Deviation from the SID due to adverse weather
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Deviation from the SID due to adverse weather
Hello everybody!
This is my first post here, and I would like to pose a question regarding the dilemma of authorizing a SID deviation below the MSA or MVA due to adverse meteorological conditions (even if the pilot reports having visual contact with the ground).
According to the Doc 4444, PANS-ATM: "when vectoring an IFR flight and when giving an IFR flight a direct routing which takes the aircraft off an ATS route, the controller shall issue clearances such that the prescribed obstacle clearance will exist at all times until the aircraft reaches the point where the pilot will resume own navigation". Since a SID is an ATS route and a turn to some heading is a clearance issued by the controller, the SID deviation cannot be provided by the controller before reaching the MVA or MSA.
The problem appears when either
In those circumstances, the controller faces the following dilemma:
Thank you beforehand.
This is my first post here, and I would like to pose a question regarding the dilemma of authorizing a SID deviation below the MSA or MVA due to adverse meteorological conditions (even if the pilot reports having visual contact with the ground).
According to the Doc 4444, PANS-ATM: "when vectoring an IFR flight and when giving an IFR flight a direct routing which takes the aircraft off an ATS route, the controller shall issue clearances such that the prescribed obstacle clearance will exist at all times until the aircraft reaches the point where the pilot will resume own navigation". Since a SID is an ATS route and a turn to some heading is a clearance issued by the controller, the SID deviation cannot be provided by the controller before reaching the MVA or MSA.
The problem appears when either
- the aircraft is lined up on the runway and the pilot asks the TWR controller for an immediate turn after being airborne, or
- the aircraft has already taken off, and the pilot asks the approach controller for an immediate turn to some heading for weather avoidance
In those circumstances, the controller faces the following dilemma:
- Deny the SID deviation until the plane has reached the MVA (causing the aircraft to enter the storm cell), or
- Authorize the SID deviation, against the rules (with the implications that decision might have in case of an accident).
Thank you beforehand.
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I cannot possibly speak authoritatively, but it seems that the crux of your problem and the possibility is your statement that the pilot is requesting the heading and has visual contact with the ground (and therefore is maintaining visual separation from terrain)
ATC is therefore NOT vectoring. You are not telling the pilot to fly a certain heading, he is requesting a heading. I would expect, if making the same sort of request, to hear something like this-----"Cleared to avoid at your discretion, maintain visual separation from the ground, inform me when you can proceed on course."
All over the world, I have had similar clearances. Take a MSA.....It relates to a safe altitude, based on an obstacle within 25 miles of the (for example) VOR. So this could be a hill, a radio mast or what-ever. If the pilot knows this obstacle, and it could be a tower he has passed already or a hilltop 24 nm away, then he knows he is safe, even though he is lower than the MSA, because he knows his position relative to the obstacle or terrain feature.
Approaching a ridge south of Albuequeque, ATC got an automated terrain warning on me. I told him I had good VMC, terrain in sight and I would remain at present altitude and maintain own separation from terrain. Roger. I was landing at an uncontrolled airport on the other side of the ridge and climbing to his MVA for the area was impractical and unnecessary.
Hope that helps
ATC is therefore NOT vectoring. You are not telling the pilot to fly a certain heading, he is requesting a heading. I would expect, if making the same sort of request, to hear something like this-----"Cleared to avoid at your discretion, maintain visual separation from the ground, inform me when you can proceed on course."
All over the world, I have had similar clearances. Take a MSA.....It relates to a safe altitude, based on an obstacle within 25 miles of the (for example) VOR. So this could be a hill, a radio mast or what-ever. If the pilot knows this obstacle, and it could be a tower he has passed already or a hilltop 24 nm away, then he knows he is safe, even though he is lower than the MSA, because he knows his position relative to the obstacle or terrain feature.
