New ICAO Obstacle Limitation Surfaces (OLS)

Overview of the New OLS Surfaces Applicable in November 2030 - Meeting Transcript

April 30, 2026, 8:59AM

1h 11m 42s

Nyree Millar-Bell   0:26
Good Morning everyone and welcome to the New ICAO Obstacle Limitation Webinar 2026. Our presenters today, we've got Matt Roberts, Policy Principal Aerodromes at the Civil Aviation Authority. We have Malte Karger, Director of Airsight. We've got myself, Nyree Millar-Bell, the Obstacle and Safeguarding Policy Specialist at the CAA.
And then we've got Mark Ashley, who's a Senior Policy Advisor, Aviation Strategy, Domestic Safety, Aviation Safety, Innovation and Skills Division for the DFT as well.

 

Due to time constraints, there will not be a Q&A session at the end of the presentation. So if you do have any questions, please use the chat function in Microsoft Teams. Alternatively, you can email at NewOLS@caa.co.uk.

So moving into the agenda for today then, so we're first going to talk about the background on why ICAO updated the new OLS. The legacy, we'll go into the legacy OLS framework, drivers for change, global developments influencing OLS changes. We'll then go into detail of the new ICAO OLS framework and that will discuss the Aeroplane Design Group, Obstacle-Free Surfaces and Obstacle Evaluation Surfaces. We'll then move on to aeronautical studies, what the new OLS will mean for Aerodromes, the UK implementation approach and aerodrome safeguarding circular, with an update and next steps as well. So I will now hand over to Matt Roberts who is going to look into the background of why ICAO updated the OLS.

Matt Roberts   2:49
Good Morning all, thanks Nyree

OK, I will go through the next few slides, give a bit of a background of what the old OLS that is currently established is, and how it became, and how we got to where we are today and what we are transitioning to. Next slide please.

So the current OLS that's in place in the majority of aerodromes and across the UK is attached to the old framework from the 1950s. That was when it was designed and established. When it was designed and established, it was designed around a lot older aircraft with less performance, older navigation aids and navigation criteria and the old airspace designing concepts that were in place in the 1950s. Since then the framework hasn't changed and things have evolved in them areas.

When it was established, for the reasons of what was in place at the time, it was appropriate to have a rigid geometry fixed surfaces that was applicable to all with very little flexibility. They were set slopes and set dimensions, no matter what the aerodrome operation was and that's how it is implemented today and that's then leads onto extra constraints sometimes where not necessary. So that's what was set back in the days in 1950s.

From now things have obviously evolved and when that was designed, it was all set on assumptions of straight in approach. There was no modern performance-based navigation and instrument flight procedures were in the early stages as well.
So then instrument flight procedures and communication, navigation, surveillance systems developed, matured over the years. Which resulted in some disjoint and poor alignment to what the OLS was at the time and now established. So there is now a disjoint because of the evolvement of the IFP and the CNS safeguarding surfaces. Which ultimately then means that sometimes it's over conservative and over restrictive and an administrative burden at times in safeguarding. Where it doesn't need to be and this is all due to the dated surfaces that are established today. Next slide please.

So then there was a driver for change because of this. The reasons shown on this slide and I won't go into too much detail, but it's for better alignment to modern procedures. So now we've evolved more and it is performance based navigation.
The instrument flight procedures are more common and different and different ways of the instrument flight procedures. So it was to get a better alignment with the modern procedures that are in place today to stop that disjoint that is currently in place. It then also another driver from that was to give more flexibility and also bring in proportionality to the safeguarding. So get away from over onerous safeguarding surfaces and safeguarding areas that don't need to be safeguarded and become more proportionate and more flexible where you can. And moving towards a more risk based protection as opposed to a fixed surface protection that was over onerous.
This is aligning to where we are today with other elements. And it also then brings in greater flexibility and performance based.

So this time gives a clear protection layer and it also improves the OLS, IFP protection that we talked about in the previous slide and also the CNS safeguarding that can then be brought in and aligned to the new surfaces and established to be proportionate and cover the areas that you need to cover, which currently is a challenging way to do safeguarding in a disjointed manner. Next slide please.

So the global development influence OLS change also because there's growing air traffic and capacity needs. Things are more modern now, airspace is expanding, airports are expanding and also developments are expanding, which then brings you on to the urban expansion near airports. So not only are airports expanding and needing more space and more infrastructure on the airport, but urban areas close to airports are also expanding. The tower blocks, they need to build higher, sometimes closer, and this then gives the flexibility to achieve this where it's safe to do so, and currently that's not achievable at times due to the fixed over onerous surfaces that are in place. This is now achievable because of going to the performance based, but also the advances in aircraft performance. Back in the 1950s, the aircraft that were operating then the performance wasn't as good as it is today, so you got greater capabilities, more accurate navigation, better performance, better climb rates, better descent rates, etc. This then allowing the surfaces to be geared to the operation and be performance based and this is all around the operation of the aerodrome as opposed to one fixed surface no matter what the aerodrome operation is.

And then moving more towards a digital driven safeguarding. So bringing technology into place, we are now of the eTOD digital data. So you get better data, more accurate data, which then allows us to use GIS tools or other tools and technology to align the surfaces to them obstacles and data to keep them separated so obstacles remain outside of protected areas or are assessed when they go into protected areas appropriately. Next slide please.

