Question about separation of air traffic on approach

[Nicholas49]

Hello

We know that a common reason for a go-around is that the aircraft landing ahead has not yet vacated the runway. Can I ask a few questions about the specifics of this procedure?

At what stage of the approach must you go-around due to the previous landing aircraft still being on the runway? Is it when you reach a certain altitude? Does it vary from one approach/airport to another?

Is the weather a factor? Would the separation be increased in fog, for example?

Whose call is it? The tower controller or the captain? (I appreciate both can instigate a go-around.)

And if I may add a cheeky sub-question (perhaps related?): when does a missed approach become a go-around? Again, is it a certain stage of the approach?

Thanks

[HEATHROW DIRECTOR]

In poor visibility - e.g. LVPs - final approach separation will be greatly increased. It may also be increased for other weather factors - wind, rain, snow, etc. The spacing is decided by the Tower and implemented by Approach Control.

ATC will usually instigate a go-around for traffic reasons and most pilots will keep coming.... I have never seen a go-around instigated by a pilot for traffic reasons although I'm sure it must happen..

[Meikleour]

There is no specific rule and generally ATC will issue the instruction to go around. However at some airports in the UK rules exist ( known as `land after` ) which allow, provided certain criteria regarding spacing and visibility are complied with, for the second aircraft to touch down with another aircraft still on the runway.

When it is foggy then a whole different set of rules apply. Greater spacing is needed to protect the ILS integrity and allow time for slower speed egress from the runway. Generally around 2min. spacing is applied but I am sure more knowledgeable ATC guys can speak about these rules.

[BOAC]

Q1 - nothing firm - sometimes it is worth 'hanging on' for a slow vacator. Wheels on the ground is just too late.

Q2. Covered by Meikle

Q3. Either, normally ATC. Captain has ultimate responsibility.

Q4. If there is a figure, I would guess 1000'AAL would do.

[mutt]

I have never seen a go-around instigated by a pilot for traffic reasons although I'm sure it must happen.. It happens, I saw a LH A340 initiate a Missed Approach in Jeddah, ATC asked him why and he stated that he wasn't happy with the separation....

[fujii]

And if I may add a cheeky sub-question (perhaps related?): when does a missed approach become a go-around? Again, is it a certain stage of the approach?"

Without too much technicality:

A missed approach is an instrument approach procedure covering the track/altitude the aircraft flies after the go around and is initiated at the missed approach point if visual reference is not obtained.
E.g. Track 160 climb to 4000 or as directed bt ATC.

The aircraft then goes around following the both aircraft's (power, climb, flaps, undercarriage) requirements and the instrument chart/ATC instructions. On large aircraft the go around is initiated by the TOGA (take off/go around) button on the throttle lever.

Go around is also the phrase used by ATC to instruct an aircraft to discontinue the approach and may be used at any time until wheels are on the deck. A go around can be given very late by ATC and could be for numerous reasons: Preceding aircraft slow to roll or vacate, rejected takeoff, FOD, animals, runway incursion.

ATC should give the instruction before the landing crosses the threshold.

[HEATHROW DIRECTOR]

<<ATC should give the instruction before the landing crosses the threshold.>>

I presume that a new instruction as I never heard it before. Is there dispensation for a displaced threshold?

[fujii]

I presume that a new instruction as I never heard it before. Is there dispensation for a displaced threshold?

This side of the equator it's a runway separation standard. This is the Spectator's Balcony and I did point out that I wasn't being too technical.

The preceding aircraft must have vacated the runway and be taxiing away or, airborne and have passed the point at which the landing would be expected to vacate the runway, before the landing crosses the threshold. (Different for light aircraft.)

So if the landing is in the flare and crossed the threshold when the go around is given, chances are that the separation standard has already been broken.

A displaced threshold is just that, a displaced threshold. Mind you it gets a bit more complicated if it is dislaced for landing but not for takeoff.

[reportyourlevel]

<<ATC should give the instruction before the landing crosses the threshold.>>

I presume that a new instruction as I never heard it before. Is there dispensation for a displaced threshold?

Definitely not new, and it is a daily concern for those of us not fortunate enough to have parallel strips of tarmac in segregated mode. The MATS Pt 1 take on it is that "a landing aircraft shall not be permitted to cross the beginning of the runway on its final approach until a preceding aircraft, departing from the same runway, is airborne".