Approaching a ridge south of Albuequeque, ATC got an automated terrain warning on me. I told him I had good VMC, terrain in sight and I would remain at present altitude and maintain own separation from terrain. Roger. I was landing at an uncontrolled airport on the other side of the ridge and climbing to his MVA for the area was impractical and unnecessary.
Hope that helps
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Our noise abatement regulation prohibits the authorization to deviate from an SID if the request is made before take-off, in such a case the aircraft should take a different departure runway. Of course the obvious outcome since the implementation of this rule was that at least the local crews didnīt ask anymore but made the initial call after departure with the request to turn early (or sometimes after having already turned).
Now we have intersecting runways and itīs quite interesting and unsafe having the departure turn early with no warning and going opposite to the inbound traffic for the other runway. Therefore most guys have found ways to avoid adhering to the rule.
The MSA/MRVA is no big problem for us, most departures are above it while still over the runway.
Now we have intersecting runways and itīs quite interesting and unsafe having the departure turn early with no warning and going opposite to the inbound traffic for the other runway. Therefore most guys have found ways to avoid adhering to the rule.
The MSA/MRVA is no big problem for us, most departures are above it while still over the runway.
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Thank you very much for your reply!
I know I am not vectoring the aircraft, but the regulations in force forbid me to provide an instruction which takes the flight out of its route below a safe altitude (read the second part of the Doc 4444, PANS-ATM statement I referred to). You would probably think that it is enough to state something like "Cleared to avoid at your discretion, maintain visual separation from the ground, inform me when you can proceed on course.", but I cannot hand over the responsibility to the pilot, even if he is willing to assume it.
Just to give you an example that takes place every day, imagine you are arriving to an airport along a designated STAR, and at some point, ATC clears you to fly to some direct point or navigation aid in the STAR (no radar vectoring, therefore). The controller cannot clear you below his minima, even if it is cavok and during daylight, and you state that you have ground contact and able to assume terrain separation.
As far as I know, the only chance the ATC has to hand the responsibility of terrain avoidance over to the crew is when performing a visual approach or a approach in contact. But there is not such an equivalence for a departing aircraft, let alone with adverse meteorological conditions.
With regard to your comment about the pilot's knowledge of surrounding obstacles, I don't find it safe to rely in such "procedures". MSA or MVA are published not as references, but as minimum altitudes (as the initial letter says). There have been numerous CFIT accidents as a result of minimum altitude violations by overconfident pilots who somehow lost their situational awareness. It also seems to me strange that airline regulations allow such behaviours.
Wouldn't it be safer and more reasonable to delay the take off until you think you can reach a minimum altitude above which the controller can give you the requested turn?
Just to give you an example that takes place every day, imagine you are arriving to an airport along a designated STAR, and at some point, ATC clears you to fly to some direct point or navigation aid in the STAR (no radar vectoring, therefore). The controller cannot clear you below his minima, even if it is cavok and during daylight, and you state that you have ground contact and able to assume terrain separation.
As far as I know, the only chance the ATC has to hand the responsibility of terrain avoidance over to the crew is when performing a visual approach or a approach in contact. But there is not such an equivalence for a departing aircraft, let alone with adverse meteorological conditions.
With regard to your comment about the pilot's knowledge of surrounding obstacles, I don't find it safe to rely in such "procedures". MSA or MVA are published not as references, but as minimum altitudes (as the initial letter says). There have been numerous CFIT accidents as a result of minimum altitude violations by overconfident pilots who somehow lost their situational awareness. It also seems to me strange that airline regulations allow such behaviours.
Wouldn't it be safer and more reasonable to delay the take off until you think you can reach a minimum altitude above which the controller can give you the requested turn?
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Thank you
We don't have national rules about this. It seems logical to me and also convenient to have standard international rules. Otherwise it would be a mess, since pilots and airlines come from everywhere.
I have some knowledge of nearby obstacles, but that doesn't allow me to provide such instructions, because I cannot guarantee, for example, that ground proximity warnings will not be triggered in the cockpit, nor do I know navigation tolerance errors in the instruments of the aircraft, or required minimum rates of climb to clear the obstacles (what would happen in the event of engine failure, for example?), etc.
