A320 MCDU "Sequence the flight plan" instead of DIR to?

[CW247]

Why do some pilots insist on sequencing the flight plan instead of a DIR to? I fly with some skippers who will quite happily tell me to manually clear 10 way points in busy airspace below transition knowing full well they are on a radar heading to intercept final. Only once have I ever been in a situation where after initially being given a radar heading I was told to go to another waypoint which I had just cleared. No big deal, just type it! 5 years flying the bus, I've still not managed to comprehend why you would do this as a rule. Can anybody offer me an alternative viewpoint?

[Piltdown Man]

Yup - the people who insist on this sort of activity will tell you that this sort of thing is illegal and you might be arrested by the Air Police on arrival. I believe it is due to a lack of confidence. The only real explanation for their reluctance to delete superfluous waypoints is that they'd like them to remain in the FMS "Just in case." My personal preference is to have a what I'm most likely to do punched into the box. If ATC add extra waypoints, we'll put those in on an "as and when basis".

[Goldenrivett]

I fly with some skippers who will quite happily tell me to manually clear 10 way points in busy airspace

Why not type the 11th way point in the scratch pad, place it on line 3L and clear line 2? You'll have PPos, discontinuity and your desired way point without engaging NAV.

[MD83FO]

I hear you, some people have been on the airplane for decades and still don't know how to use the mcdu to their advantage.
once on vectors it is most helpful to have track miles to touchdown to calculate an immaculate descent, and this is achieved by doing what goldenrivet suggests, though having PPOS will not give you accurate track miles, I'd have a From-To leg on the final approach course making sure the TO waypoint will be overflown (FAF) so typically ill have the FAF as the To way point and anything else on the centerline right behind it, you can also achieve this with a radial TO intercept to the FAF or equivalent.
just copy the active before you do this if you need to recall what was there.

and always ready to learn something new.

[Skornogr4phy]

A common action in our company (not SOP as far as I know), is to set the reciprocal radial in to the localiser on the DIR page, and then pull heading (so that it won't turn onto finals if you haven't been cleared yet) to get a good visual representation of the extended centreline. Of course this is only at the very end of the approach, and I'm quite happy to get rid of those superfluous waypoints at other times.

[PENKO]

In my company it's actually quite opposite.

'Do you want an extended centerline, sir?' (=you moron, how can you fly an ILS without extending the Airbus centerline!)

Ehh...now I don't!

But seriously, I think this is a case of 'give the guy what he wants' and be done with it. If he wants his waypoints, then that's the way it is. Maybe one of the waypoints passes over his grandma's house, or maybe he really does not expect straight in radar vectors, in which case an extended center line will give you way too optimistic track miles. The extended centerline has its merits, but it is not at all compulsory.

[vilas]

PENKO
There is no function to extend the centre line in Airbus FMGS except if you select the RW only. This is a radial in function. It extends the radial. On some NPAs the RW heading and inbound final approach track is different and you need to extend the inbound track. Extend centre line is a misleading term. Some tend to think that it is done to help turn inbound and not to get NAV during GA. No Airbus document uses this term.

[PENKO]

What are you trying to say vilas?
Radial in, extended centreline...the end result is the same if you pull HDG :E

[vilas]

Not when inbound course is different. You do not put RW you put FAF and radial gets extended.

[speedbird787]

In our company we extend the RW centerline ( sequence the flight plan is the command) only in case of radar vector ILS approach..or in case of a visual approach and its done by using the direct to radial in on the mcdu. Gives better prediction on the prog page and better situational awareness as well.

[tubby linton]

If you do not sequence the flight plan correctly nav will not engage in the event of a Go-around.

[737Jock]

pfff, as long as the flightplan is sequenced when you start the approach. Otherwise you might have a surprise for the go-around.

For the rest why is this a discussion?

[BulePilot]

I agree with Vilas that "extend the centre line" is a misleading term. Maybe it should be called "extend the final approach course" instead (except if making a visual approach, in which case RW centre line would be appropriate).

[TyroPicard]

Sometimes it is good to use radial in to the FAF or CI..... Other times it is good to leave the waypoints in.. We should not be prescriptive, we must allow for different thought processes, and as PNF/PM accept the wishes of the PF unless it is unsafe.

[vilas]

To get the GA procedure in NAV you have to sequence the FPL before intercepting inbound track/ LOC/ILS. You need the TO way point that is on final track generally FAF , either you use radial in or clear each way point. Extend centre line become so routine that it gets used even when RW centre line is different than inbound track and people start misunderstanding the purpose of doing it. What is centre line for Canarsie approach at JFK or Kai Tak HK ILS?

[Goldenrivett]

vilas

You must be a Time Lord if you can still fly the Kai Tak HK IGS.

[PENKO]

vilas, you can sequence the flightplan after the intercept as well.
If the extended centreline is different from the inbound track, as with most of our VOR approaches, every idiot will understand that you want the final approach track extended and not the runway QDM.

But I agree with you, technically speaking it is not the centerline. Try to change this habit in 2000 pilots who have been saying 'extend the centerline' for more than a decade.