So just do a quick refresh now on the key differences in the high-level way from where we are today currently and where we're going to moving transition to for the new surfaces. So at the moment on the left hand side you see the current areas there we are. So it's one fixed surface. They're over conservative at times. The traditional fixed surfaces, limited flexibility, penetration of OLS is generally not permitted, so then moving forward. We're not been more to a tailored surfaces that are performance based and geared to what the aerodrome operation is.

The introduction of the two types of surfaces that will be talked about later on in this webinar, which is the obstacle free surface and the obstacle evaluation surface, gives you ways and means to then manage obstacles and assess an appropriate manner in a multi-stakeholder engagement. This then giving greater flexibility for specific procedures and operational needs.

Penetration of the OES or adoption of the OFS established specific OES and other means can be done under an aeronautical study. This also complements the flexibility and the proportionality of the new services and engaging a multi stakeholder environment. And that is the key differences between where we are today and where we're moving to. We're moving more towards a performance based multistakeholder engagement and geared around the operation and the aircraft operation environment at the aerodromes. Next slide please.

OK, so that's me. I'm now going to hand over to my colleague Malte, who will take you through the next part of this webinar, give you more details on the new ICAO OLS framework.

Malte Karger   11:38
Hello, everybody. Thanks, Matt. The new concept of the new OLS includes two different sets of surfaces. So on one hand, we do have obstacle free surfaces and on the other hand, we do have obstacle limitation surfaces and both together made this concept of the new obstacle limitation surfaces. These types of surfaces are significantly different and the name actually indicates. the idea behind those sets of services. So on the one hand, the OFS (obstacle free surface) is a set of surfaces in the near runway environment. It's a set of set of surfaces which was derived from a safety perspective. It was a set of surfaces which, while making while coming up with the new dimensions was try to make it as small as possible, really from as I mentioned to the safety perspective. But on the other hand, this set of surfaces is to be meant free of obstacles, so it's much stricter, than what you use today, so it's really meant to be free, but on the other hand, is as small as possible.

The obstacle evaluation surfaces instead, it's a broader set of surfaces. This is where really flexibility comes in. You're going to see that we will have different obstacle evaluation surfaces. They can be modified, they can be tailored. And those surfaces have the intent to identify obstacles which may have an impact to your operations and to your flight procedures. These obstacles as they're further away from the runway normally, although they may have an impact and it does not always mean that there is a safety issue. You may come up with suitable mitigation measures, for instance, changes of your procedures, where a discussion needs to be made.
If it's obstacle, if it's acceptable, If potential mitigation measures are acceptable and can they be implemented, So what needs to be done is that you start this evaluation process. You start this discussion process with the stakeholders. So the obstacle evaluation surfaces trigger an aeronautical study. So they trigger the whole process of evaluation, mitigation measures, discussion and then the decision making of a new proposed obstacle. So the OES do not limit it limit obstacles per se. They really just trigger this aeronautical study process. The OFS again. They are, however, meant to be free of obstacles.

These sets of surfaces, and I will dial into an overview just in a second. They are, compared to the old obstacle limitation surfaces, much more performance driven. They are much more linked to the actually aircraft operating. They are much more linked to the operations and flight procedures which you have at a particular aerodrome. Which means that those surfaces, and especially the OES as they replicate the operational needs around the aerodromes, can be very different from airport to airport, and this is one of the aspects why the new concept is bringing much more flexible application and a much more performance-based approach from an aerodrome safeguarding perspective. Next slide please.

For the design of the new surfaces, and this is another key change which is included in the new provisions, is a new systematic of grouping aircraft, which is actually the aeroplane design groups, the ADG. So you're all familiar, I guess, with the Aerodrome Reference Code systematic, consisting of the code number and the code letter. However, this systematic does have its issues, especially when it comes to the code number systematic and those issues and further analysis has shown that for the design of surfaces, another systematic is more appropriate. So as part of developing the new OFS and OES, this new ADG was developed which utilizes again, 2 parameters. One parameter is known to you, which is the wingspan. So it refers to the size of aircraft. And of course with the size of aircraft, airspace protection is linked, but on the other hand it also refers much better way to performance of aircraft and one of the dominant performance parameters which we have is actually the speed of aircraft and what it considers is an existing categorization of speeds which we have in the ICAO domain, which is the approach speed categorization, which is defined in the ICAO PANSOPS document, which is defining the criteria for flight procedure design.

 

So the new design groups take those two elements, so wingspans or code letters, which is already familiar to you, so referring to dimensions of aircraft, on the one hand and on the other hand, it's referring to the approach speed and the existing categorization we find in PANSOPS from a performance perspective. And the combination of those two is the new aerodrome design groups and the new surfaces you're going to see they are much linked to these new groupings of ADG and the size of the surfaces can quite much differ depending on which aerodrome design group the surfaces are based on. So larger higher design groups result also larger,
more extensive surfaces and of course for smaller ADGS, so referred to slower smaller aircraft, less air space protection is needed and this is replicated with the new concept. Next slide please.

