Fatal crash Arizona

Don't do 60 degree banked turns close to the ground! I don't want to tell someone that's he's wrong, but I think that some people may think that the conclusions are right just because there are some numbers behind them, and start practicing rope breaks with 60 deg banks.
I went through the spread sheet and I found everything correct except for the calculation of the "enhanced sink rate". The sink rate is not just the unbanked rate multiplied by the load factor!
Some manufactures include a circling polar. Using the circling polar of an asw-24 with a total weight of 750 lbs, the speed and sink a

at 30 deg: 45 kt, 150 ft/min
at 45 deg: 50 kt, 205 ft/min
at 60 deg: 59 kt, 345 ft/min

Now, the time and height lost to complete a full turn (divide by two for a 180 deg turn):

at 30 deg: 26 secs, 64 ft
at 45 deg: 16 secs, 56 ft
at 60 deg: 11 secs, 65 ft

The differences are not much, anyway, but it is easier to bank and unbank at 45 deg.

I gotta go and can't expand, but I'll try to get the numbers based on the real formulas at a later time. In the mean time, you can check Fred Thomas book, Fundamentals of Sailplane Design, pgs 64 and 65. The minimum sink rate in a turn will be higher than the minimum sink rate in level flight by a factor of 1/(cosangle)^1.5

On Sunday, May 11, 2014 3:01:30 AM UTC+12, wrote:
I went through the spread sheet and I found everything correct except for the calculation of the "enhanced sink rate". The sink rate is not just the unbanked rate multiplied by the load factor!

Ahh . yes .. you are correct. That's right for the descent angle, but then you need to adjust that by the ratio of the airspeeds to get the descent rate.


Some manufactures include a circling polar. Using the circling polar of an asw-24 with a total weight of 750 lbs, the speed and sink a

at 30 deg: 45 kt, 150 ft/min
at 45 deg: 50 kt, 205 ft/min
at 60 deg: 59 kt, 345 ft/min

With the correction of multiplying the sink rate by "speed needed"/"min sink speed" my spreadsheet gets the above numbers (and same turn times and height loss) for a glider with a min sink of 122 fpm at 42 knots.

On Saturday, May 10, 2014 8:25:35 PM UTC-7, Bruce Hoult wrote:

With the correction of multiplying the sink rate by "speed needed"/"min sink speed" my spreadsheet gets the above numbers (and same turn times and height loss) for a glider with a min sink of 122 fpm at 42 knots.

New summary chart with correction: https://drive.google.com/file/d/0Bw1...it?usp=sharing

The new minimum altitude loss bank angle is...drum roll...45 degrees.

If for some reason you are worried about dragging the wingtip the bank angle that keeps the wingtip the highest is 36 degrees, though obviously this only matters as you sink lower and/or encounter obstacles.

The discussion about offset from the runway is unchanged going from 45 to 60 degrees of bank will reduce the runway offset by 80 feet or so - I don't think it's worth the risk to crank it over that far in most situations. The simple observation is that between 30 and 55 degrees the amount of altitude lost doesn't vary much, so do whatever allows you to control the airplane and get to a laudable spot in go shape to land.

9B

On Saturday, May 10, 2014 10:51:36 PM UTC-7, wrote:
On Saturday, May 10, 2014 8:25:35 PM UTC-7, Bruce Hoult wrote:



With the correction of multiplying the sink rate by "speed needed"/"min sink speed" my spreadsheet gets the above numbers (and same turn times and height loss) for a glider with a min sink of 122 fpm at 42 knots.



New summary chart with correction: https://drive.google.com/file/d/0Bw1...it?usp=sharing



The new minimum altitude loss bank angle is...drum roll...45 degrees.



If for some reason you are worried about dragging the wingtip the bank angle that keeps the wingtip the highest is 36 degrees, though obviously this only matters as you sink lower and/or encounter obstacles.



The discussion about offset from the runway is unchanged going from 45 to 60 degrees of bank will reduce the runway offset by 80 feet or so - I don't think it's worth the risk to crank it over that far in most situations. The simple observation is that between 30 and 55 degrees the amount of altitude lost doesn't vary much, so do whatever allows you to control the airplane and get to a laudable spot in go shape to land.



9B

....get to a landable spot in good shape to land.

On 2014-05-11,
wrote:
On Saturday, May 10, 2014 10:51:36 PM UTC-7, wrote:
... get to a laudable spot in go shape to land.
...get to a landable spot in good shape to land.

a laudible goal