When to turn in on a visual approach from aloft downwind:
On a Boeing, be gear down flap15 (737) or 20 (75/767) passing abeam the touchdown threshold, 2 miles out abeam. Start a stopwatch and descend at idle thrust. The timing to extend downwind is;
Height above T/D threshold/100 x 1.5 and if you want to really cream it take off 1/2 the tailwind component in kts.
e.g. Pass abeam at 5000' AGL.
5000/100=50 50 x 1.5 = 75 seconds
This works well when new/training. With experience and if you want to really nail it, say with a 15kt tailwind downwind, take off about 7-8 seconds....it looks quite tight and it is, but you will stabilise on final into a 3 degree descent from above......
Take landing flap as appropriate, usually turning final. If the timing works out less than 45 seconds then make it a normal visual circuit, i.e. level off at 1500' AGL and turn in at 45 seconds (i.e. if you are passing 3000' AGL or less as you pass abeam, you are not really flying a visual approach from 'aloft', merely descending to circuit altitude before turning base/final).
Works a treat, especially at places like Pafos where you are often kept high and pass abeam at something like 8000' AGL.
PP