And you say that If I authorize a SID deviation requested by the pilot below minima I am not vectoring the aircraft nor providing a direct route, but what is the difference? I am authorizing a turn to some heading or some point below minimum safe altitude. The pilot is just asking for such clearance. It doesn't really matter who is the first to propose it, because in the end, it has to be approved by the ATC.
I have some knowledge of nearby obstacles, but that doesn't allow me to provide such instructions, because I cannot guarantee, for example, that ground proximity warnings will not be triggered in the cockpit, nor do I know navigation tolerance errors in the instruments of the aircraft, or required minimum rates of climb to clear the obstacles (what would happen in the event of engine failure, for example?), etc.
And you say that If I authorize a SID deviation requested by the pilot below minima I am not vectoring the aircraft nor providing a direct route, but what is the difference? I am authorizing a turn to some heading or some point below minimum safe altitude. The pilot is just asking for such clearance. It doesn't really matter who is the first to propose it, because in the end, it has to be approved by the ATC.
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You have to assume the pilot is aware of the local terrain and is therefore not going to request a heading that will put them in a dangerous position.
Therefore: if the pilot asks for a certain track or heading for weather: "approved"
As an ATCO, I only tend to have to worry about separating against other traffic. Modern aircraft, with latest generation weather radar and EGPWS, can probably plot safer routes out of my airport than I can in Cb activity.
Therefore: if the pilot asks for a certain track or heading for weather: "approved"
As an ATCO, I only tend to have to worry about separating against other traffic. Modern aircraft, with latest generation weather radar and EGPWS, can probably plot safer routes out of my airport than I can in Cb activity.
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You have to assume the pilot is aware of the local terrain and is therefore not going to request a heading that will put them in a dangerous position.
However, not all pilots are familiar with local terrain. If one of them requests some heading because of adverse weather ahead and I approve it (assuming that he knows what he is doing), the pilot might think that flying that heading is safe. That's the danger of the double assumption.
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You refer me to the second part of the text from Doc 4444 - which applies only if the first part is true.
No, the bit of Doc 4444 quite clearly explains the times that ATC is responsible for issuing clearances and instructions that assure terrain clearance. In all other situations it is the pilot's responsibility.
What I did say was that the controller should know about the surrounding terrain.
The difference is that when you vector the aircraft, you are telling it where to go, if you authorise a direct track, you are effectively aware of the track it will follow - and the books say that you have to make sure that it is terrain safe. When you authorise a pilot to deviate from a route without knowing where it will go, i.e. the pilot is doing the navigating, then it's got to be up to the pilot to look after the terrain clearance.
you are trying to apply a rule that, firstly, doesn't really apply in the situation you're talking about
I don't know where you work (or where your example comes from)
but think about an airport without SIDs and without approach radar control. There are thousands of take-offs every day from airports like that - how are they allowed to happen?
Thank you very much.
Last edited by SquawkStandby; 16th Oct 2013 at 16:51.
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The definition of a SID as per Doc 4444 is " A designated instrument flight rule (IFR) departure route linking the aerodrome or a specified runway of the aerodrome with a specified significant point, normally on a designated ATS route, at which the en-route phase of a flight commences. "
Note it is from the runway to a designated route.
A controller cannot authorise a deviation from a SID as any variation to the SID may compromise the design of the SID. There could be more to it than just being above an MSA such as nav aid reception or a climb gradient to reach a subsequent MSA (PBN SIDs in particular). The procedure designer has taken this into account in the SID design. Strictly speaking the controller cannot even offer "at your discretion" for a deviation since the controller does not have the authority to give the pilot the choice, the pilot is required to maintain the centreline of the procedure (SID).
As soon as the aircraft is above a recognised MSA then the controller can cancel the SID and provide a radar control service or continue under the provisos for direct routing in a procedural environment. Up till that time the pilot is on his own.
