Final Approach Criteria

25.10.2004

Submission:

How did amendment 10 (Nov 1998) to PANS OPS change the non-precision straight-in criteria for final approach?

Jerry Willmott

Senior lecturer, Western Michigan University College of Aviation Sciences.

Answer or Commentary:

(I.W:

It was changed so that now quite a few parameters come into play when determining the final approach track and the OCA/H. Previously it was a simple matter of getting through a 150m gate at 900m from the threshold. Now it is split into a few parts: -

1. If the approach is restricted to category A/B aircraft then the interception of the final approach track and the runway centre line is no greater than 30° and no closer than 1400m to the threshold.

2. If category C/D/E aircraft are involved then the interception of the final approach track and the runway centre line is no greater than 15° and no closer than 1400m to the threshold.

3. However there is an additional criterion, if the final approach track does not intercept the runway centre line and is within 5° of it. Then it is acceptable to go through a 150m gate at 1400m from the threshold.

4. Also was an added criterion to establish the minimal permissible OCA/H. This minimum OCA/H is determined by the following formula: -

15m + (descent gradient)*(1400m + r*tan(course change/2) + 5s of flight)

Where the course change is the difference between the final approach track and the runway centre line.

5. With descent gradients above 5% (3°=5.24%) you have to increase the value in point 4 by 18% for each gradient above 5%.

6. Oh and don't forget the excessive length of final. If the length of final approach is greater than 6nm (most final approaches are 10nm) then you have to increase the MOC by 1.5m for every 0.1nm more than 6nm.

6. Finally check the criteria for mountainous terrain and remote altimeter settings.



So if your airport is: -

In the mountains

The meteorological office in town determines the airport altimeter setting, 5km away.

You have a 30° offset approach down the valley and aircraft categories A/C use the airport regularly.

The holding NDB/FAF is 10nm away on the top of a mountain and the descent gradient is 6.63% due to noise concerns.



You have a bit of a problem before you even start checking the obstacles.

Is Pans-Ops becoming too complex? Any comments please I.W.)