Alex,
What was the aeronautical training of the engineer you talked to? The plane does NOT move sideways and then weathervane into the wind and thus, turn. You started out with your first sentence correct, and then deviated off into left field. Stick with "No question that the horizontal component of lift is what starts moving the plane to the left (or right)." and just stop there. You just watched a video in which an airplane was banked left, and initially there was no turn, then the pilot started a turn to the right, and then the pilot did a turn to the left. All the while the AOB remained essentially unchanged. (Except for minor deviations by the pilot. haha) It becomes obvious from that that bank alone does not make an airplane turn.
I'm not sure what you mean when you say, "But if that (horizontal component of lift) were ALL that was going on when you bank left all that would happen would be the plane horizontally moving sideways to the left..." because that IS all that's going on. That's what a level left turn is, nothing more than a horizontal turn to the left.
Then you ask, "The remaining question is "What turns the _nose_ of the plane to the left and keeps it turning?" That's easy. The horizontal component of lift. There has to be a vertical component of lift to counteract gravity. If the lift is tipped off vertical by banking the airplane, then there is now a horizontal component as well. That component pulls the airplane in the direction of the component. If you increase lift by pulling the stick back, the nose begins to climb, right? This is how a loop is done. Pull back on the stick, and the nose starts up and the plane goes around in a vertical circle. If you roll into a 90 deg angle of bank and do the same thing, you can make a loop in the horizontal. Of course, gravity is in the equation so we must counter that in some way, and some lift must remain in the vertical from somewhere. In my video, that lift was being provided mostly by the fuselage.
So in your last sentence when you say "we all know you can turn an airplane by banking" then can you explain to me why it can happen that an airplane can be banked and a turn not occur? Or even be turned in the opposite direction from the bank? You just watched a video of an airplane doing exactly that. How do you explain it?
So, the classic answer we give on the FAA test and asked by CFIs is not only acceptable, but complete. If it is incomplete, it is because you don't understand it and your engineer friend most definitely does not understand it. I may redo the video because I wasn't pleased with the camera placement. I know the back of my head is quite attractive, but it wasn't supposed to be the main focus of the video. I may put the camera right on the glare shield and the view of the horizon might be better and help with understanding. A friend of mine said that a view of what I was doing with the flight controls might be helpful and help understanding as well. I'm not quite sure how to locate the camera to get the best view to explain what's going on, I just know looking at my head isn't it.
Jim
Sent: Thursday, October 04, 2012 11:44 AM
Subject: Light-Sport Aircraft Yahoo group Re: What makes an airplane turn?
No question that the horizontal component of lift when plane is banked left is what starts moving the plane to the left.
{And of course as we all know the plane WILL turn with no rudder applied (even if it's a lousy uncoordinated turn you CFI would frown on).}
But if that (horizontal component of lift) were ALL that was going on when you bank left all that would happen would be the plane horizontally moving sideways to the left and or sliding slipping downward to the right if insufficient vertical upward component were left.
In other words, the classic answer we give on FAA written tests and when asked by CFIs ("the horizonatal component of lift in a bank is what makes the plane turn") is accepted but incomplete.
The remaining question is "What turns the _nose_ of the plane to the left and keeps it turning?"
What is missing IMO in the often sophisticated explainations I see here an other places claiming to answer that remaining question is a clear credible answer to that question... .At least those answers have never been clear and credible to me.
I finally got a clear and very simple answer to that one from one engineer that I paraphrase in my own words as follows:
"OK, you bank left, and as you say the plane begins to move SIDEWARDS to the left from that horizontal component of lift. So now the plane almost immeadiatly has a relative-wind component coming against it from the left. In fact I should say 'almost immeadiatly' as you notice there's a slight delay between the time you bank and the nose starts turning left. As you know all planes 'weather vane' turning their nose into the wind even on the ground if nothing (such as brakes tie-downs, or chocks) stop them. That's because among other things there's that big vertical horizontal tail catching all that relative wind on its left side and being pushed to the right."
So in a manner of speaking very nitpickingly banking left and left horizonatal component of lift doesn't make the plane _turn_ but initiates conditions (left horizontal slide and relative wind compenent coming from the left) that in turn makes the plane turn.
As a practical matter of course we all know you can turn a plane left by banking, rudder, or of course coordinated use of both.
My two cents.
Alex
--- In mailto:Sport_Aircraft%40yahoogroups.com, "Jim Bair" <jimbair@...> wrote:
>
> Is this the list where we had the discussion about what makes an airplane turn? I think the original question was, What is the primary control used in turning an aircraft?
> I made a little video that attempts to answer that question. http://www.youtube.com/watch?v=VbaexiBw7jg
>
> Jim
>
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