Note it is from the runway to a designated route.
A controller cannot authorise a deviation from a SID as any variation to the SID may compromise the design of the SID. There could be more to it than just being above an MSA such as nav aid reception or a climb gradient to reach a subsequent MSA (PBN SIDs in particular). The procedure designer has taken this into account in the SID design. Strictly speaking the controller cannot even offer "at your discretion" for a deviation since the controller does not have the authority to give the pilot the choice, the pilot is required to maintain the centreline of the procedure (SID).
As soon as the aircraft is above a recognised MSA then the controller can cancel the SID and provide a radar control service or continue under the provisos for direct routing in a procedural environment. Up till that time the pilot is on his own.
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Back to the initial quote, you are referring to DOC 4444, par.8.6.5.2, ATS Surveillance Services, so anything written there applies to radar environment. In Procedural you cannot even authorize direct routing..."riteorbit" would you please point out the doc that states otherwise? I'm not being ironical, just interested.
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The definition of a SID I quoted came from D4444 Chap 1 Definitions page 1-15.
NZ MATS allows direct routing in a procedural environment with conditions of pilot request, pilot navigation, above an area MSA. I'll have to search a bit further to see if that is ICAO.
NZ MATS allows direct routing in a procedural environment with conditions of pilot request, pilot navigation, above an area MSA. I'll have to search a bit further to see if that is ICAO.
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I had (and still have in proc enviroment) simillar problem in the past.
high terrain area , adverse weeather,and one runway for departing (when weather is adverse ) ,non collaborative ATC authority,and pilots that must fly at that very moment.
To avoid to lengty explanation, for us it has worked perfectly .
radar, we would like to divert due to....
aircraft, any SID deviation below MSA (we are talking about 6000 ft minimu,but in some direction fl 100 is more accurate value ) AT YOUR OWN RENSPOSIBILITY ! report completed
If it is immediattelly after departure, than its met radar should (and do in real life ) warned him/her about CB cell in front of their nose. In that case they shouldn't depart
but they departed, and then waiting for someone else to take their part of responsibility. how yes no.
if it happens ,some time between departure and 6000, than because of high airpost elevation (close to 2000ft ) it si not big deal to reach 6000' ,and thare is no real threat,if real threat exists, than pilot either will have full ground contact (that will allow him to make his own separation )
or will climb enough fast for MSA,and than safe vectoring.
Whatever is applicable in your case,remember that nobody will bring cigarets abnd towels in jail, if you have to expalin to public prosecutor' question :
What was reason behind vectoring aircraft below MSA ???
In our legislation, only 5 years of prison.
Interesting or not,I changed airport, from rad to proc,and FL 100 minimum for all combinations.
I have had, many of such cases( our summers are excellent,Cbs appear only in the afternoon ) and
below FL 100 at your own rensposibility
works even better,once they learned that rules are rules.
so keep it to doc 4444,if it is ok for local authorities than it is even more ok for us.
high terrain area , adverse weeather,and one runway for departing (when weather is adverse ) ,non collaborative ATC authority,and pilots that must fly at that very moment.
To avoid to lengty explanation, for us it has worked perfectly .
radar, we would like to divert due to....
aircraft, any SID deviation below MSA (we are talking about 6000 ft minimu,but in some direction fl 100 is more accurate value ) AT YOUR OWN RENSPOSIBILITY ! report completed
If it is immediattelly after departure, than its met radar should (and do in real life ) warned him/her about CB cell in front of their nose. In that case they shouldn't depart
but they departed, and then waiting for someone else to take their part of responsibility. how yes no.
if it happens ,some time between departure and 6000, than because of high airpost elevation (close to 2000ft ) it si not big deal to reach 6000' ,and thare is no real threat,if real threat exists, than pilot either will have full ground contact (that will allow him to make his own separation )
or will climb enough fast for MSA,and than safe vectoring.
