A320 missed approach from above missed approach alt

[Flaperon75]

Hi all,

Just trying to get my head around how to fly a missed approach from above missed approach alt on the airbus......

Say I'm happily trundling down an ILS, missed approach alt set in the FCU at 2000ft and I'm instructed to go around at 2800ft. To my mind, I could pull v/s at current rate which would then arm ALT which would capture at 2000ft. I think the lateral mode would revert to HDG. If I pushed for managed NAV would it then continue along the missed approach path? Obviously I haven't (and wouldn't want to) select thrust levers to TOGA at any point so the flight plan wouldn't have sequenced to the go-around phase. What are the implications of this? Would the arrival airport drop out as I fly over the threshold?

Any help appreciated!

Cheers

[rudderrudderrat]

Hi Flaperon75,

Would the arrival airport drop out as I fly over the threshold?

It depends on the software Mod of your FMGCs.

What you described is what we now call a discontinued approach. Our FMGCs will sequence the GA procedure, but we would have to re-enter the Approach for the runway again.

Older FMGCs will loose the GA procedure unless you selected TOGA briefly.
FCTM Page 198 (NO-170 P 2/4) gives some advice:
"If TOGA thrust is not required during a go-around for any reason, e.g. an early go-around ordered by ATC, it is essential that thrust levers are set momentarily but without delay, to the TOGA detent, the full forward thrust levers position, to ensure proper go-around (SRS/NAV) mode activation, and to sequence the F-PLN."

With older FMGCs, you could select TOGA briefly to sequence the flight plan, then retard the TLs to approach power (so aircraft doesn't climb at SRS speed), pull VS (select say -700ft/min), check for "Speed" mode, restore TLs to climb gate.
Or some other acceptable method.

[mcdhu]

Push to level off
Select GRN Dot
Disarm App (to avoid false GS capture)
Flaps in 1 Stage
Gear Up (if appropriate)
Make appropriate selections on FCU to reflect ATC instructions.

Actually I don't think Atc would order a GA if you were still descending to the platform. One for the ATC forum?

[rogerg]

Sometimes you have GA due to, say the gear not coming down. When that happened to me I could not recall the correct things to select so I just got rid of the AP and flew down to the GA alt and continued. It was a bit of a surprise tho!

[Flaperon75]

Thanks guys.

Rudderrat - Thanks for the info - very useful - I was aware of the technique of selecting TOGA detent and then back to climb to sequence flight plan. This would just seem a bit counterintuitive as you wouldn't really want to request TOGA power (even if only momentarily) when still descending to missed app alt. Maybe I would wait until ALT capture before selecting TOGA to keep the speed under control.

Mcdhu - you could be below platform altitude on ILS but still be above missed approach alt and instructed to go-around.

[dream747]

If you're descending on the ILS through say 2800 feet and the missed approach altitude is 2000 on the missed approach procedure and you have 2000 set on the FCU, if ATC orders you to go around and you push TOGA, what would the FMA read? In this case if you don't change the altitude selection on the FCU would SRS remain engaged (if you do nothing about it) as there is no altitude to capture?

In the above case, what's the best way to fly the missed approach procedure? Selecting TOGA seems necessary to engage the GA phase and sequence the missed approach procedure in the FMGS, but on the other hand TOGA thrust isn't quite necessary at that altitude for passenger comfort, etc.

Any advice?

[bubbers44]

Just fly the airplane to 2,000 ft. as the go around requires. It is not rocket science. LAX for example won't let you exceed 2,000 feet until over the ocean because of the VFR corridor. Getting checked out as FO in the B767 had a checkairman so screwed up I made him reduce to idle and descend back to 2,000 ft because he had busted the 2,000 ft altitude and was exceeding 300 knots at 2300 ft.

Smetimes line pilots can fly a lot better than check airmen. This wasn't the only time, it happened multiple times. We do it every sequence, the check pilots with no more experience than us but don't fly much sometimes get caught in a corner .

[EIU_EEC]

okay. The conditions are ,final approach,current altitude higher than acceleration altitude and fcu altitude set to missed approach alt which is lower than current altitude. WE put TOGA,briefly, FMA flashes LVR CLB as alt is above GA thr reduction altitude. as flaps are not 0 fmgc goes to GA phase.Fma roll mode changes to NAV(new fms2) ,we bring back thr levers to clb detent quickly.
Now the sweetspot.
DISENGAGEMENT CONDITIONS

The SRS mode disengages :
Automatically,

• at the Go-around acceleration altitude (GA ACC ALT), or
• if ALT* mode engages (above 400 feet RA).

