If OLS (obstacle limitation surface) is not maintained properly and surface is penetrated by obstacles around 125% of its permissible height, how to assess the risk?
I would like to start by saying that the penetration can be 0.125% or 125% it is still a penetration, now having said that let's clear up a couple of things before.
One is that the Obstacle Limitation Surfaces act more for airport planning to control the installation of new obstacles.
Two they are not enough! You may have some structures that do not penetrate the OLS but would become obstacles from the instrument flight procedure design (IFPD) part or may affect the radio electric signals of your different navaids and radars.
So basic workflow 1. Check OLS 2. Check PANS OPS 3. Check CNS (radio signals) 4. Repeat cyclicly (put procedures in place to approve structures within certain areas around the airport)
Now back to the question, if you have determined that a surface has been penetrated and the obstacle exists you will first determine if the structure was granted legal way to be built or just someone decided to build it and no one checked. You may take this to court in order to get it torn down or other means, also check if it may be shielded by other pre-existent obstacles. If the structure can't be removed because of many reasons then after the obstacle has been identified you will need now to check if they impact your operations from a PANS OPS point of view, maybe this is not a control obstacle even if it penetrates the surface. In this case the risk of it being an issue will be lower for aircraft that are following the instrument procedures and for VFR they are supposed to be see and avoid the structure so it may need lighting and paint. Of course the best thing is for it not to be there but through procedures the risk can be minimized
If the obstacle affects your PANS OPS procedures then this will result in an increase of minimum obstacle clearances which may be annoying but not always result in a change in profile depending on how the procedure itself was designed.
The risk assessment part you will use some version of the risk matrix by identifying the different possible hazards and the probability of them ocurring, either you have operational experience or you will consult with experts to determine them, this could be pilots, ATC, etc. At the end you will need all of the risks to be addressed if applicable with the safety measures to have themm all within a tolerable state, if that is not possible and something remains in the intolerable region then you may have a big issue.
I would like to start by saying that the penetration can be 0.125% or 125% it is still a penetration, now having said that let's clear up a couple of things before.
One is that the Obstacle Limitation Surfaces act more for airport planning to control the installation of new obstacles.
Two they are not enough! You may have some structures that do not penetrate the OLS but would become obstacles from the instrument flight procedure design (IFPD) part or may affect the radio electric signals of your different navaids and radars.
So basic workflow 1. Check OLS 2. Check PANS OPS 3. Check CNS (radio signals) 4. Repeat cyclicly (put procedures in place to approve structures within certain areas around the airport)
Now back to the question, if you have determined that a surface has been penetrated and the obstacle exists you will first determine if the structure was granted legal way to be built or just someone decided to build it and no one checked. You may take this to court in order to get it torn down or other means, also check if it may be shielded by other pre-existent obstacles. If the structure can't be removed because of many reasons then after the obstacle has been identified you will need now to check if they impact your operations from a PANS OPS point of view, maybe this is not a control obstacle even if it penetrates the surface. In this case the risk of it being an issue will be lower for aircraft that are following the instrument procedures and for VFR they are supposed to be see and avoid the structure so it may need lighting and paint. Of course the best thing is for it not to be there but through procedures the risk can be minimized
If the obstacle affects your PANS OPS procedures then this will result in an increase of minimum obstacle clearances which may be annoying but not always result in a change in profile depending on how the procedure itself was designed.
The risk assessment part you will use some version of the risk matrix by identifying the different possible hazards and the probability of them ocurring, either you have operational experience or you will consult with experts to determine them, this could be pilots, ATC, etc. At the end you will need all of the risks to be addressed if applicable with the safety measures to have themm all within a tolerable state, if that is not possible and something remains in the intolerable region then you may have a big issue.