Chowonwoo

Question about bank angle.

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Hi all.

I wondered about bank angle.

My question is pretty simple.

When we doing approach and if we disengage autopilot, and LOC is estabilished, we will do turn for landing at centerline at Runway, right?

When we do turn for the landing at centerline, we turn with standard turn bank angle?? (TAS/10+5)

Thank you and please give me answer fast as possible!!

 

 

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If you turn final from the base leg to fully intercept the localizer it's just a normal/"standard" turn with bank angle = TAS/10+5, like you said.

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Your question doesn't make sense. If the localiser is established, you don't need to do a turn for the runway centreline. You're already on that extended centreline by definition if you are established, that's what 'established on the localiser' means, i.e. you are not more than half a scale deflection off it with your heading/track is aligned with the runway.

But with regard to turns, either manual or automatic, any autopilot will use the parameters you have it set on (not all of them have the ability to change the bank angle limit), but if you can and you do decide change the bank angle limit on the MCP of an airliner and are using it to capture the localiser, it can turn using that limit if it needs to (it probably won't if you have things set up early enough, since autopilots make predictive calculations for a turn, although this is not always well simulated in FS add-on aeroplanes), so it could, theoretically at least, also depend on the angle you were intercepting the localiser at. If you're only 30 degrees off the extended centreline when you pick up the localiser signal, there will be no need for either you, or the autopilot to rack the thing round in a steep turn, so generally speaking it will be done with a standard turn rate, not least for reasons of passenger comfort.

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1 hour ago, Chowonwoo said:

When we do turn for the landing at centerline, we turn with standard turn bank angle?? (TAS/10+5)

Maybe.  When turning to join the LOC I use what ever bank angle I need to roll out smoothly on the LOC, never to exceed 30 degrees.  I've been doing this a while so it tends to be instinctive.  It's a feel thingy. :smile:

blaustern

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I usually snap hard into 90 degree banks and back to level to correct for deviations off the localizer while on final approach?

Seriously showing, on final, just use whatever is required to stay on the localizer. It should be rather small unless you wait too long to correct. A few degrees here and there and level off.and monitor for drift.

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2 hours ago, Chowonwoo said:

I want to say about final approah and AP disengage.

When you disengage autopilot on final approach after using the localiser, you should already be on the centreline (providing your LOC / ILS approach was stable). Under these circumstances the need to make any turns should be minimal in calm conditions. However with a crosswind component you may find yourself been blown off the centreline. Knowing the wind speed and direction, you should anticipate this and be ready to apply some rudder as soon as you disengage the AP. The resultant yaw into the direction of the crosswind should be enough to keep you on the centreline and avoid the need for a banking turn at low level just using the ailerons to keep the wings level. This is the technique which I think is generally used in larger aircraft and airliners. Does this answer your question?

Bill

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2 hours ago, scianoir said:

Knowing the wind speed and direction, you should anticipate this and be ready to apply some rudder as soon as you disengage the AP. 

We have to use rudder to landing at centerline?

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Hi Folks,

Since most airliners "crab" (aileron) instead of "slip" (aileron and rudder) while on final I'm assuming the initial post was in regards to eliminating the crab and lining the plane up for touchdown ? If so - it's far more rudder and less aileron (bank angle)... Typically - you're in the flare or very close to it - as when you straighten out to line up with the runway in heavy winds - you're going to start drifting immediately... Some airliners pivot their landing gear so you can actually touch down in a crab...

Obviously everything is exaggerated in the video below due to the extreme crosswinds...

A picture is worth a thousand words:

 

Regards,
Scott

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44 minutes ago, scottb613 said:

Since most airliners "crab" (aileron) instead of "slip" (aileron and rudder)

I shutter to think about a slip in an airliner, at least any I've flown. :smile:

What most folks don't realize is that most airliners will take a lot of side load on the gear when landing.  I only know about Boeing and Douglas, but would think that Airbus would be the same.

blaustern

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1 hour ago, Chowonwoo said:

We have to use rudder to landing at centerline?

If you are flying the ILS on autopilot, it is usual to disengage the AP about 500ft above the runway (unless you are flying an airliner with full autoland capability). If your approach is stable, the AP should have your aircraft positioned on the centreline and on the glidepath well before the 500ft disengage point, but if you are not on the centreline and glidepath then your approach is considered unstable and, in the real world, if you were flying an airliner you would have to initiate a go-around.

Once the AP is disengaged after a stable approach you should only need to make small directional corrections and in airliners these directional corrections are generally made using more rudder movement than aileron, with the aileron primarily being used to keep the wings level. The amount of rudder movement, albeit in extreme conditions, is well demonstrated in the video posted by Scott above but note that the pilots are not banking but are most likely applying aileron as necessary just to keep the wings level. Obviously if you allow the aircraft to drift too far off the centreline then you may need an actual balanced turn (using rudder and ailerons) to bring it back on but, as I said above, in an airliner that would almost certainly be a reason for a go around.

Bill

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Hi Folks,

All good info...

For those who just can't get enough of this stuff - me... I've watched these countless times...

Here's one from 5 years ago - and most pilots in this video seemed to try harder to reduce side loads than the ones in the first video I posted:

Regards,
Scott

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1 hour ago, scottb613 said:

For those who just can't get enough of this stuff - me... I've watched these countless times...

I'm someone else who can't get enough of those videos! If I remember correctly there were also some good videos of crosswind landings taken during a bad storm at Amsterdam earlier this year and there are also some impressive ones from Madeira.

Some of those landings really are a testament to the structure of modern airliners - not just the amazing strength of the undercarriage to cope with such hard landings in a crabbed position but of the aircraft as a whole looking at the amount of wing flex and also the considerable 'shaking' of the tailplanes in some of the aircraft after landing. I have no doubt that airliners of an earlier era such as Connies and DC-6/7s (and perhaps even 707s and DC-8s) would have been straight into the maintenance hangar after some of those landings! But I guess the inability of piston airliners to cope with such extreme crosswinds was the reason that airports of their era had so many runways aligned in different directions.

Bill

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4 hours ago, scianoir said:

it is usual to disengage the AP about 500ft above the runway

Some airlines have a policy of making this decision at 1,000.  At that point it's an autoland or all automation (A/P and A/T) off. :smile:

blaustern

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I think you guys said

Use rudder for small correction for the maintain centerline

Use bank for the maintain wing level.

No winds, Just pitch control

right?

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