What is the best way to align with centerline on final, rudder or slip?

Question

Like many student pilots, I consistently find myself slightly left of centerline in the last few seconds before touchdown (e.g. between crossing the threshold, through roundout and flare), despite flying a stabilized, on-course approach on Final, with no crosswind component.

My question is how to realign with centerline in those last few seconds? I've been suggested two techniques (see below), but I'm not at ease with them.

I did see the "Crosswind, crab or slip?" question, but I believe mine is different. I am wondering what is the correct technique without crosswind. Even if they have the same answer, it's not necessarily the same question, as the technique one uses MAY be different w/crosswind (or not! I don't know).

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1. My CFI suggested imagining the centerline extending vertically into the air, and using rudder pedals to align with it as if I was 'taxiing' on that centerline. So if the plane is to the left of this imaginary centerline, apply right pedal to yaw the aircraft to the right, and vice-versa. In either case, the longitudinal axis of the aircraft is intersecting the vertical centerline at some point down the runway.

Problem is, when I do this, it doesn't feel like the plane moves towards centerline at an appreciable rate. It just feels yawed, but without any "movement" towards the side that I'm pointing to.

2. Alternatively, I've seen in some videos online to use the rudder pedals to align the longitudinal axis of the aircraft PARALLEL to the vertical centerline, and instead use ailerons to slip back to centerline. So if the plane is to the left of center, point the nose of the aircraft parallel to centerline, but roll aircraft to the right.

Both unnerve me a bit, but for different reasons. For the former, I'm not used to the 'crabbed' orientation so close to the ground. For the latter, I'd prefer the wings to be level so close to the ground.

Which technique is preferable?

Answer 1

Your method #2 is consistent with current FAA doctrine, and when practiced yields acceptable results.

Rudder for longitudinal axis alignment (parallel) with the centerline.

Aileron for drift.

Have a stable approach, and maintain vigilance of both inputs when on low final. If you practice the technique for your entire final approach, you get extra practice time, and may master the technique faster.

FAA has a publication, On Landings I (and also a II and III publication) which are all great at describing the technique. Every student should have a copy for review. FAA-8740-48 a copy is here: https://www.flyingd.net/documents/on-landings-part-i.pdf

To answer a comment...if you are left of the centerline, and there is no wind, and your approach is stable, then you need some right aileron to get your longitudinal axis over the centerline, and you will have to adjust your rudder while maneuvering, to keep the longitudinal axis aligned and at least parallel to the centerline.

Drift with aileron, alignment with rudder. Constantly modifying input to get the desired drift and alignment.

Aileron for drift.

Rudder for alignment.

Pitch for airspeed.

Power for altitude.

Answer 2

The techniques you mention only work if you are already on the centerline. If you come off the centerline you will have to correct with bank. Rudder may stop the drift away from the centerline but it alone can't really get you realigned. If you are close to the threshold and not aligned, you should not be afraid to go-around.

So why are you off centerline if you've been flying a nice stabilised approach in benign conditions? You shouldn't need to make significant last minute adjustments, you should be able to plant it on the line.

I am guessing that you're doing what I and many other student pilots have done. You start realising that the ground is getting awfully close and you're going to have to do something about it. Because you're now preparing for the flare, you don't have the 'mental capacity' to remain so focused on the lateral path, so you unconsciously let the aircraft drift. It's very subtle, so you probably haven't noticed your inattention.

A student pilot on their first flight is using perhaps 90% of their mental capacity on just controlling the thing. Adding something like radio calls will push them over 100%. But as they get used to it, that percentage required for control lowers, and they can introduce radio calls, and eventually things like navigation and instrument flying.

With practice you will eventually be able to land nice and softly and on the centerline with your eyes closed (ok maybe not literally, but...). To speed that process up you just need to be disciplined - make sure your bum is on the imaginary centerline from a long way out and keep it there, no excuses. Keep your landing point on the one place in the windscreen, and be vigilant with your speed control. Most importantly, fly the aircraft all the way to the ground. The more you practice whilst focusing on those things, the sooner you will nail your landings.

Answer 3

Probably the best solution is to visualize the runway centerline extending out from the departure end out to infinity and focusing on flying parallel to this. If there is a crosswind component, it can sometimes be helpful to establish the airplane in a cross controlled slip per typical crosswind landing techniques long before touchdown, using rudder input to keep the nose parallel to this imagined infinite runway centerline and aileron inputs to hold the aircraft's flight path on the centerline. Alternatively you can fly a crabbed final approach, if you have a good intuition about the airplane's true flightpath and that it is aligned with the centerline, then cross control at flare so you upwind main landing gear makes contact with the runway first. This style of crosswind landing requires a little more precision on your part as you have to be master of where the aircraft will go when you establish the slip in the flare. Don't rush a precision landing; if you need a little more time to align the aircraft with centerline correctly, extend you downwind leg a little more.

If you are concerned about scraping a wingtip in the roundout slip, first choose your runways based on surface winds for the lowest crosswind component, and do NOT exceed the maximum demonstrated crosswind component listed in the Airplane Flight Manual. Second, take a moment to observe the airplane while it's sitting on the ramp and note the approximate roll angle the A/C would have to exceed to be in danger of wingtip rash; for most high wing trainers like C152s and C172s, this angle is pretty great, probably will over thirty degrees. Therefore don't attempt to land if it requires a roll correction greater than about 20 degrees. Remember, you have engine power, you have gas onboard, therefore you have time and you have options; YOU CAN ALWAYS GO AROUND.

Answer 4

If you are flying parallel to the runway centerline, (your ground track is parallel but offset from the centerline), but wish to move the aircraft laterally over to the centerline, you have to:
1. TURN the aircraft to change it's ground track to intercept the centerline, and then,
2. When the aircraft has moved laterally over to the centerline, ( or just prior to arriving at the centerline), you have to TURN the aircraft back the other way to change it's ground track to be again parallel with the centerline, so you won't overshoot the centerline and end up on the other side.

There are two ways you can turn the aircraft (change it's ground track). First, you can do it just like you would at altitude, establish a slight bank and hold it until the ground track has changed sufficiently to establish the desired lateral movement, and then roll wings level, or second, you can yaw the aircraft to create sufficient sideslip to establish the desired rate of turn. Bank angle will do the job faster and more efficiently. The wings generate much more aerodynamic force than the side of the fuselage. That's why it only takes a small opposite bank angle to counteract the turn rate established by almost full rudder when cross controlling in a slip.