How many people have a direct readout of TAS in the cockpit ?
The angle of bank AOB for a standard rate turn is given by: AOB = 57.3*atan(v/362.1)
Take your pick of the techniques below, but when flying in the crud I used IAS/10+7, IAS in knots. i.e 160 knots indicated = 23 degrees seems to work well.
[list=1][*]V |AOB |V/10+7|V/10+5|V/7[*]80 |12.46|15|13|11.43[*]90 |13.96|16|14|12.86[*]100|15.44|17|15|14.29[*]110|16.90|18|16|15.71[*]120|18.34|19|17|17.14[*]130|19.75|20|18|18.57[*]140|21.14|21|19|20.00[*]150|22.50|22|20|21.43[*]160|23.84|23|21 |22.86[*]170|25.15|24|22|24.29[*]180|26.43|25|23|25.71[*]190|27.69|26|24|27.14[*]200|28.92|27|25|28.57[*]210|30.11|28|26|30.00[*]220|31.28|29|27|31.43[*]230|32.43|30|28|32.86[*]240 |33.54|31|29|34.29[*]250|34.62|32|30|35.71[/list=a]