Print from Airliners.net discussion forum
http://www.airliners.net/aviation-forums/tech_ops/read.main/324551/

Topic: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Novice
Posted 2012-10-23 12:26:54 and read 2908 times.

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
Cheers

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Novice
Posted 2012-10-23 13:05:44 and read 2899 times.

Cleared up what the aau is; Altitude Alert Unit

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Starlionblue
Posted 2012-10-23 14:47:26 and read 2878 times.

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.

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Fabo
Posted 2012-10-23 17:48:53 and read 2851 times.

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.

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Starlionblue
Posted 2012-10-23 18:27:49 and read 2843 times.

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]

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Fabo
Posted 2012-10-24 04:28:30 and read 2777 times.

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.

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Pihero
Posted 2012-10-24 05:52:05 and read 2761 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Mir
Posted 2012-10-24 07:14:03 and read 2748 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Starlionblue
Posted 2012-10-24 12:56:50 and read 2682 times.

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]

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Mir
Posted 2012-10-24 19:54:13 and read 2637 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Fabo
Posted 2012-10-25 00:48:35 and read 2616 times.

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)

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: zeke
Posted 2012-10-25 01:18:03 and read 2610 times.

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 ?

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Pihero
Posted 2012-10-25 04:39:24 and read 2591 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Fabo
Posted 2012-10-25 07:26:22 and read 2574 times.

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.

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Mir
Posted 2012-10-25 19:59:19 and read 2517 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: zeke
Posted 2012-10-25 21:40:39 and read 2509 times.

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.

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Novice
Posted 2012-10-29 12:22:27 and read 2386 times.

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   

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Mir
Posted 2012-10-29 12:46:32 and read 2381 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: smartt1982
Posted 2012-11-05 14:55:42 and read 2192 times.

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

Topic: RE: Final App (Flight Director Radio Modes/APD/FPD/AUU
Username: Mir
Posted 2012-11-05 20:28:27 and read 2192 times.

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


The messages in this discussion express the views of the author of the message, not necessarily the views of Airliners.net or any entity associated with Airliners.net.

Copyright © Lundgren Aerospace. All rights reserved.
http://www.airliners.net/