When you look into this new systematic, this is the table, which will become applicable for the new design groups. We have a characterization from I to IV and those two parameters, which is the approach speed or indicated airspeed at threshold. So this is the characterization of PANSOPS and the wingspan and you see those threshold values for wingspan, for instance 24, 36, 52 and so on in metres. This is actually those categorization which you already have with the code letter in Annex 14 and the threshold values which you have for the speeds as it is existing categorization for the approach speed. So those two combined and there was a lot of analysis being done in the background to find the proper grouping. There will give you the new aeroplane design groups. So what you need to do is you need to identify the aircraft which are operating and based on those aircraft you will find the grouping of the aircraft in which airplane design group that falls in. And for this basically design the surfaces for the particular runway. Here just as a note,
already and the tip but this will be I'm pretty sure also replicated in the further rulemaking task is that you need to be careful when selecting the ADG because when you select the ADG and as the surfaces are linked to this ADG, you may want to choose an ADG which is higher than you currently need, just to future proof. For cases where new aircraft coming in or new types of aircraft like the 777X comes in, which would be a Code F or Design 5 in the air and need the airspace protection with that in Code E air groups. So things like this need to be thought of. So it's a very crucial task to actually identify the proper aeroplane design groups for the development of the of Obstacle Limitation Surfaces. Next slide please.

So let's have a look into the obstacle free surfaces. As mentioned before, it's a set of surfaces which is in the direct vicinity of the runway. It is addressing the final approach to land manoeuvre. So the last visual bit actually only. So it's for the visual approach or for the visual segment of instrument approaches straight in to really get to the final bit down to the runway and also to potential go around, for which this provides protection for. The obstacle free surfaces consists of different surfaces. On the one hand, we do have an approach and transitional surface which you are already familiar with, but with revised dimensions, and we also have the inner approach, inner transitional, bulk landing surfaces, so the obstacle free zone as of today, that's another set. So those is the obstacle free surfaces. The regular approach transitional surface, although, becoming much smaller with the new concept. This is actually the limit for your obstacles which do not need to be near the runway, so any trees, buildings, so on and so forth, as a strict limit, however, so much stricter than the current surfaces that are currently handled in practice. So this is really a no-go area from a safety perspective. So there was a lot of data analysis that was done to derive the dimensions of those surfaces. So when you want look into it, the next slide please.

For the approach surface, it's approach the surface is looking in principle the same as of today. It is has this trapezoidal shape, so starting at some distance from the one way threshold, which by the way is the same. It has a base width and then diverges on each side to a length. The key difference here is just that the width of the surface is reduced typically, especially for instrument runway types, partially a significant reduction in the size. And also the slope, there's just one continuous slope of the surface, which is typically steeper compared to what we have. So it's a smaller and steeper surface in general, especially for instrument runway types, so much less demanding. However it is strict, as I mentioned before. What comes here also is that the slope of the surface, which is then replicated in the regulations, referred to a three degree approach angle as a standard, which is typical nominal standard approach angle. However, the approach the angle of the approach surface can be varied if you have different approach angles. So you can actually raise your approach surface if you have steeper approaches or if you have a lower approach than three degrees, which would just be legacy issues normally, then you actually would have to lower the approach surface as well. So there's a little flexibility in here already when it comes to the approach surface and the sloping. Next slide please.

The transitional surface. Although there have been some, let's say, changes in the detail, but it's a surface which looks very similar to what we have today. The upper edge is a little bit defined differently, but in principle it's the same. Here as a key change is that we have a slope of this transitional surface in all cases for all runway types, for all aerodrome design groups of 20% by the way. So it used to be either 14.3% or 20% depending on runway type and code numbers. In the future it will be 20%, so typically for most runway combinations is a steeper surface, so releasing airspace along the sides of the runway and the surface is also closer to the runway because it starts at the distance which is defined by the approach surface itself, which again also gets smaller in most cases. So the approach surface and the transitional surface which belong together, which provide this protection in the final bit of the approach land manoeuvre. They're actually getting quite smaller and releasing a lot of airspace along the runways and near the runway environment. However, what must be noted, although the transitional surface comes closer to the runways.
The runway strip remains as it is, so there's no change and for the time being with respect to the runway strip. Next slide please.

So as mentioned before, approach and transitional surface. This would be the limiting surfaces for all obstacles which do not need to be near the runway. When it comes to obstacles which need to be closer are also mobile obstacles. Currently what's defined is the obstacle free zone for precision approach runways at least, which consists of an inner approach in a transition and a balked landing surface. So this concept is retained of an obstacle free zone. There have been with respect to the obstacle free zone, just slight changes being done. So the inner approach surface basically remains the same for this precision approach runway types. The slope is a little bit adjusted so it matches the one from the approach surface. The length is a little adjusted accordingly, and also the upper limit of the inner transition surface is a little bit adjusted, but in principle the obstacle free zone remains as it is. What really is new for the inner approach surface is that this surface, together with the transition surface is introduced also for the other runway types, so for a non-precision runway type and also for a non-instrument runway type. So we have this concept of an obstacle free zone, not just for precision approach runways, but also for the other runway types, which fills the gap in the current regulations where it's not really well defined to what extent, obstacles which need to be near the runway are actually allowed on those runway types. It's well defined for the precision approach runways, but not that well for the other runway types. And with the introduction of the inner approach and inner transitional surface, next slide please, this gap is being filled, so we have a more clear criteria to what limit those obstacles maybe close to the runway.

