Radius of turn
 

Has anyone got a simple idiot proof formula for working out radius of turn? Such as if you are flying at 180kts, what is the max distance away from the "abeam?

Radius of turn is equal to TAS squared, divided by (g multiplied by the tangent of bank angle).

Bugger - that sounds too difficult. So let's simplify it. First of all, use nautical miles per minute rather than knots and also assume that you'll always use 25 deg for the angle of bank. Then your radius of turn in nautical miles is is simply your (TAS in miles per minute squared) divided by 8.89. OK - make it even simpler. Radius of turn at 25 deg angle of bank is one ninth of your TAS squared in miles per minute. So at 180 KTAS it's 1 nautical mile.

OK??

[This message has been edited by BEagle (edited 05 June 2001).]

A simpler method

Take your Tas in minutes (eg 420Ktas=7NM/min)and subtract 2 (eg. 7NM/min-2=5) this is your turn radius! (180Ktas=3NM/min-2=1)

hope this help

This was done to death a few months ago. Use Search to find it.
ET

Should make that circling approach at 160 knots, on a dark and dirty night at 600 feet a cinch within the required 2 mile distance with the big heavy jet....NOT. Sure fun in the sim however, especially with new guys. If they can do the maneuver well then most everything else is a breeze.

Thanks for the replies. I was not aware of the search facility. Really like the simple TAS/60 -2.

Well then Shimoda, see if you like it at 120kts!! Try a simple test. 2nm per minute minus 2 = 0 turn radius. Not a perfect answer by any means. :)

411A
The rest of the world uses 5.2nm for heavy jets. Are you sure your not still talking about the single decker bus you drive. Off you go and play with your MS flight sim laddy.

The circling area for Cat C aircraft is defined as 4.2nm from the runway ends - thus a 2.1 nm diameter turning from downwind to final on a circling approach.

Watch the personal comments!

Checkboard,
Hope you mean a 2.1nm RADIUS. ET

The Vicar

as any rules of thumb, there are limitations: it's up to you when the rule is good or not for you!
In a cat C aircraft at 120Ktas you are stabilized at final approach (or stalled,depends on weight)really doesn't matter how much is your turn radius (infact is 0.83Nm).This rule (Tas/60-2)is very handy during intercept of final courses, at arange of speed of 180-250 or more.

Black-Dawn,
That may be but your rule does not hold true for all cases.
BEagle has it exactly right with the Nm per min squared divided by 8.89 and his practical application of rounding the divisor up to 9 still gives a near result.
Not all contributors to the forum operate only on heavy jets.
Using BEagles rule for your 420 TAS example yields a result of 5.44nm turn radius against an actual of 5.51nm which is closer than your method and has the virtue of applicability at all speeds. :)

[This message has been edited by The Vicar (edited 07 June 2001).]

Checkers,

Those who believe they rule the world have TERPS and love to ignore ICAO, hence the differences:

"46. Circling Approach Obstacle Clearance Protected Area:

a. FAA - The protected area is much smaller in the USA (1.7 mile radius for
approach category C and 2.3 mile radius for category D), this is well below ICAO
requirements, and makes the circling approach even more difficult and
dangerous.

b. ICAO - Requires a much larger area. Circling area radius from threshold in ICAO
(DOC 8168 OPS/ 611PANS-OPS-4, page 3-26): A: 1.68nm; B: 2.66nm; C: 4.20nm; D:
5.28nm; E: 6.94nm. The maximum speeds are A: 100KIAS; B: 135KIAS; C:
180KIAS; D:205KIAS; E: 240KIAS. The radius is the distance from the threshold
used to determine the circling area."

The source is from these wonderful pages but I apologise to the author because I have misplaced the proper acknowledgement.

------------------
Stay Alive,

[email protected]

Yes indeed, TERPS generally has tighter tolerances than ICAO, so 600'-2sm is the minimum for the catagory D circling maneuver. And for our friends from afar, if they come to the USA to do an FAA type rating on a heavy jet, and stray beyond 2 miles during the required circling approach, they ah......fail. The approach is generally done all engines, but most FAA guys I know want to see it done with one engine inop on three or four engine aircraft.
On the newer simulators, this is a very good confidence-building exercise and, if properly done, results in smiles all 'round.

Well now there is a difference between the defined circling area for each category versus the minimum circling visibility for that category. So we have a defined circling area assessed to decide on the minimum circling altitude prior to descending on profile to the runway and a minimum visibility required during the circling manoeuvre. So for cat C we have a 4.2nm circling area generally with a minimum visibility of 2nm. So assuming that the runway lights (sometimes other lights clearly indetifying the runway environment) are to be kept within 2nm while conducting the circle. So there is nothing supernatural about circling within 2nm.

However the first rule about circling approaches is DON"T DO THEM IF YOU DON"T HAVE TO!! Generally there are other runway oriented approaches available.

The second rule is it is NOT a VFR/VMC procedure so it must be flown in a disciplined manner primarily on instruments with visual check points. Many have come to grief looking out the window at the runway especially on the base turn. Have in mind definite minimum target altitudes; at the end of downwind leg; at mid base and lined up and STICK To THEM.

The third rule is if out of position go around. Go somewhere else if need be.

Black Dawn,
120 TAS turn radius is nearer to .45nm I think. Think you gave us the diameter.

[This message has been edited by pterodactyl (edited 10 June 2001).]

pterodactyl

you're right, turn radius at 120Ktas is 0.4NM ;i did a mistake
bye BD