Visual circling

28.10.2004

Submission:

I was wondering if someone would be able to shed some light on a question I have concerning circling approaches.

We use a Boeing 727 aircraft and our routes our primarily in the high Canadian Arctic to non precision served gravel runways so we often use a circling procedure. In training we use American Airlines and a visual for JFK. The procedure we use is to have the crew fly the localizer to runway 4R and circle to land on 31R. The missed approach procedure from 4R is a climb to 800 ft then a right turn to a 100 degree heading climbing to 4000ft.

Now as you can imagine we never give the crews the missed approach when aligned to runway 4R but rather wait until they are aligned to 31R then have them execute a missed approach while we sadistically fail an engine. Now here comes the problem, some crew will climb to 800 ft and then execute a right hand turn to a 100 degree heading since it is the shortest turn to the depicted missed approach path for runway 4R, or other crew will climb to 800 ft and execute a left turn to the 100 degree heading. The reason for the left turn is to realign the aircraft to the airport centre even though it is a longer turn with a failed engine a procedure which is common in Canada i.e. turning to airport centre on circling missed approaches.

The above diagram depicts the circling procedure in green and the two possible missed approach paths, one in red the other in blue.

The question is, for the crew who turn to the right on the missed approach, do they have or do they not have obstacle clearance?

Is there an expectation on the part of the approach planner as to which way the aircraft will turn on a missed approach from a circling procedure (especially since the aircraft may be 90 degrees from the original approach direction)?

Captain M. Meddings - Canada

Answer or Commentary:

(I.W.

Pans-Ops does not take into account a missed approach from a visual circling procedure. However Pans-Ops does provide terrain clearance during visual circling if the aircraft is not below the visual circling minima which in this case is 640ft. As a category C aircraft you have 394 ft of obstacle clearance. The area in which this minimum obstacle clearance is applicable is calculated as per the following table.

This table determines the radius (R) of a circle that is placed on each of the runway thresholds. These circles are then joined tangentially to define the entire area. As one can see in the above table this area is not very large.

Within this area you have the required minimum obstacle clearance above terrain if you are at the visual circling minimum altitude but if you are outside of the area one cannot be guaranteed of having obstacle or terrain clearance. As the visual circling area is difficult to determine when one is busy with one engine out I think that turning left to cross over the aerodrome will ensure that you remain within the obstacle protection area.)