What is interesting and you may see it on the figure that the inner transitional surface is also a new thing. So don't be surprised when you see that when you're going through the details is that the inner transitional service for a non-instrument runway type and a non-precision runway type. In the beginning has a vertical step, so it rises vertically before it slopes out and upwards. So it's a little bit different shape compared to the inner transition surface which we have for precision approach runways. So that's on purpose. Because the surface was also designed in such way that the existing runway holding points remain as they are. So there's actually no impact in practice with regards to runway holding positions. Next slide, please.

And here, for the sake of completeness, the balked landing surface, which we have for precision runways only by the way. So again, this existing obstacle free zone is basically retained for the precision approach runways. It was just minor adjustments.
OK. Next slide please.

So coming to the next set of surfaces, which are the obstacle evaluation surfaces.
This is really a complete new concept. As indicated in the beginning, this set of surfaces are not limiting obstacles. It's not a limiting surface per say. It is triggering those aeronautical studies. So the idea is that these obstacle evaluation surfaces identify the airspace where obstacles may have an impact to your operations.
But typically an environment where you may adjust operations also if wanted, of course. So it does not mean that you will always have an impact. You may have an impact, but it's not always the case, so. Therefore, as you may have an impact or not, as you may introduce mitigation measures or not, this set of service cannot be strict in nature, so it cannot be prohibiting obstacles, and this is the reason why it triggers this evaluation process that it triggers this aeronautical study process as mentioned before. These surfaces, the OES can be very flexible. They are much more linked to the actual operations and procedures you have at an aerodrome. So again, they can look very different from aerodrome to aerodrome. And even those surfaces can be modified to the needs of a particular aerodrome and its operation. The issue we have when it comes to procedures and operations of an aerodrome is that of course they can be very, very different from one aerodrome to another and as those surfaces trigger an aeronautical study, you need to be careful when defining those surfaces. And also ICAO was thinking about, well, how could such OES look like? How could they be proportionate? Because he could say, of course, when you're looking at all aerodromes worldwide, we look at all obstacles within, I don't know, 20 miles around the airfield and we pick up all the eventualities where operations of procedures take place. But this of course will trigger way too many aeronautical studies at most aerodromes for no reason. So instead of going that approach, ICAO introduced
a set of different obstacle evaluation surfaces for different types of operations. So you have different OES now in the provisions and you select the one which is appropriate to your operations at your particular runway. So let's go through this, to show you what's defined in this standard configuration. Next slide please.

So first of all, we have a horizontal surface, so it's similar to the horizontal surface which we have. So it's kind of this flat surface above the aerodrome. at specific heights with specific radii. Those radii and those heights are depending on the aerodrome design groups. So you have in the middle, closer to the runway an horizontal surface which is a little bit lower, which is a little bit smaller. For the smaller Aeroplane design groups one and IIA. This surface, by the way, is at 45 meters height. For faster and larger aircraft, which typically do not operate at such low altitudes, you have a different horizontal surface which is higher and which is larger. Larger because of the speeds, but it's also higher because the aircraft operated higher heights. So for aerodrome design group IIB, you have another horizontal surface which is a bit larger, which is not at 45, but it's at 60 meters in a standard case, so that's a bit higher and probably even higher ADGS to C up to IV, which even need more space because they are faster and they operate typically at higher heights, this horizontal surface is consequently larger and again higher. This is in the standard case 90 meters. So we have a kind of steps for this horizontal surface from 45 to 60 to 90 meters at different distances from the runways for the larger runways which have that operations. By the way, you do not need to implement all of those. Of course you don't need to only implement the horizontal service for the design groups of your particular runway, right? Because if you have just ADG I, you only need to implement the horizontal service for ADG I and that's it. So having a lot of smaller surface. However, if you have a faster aircraft, you need more space.

The surface, by the way, is designed according to the principles for circling approaches, respecting the criteria of ICAO PANSOPS from a principle applied procedure design perspective. So this is providing the protection for this visual manoeuvring and circling approaches about the airfield. These areas actually may get quite large, especially for the larger higher aerodrome design groups, larger than what we see today with the horizontal surface. But there's a reason for that, which is the criteria for the circling approaches, which is different. However, you may have aerodromes where you don't do this visual manoeuvring, where you don't do the circling approaches because you either cannot do it because of obstacles, or because you don't want to do it, be it capacity issues at large airports, or be it noise sensitive environments, where you don't want to have any kind of visual manoeuvring or circling approaches. So then in those cases you do not necessarily need this surface, you don't necessarily need to implement it. However, this surface does provide protection also for other types of operation, not just for the visual manoeuvring and circling, but it does also provide protection for, for instance, instrument approaches or early turning departures or something like this. So it does make sense to implement at least portions thereof, even if you don't have visual manoeuvring circling around the airfield. To make the decision a little bit easier, what portion thereof might be of interest, there's another obstacle evaluation surface. Next slide please.

