Calculation of turn radius?
Thread Starter
Joined: Jan 2006
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From: EU
Calculation of turn radius?
What's the easiest way to calculate a turn radius when all you have is the bank angle and velocity.
For example, calculate the turn radius of an aircraft at 45° bank and with an airspeed of 200 knots?
Any suggestions?
http://www.pprune.org/forums/showthread.php?t=159674 and others
For example, calculate the turn radius of an aircraft at 45° bank and with an airspeed of 200 knots?
Any suggestions?
http://www.pprune.org/forums/showthread.php?t=159674 and others
Joined: Nov 2005
Posts: 1,114
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From: UK
Founder for other ATPL related questions Bristol GS have a really useful forum which is open to anyone to use.
http://www.jals.co.uk/forum/
Scroll down to the Technical subject areas and dive on in. Many of the questions and solutions in their forums are from actual exams.
http://www.jals.co.uk/forum/
Scroll down to the Technical subject areas and dive on in. Many of the questions and solutions in their forums are from actual exams.
Joined: Jul 2006
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From: Earth
Originally Posted by Old Smokey
Radius = TAS^2 / Tan Bank Angle / G
Where TAS is in Ft/sec, Bank Angle is in degrees, and G is in Ft/sec^s
Feel free to convert to a metric equivalent! Vive la difference!
Regards,
Old Smokey
Where TAS is in Ft/sec, Bank Angle is in degrees, and G is in Ft/sec^s
Feel free to convert to a metric equivalent! Vive la difference!
Regards,
Old Smokey
Thread Starter
Joined: Jan 2006
Posts: 364
Likes: 0
From: EU
Originally Posted by Old Smokey
Radius = TAS^2 / Tan Bank Angle / G
Where TAS is in Ft/sec, Bank Angle is in degrees, and G is in Ft/sec^s
Feel free to convert to a metric equivalent! Vive la difference!
Regards,
Old Smokey
Where TAS is in Ft/sec, Bank Angle is in degrees, and G is in Ft/sec^s
Feel free to convert to a metric equivalent! Vive la difference!
Regards,
Old Smokey
/Tim
Joined: Jun 2004
Posts: 1,843
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From: Australia
Correct as it stands if seen as a "one liner" in a computer programme, or as a sequence to be followed if using a calculator.
Written as a conventional formula, it looks more like this -
Turn Radius = TAS^2 /(Tan Bank Angle X G)
Regards,
Old Smokey
Written as a conventional formula, it looks more like this -
Turn Radius = TAS^2 /(Tan Bank Angle X G)
Regards,
Old Smokey
Joined: Feb 2006
Posts: 73
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From: Above and beyond
Just a word of caution with the equation above. All units have to be in one unit or another. I.E Metres per second. I find if you are using nautical miles per hour (knots) (as a TAS) then an easy and general rule of thumb divide the TAS by 2 before squaring which gives you rough speed in m/s. Another quick tip, unless stated otherwise I assume G = 10. Makes the calcs a lot quicker and easier. and yes you are correct in thinking:
TAS^2/(TAN bank angle x G)
Tacho
TAS^2/(TAN bank angle x G)
Tacho
Joined: Apr 2004
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From: Europe
Founder, hey mate. Don't know if I'd start to take it square or divide or anything like that. I just take 1 % from the ground speed and it usually works.
So 250 kt GS 2,5 NM turn, its just rough calculation but its good enough.
Cheers.
So 250 kt GS 2,5 NM turn, its just rough calculation but its good enough.
Cheers.
PPRuNeaholic
Joined: Jun 2000
Posts: 3,255
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From: Cairns FNQ
As you've stated an "airspeed" of 200 knots, I can't tell whether you're referring to IAS or TAS. If the former, you need to account for altitude and temperature to derive a TAS.
Just for the hell of it though, I ran some calculations based on Pans Ops criteria for 200 KIAS, ISA +15, at various altitudes and came up with the following :-
2000 feet : 0.655 NM
4000 feet : 0.693 NM
6000 feet : 0.738 NM
8000 feet : 0.785 NM
10000 feet : 0.840 NM
These values would be used in procedure design, though I feel sure that a bank angle of 45 degrees would never be used in an instrument procedure design. Indeed, I'm not even sure that the forumula is totally accurate at that sort of bank angle.
Just for the hell of it though, I ran some calculations based on Pans Ops criteria for 200 KIAS, ISA +15, at various altitudes and came up with the following :-
2000 feet : 0.655 NM
4000 feet : 0.693 NM
6000 feet : 0.738 NM
8000 feet : 0.785 NM
10000 feet : 0.840 NM
These values would be used in procedure design, though I feel sure that a bank angle of 45 degrees would never be used in an instrument procedure design. Indeed, I'm not even sure that the forumula is totally accurate at that sort of bank angle.
