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 wanted to talk about Final approach... not turning for capture the LOC...

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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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First up, to answer the original question:

It is conventional in instrument flight to fly all turns at Rate 1, or 25 degrees AOB, whichever requires less bank. In an Instrument Rating test in a light aircraft this is what you would be expected to do.

Obviously for smaller heading changes (such as corrections when established on the localiser) you are not going to crank on 25 AOB and a good rule of thumb is to use only as much bank as degrees you are turning (i.e. 5 degree heading change = 5 degrees of bank).

However, I am assuming that the OP is referring to airliners in which case nobody is going to be measuring your rate of turn even if you have a turn indicator installed, so as Wilhelm says in practice if you are being vectored around/flying the full ILS procedure etc you are just going to use whatever bank angle you require to maintain the required ground track up to 25 AOB, with due regard for passenger comfort.

On 06/12/2017 at 4:24 PM, scianoir said:

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

I must say that I have never encountered anyone advocating steering a swept-wing transport-category jet down an ILS with one's feet (and the light aircraft IRIs I have come across wouldn't recommend it either).

Passengers don't like yaw much, and when you're flying something the length of a football pitch it can be particularly uncomfortable for those down the back when you start booting your size 10s around!

In a large jet, generally speaking rudder pedals = footrests, used in anger only during engine failure, crosswind take-offs or the late stages of a crosswind landing. Most modern jets are equipped with yaw dampers which will mostly take care of turn coordination for small turns and thus there is no need to be dancing on the pedals; just small, coordinated turns (and in an airliner on final approach I would suggest in most cases if you are using more than 5 degrees bank angle that is likely a clue your approach is becoming unstable) to re-establish on the correct heading are all that is required.

Of course, in the very final stages of the approach it will be necessary/desirable to squeeze off the drift and align the aircraft's longitudinal axis with the runway centreline. This obviously is accomplished by applying rudder to straighten up and aileron in to wind to maintain wings level or a slight lowering of the upwind wing -- the main concern with airliners fitted with underslung engines is pod and wingtip clearance and this is why they are not landed in a full sideslip like a high-wing C172 or similar. As such the amount of drift that can be removed is limited by the bank angle available, which in a B744 is virtually zero but in something like a CRJ with tail-mounted engines may be slightly more.

The other important thing is to keep flying the aeroplane after touchdown, with in-to-wind aileron as necessary to prevent the upwind wing from rising.

On 06/12/2017 at 5:58 PM, scianoir said:

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.

The issue is not one of powerplant but undercarriage. Taildraggers have a nasty habit of ground looping if you land them with any drift on and thus must be landed in a full sideslip with all the drift removed. As mentioned above, the amount of drift you can remove through a sideslip is dependent upon rudder authority and the amount of bank angle you can achieve, so for an aircraft with engines mounted on the wings you will be limited by the amount of propeller tip clearance available in the landing attitude.

This overall makes crosswinds very limiting for taildraggers in particular and this is why early airfields had either many runways or, indeed, were simply a broadly circular field such that takeoff and landing could always be accomplished in to the wind.

Tricycle landing gear is obviously inherently much more stable and hence allows for much greater crosswind limits because you can land on it with drift on.

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Well, to answer the original question abour intercepting the localiser, consider this. A guy I was flying with described to me how they would intercept the loc in his previous aircraft. They would approach the loc at a ninety degree angle, and just as the needle started to move off the edge of the hsi, they would roll into a ninety degree bank and pull back on the stick as hard as they can, loading up to maybe 5-6 g’s. With power idle, speedbrakes out, they would decelerate from 350kts to final approach speed in the turn and roll out of the turn gear down, configured, on speed on the ils. He said it works every time. Not sure what kind of aircraft the op was asking about, but this was for the F-16.

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23 hours ago, skelsey said:

I must say that I have never encountered anyone advocating steering a swept-wing transport-category jet down an ILS with one's feet (and the light aircraft IRIs I have come across wouldn't recommend it either).

I was making the point that if you have flown a stable ILS approach on the autopilot then, by definition, you should be on the centreline when you disengage the autopilot before touchdown and the corrections you need should be minimal. If there is a crosswind component then drift should be anticipated and you should be ready to apply an appropriate amount of rudder to stay on the centreline after AP disengagement. On the subject of flying the ILS "with one's feet", does the autopilot, once it captures the localiser in a crosswind scenario, then not maintain the centreline primarily using rudder to yaw into the wind? Although I was a PPL with a couple of thousand hours, I have never flown anything larger than an Aztec, so I am open to correction by any real world heavy metal flyers out there if my assumptions on flying technique for airliners on the ILS are incorrect!

Bill

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