FSX-MS Crosswind Crab Airbus

[jonfo 4]

Evening 

I have been trying to perfect my crosswind landings to absolutely no avail. I'm flying the Aerosoft A321/A320. 
Could somebody give me some advice on the crab maneuver please. When there is a crosswind, I am attempting to point the noise into the direction of the wind in an effort to get that angle where the aircraft will fly straight.
However, when I do this, the aircraft will never fly in the crab position. It drifts to the side I am pointing it into, thus, into the wind. Then, when I try to correct by turning into the opposite direction the wind together with my aileron cause me to drift to the opposite side. 

Does a 'crab' mean to dip the wings into the wind and then straighten them or turn and leave the turn? 

Then, because I am concentrating so much on the attempt at a crab I then end up ballooning the aircraft at the end and landing way left or right of the centre line. I know that rudder is required just beforetouchdown to straighten the nose up on landing but my crab position is way off before I even get to the runway. When I have played back the landing you can see the aircraft dipping from left to right far too much than you would see in a RW crosswind landing. 

Any advice here would be appreciated. 

[mikealpha 266]

There's a nice video showing the crosswind technique in the A320 at Youtube. Recorded by a former A320 pilot and demonstrated with FSLabs A320. Not sure if also applicable to the Aerosoft Airbus.

https://www.youtube.com/watch?v=93iqTd3IHmA

 

Edited August 19, 2018 by mikealpha

[skelsey 765]

Hello,

53 minutes ago, jonfo said:

Does a 'crab' mean to dip the wings into the wind and then straighten them or turn and leave the turn? 

The first; all you are doing is adjusting the aeroplane's heading to allow for the drift effect of the wind (i.e., the nose of the aeroplane will need to be pointed somewhat in to the wind). Thus, the aeroplane will be flying somewhat "sideways" over the ground -- rather like a crab walks :).

The way to think about it is - if we start off, say 10NM from the runway, exactly on the extended centreline with the nose of the aeroplane aligned exactly with the runway heading, if there is no wind the aeroplane will track wherever the nose is pointing -- in this case, down the extended centreline to the runway.

If the air in which we are flying, however, is moving from left to right, the aeroplane in addition to its forward progress will be 'carried along' with the air downwind (imagine a fast-flowing river, and a boat trying to get from a jetty on one bank to another jetty exactly opposite: if the helmsman points the bow of the boat at 90 degrees to the bank (i.e. directly at the jetty on the other side), when he casts off the boat will, naturally, be carried downstream as viewed by an observer at the intended destination).

This is obviously undesirable as we will end some some distance downwind from where we want to touch down!

How, then, can we make sure that we arrive at our intended spot?

There are a couple of options. If we consider the boat analogy, the helmsman could simply, as soon as he sees the drift downstream, steer a little bit so that the bow is pointing again at the jetty. The current will carry him a little further downstream, necessitating a further correction, and so on - what he will actually end up doing, if we were to look down from above, is transcribing an arc across the river, ending up at the other jetty with the bow of the boat pointing almost directly in to the current. This works, but is a bit untidy and not very efficient, as obviously an arc is a greater distance to travel than a straight line between the two points.

The same technique would work in the aeroplane as well, but is undesirable for the same reasons -- and in the case of landing, we could end up at a very odd angle!

The second technique would be to pick a heading which causes the boat to be moving upstream at exactly the same rate as the current is travelling downstream - thus cancelling out the drift and enabling the boat to travel in a straight line, directly between the two jetties. This is the most efficient way, because it results in a shorter ground track. However, the bow of the boat will be pointing somewhat upstream of the jetty - in other words, relative to the ground (the river bed, if you like) the bow of the boat will be pointing in a slightly different direction to that in which the boat itself is travelling.

This is exactly what we are trying to achieve in the aeroplane: to select a heading which exactly cancels out the drift effect of the wind, thus enabling us to fly a straight line (along the extended centreline) to the runway.

In the aeroplane we also have a third option, not available to the boat helmsman: we could use the ailerons to roll the aeroplane in to the wind. This will produce a force accelerating the aeroplane upwind, and by using the rudder in the opposite direction we can keep the nose aligned with the runway heading. Thus, the aeroplane will be tracking straight along the ground with the nose pointed directly toward the runway, but the wings will be banked in to the wind and the slip ball will be displaced toward the lower wing. This works, and is used often by pilots of light aircraft with high wings, but it is not the preferred technique in a large jet for a number of reasons -- firstly, it's quite awkward to fly, requiring sustained rudder and aileron pressure, and it is especially awkward when it comes to flying solely on instruments. It's inefficient, because we're actually flying the aeroplane 'upwind' -- the wind will in effect be striking the whole of the 'exposed' side area of the fuselage, creating lots of drag, and we don't want to be touching down with lots of bank on if we have jet engines slung low to the ground underneath the wings.

