Night Circling Approches
Australian AIPs as at 24 Apr 97 state:
[DAP1.5.3]
Visual Circling During visual circling, descent below the MDA may only occur when the pilot:
a. maintains the aircraft within the circling area; and
b. maintains a visibility, along the intended flight path, not less than the minimum specified for circling; and
c. maintains visual contact with the landing runway or approach lights or other markings identifiable with the approach end of the runway; and either
d. by night or day, while complying with a., b., and c. (at an altitude not less than MDA), intercepts a position on the downwind, base or final leg of the landing traffic pattern, and, from this position can complete a continuous descent to the landing threshold using rates of descent
and flight maneouvres which are normal for the aircraft type and, during the descent, maintains an obstacle clearance not less than the minimum for the aircraft category until the aircraft is aligned ith the landing runway; or
e. in daylight only, while complying with a., b., and c., maintains visual contact with obstacles along the intended flight path and an obstacle clearance not less than the minimum for the aircraft performance category until the aircraft is aligned with the landing runway.
You can use the following methods to get yourself down from circling height.
Method 1
Using a topographical map draw the circling area on it and calculate a safe height which would be the highest obstacle within the area plus your required obstacle clearance. You can have multiple heights (ie. one for downwind and one for base) if it makes the descent easier. You then step down to your calculated altitudes until you are on final. The advantages are you know where all the terrain is because you have studied a map and your terrain clearance is guaranteed. The disadvantages are that you may not always have a map of suitable scale to work with. NOTE: You cannot use the spot heights on IAL charts to do this, they are NOT complete!
Method 2
You remain at the circling height until established on final. To alleviate the possibility of high rates of descent on final you use the entire circling area available to you. To do this you start timing abeam the centre of the circling area arc (eg. in the diagram aboves case that is abeam the threshold) and then fly out for a time that given your groundspeed equates to the circling area radius less your turn radius. The theory is that after the nominated time you will start your turn and after 90 degrees of turn you will be at the extremity of the circling area and this will give you maximum distance in which to descend on finals.
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