ARTICLE. Ask the procedure designer
Obviously I can only answer these questions in generalities because I do not know the specific situation at your airport
How can a new antenna 9km away increase the minimums at our airport so that we have a significant reduction in capacity?
At 9km the antenna is at the beginning of the final approach segment. If this obstacle infringers the obstacle protection surfaces it will keep the aircraft higher as it approaches the airport. The IFR procedure designer will then design a step down fix that is passed the obstacle. However the aircraft may still be too high for a standard approach which will necessitate a steeper glide-path angle. This in turn will increase the aircraft height loss in the missed approach procedure and subsequently increase your minimums.
Help! I have just been told that a building we approved a while ago has reduced my airport capacity by 50%. At the time we checked the building against the ICAO Annex 14 obstacle limitation surfaces and it did not infringe. What is going on?
The ICAO Annex 14 surface were developed at a time when airports where mostly well away from built up areas and approaches were more simplistic. These Annex 14 surfaces only deal with straight in and missed approaches straight out. While I suspect that you have a turn in your missed approach. The ICAO Pans-ops missed approach obstacle protection areas are quiet large and will include areas that the straight ICAO annex 14 surfaces do not. Possibly an experienced procedure designer will be able to alleviate the situation with an in depth study.
The Terrain around our airport is relatively flat. We are starting parallel operations and as per the ICAO parallel operations manual and we are splitting the missed approaches by 15°. Why have all the approach minimums gone up and our profits in bad weather gone down?
The Minimum Obstacle Clearance (MOC) changes when an aircraft enters a turn on the missed approach. In a straight ILS missed approach the governing surface starts at 900m passed the threshold with a slope of 2.5%. Only obstacles or terrain that penetrates this surface needs to be considered. With a turn of up to 15° a MOC of 30m is required over every obstacle in the missed approach even the threshold.
But our ILS II approaches have the standard 100 ft minimum which is 30.5m, surely the problem is solved ?
One would think so but unfortunately not. From the 100 minimum has to be subtracted the aircraft height loss which is associated with the inertia as an aircraft transitions from descent to climb. In normal cases an aircraft will not start to climb until it has lost 26m (depending on aircraft category). Already in a 15 degree turn the MOC is infringed as the aircraft has only 4m above the runway when 30m is required. So there are 2 options. Climb straight ahead until 30m MOC can be maintained or increase your minimums by 26m? (90ft)
I have installed an ILS at my airport, why don’t we have lower minimums than what we had with the old VOR/DME approach?
This case can some times happen when the critical obstacle is close to the FAF/FAP. In the VOR/DME case the procedure designer can design a step down fix in the final approach and get lower minimums. In the ILS case there is no such thing as a step down altitude and height loss has to be added on to the height of the obstacle. To determine the approach minimum you should have a feasibility check done by an IFR procedure designer before you install a navigational aid.
Is the site of our new navigational aid important? Surely the coverage, security and accessibility are the only things I have to think about?
These factors are very important but if a procedure can not be developed the new aid is of little use. Put a VOR/DME on the top of a hill, build a fence, a road and it will cover all the requested parameters. However it is of no use as an approach aid if it is 20 km away. The ICAO obstacle protection areas splay outwards as the distance from the navigational aid increases. In such a situation the obstacle protection areas are so large that almost every obstacle will have to be included in the calculation of the minimum approach altitude.
We have spent millions to build a new parallel runway, why has capacity only increased by 60 % and not 100%
This depends on a few factors. If the runways are not staggered, this could reduce your capacity because the runways will have to be operated in a dependent mode ( i.e. 1 runway) during approaches. The reason why runways are usually staggered is because of the requirement, that aircraft start stimulations approaches in IMC to parallel runways separated by 1000ft vertically. This ensures a safety buffer but means that either one runway is at a further distance than the other or that the approach angle is greater. As mentioned previously, if the IFR missed approach procedures can not be designed such that they diverge by 15° then the runways will have to be operated in a dependent mode. ( i.e. each runway is dependent on the operation of the other runway).
