Terrain/obstacle clearance under radar control
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Terrain/obstacle clearance under radar control
Below also posted in the ATC forum, but wanted fellow pilots' view on this as well....
Hi!
As a pilot, Iīve always been taught that ATC is responsible for terrain/obstacle clearance only when an aircraft is under radar vectors (yes, I know that ultimately the final responsibility lies with the PIC and it is us getting killed, not the controller, but anyway...).
Then I came across this article on SKYbrary: http://www.skybrary.aero/index.php/M..._Altitude_(MVA)
In it, it says the following: "This includes responsibility for obstacle clearance, except when an IFR flight is being vectored or given direct routing asssited by radar."
Iīve been looking through various ICAO documents and have not been able to find any reference supporting that direct routings would be the responsibility of the controller.
So, if given a direct and a descend clearance that is below MOCA at our current position but at the direct point it is above MOCA, would the controller assume us not to desend below this until it is "safe" to do so? Of course, the controller with MVA altitudes displayed at his/her screen has a better knowledge of what is safe than us pilots that might be restricted by a high MOCA caused by an obstacle that might not be a factor at all.
Could any ATCCO please shed some light on this? Preferable with a reference to relevant ICAO text.
And, yes again, if I was at all unsure of the safety of the clearance, I would double check with ATC, but just curious.
Thanks!
Hi!
As a pilot, Iīve always been taught that ATC is responsible for terrain/obstacle clearance only when an aircraft is under radar vectors (yes, I know that ultimately the final responsibility lies with the PIC and it is us getting killed, not the controller, but anyway...).
Then I came across this article on SKYbrary: http://www.skybrary.aero/index.php/M..._Altitude_(MVA)
In it, it says the following: "This includes responsibility for obstacle clearance, except when an IFR flight is being vectored or given direct routing asssited by radar."
Iīve been looking through various ICAO documents and have not been able to find any reference supporting that direct routings would be the responsibility of the controller.
So, if given a direct and a descend clearance that is below MOCA at our current position but at the direct point it is above MOCA, would the controller assume us not to desend below this until it is "safe" to do so? Of course, the controller with MVA altitudes displayed at his/her screen has a better knowledge of what is safe than us pilots that might be restricted by a high MOCA caused by an obstacle that might not be a factor at all.
Could any ATCCO please shed some light on this? Preferable with a reference to relevant ICAO text.
And, yes again, if I was at all unsure of the safety of the clearance, I would double check with ATC, but just curious.
Thanks!
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I do recall that there are exemptions for a particular obstruction that controls the MORA in a grid...and that a radar vectoring altitude may have taken this into account.
I replied on the ATC forum, but in haste gave the wrong document as a reference, sorry:
PANS ATM (Doc 4444) 8.6.5.2 (also reflected in 4.10.3 Note 3).
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 a point where the pilot will resume own navigation.
PANS ATM (Doc 4444) 8.6.5.2 (also reflected in 4.10.3 Note 3).
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 a point where the pilot will resume own navigation.
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Thanks Bookworm, I saw your reply in the ATC forum and couldnīt quite understand the references you gave, now I understand ;-)
Iīll check out the PANS ATM. And I guess that makes perfect sense. As long as we donīt fly down a specified route it would be very difficult for us pilots to determine the safe altitude whether it is a radar heading or a direct to fly.
Iīll check out the PANS ATM. And I guess that makes perfect sense. As long as we donīt fly down a specified route it would be very difficult for us pilots to determine the safe altitude whether it is a radar heading or a direct to fly.