Which is called the surface for straight-in instrument approaches. So this is a portion of the subsection of the horizontal surface consisting of the inner circle at 45 and then the rectangular shape at 60 meters. This is a surface, which protects, let's say, the most common instrument approach types with reasonable minima. So if you don't have visual manoeuvring, no circling in the airport, you may do not need to implement this horizontal surface. That's fine, but you should think about this surface nevertheless, because it does provide you a reasonable protection of your instrument flight procedures, instrument approach procedures straight in based on PANSOPS principles, at least two reasonable minima. However, this surface or the horizontal surface do not protect the lowest minima, so something like 200 feet for a precision approach is actually not really covered with obstacles up to 45 or 60 or 90 meters.
You may end up with minima, which is higher than that. So to cope with that effect, we have yet another obstacle evaluation surface. Next slide please.

Which is the service for precision approaches. So this is a dedicated OES for runways which are surfaced with precision approaches and low minima because you need to have another identifying surface for obstacles when you have such low minima so.
100 feet for cat 2 and so on. So in these cases, again, as I just mentioned, the horizontal surface and the surface for straight-in instrument approaches would not be sufficient for such low minima, and therefore here is another standard case, a common standard case, having precision approaches with no minima, there's another surface for that particular case. This, by the way, is based on the so-called basic ILS surfaces as defined in the ICAO PANSOPS from the applied procedure design perspective. All right. That's basically for approaches, a horizontal surface for straight-in approaches and precision approaches. And then we have further obstacle evaluation surfaces for the take-off case. So next slide please.

One of the surface is the take-off climb surface. It's a surface I think you're quite familiar with. It's a surface which we already have, but here's a significant change, this take-off of climb surface is not an obstacle limitation surface in the new concept, but it's an obstacle evaluation surface. That's the key difference. It triggers an aeronautical study. The surface looks very much similar to what we have today.
I should note that we have two types of take-off climb surface as part of the new concept, one for small and light aircraft with a mass of up to 5.7 tons, which looks like the current take-off climb service code number 1 and 2. And then we have a larger take-off climb service, which looks similar to the take-off climb surface for code 3 and 4 runways. However, this larger take-off climb service has been slightly adjusted to have it aligned with the actual operational needs of the aircraft operators, according to the principles of a ICAO Annex 6 and the aircraft performance manual. So that's a better alignment. This surface is flexible, it triggers aeronautical studies and the background is in the end that aircraft performance is so different, obviously from aircraft to aircraft, from operations to air operations and also from aerodrome to aerodrome the conditions are so, so different, which means that an obstacle at one aerodrome may cause issues for the aircraft operators. At another aerodrome, the same obstacle with the same height at the same location may not be an issue at all, or even at the same runway, this one obstacle may be an issue for one type of operation for this particular aircraft, but not for another one.
So it kind of doesn't really make sense to implement this from a regular perspective as an limiting surface as an OFS, but you need to look at it. So it's implemented as an OES. So allowing this aeronautical study because aircraft performance and therefore the impact is so hugely different.

Here, by the way, the take-off climb service, as I just mentioned, aligned with the Annex 6 and the aircraft performance manual requirements. It actually addresses take-offs and in particular for the larger aircraft considering the one engine out scenario, so contingency take-offs. This is actually what it's addressing. For regular departures, and especially when talking about instrument departures, this surface is actually not large enough, according to the principles of ICAO PANSOPS and the protection of instrument departure procedures. Larger areas need to be considered and the take-off climb surface would not be sufficient. Therefore, there's another surface. Next slide please.

Which is called the instrument departure surface as an OES. So this is a larger surface which is aligned to protection requirements of ICAO PANSOPS for instrument departures. Really addressing this need if you have instrument departure procedures.
If you do not have instrument departure procedures, by the way, you don't need this surface, right. You don't need to implement it. So for smaller airfields, probably not needed. If you have instrument departures, you should think about implementing this surface in order to address new obstacles, which may have an impact to your instrument departure procedures. So it's a wider surface. It's a little bit steeper than the take-off climb surface because instrument departures relate to all engines operating. In a normal case, it's a little bit wider because of the criteria of ICAO PANSOPS

OK, so that's the set of standard obstacle evaluation surfaces. Again, horizontal surface, surface for straight of instrument approaches, precision approach, surface for precision approaches, take your time surface and the instrument departure surface. So those surfaces, again, you would choose depending on the type of operations as you at which you have at an airport and which are described from an intervention perspective for common types of operations.

 

What you can do next slide please is, and that's also a new concept with the new surfaces is that you actually can modify those surfaces with their standard dimensions so you can develop so-called specific obstacle evaluation surfaces.
As the standard surface, again, just cover the most common types. So straight-in approach, departure, straight out, more or less common approach, minima if you have situations where you differ from that. For instance, curved approach is really turning departures, missed approaches, low minima stuff like this or you're not, you're not circling on one side of the runway. You have no visual manoeuvring at all at one side of the runway or very high, high, high, minima, whatever. You have the chance to modify your obstacle evaluation surfaces, which is then called specific OES.
So you have the chance to do this. You have to the chance to add areas where needed. You have the chance to lower the areas where needed, but you also have the chance to actually cut off areas where you don't have operational procedures taking place or you have the possibility to increase heights when you have steeper gradients defined, for instance, or higher minima defined. When doing so, however, of course you need to be very careful. You need to engage all the relevant stakeholders, especially the expertise of flight procedure designers, to really look into the details, which areas might be cut off or which areas might be changed according to the operations and procedures you have at a particular runway end.

