Landing with a displaced threshold - Airbus

[John Citizen]

What are some "flying techniques" pilots use for landing on a runway with a displaced threshold.

In particular what techniques do you use in order to maintain the correct 3 degree profile to the displaced threshold.

Normally (without a displaced threshold) I use any of these :
- ILS / instrument approach
- the published profile on a chart for an instrument approach
- the vertical deviation symbol on the PFD
- Vertical deviation in the MCDU PROG page
- ongoing mental calculations using the distance to the threshold (threshold inserted in the MCDU)

However none of these will provide the correct profile for a displaced threshold.

Some techniques I see pilots use are to calculate some type of correction factor (eg +200', if threshold is displaced 1200 m) to the MCDU PROG page vertical deviation profile to the normal threshold. This seems to work OK.

Are there any other techniques pilots can use ?

I always thought that by creating a "new runway" (old runway with the displaced threshold) might be an acceptable technique but I have never actually tried it in flight. Would this be ok ?

At least this way, I can use :
- the vertical deviation symbol on the PFD
- the vertical deviation in the MCDU PROG page
- the new threshold location for mental calculations

Another technique occasionally used would be just to disregard the displaced threshold, fly a normal profile then just try and land through all the equipment and cones and see how much damage you can do :eek:

[Capn Bloggs]

John, as you know, RPT jets in Oz cannot operate without slope guidance of some sort for more than 7 days, so unless the threshhold is only very-temporarily displaced, you'll have a PAPI at least.

DME profiles or Vertical Revisions are OK further out, but I find that, when the action starts, ie less than 300ft, they're too inaccurate. Fly the same picture you always do ie with your eyeballs. There's no valid FOQA data (no ILS to ping you on) so there's no big deal being 1/2° steep or shallow, if you get it a bit wrong, as long as you don't bust the sinkrate rules.

It's entertaining watching the i generation trying to set up the FMS to show the right thing.

I will admit that it is "different" landing over a very long displaced threshold, even with a PAPI. "Where'd those big white squares go, Bloggs?!".

[John Citizen]

It's entertaining watching the i generation trying to set up the FMS to show the right thing.



I am not off the "I" generation yet I am guilty of doing the above.

Isn't that what the FMS is made for ?:confused:

Its entertaining for me watching the "other" generation struggle with the FMS, or even just with the GPS. :ok:

Though I have to admit, people of all ages including me struggle sometimes, and the "other" generation are just as good as the "I" generation.

[Capn Bloggs]

Isn't that what the FMS is made for ?
Not provide precise glidepath guidance/reference down a build-your-own approach, no.

Our box (Honeywell, but not Scarebus) allows you to create a "runway" at any location/coordinates, and from there the normal 3° slope will be projected back. That would be the most accurate way of doing it. VRs, because you can only get them to within 50ft, aren't going to help when it counts IMO.

[John Citizen]

Not provide precise glidepath guidance/reference down a build-your-own approach, no.


Then why does it display vertical deviation / VNAV information ?

Isn't this valuable information that can be used to achieve a purpose ?

[Capn Bloggs]

Isn't this valuable information that can be used to achieve a purpose ?
Yes, to a point. If you left the VNAV in, instead of using the ILS GS (discounting RNP approaches), where would you end up? And that is using database waypoints. As soon as you start putting in relatively inaccurate data rounded to the nearest 100ft eg VRs, the accuracy of the box diminishes. It's all rather academic outside 300ft but below that, an approach path/profile inaccuracy will be more obvious from looking out the front than by what the FMS is telling you.

The only system that is designed and trusted to take us to touchdown is the ILS GS. Everything else requires pilot control, because it is not accurate enough. Because of the potential inaccuracy (in my machine, every day it's hot the database profile is at least 50ft too high - nice at 200ft eh!) IMO you're better off chucking it all out the window and visually flying down "the picture" from 500ft or so. If you've got a flight path marker, then well and good, although using it is a bit like "reverse logic". Pick your normal spot on the windscreen (oh for a HUD) and down you go.

Of course, this is all academic if you have a temporary PAPI. Add 300ft/nm to a close-in waypoint eg runway-2nm and from there, look out the window and fly down the lights. :ok:

[PantLoad]

Basic airmanship and pilotage. (Or airpersonship)

What the hell did we ever do without an FMGC?

Oh? So, before the FMGC, we crashed a lot! And, now, we don't crash a lot?


Look out the window and land the damn airplane. Pretty simple....

Fly safe,


PantLoad

[engfireleft]

Yes. I was trying to find a way to say this in a way that didn't sound snarky, but what ever happened to looking out the window? Everybody learned how to do that at one time.

[John Citizen]

What the hell did we ever do without an FMGC?



Before the FMGC, we also did not have to worry about FOQA as well and so we had a lot more freedom and commonsense.

Sure I can eyeball it and fly it, however I a more concerned about satisfying the company requirements for a stable approach without setting of FOQA alerts.

In the good old days :
- you could exceed 1000 fpm and Vapp + 10 and still land land safely if you were perhaps a bit high (now we must go around)
- you could continue a shallow approach below the normal profile to reach the displaced threshold (now you are supposed to be on profile/slope at 500')

So you don't want to be too high or Low. You want to fly (ideally a continuous 3 degree descent/approach) a stable approach and be exactly on profile at 500' and that's what makes it perhaps a bit more challenging.

