EGPWS minima call-outs

[Hardy Heinlin]

Good morning,

in the existing PSX versions, all the selectable minima call-outs ("plus hundred", "fifty above", "decide", "minimums") will sound only if the minimum on the PFD refers to radio altitude, not to barometric altitude.

New feature: I will modify the system so that they can sound for the barometric minimum as well (if both radio and baro minima are set and disagree, the higher minimum is used).

Does anybody think this feature is airline specific and should not be included?


Regards,

|-|ardy

[Britjet]

Hello Hardy.

Do you ever have a weekend off??!

With regard to the disagree logic.  What happens is that the Captain's MINS selector determines which reference is used.. I don't think this is an airline-specific option.
The reason that I am personally sure of this is that if you think about a non-precision approach over undulating ground, RADIO minima are useless and are not published, so there HAS to be an option for the decision being an MDA ( Minimum Descent Altitude) based on BARO. Whether this is used for a precision approach such as an ILS would be an airline-specific SOP.
 
The following is airline-specific...other airlines would no doubt have different SOPs...

RADIO minima would normally be selected for the callouts for an AUTOLAND, and BARO minima for a MANLAND, (even an ILS).

For a BARO landing, BARO minima would be set,  RADIO minima would be set below zero and hence not visible, and the Capts MINS selector would be set at BARO.
For a RADIO landing, both relevant minima would be set, and the Capts MINS selector set at RADIO.

It would of course be normal for the minima to disagree even if you try and make them tie in due to terrain effects and barometric lag, or miss-set. The idea of having both RADIO and BARO minima displayed at the same time seems a rather strange one, I grant you, and would definitely be Airline-specific, but the logic is that if you are conducting a low-visibility approach using autoland minima, and you for some reason lose your autoland capability on final approach, you will still have your BARO minima visible and can land visually using your normal SOP callouts..

I hope this helps, but as I say, the important thing is that there is no disagree/use the highest minima logic.

Regards,

Brit

[Christo van der Loo]

Hi Hardy,

I think it will be nice to have it included.

Think some of it may be airline specific. We have the "plus hundred" and then "minimums" and that is reverenced to either the barometric or radio.

We never have both displayed at the same time. It's normally barometric unless we're doing a CAT II or III approach then we obviously set a radio altitude and the barometric blanked. The call is then still "plus hundred" then "minimums" based on the radio then.

We don't have "fifty above" and "decide"

Cheers
Chris

[Hardy Heinlin]

Do you ever have a weekend off??!

Hopefully soon, hopefully before I turn 60 :-)

What happens is that the Captain's MINS selector determines which reference is used.

Now I see what you mean.

I thought you mean the captain's EFIS control, not the F/O's EFIS control.

Now I see you mean the captain's RADIO-BARO switch (outer ring).

So, is it true that you will hear no such call-outs when the captain's radio DH is set above zero and the captain's outer ring is switched to BARO? Or is the outer ring position relevant only when both RA minimum and baro minimum are shown on the PFD?


Thanks,

|-|ardy

[Britjet]

Hi Hardy,

Sorry for the confusion!
It is indeed true that the callout is referenced to the captain's outer ring position only.
It doesn't matter what, if anything, is displayed on the other reference.

Peter

[Hardy Heinlin]

Hi Peter,

by "the other reference" you mean the F/O's reference?

It's clear that the reference is always the captain's setting.

I edited my last post as this outer ring stuff rises a new question:
Is it true that you will hear no such call-outs when the captain's radio DH is set above zero and the captain's outer ring is switched to BARO? Or is the outer ring position relevant only when both RA minimum and baro minimum are shown on the PFD?


Regards,

|-|ardy

[Jeroen Hoppenbrouwers]

Just to fill in a missing condition: as far as I understand this discussion, the logic seems:

1. Captain's outer ring on BARO -> callouts all based on baro setting.
     else
2. Captain's outer ring on RADIO -> callouts all based on radio setting.

1. If on BARO and setting below zero -> no callouts.
     else
2. If on RADIO and setting below zero -> no callouts.

Hence to Hardy's question,

Is it true that you will hear no such call-outs when the captain's radio DH is set above zero and the captain's outer ring is switched to BARO?

the answer shall be "don't know, because it is the BARO setting that is relevant, and only the BARO setting."

If BARO above zero, then callouts will come.
If BARO below zero, then callouts will not come.
DH irrelevant.


Hoppie

[Hardy Heinlin]

I thought of this too. But if the captain accidentally turns the ring to the BARO position after an RA minimum is set, the crew may hear no call-outs!

How many pilots know that, if they hear no sound, to look at this outer ring first?

How many pilots know that this outer ring is able to silence the call-outs at all?

Which AOM has this information?

That's what I'm thinking now :-)

I would take the outer ring into the priority logic only when both RA and baro minima are shown. If there is only one of them shown, there is no priority to check.


|-|ardy

[Jeroen Hoppenbrouwers]

A valid argument, however I suppose that the PM should back up the aircraft and I wonder whether in real ops, the callouts are not already voiced over by the PM anyway?

As an engineer, not a pilot, I would expect some warning if you have RADIO selected with the value below zero and A/C descending more than 1000 ft since the selection, or something. I would not expect fumbling with selectors basically AT the decision height.

Your suggestion to use BARO for callouts if (CPT BARO selected and value >0), and to use RADIO for callouts if (CPT RADIO selected and value>0), and to use either BARO or RADIO if just one value >0, seems fair enough.