In addition to the modifications of those standard surfaces, you can even go one step ahead, which is defining your own obstacle evaluation surface. So really have tailored obstacle evaluation service to optimize the system to really identify all potential areas which are needed. And at the same time to balance the needs of the aviation environment, but also on the urban environment on the other side. So you have to have in mind that those OES trigger aeronautical studies, right. And so the larger the surfaces are, the more aeronautical studies you need to do, the smaller they are, less aeronautical studies you need to do. However, then you lose flexibility also in the flight procedure design perspective, but with the means of modified and especially with the means of tailored OES, you can try to find the right balance between needs of aviation and environment, between the need for aeronautical studies on the one side, but also with respect to release of airspace for urban developments, for instance, so this was possibility.

 

Another possibility which you have, when you have tailored OES, you may if wanted, and if it's reasonable, also to include other safeguarding aspects. For instance, protection of CNS facilities, protection of lighting equipment if deemed necessary. If deemed appropriate, it could be integrated. It does not need to be. But that's also a possibility, which means altogether that the OES may look very, very different from one airport to another airport from one runway end another runway end. Either using the standard OES depending on which OES we actually choose, starting from there, how they are being modified, if they're modified, or even if you come up with tailored OES. Next slide please.

 

They may look very, very different and here just a couple of different examples how tailored OES may look like and as you can see the variety is tremendous depending on the type of operations and procedures you have of course when doing so. However, you need to be very very careful because once the surfaces are established, of course, the likelihood is quite high that obstacles will encroach, and over time you may lose the flexibility into changing your procedures. So again, the same as we have for the selection of the aeroplane design groups, also, when selecting and modifying and coming up with tailored OES, you should be very careful. You should have not only the existing procedures and operations in mind, but also potentially new procedures, for the future new types of aircraft to be future proof in the end.
So to say. And with that, I'd like to hand over back to Matt, for aeronautical studies. Thank you.

 

Matt Roberts   46:48
Thanks, Malte. OK, so I'm going to now just briefly talk about aeronautical studies and the reasoning and how they are established moving forward, so the aeronautical study, you can see the definition on this slide. It's a structured way to assess safety when there is a potential penetration of an obstacle evaluation surface, to see if it can be accepted or not, and what mitigations need to be in place. Also, what changes may need to be done to accommodate the obstacle. So that's what the idea of the aeronautical study is.

The goals of it are to ensure that any changes in the airspace environments don't compromise flight safety or the operation, they're efficient and they meet regulatory compliance. It's a multi stakeholder study, so it's not a silo. One of the key things when you do an aeronautical study is you need to identify your stakeholders. There'll be standard stakeholders, but not limited to, and that's so you can identify potential hazards to aircraft operation from all angles, but also that helps to bring in potential mitigations and potential solutions in a multi stakeholder environment. By doing that, by having a multi stakeholder environment and multi stakeholder engagement and discussions and safety assessments in this study, it also then makes it a proportionate way. It makes it an informed way, for decision making and then maintaining a proportionate, reasonable way of protecting flight safety, but also releasing airspace to the urban environment as and when necessary. Next slide, please.

So what is required? An aeronautical study is typically triggered if there's penetration of the OES. You can see on the slide here the OES surfaces are listed, and it's also penetrated and it also activated if there's a penetration to airspace that could have an impact on the current flight procedures, but also as we've mentioned briefly Malte there, before planned flight procedures, where your surfaces will be established to protect that, and that's where the aeronautical study will come into play. The idea of the study is to look at safety, so assess the object and the obstacle in an informed manner with multi stakeholder to see if it adversely affects the flight safety in them areas, depending on what it's penetrating, and also what mitigation could be brought in place to make it safe, if it does adversely affect it or what changes can take place. That also supports the operational side and the operation can then potentially be adjusted if reasonable to make the obstacle be accepted and also
maintain safety or on the other hand, it may be not appropriate for the obstacle be there to maintain operational regularity and also compliance. So they're the key things that we're looking at when you get the multi stakeholder engagement, for this, and if required. It's to look at safety and look at operational situations at the airport and to see what the obstacle impact is to them. Next slide please.

So this is a typical input, not limited to, but typical inputs to an aeronautical study. So you'll find that you probably do this when you're penetrating an OLS and doing your safety assessment today. But what this is doing now moving forward is doing it in a more structured way and it's making sure that full engagement is there so, the obstacle information, you'll need all the information about the obstacle, the accuracy of the precision of the height, location, etc. This then feeds into seeing if there’s any impact on the operation. You look at where it is in relation to the runways and the flight procedures, you look at your aircraft mix etc. This is where bringing your multi stakeholder into this environment, makes it more accurate. You're getting the most up-to-date information from your operational side, your flight operations, your based operators. This helps to feed the aeronautical study. You then look at the existing planned instrument flight procedure. So this is where if you've got instrument flight procedure, you'll be bringing your APDO into the aeronautical study to give informed information on the exact criteria that needs to be met and any mitigations or any changes that can be accommodated, but also need to look at any future plans or changes to the flight procedures also when assessing this in the aeronautical study.