In the good old days you did whatever you wanted (to an extent).

[Capn Bloggs]

Sure I can eyeball it and fly it, however I a more concerned about satisfying the company requirements for a stable approach without setting of FOQA alerts.
If the threshold is displaced the ILS will be unusable by the FOQA and unless the PF is grossly "out", you'll never exceed the sinkrate or speed rules.

Do you routinely operate with a PAPI when there is a displaced threshold?

[John Citizen]

Do you routinely operate with a PAPI when there is a displaced threshold?

Yes, it usually does have a PAPI.

However the PAPI is useless if in IMC. :uhoh:

Look out the window and land the damn airplane. Pretty simple....


Not so damn simple in IMC :eek:

The published intrument approach profile (FMS/FMC/FMGC profile) is also useless for a temporarily displaced threshold. :uhoh:

If I follow the published profile, it means I will see 4 reds when when I get visual at the minima, and possibly not meet the company requirements to be stable and able to continue the approach. :uhoh:

If it happens to be at night (below slope at minima), you will not meet the requirements to make a visual approach therefore you will have to go around/execute a missed approach. :eek:

[NigelOnDraft]

JC...

Firstly, fly the Ac, not the FOQA or whatever... and remember, "it" cannot see anything you can't, but you can see the visual picture which it can't.

Ignore the ILS G/S below it's protected value, typically 200' unless LVPs in place etc. If you're not flying / been given an ILS approach, be cautious about flying with reference to it...

The VDEV bar is not a precision approach aid, so again, it's advice, but do not follow it slavishly. It is only as good as the FMC programming and the Nav accuracy... again, I'd ignore below typical NPA minima (500').

The best briefing / flying aid, and the one I see most poorly flown, is the VSI. 5x G/S or whatever as a datum. Then use an IAP check height / PAPIs to monitor the inital approach and get you stable / "in the slot". If you know the T'hd is 1500' inset, you could add 80' or so etc. Personally, I'd fly the IAP to minima/visual, and then slightly reduce the RoD.

"Stable" at 500' / 1000' does not mean "perfect". It usually means configured, on speed, some power, and on the correct V profile. You are essentially, in this case doing a visual approach, so in a typical jet, anything from 400'/m to 1000'/m I would suggest as acceptable. Outside those values, getting dodgy, G/A and try again?

There should be at least 2 sets of eyes as well. Brief to keep talking, elicit what the other guy thinks to the profile... "Tad high"..."Spot on" etc.

NoD

Look out the window and land the damn airplane. Pretty simple....
:ok:

[Capn Bloggs]

However the PAPI is useless if in IMC.
True. If you're on an NPA to a displaced threshold with a temporary PAPI and your state authority does not allow you to create your own profiles (you certainly can't do that in Australia) then all you need to do is adjust the chart profile by the displaced threshold amount (320ft/nm) and do the approach in VS or FPA, down your profile.

Alternatively, VS or FPA down using the VDEV bar but sit for example 50-100ft above it depending on the amount of the displaced threshold (I'm in a Boeing but sounds similar to yours).

You should keep a practical mind to all of this though; deliberately popping out low on the PAPI isn't a big issue; raise the nose a bit and fly into the proper slope.

If this is a big issue, then your company Flt Ops management should have issued guidance on how to tackle the problem eg raise the MDA so that you have enough time to pop out low on the PAPI (after following the database profile) and correct back to on-slope by 500ft.

[sevenstrokeroll]

just for fun...is the runway in question now a VFR only runway? if so, just look out the window and fly.

we have one airport here in the USA, in which you are allowed to land on the runway prior to the threshold provided you are day vfr and there are no ships in the harbor (boston)

[John Citizen]

Thanks for all your replies.

your state authority does not allow you to create your own profiles (you certainly can't do that in Australia)

I am not sure what you mean here ? :confused:

Some charts don't even have a published profile so you have to create your own :confused:

raise the MDA so that you have enough time to pop out low on the PAPI (after following the database profile) and correct back to on-slope by 500ft.

I suppose that is why the NOTAM raised the minima to the circling minima, for the reason you said.

[John Citizen]

It is an IFR runway with perhaps a few instrument approaches to it

[Capn Bloggs]

your state authority does not allow you to create your own profiles (you certainly can't do that in Australia)

I am not sure what you mean here ?

You cannot create your own FMS approach profile, load it into the box and let the aircraft fly it.

Some charts don't even have a published profile so you have to create your own
If an approach doesn't have a published profile, create your own 300ft/nm profile (320 for the pedants, or was it 319?:)) based on the location of the DME and the threshold elevation and fly it in VS or FPA. Write down each altitude for each nm back to 10nm (or the MSA if higher), confirm your profile misses any limiting steps and down you go. CDAs for the masses. :ok:

[compressor stall]

Sure I can eyeball it and fly it, however I a more concerned about satisfying the company requirements for a stable approach without setting of FOQA alerts.

I would have thought that any decent FOQA analysis would recognise the displaced threshold and take that into account? Remember, FOQA represents events outside a theoretical perfect flight profilenwhere everything is by the book.

That's not to say your approach should not be stable though, and can't that be achieved by looking out the window?