The best option, therefore, is the second -- to select a heading, with wings level and the aircraft in balance (slip ball in the middle), that allows us to offset the drift and track straight along the extended centreline.

My first piece of advice is to not over-think it. The video linked above gives you a sense of what you are looking at (in a very strong crosswind) - obviously in most cases the crosswind component will be somewhat less extreme and therefore the drift angle required lesser - even quite subtle. In the absence of having an instructor alongside you to demonstrate the correct technique, the first thing I would suggest is to fly the initial approach with the autopilot engaged and observe the divergence between the aircraft's heading and its ground track when established on the localiser -- one tip is to select the lowest possible range on the ND so that you can actually see the runway displayed -- if you are tracking the localiser then the green track line will be running up the middle of the runway symbol on the ND. This will be somewhat offset from the aircraft's heading, displayed at the top of the ND.

When you disengage the autopilot, the first thing to do is to avoid making too many inputs -- after all, the aircraft was nicely stabilised on the right heading and at the right rate of descent when you took over, so why rush to change it? Of course, the wind is likely to change in speed and direction as you continue down the approach and so small corrections will be necessary, but again use all the tools -- the ILS pointers, the ND runway symbol/track line, and indeed your Mk 1 eyeball out the window, to keep the aircraft tracking down the extended centreline. You will need to offset the flight deck slightly upwind of the centreline, so this will cause the perspective to look slightly odd. Small, smooth corrections are the order of the day: it sounds to me as if you are overcontrolling a little. Make a small input, wait for the aircraft to respond, allow the heading to change, then roll the wings back level and reassess. As I say, the wind will change as you go down the approach so you will need to make small inputs to correct but relax; just maintain a loose grip on the stick and remember that less is often more.

Finally, as you get to the flare -- look toward the end of the runway and smoothly apply rudder to align the nose with the centreline. As you do so the FBW on the Airbus will attempt to maintain wings-level, so unlike a conventional aircraft you don't need a lot of stick in the opposite direction, but a small 'squirt' of sidestick in to the wind (i.e. in the opposite direction to the rudder) may be necessary to prevent the aircraft from drifting too far downwind or to prevent any roll developing as a result of your rudder input.

Hope that helps!

[jonfo 4]

1 hour ago, mikealpha said:

There's a nice video showing the crosswind technique in the A320 at Youtube. Recorded by a former A320 pilot and demonstrated with FSLabs A320. Not sure if also applicable to the Aerosoft Airbus.

https://www.youtube.com/watch?v=93iqTd3IHmA

 

Thanks, I will definitely take a look at this. 

[jonfo 4]

43 minutes ago, skelsey said:

Hello,

The first; all you are doing is adjusting the aeroplane's heading to allow for the drift effect of the wind (i.e., the nose of the aeroplane will need to be pointed somewhat in to the wind). Thus, the aeroplane will be flying somewhat "sideways" over the ground -- rather like a crab walks :).

The way to think about it is - if we start off, say 10NM from the runway, exactly on the extended centreline with the nose of the aeroplane aligned exactly with the runway heading, if there is no wind the aeroplane will track wherever the nose is pointing -- in this case, down the extended centreline to the runway.

If the air in which we are flying, however, is moving from left to right, the aeroplane in addition to its forward progress will be 'carried along' with the air downwind (imagine a fast-flowing river, and a boat trying to get from a jetty on one bank to another jetty exactly opposite: if the helmsman points the bow of the boat at 90 degrees to the bank (i.e. directly at the jetty on the other side), when he casts off the boat will, naturally, be carried downstream as viewed by an observer at the intended destination).

This is obviously undesirable as we will end some some distance downwind from where we want to touch down!

How, then, can we make sure that we arrive at our intended spot?

There are a couple of options. If we consider the boat analogy, the helmsman could simply, as soon as he sees the drift downstream, steer a little bit so that the bow is pointing again at the jetty. The current will carry him a little further downstream, necessitating a further correction, and so on - what he will actually end up doing, if we were to look down from above, is transcribing an arc across the river, ending up at the other jetty with the bow of the boat pointing almost directly in to the current. This works, but is a bit untidy and not very efficient, as obviously an arc is a greater distance to travel than a straight line between the two points.

The same technique would work in the aeroplane as well, but is undesirable for the same reasons -- and in the case of landing, we could end up at a very odd angle!

The second technique would be to pick a heading which causes the boat to be moving upstream at exactly the same rate as the current is travelling downstream - thus cancelling out the drift and enabling the boat to travel in a straight line, directly between the two jetties. This is the most efficient way, because it results in a shorter ground track. However, the bow of the boat will be pointing somewhat upstream of the jetty - in other words, relative to the ground (the river bed, if you like) the bow of the boat will be pointing in a slightly different direction to that in which the boat itself is travelling.

