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I'm looking for some rule-of-thumb guidance on this matter. It relates to route 4, the westerly take off from London Gatwick (LGW).

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marked as duplicate by mins, fooot, Ralph J, SMS von der Tann, Farhan Nov 13 '17 at 14:49

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ Related: What does it take to turn a 747 around 180 degrees?. If you are looking for the simple figure, then it seems to be 8.28 nautical miles at cruise speed, taking off will be smaller. $\endgroup$ – mins Nov 12 '17 at 17:37
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    $\begingroup$ Not sure it's a duplicate. The 747 question is about a 180 at cruise and the heavy a/c question is about limited turn rates. This question is asking for the turn radius with a normal bank limit (15 deg?) at Green Dot airspeed. $\endgroup$ – Gerry Nov 13 '17 at 13:01
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While in theory possibly a duplicate of the other question, and while the physics are very well explained there, the numbers to be used for takeoff and landing aren’t given in the other thread.

The following works as a rule of thumb for most commercial airliners: Maximum bank angle after takeoff with all engines would be around 25 degrees, with a failed engine it would be around 15 degrees until minimum clean speed is reached and the flaps are up and 25 degrees after that.

True air speed shortly after takeoff shouldn’t be much above 200 knots for most weights, airfield elevations and temperatures encountered except in extreme circumstances.

Plugging both these into the formula for turn radius explained elsewhere gives just above 2300m radius on all engines, and just above 4000m radius with a failed engine and before cleanup.

Brief answer, but I hope it helps!

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You could look to the Standard Instrument Departure (SID) routes published by NATS for a guide as to what is done - as opposed to what could be achieved.

http://www.nats-uk.ead-it.com/public/index.php%3Foption=com_content&task=blogcategory&id=94&Itemid=143.html

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  • $\begingroup$ Welcome to Aviation.SE! This answer could be improved by providing radii from those procedures. $\endgroup$ – fooot Nov 12 '17 at 23:12
  • $\begingroup$ This doesn’t change the answer but touches upon a wide issue in the industry for some background information: SIDs (in fact, all procedures, but SIDs are most critical) are designed to standards which work most of the time, but which still are not aligned with aircraft performance at all. There are many procedures where airlines need to take precautions (most often: restrict takeoff weight) in order to meet e.g. turn radius or climb rate requirements. Checking departure plates for turn radii is therefore relevant and interesting, but not necessarily indicative of what aircraft will achieve. $\endgroup$ – Cpt Reynolds Nov 13 '17 at 6:05

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