Ferris,
You seem to have missed the whole idea of issuing a heading to an aircraft..........i.e. for the controller to position that aircraft where the controller chooses and not rely on the pilot hopefully positioning the aircraft where the controller hopes it will go.
Note the frequent use of "hope" in the above.........not good to say after........."I had hoped the pilot would.....".
What would you say the equivalent RNP for an experienced controller in enroute airspace under moderate traffic load is........i.e. when they put aircraft on headings, how close will they keep the aircraft to the desired track for 95% of the time? (assume an area where 5nm separation is permitted)
I would guess that it is about RNP2.........i.e. controllers frequently vector aircraft along one side of the airway 2 miles from the edge without going outside. Provided that the resultant radar returns or responses do not get closer than the required minimum radar separation (say 5nm) then the required separation has been acheived in a compact piece of airspace.
Compare this theoretical RNP2 figure to the figures I quoted earlier for traffic on own navigation.
As for calculating the drift it is not hard at all.........we simple pilots do it day in day out even when we are half asleep!
Simply put - at 420 Kt for every 7 Kt of crosswind there will be 1 degree of drift.
Each degree of drift puts the aircraft 1nm off track in 60nm
However here comes the crunch - being a good controller and aware of the upper winds you will momnitor the actual tracking of the aircraft atleast every minute or two and issue a correction to the heading. So the most the aircraft is going to get off track is 2nm 95 % of the time provided you do your job properly.
You quoted an extreme case but provided you take charge of the situation and you do you job well the only person who can be blamed for a loss of separation is you.
Note the frequent use of "you" in the above situation.
If you did loose separation, the question I would ask is why knowing the wind situation did you not climb to 1000ft below initially to check that separation was being ensured?
Finally you seem to base all your assumptions regarding tracking on the aircraft's ability to automatically follow a track accurately.
Never assume.
We can quite happily fly the aircraft in heading mode- we change the heading to try and acheive the required tracking or we can even manually fly the aircraft as accurately as we can (wandering over the sky if the winds are shifting and the bumps are hard!). What is important is that we do not have to tell you how we are flying the aircraft provided we acheive the required RNP.
Do you not think that a large part of controller workload in busy enroute airspace comes from having to vector aircraft? If so then do you not also think that moves would have been made to increase capacity (reduce workload) by reducing the requirement for vectors?..........The answer lies in the Eurpean study from where I got those separation figures for parallel tracks earlier.
Regards,
DFC
PS as Captain I don't trust you to save my licence - that's my job.............don't expect me to do anything to save yours!
