You have a good point. I'm finding that it's not all that easy to learn for some reason. I'm looking forward to the time when it's easy to perform.
[Well, so far I've experienced all the "common errors" listed and then some. At 180 degrees, my wings aren't level. I'm coming out of it with a much higher air speed than I like or want. I don't know if I'm pulling too hard in the pull up or not hard enough and I think I'm not letting up on back pressure enough at the top. I'm not sure if I'm using too much aileron or not enough.]
One thing that can really screw you up in visualizing a barrel roll is in how you deal with it reference wise when visualizing it to yourself. Since the roll is really a roll and a loop performed at the same time your point of reference is important. For example, at your "180 degree" position in the roll, you are 180 degrees through the roll and 180 degrees through the loop BUT this position has been achieved at only 90 degrees change in heading. In barrel rolls using the maximum roll axis capable to the aircraft (ANY aircraft) , it's this meeting at inverted that constitutes the main reference point. (Keep in mind that barrel rolls are possible using a much narrower roll axis than this 90 degree change in heading at the 180 degree point. Any roll you perform using 3 dimensions coupled with positive g all the way around in that roll is a barrel roll.
For the "classic" barrel roll, diving in after your last clearing turn to pick up entry airspeed, pick a good reference point 90 degrees off your wingtip. That point will be where you want the airplane to be inverted at the top halfway through the roll. At that point you will want to be looking directly at it inverted passing through wings level. The trick with barrel rolls is to get your control pressures all blended in correctly so that you achieve that reference point exactly inverted wings level.
The back side back to level flight is just more of the same only this time the reference point will be back under your wing again and the new cues are the recovery altitude, the entry airspeed regained and wings level flight.
Doing a good barrel roll isn't easy Diane and you will find that the only way to get it down pat is by practicing it over and over again, letting the airplane instruct you. The airplane will tell you immediately if the roll is good or bad. In acro, the aircraft is the finest instructor you will ever have. It NEVER lies. You can't cheat it. The aircraft is brutally truthful in telling you how good or bad you are doing at any given instant in time.
[I had the center point picked out ahead and off to the side and lost it on the pull up and didn't find it again.]
Easy to do with a high wing barrel roll. Learn to pick it back up through the windshield as you come on up and around. After a while, as you get more familiar doing the rolls, picking up the point will be natural for you.
[Well, I normally don't look at it (eyes are outside), but was basically answering the original question. Although, I do glance at my airspeed and RPM on occasion.]
Yes, these are peripherals and you are right to include them in your acro scan. Fixed pitch prop especially; watch that RPM if using power. You don't want an overspeed coming down the back side of a maneuver.
[Maybe I looked at the wrong place at the beginning of the roll.]
You'll find as you progress that rather than looking at any single point, you will have not only the point you pick, but the terrain around that point as well. In effect, you will be maneuvering into and out of a reference point "area" where your scan will be picking up a continuation of never ending visual cues that form a pattern you are following through the maneuver. Make no mistake, your POINT will still be your target, but using the surrounding terrain, getting to the point will become easier as you start using a more "complete maneuvering picture".
[Well, so far my initial barrel rolls have been an interesting combination of a loop and a roll, but certainly aren't pretty or what I'm hoping for. Although, on my score sheet from competition, I have lots of comments about "barreling" on the maneuvers.
]
If you want to experience an almost perfect barrel roll with not much fuss, simply begin a straight climb at normal barrel roll entry airspeed, then roll off that climb by continuing the back pressure diagnally instead of straight back. Don't forget to feed in a bit of inside rudder to coordinate. Ease off the rudder once into the roll as bottom rudder will pull the nose down as you pass knife edge. Reapply rolling rudder again on the back side. The airplane should roll right on around for you. Just monitor the RPM if fixed pitch.
[Thank you for your comments Dudley, I appreciate it.
