On Saturday, May 10, 2014 5:28:51 AM UTC-6, wrote:
On Saturday, May 10, 2014 6:49:57 AM UTC-4, 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.







Feel free to play.







Thanks Bruce - I did play with this a bit. Always helpful to do the math.







Several observations pop out from the numbers:







1) The 25-30' height loss for a 180 is small compared to the 200' I always use as the minimum safe altitude to make this maneuver. Not that I'm recommending a smaller margin - there are considerations of sink and wind and clearance for the bottom wingtip in the bank.







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.







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 conclusion this draws me to is that the most important consideration in PTT is to make a smooth, coordinated, deliberate turn that you can manage easily - and to make sure not to dig the bottom wing into the ground. Within a pretty broad range, there isn't much percentage in optimizing the bank angle.







9B



I agree with B. Further,advocating very steep turns near the ground, even if technically optimum, is likely to result in a less safe result for a number of reasons.

First- few pilots can execute such a turn accurately. Speed control goes to crap as bank gets steeper.

Second- The effect of wind shear is much greater at very steep banks.

Third- Timing of the turn is much harder at high turn rate usually leading to overshoot.

UH

Ground reference maneuver training teaches pilots how to very accurately fly turns at low altitudes.