Dan I believe that it is going to be a case by case basis. If the area is relatively obstruction free, say over fields and grass, then a standard KR2 or S solo should be able to complete a 180 degree turn and land backwards in an emergency with between 400 to 500 feet. However, if the field is bordered by rows of trees, antennas and such like Sanford is, then landing straight ahead is a much better option than trying to make a 180 degree turn. The increase in the descent rate during a turn and glide can be on the order of 2/3 to double the normal glide descent rate, depending on the angle of bank maintained. A 45 degree bank can easily result in the loss of 300 feet without power in a 180 degree turn.
As a rule of thumb, and this is subjective to individual situations and environments, but it is considered prudent to only consider landing straight ahead or maximum 45 degree angle to one side or the other to avoid obstuctions, if you are below 500 feet AGL. Once you are at or above 700 feet AGL, it is taught by CFI's that if good flying techniques are applied, the pilot should be able to land back on a runway in the airport environment safely. Obviously, for every time that this is the safe thing to do, there will be a time where it is not. That is where good planning in advance of the first flight day, and subsequent test days is necessary for effective plans of action and back up plans if those are not safe or practical to execute. Rod Machado, and the Kings are known for teaching that statistcally (I know they can be what you want them to be) you are better off landing straight ahead under 700 feet, but definitely under 500 feet AGL. Your chances of a controlled descent and emergency landing are far improved over trying to turn back. Any questions by anyone are easy to simulate. Climb to 3000 Feet; pull the power out, and then make a best glide 180 degree turn and note the altitude loss. Practice at different angles of bank to see the effect. I think you will be surprised... Colin N96TA
