Quoting Pihero (Reply 12):
That was written with a broad brush as the discussion wasn't on AWOps.

Fair enough.
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Mir
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Fri Oct 26, 2012 2:59 am

Quoting zeke (Reply 11):
Cold Wx ops and QFE approaches would not reference MSL

We do reference MSL in cold weather operations, with the use of a correction table for the altitudes to make sure that we're not descending too low.

Quoting zeke (Reply 11):
Rad alts are reliable under 2500 ft, I am not aware of an approach where the rad lt I unreliable.

It's not a question of the radar altimeter being unreliable, it's a question of the published minimums just not being in AGL. 200 feet above TDZE is hardly ever 200 feet AGL at that particular location.

-Mr
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zeke
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Fri Oct 26, 2012 4:40 am

Quoting Mir (Reply 14):
We do reference MSL in cold weather operations, with the use of a correction table for the altitudes to make sure that we're not descending too low.

The corrections we use are in relation to the height above the elevation of the altimeter setting source, which is normally the airfield, not MSL.
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novice
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Mon Oct 29, 2012 7:22 pm

Quoting Novice (Thread starter):
Tuning the ADF to the LOCATOR is invaluable in confirming the validity of the localiser indications

How is tuning the ADF to the LOCATOR invaluable in confirming the validity of the localiser?
Thanks for the help guys   
 
Mir
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Mon Oct 29, 2012 7:46 pm

Quoting Novice (Reply 16):
How is tuning the ADF to the LOCATOR invaluable in confirming the validity of the localiser?

If the ADF needle lines up with the localizer when established inbound, that's an indication that the localizer is correct and valid.

-Mir
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smartt1982
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Mon Nov 05, 2012 10:55 pm

Quoting Mir (Reply 17):

All that does is suggest that the your going In the right direction, nothing to do with checking if the loc is valid or not. The only use I've found is when flying raw data when it gives a good,indication to turn onto the approach course, other than that I sometimes find they are depicted as g/s checks if prescribed on the procedure
 
Mir
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RE: Final App (Flight Director Radio Modes/APD/FPD/AUU

Tue Nov 06, 2012 4:28 am

Quoting smartt1982 (Reply 18):
All that does is suggest that the your going In the right direction, nothing to do with checking if the loc is valid or not.

The primary check of the localizer's validity should be the ID code and the absence of flags, of course. But if you're established on the localizer (needle centered) and the ADF needle isn't aligned with the inbound course, you're not on the correct localizer (excluding swings of the needle for station passage).

-Mir
7 billion, one nation, imagination...it's a beautiful day

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