This is exactly what we are trying to achieve in the aeroplane: to select a heading which exactly cancels out the drift effect of the wind, thus enabling us to fly a straight line (along the extended centreline) to the runway.

In the aeroplane we also have a third option, not available to the boat helmsman: we could use the ailerons to roll the aeroplane in to the wind. This will produce a force accelerating the aeroplane upwind, and by using the rudder in the opposite direction we can keep the nose aligned with the runway heading. Thus, the aeroplane will be tracking straight along the ground with the nose pointed directly toward the runway, but the wings will be banked in to the wind and the slip ball will be displaced toward the lower wing. This works, and is used often by pilots of light aircraft with high wings, but it is not the preferred technique in a large jet for a number of reasons -- firstly, it's quite awkward to fly, requiring sustained rudder and aileron pressure, and it is especially awkward when it comes to flying solely on instruments. It's inefficient, because we're actually flying the aeroplane 'upwind' -- the wind will in effect be striking the whole of the 'exposed' side area of the fuselage, creating lots of drag, and we don't want to be touching down with lots of bank on if we have jet engines slung low to the ground underneath the wings.

The best option, therefore, is the second -- to select a heading, with wings level and the aircraft in balance (slip ball in the middle), that allows us to offset the drift and track straight along the extended centreline.

My first piece of advice is to not over-think it. The video linked above gives you a sense of what you are looking at (in a very strong crosswind) - obviously in most cases the crosswind component will be somewhat less extreme and therefore the drift angle required lesser - even quite subtle. In the absence of having an instructor alongside you to demonstrate the correct technique, the first thing I would suggest is to fly the initial approach with the autopilot engaged and observe the divergence between the aircraft's heading and its ground track when established on the localiser -- one tip is to select the lowest possible range on the ND so that you can actually see the runway displayed -- if you are tracking the localiser then the green track line will be running up the middle of the runway symbol on the ND. This will be somewhat offset from the aircraft's heading, displayed at the top of the ND.

When you disengage the autopilot, the first thing to do is to avoid making too many inputs -- after all, the aircraft was nicely stabilised on the right heading and at the right rate of descent when you took over, so why rush to change it? Of course, the wind is likely to change in speed and direction as you continue down the approach and so small corrections will be necessary, but again use all the tools -- the ILS pointers, the ND runway symbol/track line, and indeed your Mk 1 eyeball out the window, to keep the aircraft tracking down the extended centreline. You will need to offset the flight deck slightly upwind of the centreline, so this will cause the perspective to look slightly odd. Small, smooth corrections are the order of the day: it sounds to me as if you are overcontrolling a little. Make a small input, wait for the aircraft to respond, allow the heading to change, then roll the wings back level and reassess. As I say, the wind will change as you go down the approach so you will need to make small inputs to correct but relax; just maintain a loose grip on the stick and remember that less is often more.

Finally, as you get to the flare -- look toward the end of the runway and smoothly apply rudder to align the nose with the centreline. As you do so the FBW on the Airbus will attempt to maintain wings-level, so unlike a conventional aircraft you don't need a lot of stick in the opposite direction, but a small 'squirt' of sidestick in to the wind (i.e. in the opposite direction to the rudder) may be necessary to prevent the aircraft from drifting too far downwind or to prevent any roll developing as a result of your rudder input.

Hope that helps!

Can't thank you enough for an extremely detailed and descriptive response. 

The comments you have stated make absolute sense and I will be sure to watch the video and also make the corrections you have suggested. I think, as you say, I am over doing some of the inputs into the controls and massively overthinking the entire approach. 

I will give it a go and try to include as much as what you have said as possible. 
Thank you once again!!

[jonfo 4]

While on the topic of landings, when people say "in the flare, look to the end of the runway" what does that actually mean? What is it that you are looking for at the end of the runway? 

I've never really understood that. 

[skelsey 765]

It's not so much that you're looking for something in particular, more a case of shifting your focal point. 

When you are coming down the approach, you will generally be looking at the touchdown point and ensuring that it remains static in the windscreen. 

However, if you are still looking at the touchdown point/very near to the nose of the aircraft in the flare, you will find it very difficult to accurately judge your rate of descent and the ground will appear to be rushing toward you, neither of which are particularly conducive to good landings.

So as you come through about 50ft you shift your focus to the far end of - or at least some distance along - the runway. This will enable you to better judge the change in pitch attitude and sink rate during the flare, as well as giving you a better sense of the aeroplane's lateral drift and heading relative to the centerline (enabling you to use the rudder to accurately line the aeroplane up with the runway axis as discussed earlier).

[jonfo 4]

Ah, I see. I think a lot of what you describe is where I have been going wrong, which basically boils down to lack of expertise and knoedge around landings. 

You have definitely put things into context for me and I really appreciate it! Thanks again for the detailed advice and tuition.