Whatever is applicable in your case,remember that nobody will bring cigarets abnd towels in jail, if you have to expalin to public prosecutor' question :
What was reason behind vectoring aircraft below MSA ???
In our legislation, only 5 years of prison.
Interesting or not,I changed airport, from rad to proc,and FL 100 minimum for all combinations.
I have had, many of such cases( our summers are excellent,Cbs appear only in the afternoon
) and below FL 100 at your own rensposibility
works even better,once they learned that rules are rules.
so keep it to doc 4444,if it is ok for local authorities than it is even more ok for us.
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Squawk standby ...
I'm not sure my answer would completely answer your questions and clear all the dilemas you have about the subject ...
Visual departures are defined to some extent ... check out Regional Suplementary Procedures Doc.7030 (6.5.4. Visual departures) for EU Region ... so this one could be used if pilots want some immediate turns after departure where they are legally responsible for the terrain separation ..
In-flight situation: any deviation from SIDs would not be approved by me until above MRVA(MSA) due radar minima ... but i guess PIC (whos responsible for her\his plane and the passengers would take any action necessary in their view to conduct a safe operation. Thats their responsibility.
1999
I'm not sure my answer would completely answer your questions and clear all the dilemas you have about the subject ...
Visual departures are defined to some extent ... check out Regional Suplementary Procedures Doc.7030 (6.5.4. Visual departures) for EU Region ... so this one could be used if pilots want some immediate turns after departure where they are legally responsible for the terrain separation ..
In-flight situation: any deviation from SIDs would not be approved by me until above MRVA(MSA) due radar minima ... but i guess PIC (whos responsible for her\his plane and the passengers would take any action necessary in their view to conduct a safe operation. Thats their responsibility.
1999
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Deny the SID deviation until the plane has reached the MVA (causing the aircraft to enter the storm cell), or
I understand your dilemma; if your regulations do not allow a deviation from SID/ATS route below MVA, you don't want to use the word "approved" as you cannot actually legally approve. Also I agree that, however you view this situation, some pilots will take this as a verification that the deviation is safe and you do not want to introduce that doubt.
But if you deny the deviation, it is unlikely the aircraft will enter the storm cell. The commander (if he/she has *any* sense whatsoever) will use his emergency authority to make the deviation anyway.
How about the wording "Unable to approve below FLxxx/xxxxFT due minimum vectoring/safe altitude".
Any pilot with some sense will either: expedite until reaching safe, or turn anyway reporting unable to follow routeing. Probably a combination of both.
Either way, you have made it clear that a) you do not take any responsibility for the aircraft course, and b) there is no traffic issue as you specifically mention terrain.
Let the commander do the rest. He did, as already mentioned, take-off into known storm conditions so let him work out his plan without putting it on your shoulders.
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The statement to be issued to the pilot is that you must fly through potentially dangerous weather or hold on the ground because of inflexible local/national regulations. How they can be possibly justified is another discussion.
PM
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I don't agree with that at all. It's nothing to do with national rules, but with responsibility. And the way to make sure that it's clear who is taking responsibility for what. It's actually a good thing to have that clear, ambiguity is a big threat to aviation (or any sector).
It's about making sure the pilot knows that the controller cannot guarantee that the actions he is about to take are safe. And again, that is a good thing.
It's about making sure the pilot knows that the controller cannot guarantee that the actions he is about to take are safe. And again, that is a good thing.
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I truly wish that the reason for denying SID deviations was due solely to terrain separation. The first obstruction is generally "noise". Airports are now regularly insisting that the one departure track is ever flown. A noise maximisation program if you like: the same people will get the noise, every departure, no respite. The next is that we are not trusted to fly visually (referring to the OP's initial post) because as I see it, a "jobsworth" is standing between a problem and a solution. What's worse is that these decisions are taken on our behalf with apparently little or no consultation.
Honestly, most days when I fly I feel that I'm an inconvenience and not customer of a service industry.
PM
Honestly, most days when I fly I feel that I'm an inconvenience and not customer of a service industry.
PM
