View Full Version : Radius of Turn

Hi Guys,

Read the stuff on google/wikipedia but can't remember the rule of thumb for calculating radius of turn for a given bank angle and speed.....

Anybody any ideas?

matt_hooks

19th Feb 2008, 14:46

Well, for a rate one turn (180 degrees per minute) the required bank angle is, approximately, (airspeed/10)+7.

For exapmle at 120 knots, the angle of bank for a rate on turn is 19 degrees.

As for radius etc. that would mean a quick revisiting of the ATPL notes.

If you have an Excel spreadsheet, paste in this:

=ROUND(PRODUCT(E3,E3)/(11.26*TAN(E4*PI()/180)),0)

Cell E3 is the TAS

Cell E4 is the bank angle

gives the radius in feet.

There are several threads about this.

HERE (http://www.pprune.org/forums/showthread.php?s=&threadid=159674)

and

HERE TOO (http://www.pprune.org/forums/showthread.php?s=&threadid=159674)

vanderlay

9th Mar 2008, 11:20

Hi All, given the inverse data,

speed = 160kts

radius = 3.4nm

degrees of turn = 205

can I calculate the bank angle needed?

Thanks

Art

PS not a pilot just a special fx person and I need to match some internal and external shots to a wescam plate for a movie, just in case that question seems a little dumb.

Vsplat

9th Mar 2008, 14:43

Good morning Vanderlay. 3.4 nm (just under 20700 ft) gives you a lot of room to turn at 160 knots. At 15 deg of bank and a 160 knot ground speed, you'd need approx 8500 feet.

A few questions, though.

Is your goal to stick precisely to a radius, stay inside it, or stay outside it?

Are we looking at a sea level location?

Is the airspeed going to be constant through the turn, and

What is the wind like in the area you are considering? For the arc you are describing, for a constant airspeed, the wind may signficantly decrease the groundspeed (and with it, radius) at one point in the turn and increase both for the other.

Cheers

Vs

littlejet

9th Mar 2008, 14:54

This applies for standard turns only (3deg/sec):

Radius (m) = GS(kt) x 10

Bank = TAS/10 + TAS/20

gearpins

10th Mar 2008, 01:46

For a rate 1 turn the diameter of a turn is 1% of TAS

eg.TAS 220kts dia=2.2nm

radius is half that:)

vanderlay

10th Mar 2008, 03:18

Thank you all,

there are actually several shots, these were done with a large RC(or small UAV depending on the way you measure it I suppose.) the shots are to recreate a UAV monitoring several targets and we then add several other AC and objects to match. The data we got was all great(even GPS) with the exception of bank angle. however the BA is an easier interface to work with than computing radials etc. I will try and post some of the work in small parts if we get permission in a few months after we have done some renders.

Again thank you for your speedy and informative responses

ART

sameep

10th Mar 2008, 06:00

Hi.. this is from the aviation formulary website.. Hope it helps..

In a steady turn, in no wind, with bank angle, b at an airspeed v

tan(b)= v^2/(R g) v= w R where g is the acceleration due to gravity, R is the radius of turn and w is the rate of turn.

Pivotal altitude h_p is given by

h = v^2/g With R in feet, v in knots, b in degrees and w in degrees/sec (inconsistent units!), numerical constants are introduced:

R =v^2/(11.23*tan(0.01745*b)) (Example) At 100 knots, with a 45 degree bank, the radius of turn is 100^2/(11.23*tan(0.01745*45))= 891 feet.

The rate of turn w is given by:

w = 96.7*v/R (Example) = 96.7*100/891= 10.9 degs/sec

The bank angle b_s for a standard rate turn is given by:

b_s = 57.3*atan(v/362.1) (Example) for 100 knots, b_s = 57.3*atan(100/362.1) = 15.4 degrees

A useful rule-of-thumb, accurate to ~1 degree for speeds less than 250 knots, is b_s= v/7 (v in knots).

The pivotal altitude is given by:

h_p = v^2/11.23 (Example) At 100 knots groundspeed the pivotal altitude is 100^2/11.23 = 890 feet.

:eek:

henry crun

10th Mar 2008, 07:41

sameep: That is great rule of thumb............................... if you have a good memory and are an ace at mental arithmetic !

sameep

17th Mar 2008, 15:50

LoL.. sorry... ;-)