We could not split the missed approaches by 15° because we have significant terrain to the west of the airport. So we plan to have 1 missed approach or departure straight ahead while the procedures on the other runway will diverge to the east by 30°
Unfortunately as soon as a procedure diverges from runway centre line by more than 15° it becomes a turning procedure and more restrictive criteria comes into play. Instead of the 30m MOC, in the missed approach, 50m is required and a departure requires 90m MOC. This can increase the minimums or the climb out gradient significantly.
We have built an airport with 4 parallel runways an efficient taxiway system, and more than enough aircraft stands. Why are we not getting 4 times the capacity of a single runway?
As I mentioned, to efficiently run parallel operations the tracks from each pair of runways has to diverge by 30°. Only 2 runways at a time can be operated independently with out conflicting with the other 2 runways.
What benefits would my airport get from installing a GBAS system?
Using 1 piece of equipment, ILS like approaches to multiple runways can be designed.
Also because there is no physical beam to follow cloud break ILS like procedures can be designed to pseudo runways. This allows precision “point in space” approaches and missed approaches to areas from which a visual approach can be carried out. Such a “point in space” approach is no longer dependent on the sitting of the LLZ but is now merely a Latitude / Longitude position. For example at demanding terrain rich airports there is now the possibility to design a precision approach to a pseudo runway in the middle of the lake and a safe missed approach. Obviously pilot training is required and company visual procedures must be in place. However you can get lower, below cloud, on a safe stabilized approach and that is important.
How can an IFR procedure designer increase my cargo operations?
What most airport operations do not realise is that the departures concerning their aerodrome in the AIP are not written in stone, they can be changed. An analysis of a departure by a procedure designer could result in a change in the departure climb gradient routing or both. This will have an effect on the amount of cargo that aircraft can carry on each flight which will consequently increase revenue on the ground. However a bit of advice, it is important that you receive full documentation of all the calculations and drawings of the obstacle protection areas done by the procedure designer otherwise the new departure will never pass through the CAA for implementation.
P.S. These occurances are real and have happened somewhere in the world
Obviously I can only answer these questions in generalities because I do not know the specific situation at your airport
How can a new antenna 9km away increase the minimums at our airport so that we have a significant reduction in capacity?
At 9km the antenna is at the beginning of the final approach segment. If this obstacle infringers the obstacle protection surfaces it will keep the aircraft higher as it approaches the airport. The IFR procedure designer will then design a step down fix that is passed the obstacle. However the aircraft may still be too high for a standard approach which will necessitate a steeper glide-path angle. This in turn will increase the aircraft height loss in the missed approach procedure and subsequently increase your minimums.
Help! I have just been told that a building we approved a while ago has reduced my airport capacity by 50%. At the time we checked the building against the ICAO Annex 14 obstacle limitation surfaces and it did not infringe. What is going on?
The ICAO Annex 14 surface were developed at a time when airports where mostly well away from built up areas and approaches were more simplistic. These Annex 14 surfaces only deal with straight in and missed approaches straight out. While I suspect that you have a turn in your missed approach. The ICAO Pans-ops missed approach obstacle protection areas are quiet large and will include areas that the straight ICAO annex 14 surfaces do not. Possibly an experienced procedure designer will be able to alleviate the situation with an in depth study.
The Terrain around our airport is relatively flat. We are starting parallel operations and as per the ICAO parallel operations manual and we are splitting the missed approaches by 15°. Why have all the approach minimums gone up and our profits in bad weather gone down?
The Minimum Obstacle Clearance (MOC) changes when an aircraft enters a turn on the missed approach. In a straight ILS missed approach the governing surface starts at 900m passed the threshold with a slope of 2.5%. Only obstacles or terrain that penetrates this surface needs to be considered. With a turn of up to 15° a MOC of 30m is required over every obstacle in the missed approach even the threshold.
But our ILS II approaches have the standard 100 ft minimum which is 30.5m, surely the problem is solved ?