[vilas]

PENKO
Quoted below from FCTM NO-110 P4/10


The flight crew should sequence the F-PLN first, and then press the APPR pb. When the LOC mode is armed or engaged, the flight crew should not perform a DIR TO, in order to sequence the F-PLN as this will result in the FMGS to revert to the NAV mode. In this case, the LOC mode will have to be re-armed and re-engaged, increasing workload unduly.

[Goldenrivett]

vilas,

Eee by hecky thump you are pedantic.

Nobody said perform a DIR TO, simply deleting the way points which are uselessly behind you will sequence the flight plan without engaging NAV.

If you want to be really picky - then it was the IGS at Kai Tak HK (not the ILS) which was 48 degree off set.
The ILS 32 was in line with the runway.

[vilas]

I don't see a situation when you leave sequencing until after intercepting ILS unless off course you had forgotten. If you start doing things differently you allow Mr Murphy to sneak in. I feel since we have no instincts in the air we need to follow procedures. Theoretically there may be many ways of doing a thing but under pressure we may do something inappropriate for that situation and I meant the IGS at Kai Tak.

[A360]

There is a note in the PBN manual which talks about not clearing wpts derived from nav db when doing sid/star even if they are not overflow, under radar vectors or clearing weather.
Sorry I do not have the manual handy for exact ref.

[vilas]

A360
We were discussing sequencing FLTPLN for approach because you won't get NAV mode for GA. Even during departure or clearing weather if you do not overfly way points and leave them in flight plan when you are asked to join the departure or wished to get back in NAV you won't get it. NAV can only be engaged when MCDU FROM and TO way points match ND way points.

[A360]

Hello Vilas,


During the STARs (or SIDs), if U wish not to fly the STAR's waypoints for any reason (radar vectors, weather) you can do so but do not clear the STAR's waypoints until you are on final intercept heading. After that either to perform DIR TO or clear the waypoints behind you.


This is applicable for RNAV APPs as per the PBN manual.


Thanks

[Metro man]

Lateral Revision and type in the next waypoint may be quicker than clearing.

Having the original route in the secondary can be useful if you get cleared to a way point you thought didn't apply anymore.

Remember you can't activate the Secondary Flight Plan in NAV without going into heading first, unless it is sequenced with the active. Direct To will stop the sequencing of the secondary.

Extending the centreline and having NAV armed whilst in heading will prevent you from flying through your final course and possibly infringing on a parallel runway. I do this if cleared for ILS approach whilst outside the 25nm protected area.

The FMS is a tool box and there are differences in how people use it.

[vilas]

A360
There was never any doubt about that. You need to do it before intercepting final track.

[OPEN DES]

Toptip

If despite all best intents you have messed up the flightplan sequencing and you discover this late on final approach:

Below 700ft RA (MCDU datalock):
-Direct to ¨Runway¨
-LOC - G/S remain engaged and flightplan is sequenced correctly for G/A

Obviously, before someone will jump at me, there are cons to going heads down at this height.

[A360]

OPN DES


If you perform DIR TO after you are locked on the ILS, the APPR (LOC & GS) will disengage and NAV will engage.

[Microburst2002]

There are several ways to achieve the same target, which is to have a "correct" waypoint TO.

Some like sequencing by clearing the waypoint from, or a couple of waypoints.
If there is a lot of waypoints to clear perhaps is better the next method:

make a DIR TO to the desired WPT TO and then pull HDG.

make a DIR TO with radial in to a suitable waypoint in final (if your FMGS standard allows it) and then pull HDG

In some cases I think it would be OK not to pull HDG. That would give better VDEV (if you pull HDG the FMGS computes direct distance from a/c to the WPT TO.)

[vilas]

A360
Refer to my post 19. This thread going round in circles.

[b215]

Vilas,maybe if we did a lateral revision on post #19 and inserted this post we would end up with a proper sequenced flight plan...

[OPEN DES]

A360 read mypost again. Not if done below700ft ra! Mcdu datalock....

[punkalouver]

In some cases I think it would be OK not to pull HDG. That would give better VDEV (if you pull HDG the FMGS computes direct distance from a/c to the WPT TO.)

The FCOM does talk about using the Direct To function with one reason given being "The VDEV to be computed on reasonable distance assumptions".
Anybody have a good explanation for this?

[a350pilots]

PENKO
Quoted below from FCTM NO-110 P4/10


The flight crew should sequence the F-PLN first, and then press the APPR pb. When the LOC mode is armed or engaged, the flight crew should not perform a DIR TO, in order to sequence the F-PLN as this will result in the FMGS to revert to the NAV mode. In this case, the LOC mode will have to be re-armed and re-engaged, increasing workload unduly.

This is why you ask to sequence the FPLAN BEFORE the approach is armed.
Quite logical.

[a350pilots]

Toptip

If despite all best intents you have messed up the flightplan sequencing and you discover this late on final approach:

Below 700ft RA (MCDU datalock):
-Direct to ¨Runway¨
-LOC - G/S remain engaged and flightplan is sequenced correctly for G/A

Obviously, before someone will jump at me, there are cons to going heads down at this height.

???

Seriously?
I rather fly the MAP by RAW Data selected, unless it is REALLY complicated to fly, but then I should not be flying.

[sonicbum]

???

Seriously?
I rather fly the MAP by RAW Data selected, unless it is REALLY complicated to fly, but then I should not be flying.

Fly an RNP1 go around raw data and let us know how it worked.