Question re. decision height/go-arounds

[Nicholas49]

Hello

In this video (and wow, how fantastic to see a cross-wind landing pulled off so expertly/made to look so easy!), you hear one of the pilots call 'Landing' on reaching the minimums on approach.

My question is: what is the significance of this call, given that it would be possible to decide to go-around at a later stage of the approach? (In other words, the call cannot mean that the pilot flying has definitely decided to land). Does it have to do with having visual contact with the runway (i.e. is visibility-related)?

[99jolegg]

That call purely relates to attaining the required runway visual reference, and in conditions of low cloud or poor visibility it lets the pilot not flying know that you have that visual reference and are continuing to land.

If you then go around later for whatever reason then so be it.

I think its history might lie from the time before auto land and primitive low vis ops procedures where the monitored approach to minimums was flown by one pilot with control given to the other pilot (solely looking outside) on sight of the necessary visual cues.

BA still use this monitored approach procedure, I believe, but the "100 above...checked" and "minimums...continue or land" still exists in airlines without the monitored approach.

[Bealzebub]

the call cannot mean that the pilot flying has definitely decided to land

Yes, that is exactly what it means. At the decision altitude, the "pilot flying" is confirming his decision, and that decision is to land.

Nothing precludes the pilot from going around subsequently if that course of action becomes warranted, but at the "decision point" the handling pilot is announcing to the non-handling pilot what his decision is.

[mustafagander]

Exactly as Bealzebub says, there is no absolute commitment to land until we are in reverse slowing down under brakes. It is a statement of INTENT for this moment.

It is extremely important to always be prepared and ready to abandon any and all approaches until reverse thrust is selected. It is a mind-set thing, never be mentally locked in to landing until you have landed.

[Nicholas49]

OK-thanks-I see your point.

I suppose it is important to separate the 'decision to land' made at minima from any subsequent decision to go-around.

[Nicholas49]

Hello

May I ask one more follow-up question on this thread?

I was wondering how you measure when the tolerances (either of the aircraft or the company SOPs) on cross-wind landing limits have been exceeded? Is there a particular instrument on the flight deck that gives you a reading of the cross-wind you're flying in? In the clip, you hear ATC giving aircraft wind readings - is this information used too? I ask because I know that most modern airliners have a 'wind-shear' aural warning for the pilots, so I imagine that's a different kettle of fish?

[Denti]

Indeed, windshear is a completely different thing.

Yes, on some airliners you can see the crosswind component displayed, however usually in some subpage of the FMC. The controlling wind is the tower given wind and we have to calculate the crosswind component on the go and check if it is within limits.

[Daysleeper]

Different airlines , different calls.

I prefer "visual" at minimums. Landing is just one of the options!

[Nicholas49]

we have to calculate the crosswind component on the go

But how? I imagine that final approach is no time to be looking at the FMC sub-pages! From where do you source the information you need to know whether the cross-wind exceeds limits during an approach?

[Armchairflyer]

There are quick and easy (and sufficiently accurate) approximations like the "clock-face": wind direction up to 15 degrees off runway heading: crosswind component is 1/4 of wind (15 minutes = 1/4 hour); for 20 degrees off it's 1/3, for 30 degrees off it's 1/2, for 45 degrees it's 3/4 and for 60 or more degrees one can calculate the full windspeed as crosswind. The pros might have even better approximations, so I don't think anyone has to look at an FMC for that ;).

[Bealzebub]

There is no crosswind limit for the approach, it is simply for the take off and landing.

It is very simple to have an FMC page up displaying the calculated crosswind, and therefore monitoring it is not a particular problem.

The reported wind by the tower is the relevant number.

Crosswinds are more often than not subject to gust variation, so that has to be taken into account on a common sense basis.

The crosswind limit is rarely limiting in the structural sense, rather it is a demonstrated safety limit set by the manufacturer.

There are often different limits set for Take off and landing, and those are further modified for dry, wet and slippery runway conditions.

[Nicholas49]

Bealzebub: this will sound like a basic question (and you'll tell it's a non-pilot speaking!), but... if there is no crosswind limit for the approach, how do you know that the crosswind isn't going to be sufficiently strong to mean that you can't align the aircraft with the runway on touch-down (that is a potential consequence of a strong cross-wind, isn't it)? When you see aircraft landing in a cross-wind, they're not aligned with the runway, but - as I understand it - the pilots/aircraft have factored in the drift so that they will be able to land on the threshold. If there's no limit, how do you know when too much is too much?

[Bealzebub]

The reported wind by the tower is the relevant number.
There will be a gradient in the wind speed (often steeper at night) as the height reduces. Rapid changes in this gradient are usually referred to as windsheer and may cause an approach to be discontinued if that approach becomes unstable as a result of those changes (or indeed anything else!)

If the reported wind at touchdown is within the limit for the particular aircraft and adjusted for the relevant runway conditions, then the wind on the approach is usually within the gradient profile to complete the approach and landing.

When it isn't you throw the approach away.