One would think so but unfortunately not. From the 100 minimum has to be subtracted the aircraft height loss which is associated with the inertia as an aircraft transitions from descent to climb. In normal cases an aircraft will not start to climb until it has lost 26m (depending on aircraft category). Already in a 15 degree turn the MOC is infringed as the aircraft has only 4m above the runway when 30m is required. So there are 2 options. Climb straight ahead until 30m MOC can be maintained or increase your minimums by 26m? (90ft)
I have installed an ILS at my airport, why don’t we have lower minimums than what we had with the old VOR/DME approach?
This case can some times happen when the critical obstacle is close to the FAF/FAP. In the VOR/DME case the procedure designer can design a step down fix in the final approach and get lower minimums. In the ILS case there is no such thing as a step down altitude and height loss has to be added on to the height of the obstacle. To determine the approach minimum you should have a feasibility check done by an IFR procedure designer before you install a navigational aid.
Is the site of our new navigational aid important? Surely the coverage, security and accessibility are the only things I have to think about?
These factors are very important but if a procedure can not be developed the new aid is of little use. Put a VOR/DME on the top of a hill, build a fence, a road and it will cover all the requested parameters. However it is of no use as an approach aid if it is 20 km away. The ICAO obstacle protection areas splay outwards as the distance from the navigational aid increases. In such a situation the obstacle protection areas are so large that almost every obstacle will have to be included in the calculation of the minimum approach altitude.
We have spent millions to build a new parallel runway, why has capacity only increased by 60 % and not 100%
This depends on a few factors. If the runways are not staggered, this could reduce your capacity because the runways will have to be operated in a dependent mode ( i.e. 1 runway) during approaches. The reason why runways are usually staggered is because of the requirement, that aircraft start stimulations approaches in IMC to parallel runways separated by 1000ft vertically. This ensures a safety buffer but means that either one runway is at a further distance than the other or that the approach angle is greater. As mentioned previously, if the IFR missed approach procedures can not be designed such that they diverge by 15° then the runways will have to be operated in a dependent mode. ( i.e. each runway is dependent on the operation of the other runway).
We could not split the missed approaches by 15° because we have significant terrain to the west of the airport. So we plan to have 1 missed approach or departure straight ahead while the procedures on the other runway will diverge to the east by 30°
Unfortunately as soon as a procedure diverges from runway centre line by more than 15° it becomes a turning procedure and more restrictive criteria comes into play. Instead of the 30m MOC, in the missed approach, 50m is required and a departure requires 90m MOC. This can increase the minimums or the climb out gradient significantly.
We have built an airport with 4 parallel runways an efficient taxiway system, and more than enough aircraft stands. Why are we not getting 4 times the capacity of a single runway?
As I mentioned, to efficiently run parallel operations the tracks from each pair of runways has to diverge by 30°. Only 2 runways at a time can be operated independently with out conflicting with the other 2 runways.
What benefits would my airport get from installing a GBAS system?
Using 1 piece of equipment, ILS like approaches to multiple runways can be designed.
Also because there is no physical beam to follow cloud break ILS like procedures can be designed to pseudo runways. This allows precision “point in space” approaches and missed approaches to areas from which a visual approach can be carried out. Such a “point in space” approach is no longer dependent on the sitting of the LLZ but is now merely a Latitude / Longitude position. For example at demanding terrain rich airports there is now the possibility to design a precision approach to a pseudo runway in the middle of the lake and a safe missed approach. Obviously pilot training is required and company visual procedures must be in place. However you can get lower, below cloud, on a safe stabilized approach and that is important.
How can an IFR procedure designer increase my cargo operations?
What most airport operations do not realise is that the departures concerning their aerodrome in the AIP are not written in stone, they can be changed. An analysis of a departure by a procedure designer could result in a change in the departure climb gradient routing or both. This will have an effect on the amount of cargo that aircraft can carry on each flight which will consequently increase revenue on the ground. However a bit of advice, it is important that you receive full documentation of all the calculations and drawings of the obstacle protection areas done by the procedure designer otherwise the new departure will never pass through the CAA for implementation.
P.S. These occurances are real and have happened somewhere in the world