What does 'laterally aligned' mean in this description?

Question

In the Airplane Flying Handbook there is a section on crosswind takeoffs that mostly makes sense. However, this paragraph confuses me.

Takeoff Roll

As the forward speed of the airplane increases, the pilot should only apply enough aileron pressure to keep the airplane laterally aligned with the runway centerline. The rudders keep the airplane pointed parallel with the runway centerline, while the ailerons keep the airplane laterally aligned with the centerline.

Laterally is an adverb meaning 'Relating to the direction to the side.'

Later on they use this image which shows the lateral axis.

When I take off in a crosswind in an airplane with nose-wheel steering the rudder pedals are used to keep the plane on the centerline. The ailerons are deflected into the wind to keep the windward wing from rising.

So what do they mean when they say that “the pilot should only apply enough aileron pressure to keep the airplane laterally aligned with the runway centerline”?

Edit: I don’t think they are referring to keeping the wings level as some commenters say. This image from the same section somewhat exaggerates the effect but ailerons are used to keep the upwind wing down.

Answer 1

The only meaning that I can conceive of is that "laterally aligned with the centerline" is a fancy way of saying "on the centerline"—or, at least, keeping the distance from the centerline under control, so that you don't drift off of the runway.

The paragraph seems to be describing the following technique for lateral control during a crosswind takeoff:

• Use the rudder to keep the heading (the direction the nose is pointing) parallel to the runway centerline.
• Use the ailerons to control the bank angle so that the airplane stays approximately over the runway centerline.

The reason the Airplane Flying Handbook uses the word "laterally" here is that the ailerons are being used to control the airplane's lateral (left-to-right) motion.

Some comments speculate that the paragraph is really saying that the ailerons should be used to keep the wings level. That doesn't make sense to me; in a crosswind, if you're using rudder to keep the nose parallel to the centerline, and you're keeping the wings level, then you'll drift downwind off the runway.

Answer 2

The lateral axis is the left/right axis. “Laterally aligned with the runway centerline” means: on top of the centerline. Not a very clear way of phrasing, I agree.

Answer 3

This thing is horribly written. I think Tanner is correct, in that the writer is referring to using ailerons to establish a bank angle to prevent lateral drift. But while rolling, the bank angle you can create is limited to the compliance of the landing gear. On an airplane with wide oleo gear, this is effectively zero. So it's really about using rudder to keep alignment and using aileron to hold the wing down.

As you lift off, the into wind aileron will cause the downwind wing to liftoff slightly ahead of the other, putting you into a very brief cross-controlled wing down condition where you will be side slipping briefly; then for a brief moment, you are using aileron to maintain lateral position.

Which you immediately remove as you center the rudder and adjust the heading into wind as required, then level the wings to climb out (except on an IFR departure where you just maintain the runway heading).

Surprising to see something this poorly worded in an official FAA publication.

Answer 4

Can't always believe you read. Notice the rudder deflection is also incorrect in the third picture. This is why finding a good instructor is so important.

A cross wind take-off is in many ways a mirror image of a cross wind landing: aileron into the wind, rudder away. Yes, the downwind wing may rise first, and the plane is up on one wheel before lifting off, just as you would do in a cross wind landing. No big deal. Be on that rudder.

Some may choose to delay rotation a few knots, and then bring plane off the ground a bit more briskly, then transition into a crab. Some may hold the side slip a little longer. But airspeed is most important here. Watch it and keep climbing safely.

Cross controlled slow flight practice should give you confidence in these situations. Remember to stay at a safe margin above stall.

Best interpretation of "laterally aligned" would probably be the same as in the air: roll into the wind to keep from being pushed sideways. So if your leeward wing comes up too much before rotation, simply ease off on the ailerons some.