If both values are <= 0 they are both invisible and should have been caught a few times already since before the descent briefing. This silences the callouts and is desired. If no minima are set, the pilots must have a reason to do so.



Hoppie

[Sylle]

Hoppie's summary above in post 7 seems correct to me.

I thought of this too. But if the captain accidentally turns the ring to the BARO position after an RA minimum is set, the crew may hear no call-outs!

In case the captains BARO minimums are set at a negative value that would be correct indeed. If BARO minimums are set at a positive value, the minima callouts will be based on barometric altitude.

I would take the outer ring into the priority logic only when both RA and baro minima are shown. If there is only one of them shown, there is no priority to check.

Cannot speak for the 744 but I would be VERY surprised if you could display both RA and BARO minima at the same time on the PFD! (Certainly not the case on the 737NG)

This is what I could find in the FCOM

Minimums (MINS) Selector (outer)
RADIO - selects radio altitude for display on the PFD and as reference for minimums voice alert.
BARO - Selects barometric altitude for display on the PFD and as reference for minimums voice alert.

Regards,
S.

PS: Worth checking with 744 drivers -
On the B737NG if you first set BARO minima at a positive value and then rotate the MINS selector to RA, the numerical BARO minima value on the PFD disappears but the BARO pointer (on the altitude tape) remains displayed. The callouts will be based on radio altitude.

[Britjet]

Yes, you can display both...sorry 737 NG, - not the same...
and no, you won't get a callout if the outer ring is selected to something that is not displayed.
It is as Jeroen has said.
Please see the FCOM reference supplied by Syllie.. it is correct.
While it might be nice to re-design the system to make it "safer", it isn't the 744 ;-)

...just trying to tell you what happens  

Brit

[Sylle]

Hi Brit,

Yep... although the MIP of the 737NG almost looks the same as the 744 (speaking about layout/instruments and not the color obviously ) it's clear to me by now that there are a lot of differences... The fact that the 744 was the very first implementation of this design and the NG the third one (777 in between) has probably a lot to do with it.

The FCOM extract above seems to suggest with the wording 'selects... for display' that you can only have one displayed at the same time.
Are you flying on 744 with RADIO/BARO or with DH/MDA written on the EFIS control panel?

Just making sure we are all talking about the minimums selector with RADIO/BARO as the FCOM I have contains a different description for DH/MDA.

Decision Height/Minimum Descent Altitude Selector (outer)
Passenger P&W
DH - selects radio altitude as PFD minimums reference.
MDA - selects barometric altitude as PFD minimums reference.

Minimums (MINS) Selector (outer)
Freighter
RADIO - selects radio altitude for display on the PFD and as reference for minimums voice alert.
BARO - Selects barometric altitude for display on the PFD and as reference for minimums voice alert.

You gotta love all those different customer options  :lol:

Sylvain

[Hardy Heinlin]

Hi Sylvain,

I think the design change from DH/MDA to RADIO/BARO happened at the time when the TERR button was added (and when the ND range "5" was added, and when the FPV button was no longer optional but standard); circa 10 to 15 years ago. Or maybe it happened when LCDs were introduced. Anyway, the "RADIO/BARO" lettering is not an airline option, I think.


Cheers,

|-|ardy

[John H Watson]

You gotta love all those different customer options

I think the DH/MDA panels are simply an older type. A committee probably got together and found the nomenclature was unsafe and decided to create a new type panel with BARO/RADIO to make it clear which height source was being used (Air Data Computers or Radio Altimeters)

In the wiring schematics, there appears to be no direct input from the EFIS CP/Left CDU to the EGPWS. It looks like the Left CDU sends the data to both the Left and Right EIU's* and the EGPWS gets it's info from there. The EGPWS box decides which EIU to use.

*The Centre EIU may not be available as a backup.

Rgds
JHW

(Cross-posted with Hardy)

[Hardy Heinlin]

I conclude all minima call-outs in PSX should be muted when EIU L and R are inoperative.


|-|ardy

[John H Watson]

Likewise : )

[Britjet]

Hi Sylvain,

Yes, I am talking about "RADIO/BARO" written in the EFIS selector...

Brit.

[Britjet]

One thing that may be of interest here and demonstrates why the callouts are muted if the DH/MDA is wound out of sight and the outer ring selected appropriately is that for a full CAT3B No DH approach - the RADIO DH is set below zero (so it is out of sight), and the outer ring stays on RADIO - so there is no DECIDE callout - the aircraft just lands. Scary, I know, but this is what happens..:-)
(in other words, you don't set "0" for a DH in this case as you will get a "50-above" call at 50ft which is inapplicable as there is no decision to be made .

Brit

[Jeroen Hoppenbrouwers]

Set the RA at 2500 ... DECIDE ... then relax    :-)

[Hardy Heinlin]

Aren't there also airlines (LH?) that want their crews to set DH to 17 ft for CAT III autoland? (Or 23 ft for e/o in the same category.) Edit: I mean airlines that don't use +50 or +100 calls but exact minima.

Why don't you want to go around when the runway is not in sight at the decision height? Respectively, why don't you want to hear a decision alert in this category?

Why is the DH system on the EFIS not rounded to tens of feet but does allow settings like "17" and "23"?

Edit: Ah OK, you have the "50 above" call. Well, anyway ...


Cheers,

|-|ardy


If I recall the numbers correctly, below 5 ft RA you have 2 seconds left to push TOGA. You may try this in PSX :-)