NW1 - a little confused?

DH (for ILS) or runway threshold (VFR/Visuallly) is the latest point in an approach at which you go-around for safety - e.g. you don't have required visual reference or a you don't have a landing clearance therefore it is considered not safe to continue to land.

The 400 feet thing is different;

Basically the 'not below 400 feet above threshold elevation' rule and phase is used by ATC for aircraft who intend to make a go-around regardless of whether it's VFR in the circuit or IFR doing instrument training.

It's commonly used to allow another aircraft or vehicle to occupy the runway. An example would be a light aircraft in the circuit would be cleared to 'go around not below 400 feet above threshold elevation' to allow a B737 to backtrack and line up ready for departure and give the best runway utilisation.

At all other times the usual rules apply as you state.
1)You're doing an ILS approach and haven't received landing clearance by DH, then go-around
2)If you're flying visually and haven't received a landing clearance by the Threshold then go-around.
3)If ATC state 'go-around', do it immediately

Hope it clears it up. Don't know whether it's a UK thing or common elsewhere.

Spudmonkey
 

Not confused - but interested that there is a possible source of misunderstanding here, and keen to clear it up.

Firstly , you need to be aware that neither the DH nor the threshold are the "latest point at which you go-around for safety". It is true that at or below DH without visual reference you should go-around, but you may safely execute a go-around from any point up until the reversers are engaged. Without landing clearance, the only thing you may not do is land: you may go-around safely even from the flare as long as you do not land.

I was interested in the "400' rule" only because it does not exist on this side of the flight deck door (it may be in MATS, but that is for ATC guidance) and we need to understand each other in this job(!): by which I mean if told explicitly to approach and go-around "not below 400' " then that is one thing, but it is not a standing rule if not so stated in the clearance. I have flown to well below 400' with traffic occupying the runway before subsequent clearance many times. I landed at LHR today having had landing clearance decidedly later than 400' - the fact that the runway had vehicular traffic and my jet was lower than 400' did not matter, we got clearance eventually and we landed. Happens all the time.

Regarding your points:

"1)You're doing an ILS approach and haven't received landing clearance by DH, then go-around"

No: If you haven't received landing clearance then you go-around before landing. There is no rule which prevents you continuing beyond DH without landing clearance, its up to you as PIC - you may judge how far to continue depending on why clearance to land is being delayed (this judgement is often used at my home base in the UK!!)

"2)If you're flying visually and haven't received a landing clearance by the Threshold then go-around."
Again, no. There is no rule requring landing clearance before crossing the threshold. All that lack of landing clearance prevents you from doing is landing - i.e. wheels on the runway.

"3)If ATC state 'go-around', do it immediately". Agreed, unless you, as the commander, judge that you must land to secure the safety of your passengers, crew and aircraft. In which case it is your call - that is why you're the Captain.

nw1, ref your 3)

I really can't think of a situation where it would be safer for an aircraft not to go around when instructed.

goddammit
 

Well, the nature of emergency situations is usually unpredictable (hence your comment).

Just by way of example, though; the statistics regarding a fire within the cabin or flightdeck are that if it is not extinguished within 2 minutes then it will never be; and you then have a further 12 minutes until total loss of the aircraft (i.e. you choose between a controlled arrival with the ground/water or an uncontrolled loss). That might be one situation from which you might decide not to go around under any circumstances. Failures leading to lack of aircraft control might be another.

Slightly less dramatic might be a critically low fuel situation - if a go-around would definately result in a loss of all engines then I wouldn't do it. But, obviously, if you (atc) and I (pic) have done our jobs properly then we would understand the situation well enough for these eventualities not to arise. It would obviously take a massive "force majeur" to elect to ignore a go-around instruction - but there might be (very rare) circumstances which would require that decision.

Good fuel for discussion, though. Pardon the pun.