Surface interaction - So which means the OES surface are penetrated by how much. So the depth and extent to that penetration that needs to be assessed and looked at and that will be where potentially you'll bring the body in, the stakeholder that's constructing or managing this permanent or temporary obstacle to work with them and to get that more accurate information, to get that exact details. This way in the aeronautical study, you're not doing any safety assessments or studies in a silo. You're doing a lot of safety assessments that form an informed study, which then gives you the full picture and the full holistic view of the actual safety risk. And that's the typical inputs to an aeronautical study from multi stakeholders. Next slide please.

 

So you'll see the steps that you go through with an aeronautical study. So it's classifying first what the infringement is, where it is, is it OFS, is it OES? You then move on to determine what the impacts are, which we've talked about in the previous slide, some of the areas. So that's your next stage. When you get to that, you'll then move on to the evaluation and that's where you get into your further multi stakeholder engagements, to look at the obstacle requirements, changes, etc.
Then when you've done that, that allows you then to move into the mitigation areas of seeing what can be mitigated, what can be redesigned, what can be eliminated or changed. And further safety assessments may take place when you're doing these mitigations as part of the study. And the key thing then is this multi stakeholder study is then documented and the documented conclusion is there. Any rationales, any mitigations that are in place, and it's all documented in a clear manner, because sometimes if there's a lot of mitigations, you need to make sure that their mitigations are implemented when the obstacle is erected. Next slide please.

So the outputs and decisions, so a robust aeronautical study, should have a clear statement and it should show what's affected, what service is affected and how. It should also give the safety and regulatory determination, so explaining what the obstacle is, where it is, what it's penetrating, if it is or isn't acceptable. And then attached to that mitigations to make that obstacle acceptable or not acceptable and documenting that. So it's showing them clearly and showing all mitigations, not just certain stakeholders mitigations, it's the full holistic overview of the risk that needs to be mitigated and safety assessed. And then the key thing is recording for stakeholders and recording of the stakeholders that took place in that aeronautical study and they could be not limited to the stakeholders that have mentioned in this here, the aerodrome operator ANSP procedure, design and planning authorities, there may be further people that you need to bring into these stakeholders, into these aeronautical studies depending on what it is you might need to bring your flight operation based operators into this. You may need to bring construction companies into this, etc. So it's not a limited list, it's a basic standard list to start off as a minimum, but certainly not a list. That can’t be expanded if required. Next slide, next slide please. Next slide please. I don't know if it's moving and I can't see the slide moving on my side. Hello. Nyree or Mike, can you hear me?

Mike Sparrow   57:35
Yes, I can hear Matt. I'll just try just to contact Nyree, see what the issue is.

Matt Roberts   57:40
Ok, sorry about this, just a minor technical issue on moving the slide on.
While we're waiting for the slides to come back, I can actually, I will talk through what will be shown on this slide when it reappears. So it's the roles and responsibilities of the stakeholders. Might be just in time. Move on to the next slide, please.

OK, that's great. So we get the roles and responsibilities, an aerodrome operator, their role and responsibility when they're a stakeholder, it's the implementation of a new OLS locally and the managing of that OLS when it is established. The safeguarding of and the supporting an evidence gathering. They're the key person, the aerodrome operator from the safeguarding point of view, cause they're the ones that are responsible for protecting the surfaces but also managing the surfaces. So that is their key responsibility and key part of the stakeholder engagement on the aeronautical study. They will bring all of the up-to-date technical information to the to the group. The CAA, so we're responsible for integrating the new OLS into the National Regulatory framework and provide oversight. And we're also there to enable aeronautical studies to be processed and take place. So that's part of where we will fit into the aeronautical study and that's not limited to that may change moving forward and all of this is open to consultation moving forward in the coming weeks to months anyway. Flight procedures, designers and ANSPs, they're there to
assess and advise and mitigate and also redesign where required the instrument flight procedures that are solely within their domain as and when you have an instrument flight procedure that you need to assess and mitigate or change for potential impacts within an aeronautical study. It may be the fact that you don't always need this stakeholder, particularly if you haven't got instrument flight procedures or the instrument flight procedure is not being impacted in any way.
Planning authorities and developers. So the planning authorities are there to proactively provide accurate obstacle filtration, but also when you hit them, filtrations are there to provide the accurate data, the engagement and recognising the OES penetrations and the requirements of an aeronautical study when such penetrations take place. So they're the first point of call that you will be alerted to any kind of penetration that has been planned for your OLS surfaces. And that is the key responsibility of them stakeholders in a very brief high-level way, not limited to, but that's where their area of expertise lies within the studies. Next slide please.

OK, I'm now going to hand back to Nyree, who will now talk through the new OLS and what it means for aerodromes. Thanks for your time.

Nyree Millar-Bell   1:01:51
Thanks, Matt. So the new ICAO OLS, So what we'll be looking for, aerodromes updating their safeguarding requirements. So aerodromes will need to adopt the new OFS and OES structure replacing the legacy OLS surfaces that we have in today.
So safeguarding maps that are lodged with local planning authorities will need updated to make sure that it reflects the new surfaces. Impact on planning and development control. So local planning authorities may need to update their guidance to reflect modernised criteria.
Aerodrome may experience changes in the types and frequencies of consultations just due to the more proportionate safeguarding triggers. Transition and Change Management, so existing obstacles and developments mainly reviewed under the new criteria. And staff training, updating of your policies and communications with stakeholders, particularly local planning authorities, developers and industry will be essential. So really successful implementation will really depend on effective change management and early engagement with stakeholders, ensuring that the new framework is understood and applied consistently.