Pitch mode should not remain SRS as we are above GA acceleration altiude, fma roll mode will be current VS and ALT blue. and thrust will be SPEED due pitch mode.
Therefore, no issue if atc tells us to go missed at high alt. simply select speed to higher than vapp, as desired, the aircraft will automatically level off at the lower missed app altitude. The aircraft will NOT go into SRS and therefore shall not climb, but will descend with current V/S. There will be a momentary speed increase as we go to TOGA but will return with SPEED mode engaging.

[I-2021]

Hi EIU,

according to the FCOM :

To interrupt the approach, or to perform a go-around, from an intermediate altitude in the approach,
and if TOGA thrust is not required, proceed as follows :

SET the thrust levers to TOGA detent, then retard the thrust levers as required.
This enables to engage the GO-AROUND phase, with associated AP/FD modes.
SELECT the applicable AP/FD and A/THR modes on the FCU.
Note: If the thrust levers are not set briefly to TOGA detent, the FMS does not engage the
GO-AROUND phase, and flying over, or close to the airport (less than 7 nm) will sequence the destination waypoint in the F-PLN.

Now the associated AP/FD modes are, always according to the FCOM : Setting at least one thrust lever to the TOGA detent engages both SRS/GA TRK modes, if:
‐ The flaps lever is at least in position 1, and
‐ The aircraft is in flight, or
‐ The aircraft has been on ground for less than 30 s (AP disengages and can be re-engaged 5 s Which is our scenario.

For what concerns the disengagement conditions the FCOM states :

The SRS mode disengages:
‐ Automatically, at the go-around acceleration altitude (GA ACC ALT), or if ALT* or ALT CST* mode
engages (above 400 ft RA)
‐ If the flight crew engages another vertical mode
‐ If the flight crew selects a speed while in SRS mode: SRS reverts to OP CLB mode and a
triple-click aural warning is heard.

As you mentioned we are above the go-around acceleration altitude, so the airplane doesn't have a target altitude to level off. It will thus remain in SRS. Another input for this condition can be read from the explanation of the SRS system which adds a note : Note: If during takeoff the flight crew inadvertently sets an altitude on the FCU below the
current altitude, the aircraft will remain in SRS mode until the flight crew takes some other action. Basically you can just push v/s 0.
That's only to mention the book explanation, pilot techniques are obviously personal and all inputs are welcome !

[I-2021]

Just fly the f**king airplane to 2,000 ft. as the go around requires. It is not rocket science. LAX for example won't let you exceed 2,000 feet until over the ocean because of the VFR corridor. Getting checked out as FO in the B767 had a checkairman so screwed up I made him reduce to idle and descend back to 2,000 ft because he had busted the 2,000 ft altitude and was exceeding 300 knots at 2300 ft.

Smetimes line pilots can fly a lot better than check airmen. This wasn't the only time, it happened multiple times. We do it every sequence, the check pilots with no more experience than us but don't fly much sometimes get caught in a corner .

Hi bubbers,

in this thread we are dealing with a type specific feature involving a scenario that is not frequent and that can create some confusion due to type specific automation features. One of the golden rules of Airbus is to take over when things don't work as expected, therefore your inputs are partially correct, but we are just trying to focus on the type specific technical aspect.

[EIU_EEC]

so the airplane doesn't have a target altitude to level off

we have set missed app altitude in FCU. and by FCOM
The ALT mode maintains a target altitude. This target altitude is either the FCU selected altitude or
an altitude constraint delivered by Flight Management.
ARMING CONDITIONS
Applicable to: ALL
The ALT mode arms automatically whenever the aircraft climbs or descends toward the target
altitude.
Note: The ALT mode arms only if the difference between the current altitude and the FCU
selected altitude is at least 250 ft.
When ALT is armed, the FMA displays the ALT message on its second line:
‐ Blue when the target altitude is the FCU selected altitude
‐ Magenta if the target altitude is an altitude constraint.

as per the note its applicable for takeoff phase, in fcom nothing is mentioned about goaround phase.

[I-2021]

EIU,

The aircraft will NOT go into SRS and therefore shall not climb, but will descend with current V/S. There will be a momentary speed increase as we go to TOGA but will return with SPEED mode engaging.

Therefore which FMA will you get once you set the thrust levers to TOGA ?

we have set missed app altitude in FCU.

Absolutely, but it is a lower altitude than the current one.

Cheers.

[EIU_EEC]

Hi, i-2021, this is a very interesting case indeed! since fcom doesnt delve into this straight, its a good scenario to think..according to me FMA is:
MAN VS-XXX NAV
TOGA ALT
[LVR CLB]
you can compare to the case to mode reversion when you select a lower altitude when the aircraft climbs,or vice versa.
I may be wrong, but the FCOM + FCTM is not clear about this scenario.
I cant find the reference , where it says SRS remains engaged after GA acceleration altitude like in the takeoff scenario.

