On Saturday, May 10, 2014 10:49:57 PM UTC+12, wrote:
On Wednesday, May 7, 2014 6:24:23 PM UTC-7, Bruce Hoult wrote:
No matter what your stall speed or L/D, it turns out the optimum to minimise loss of height in a turn is to bank at 54.7 degrees.

2) Speaking of the bottom wingtip in the bank, if you subtract that height difference for each different bank angle you get a height loss for a 180 measured at the bottom wingtip that is actually minimal at a lower bank angle than 54.7 degrees. Obviously this would be most likely to apply at the end of the maneuver, not the beginning, unless there is unusual terrain.

You also can't change bank angle instantaneously.

I think it makes sense to peak at around 60 degrees of bank as you're about halfway through the turn, and decrease it by the time you're only 45º or so from having reversed direction.


3) Whether you include the wingtip clearance in the calculation or not, the total height loss doesn't vary all that much between 30 and 60 degrees of bank - about 6 feet of difference for the center of the aircraft and only a foot or two of difference at the lower wingtip.

The biggest difference between 30º and 60º isn't the couple of meters of difference in height lost, but the 100m difference in lateral displacement at the end of the turn. That means you have to turn further and take more time and height to get back in line with the runway (assuming you don't just have a very wide airfield), and increases the chances of finding yourself on the wrong side of some obstacle.


I think it's completely reasonable to expect students to be able to do a crisp 180º reversal turn using between 45º and 60º of bank more or less instinctively before they get to solo. You use such turns all the time when ridge soaring, either when you discover you've gone too far and got into sink, or just to end up no too far out in front of the ridge.