So moving on then to the UK implementation approach. So the ICAO applicability date is 21st of November 2030 and that's as stated in the ICAO state letter. So it will be a phased UK transition. So the UK will move towards the new OFS/OES structure through a phased implementation aligned with national regulatory updates and project milestones. Preparatory work and engagement and regulatory alignment will continue through quarter one of 2026 ahead of the ICAO applicability date.

Regulatory alignment, so integration of the new OLS into updates of CAP 168, CAP 738, CAP 1732 and CAP 232. So all this new structure and framework will be integrated into those CAP documents ensuring UK standards reflect ICAO guidance while supporting UK specific safeguarding needs. Then stakeholder engagement. So ongoing collaboration with aerodromes and we have a number of OLS workshops that we're running this year, across the UK for everyone to join, we have ongoing discussion and collaboration with the DfT, which will be explained in the next slide, local planning authorities and the industry as well, and we'll also have a formal consultation planned as part of the UK adoption process.

OK, I'm going to hand over to Mark, who's going to give an update on where we are with the Aerodrome safeguarding circular.

Mark Ashley   1:05:03
Hi everybody, I'm Mark Ashley. I'm Aviation Safety Policy Advisor at the UK Department for Transport and this part of the session is just to explain the direction of travel in how we're updating the aerodrome safeguarding circular. Explain how that fits in with the planning system and talk through the process from here. The aim of this session is just to set out the direction of travel rather than to announce any decisions. Next slide please.

So if we can just touch briefly on the problem that we're addressing. So the driver for this policy development is outdated and unclear guidance, not a change in risk appetite in itself. And we've got a current safeguarding circular which dates back to 2002 and the last time it was refreshed was in 2016, and the problem with that is it no longer reflects how planning or aviation works in practice today, and it needs to be updated in line with the new ICAO requirements. Development around aerodromes has become more complex, with taller buildings, renewables and temporary structures, and as touched on throughout this webinar, international standards have also moved on. So the issue that we're addressing here is really about clarity, consistency and keeping the guidance up to date. Next slide.

So I can just sort of go through the planning law hook. So safeguarding operates practically through planning and the circular is the practical interface. So yes, aviation safeguarding live through the planning system via planning applications and consultations and it's not through a separate aviation consent mechanism and the safeguarding circular is the key planning facing document that explains when consultation is required and how aviation safety considerations should be taken into account. Just to know as well that MHCLG, so the Ministry of Housing, Communities and Local Government is the formal owner of National Planning guidance and legislation, whereas DfT leads on aviation safeguarding policy and technical content and working closely with the CAA and others. So the update is really about making sure that the planning aviation interface is clearer and more consistent in practice. Next slide please.

So the intent of this is basically to protect aviation safety while supporting sustainable development, and that means enabling growth where risks can appropriately be managed. And importantly, it's not about restricting development or introducing new hurdles. It's about clearer, more predictable guidance so that everybody involved in the process, so that's developers, local authorities, aerodrome operators, understands what's needed and engages early in the process. And people are, you know, those parties are talking to each other. Next slide, please.

So this is just really to just understand a little bit more about what this update will and will not do and just to kind of clarify expectations. So there are no new powers or a shift in decision making. This is about clarifying roles and expectations and supporting that more consistent application of safeguarding guidance and encouraging early engagement to reduce late-stage issues in the process. So it won't introduce new planning powers, change who makes planning decisions, or alter the wider statutory safeguarding framework. And learning decisions will continue to sit with local authorities or where relevant, the Secretary of State and the safeguarding circular, when it's updated, needs to reflect, as we've discussed throughout this webinar, the shift from binary OLS to obstacle free surfaces and obstacle evaluation surfaces and update that terminology and references to align with the revised ICAO Annex 14 and clarify the role of risk based assessment and proportionality and planning decisions. It will also need to explain that transition to implementation while making clear that there's no new aviation consent regime or change to planning powers. Next slide, please.

Sorry, if I could just have the next slide. I don't know if it's coming up. I can talk to you otherwise if here we are. So yes, so just to touch on how we get there. So the key message here is that we are developing a stage process and consultation will be built into that process. So we're at an early scoping stage. DfT is leading the work on the safeguarding circular, working with CAA and other government departments, including MHCLG, who are the former owner of the guidance. And there's also a crossover with other government departments such as Defra, when we're looking at bird strike risks and defence, when we're looking at military aerodromes, so we working across Whitehall to clarify scope and approach, we then expect to move into a public consultation so stakeholders can help shape the clarity and the practical application of the guidance and following that the circular would be finalised and published to sit alongside national planning policy. So yes, so there will be opportunities for industry and others to engage as that develops and yes, that's all I had to hopefully that is that is helpful, and I just want to thank everybody for their time today and if I can hand back to you Nyree if that's OK.

Nyree Millar-Bell   1:11:08
Thanks for that, Mark. So that takes us to the end of the webinar. Please, if you have any questions, please leave them in the chat box or alternatively e-mail NewOLS@caa.co.uk. And just want to thank everybody that's registered and is on the call. I appreciate you listening. Thank you very much.