[I-2021]

Hi EIU,

according to me FMA is:
MAN VS-XXX NAV
TOGA ALT
[LVR CLB]

the FMA can't look like this for the following reason : Setting at least one thrust lever to the TOGA detent engages both SRS/GA TRK modes, if:
‐ The flaps lever is at least in position 1, and
‐ The aircraft is in flight, or
‐ The aircraft has been on ground for less than 30 s (AP disengages and can be re-engaged 5 s Which is our scenario.

It is independent of the altitude that you have set in the FCU. To display the FMA that you suggest you need to pull the V/S knob otherwise the SRS will remain engaged.

[Squadronbrat]

Just fly the airplane to 2,000 ft. as the go around requires

I couldn't agree more. What's the world coming to when a simple manoeuvre has got this 'complicated'.

[rudderrudderrat]

Hi Squadronbrat,

We never designed nor built the thing. We just operate it.
Please tell us how you get the FMGCs to sequence the flight plan using your method.

[PT6A]

GO-AROUND FROM AN INTERMEDIATE APPROACH ALTITUDE /
DISCONTINUED APPROACH PROCEUDRE

Two scenarios need to be considered:
　
1) Go-Around from an intermediate approach altitude
To perform a go-around, from an intermediate altitude in the approach (e.g. Go-around from 1000ft with stop altitude of 2000ft) and if TOGA thrust is not required, proceed as follows:
SET the thrust levers to TOGA detent, then retard the thrust levers as required back to CLB (remember – "CLICK, CLICK" !)
This enables the engagement of the GO-AROUND phase, with associated AP/FD modes.
ALT* could occur very quickly. Clean up as normal. Follow Go-Around lateral procedure as normal. The previously flown approach will be strung automatically into the F-PLN.
2) Discontinued Approach Procedure
This procedure involves intervening with selected guidance and accelerating to green dot speed.
It avoids the possibility of engaging SRS mode with the FCU altitude set below the present aircraft altitude and also allows a less severe manoeuvre if climb performance is not a factor.
The following instructions are applicable when a discontinued approach is required from an altitude above missed approach altitude, or where the aircraft is not configured to transition to SRS mode, or when completing a go-around from an altitude that is close to missed approach altitude.
(e.g. Go-Around from 1800ft with a stop altitude of 2000ft; if TOGA thrust were used in this example, it would probably result in an altitude bust and flap overspeed.)
- Push V/S
- Select Green Dot speed
- If G/S is armed; push APPR Pb (LOC and G/S modes are disengaged)*
- PNF selects flap in one stage if required and requested by PF
- Retract landing gear if applicable
- PF uses V/S to achieve the desired altitude
- Flap retract on schedule (At no time are the trust levers moved to the TOGA detent)

* to prevent a possible false glideslope capture later.

NOTE: If the thrust levers are not set briefly to the TOGA detent (e.g. if flying the Discontinued Approach Procedure), flying over, or close to the airport (less than 7nm) may sequence the Destination waypoint in the F-PLN. In this case select a suitable DIR TO waypoint and reprogram the FMGS.

[Bengerman]

Right way up, sorry mate, wrong!

Select TOGA momentarily is EXACTLY the way to go, there is no big speed excursion and the aircraft will do what you want it to do, ie fly down to missed app alt and follow the lateral guidance for a missed app.....been there, done it.

[Right Way Up]

Sorry Bengerman....had just deleted my post before you posted as I am not sure what different mods of FMGC will do.

On my aircraft selecting TOGA is not a great idea and will climb in SRS......I have seen it a fair few times mostly sat on the jumpseat. It is a hamfisted way of flying the go-around just to sequence the fltplan.

The discontinued approach procedure is simple and gives you thinking time. I believe it was introduced after a few aircraft at LHR went around above missed approach altitude and ended up at 6000ft!!

[MD83FO]

Adding to PT6A
If TOGA tap not performed, and colleague very slow on the keyboard,
Plan ahead and delete the secondary, press secondary INIT and type the destination in the from and to field (KLAX/KLAX)
Select your approach and its ready to be activated, even after the done phase, because it will not sequence as it is strung differently from the primary flight plan.
Or you can just toga tap after slats retracted to prevent srs, then back to CLB,
To restring the approach. NAV will engage on the latest RNP AR ready FMGC.

You could also select geen dot ,then TOGA tap with the AP OFF and ignore srs, reengage vertical mode and clean up.