Radar vs non-radar assigned altitude

[Jonathan_tcu]

Just wondering, when an aircraft requests IFR clearance in a non-radar environment, he's given lower than his radar i.d. altitude.  For example, tonight, Cree 602 departed Kashechewan, requested the IFR to Sudbury CYSB, at FL 200.  He was given 16 000 until he appears on radar, which he did and was re-cleared to his requested altitude.  Does ATC restrict higher than FL 200 altitudes to lower levels due to non-radar coverage?  One other example is when Georgian flights depart Timmins (CYTS) and fly to Earlton (CYXR) and request only say, 7000 which is non-radar all the way through, THAT altitude is requested, assigned and maintained until the final approach.  Any insights on this?

[davys747]

There is nothing unusual about controlling an aircraft from departure to destination using non-radar procedures. By unusual I mean that there is nothing illegal or wrong with using non-radar procedures for separating traffic. You'll find that most controllers would prefer to use radar, however there are some people that enjoy a non-radar environment.

Controllers are trying to keep positive separation between aircraft (and terrain) for IFR aircraft from the time they pick up a clearance until the time their IFR clearance is cancelled. This applies even if you can't see the guy on the radar. In the USA there is only a 3 ways (that I know of) of getting off the ground IFR. One is a SID/DP, the other is an approved radar heading and the last is whats know as an Obstacle Departure Procedure (ODP). These guarantee that you (as an IFR aircraft) will be separated from terrain until reaching the Minimum Enroute Altitude (MEA) of a local airway or the Minimum Safe Altitude (MSA) of the local area. (Somebody correct me if im wrong). If you airport doesn't have one of these 3 things the pilot has to accept responsibility for his/her own terrain separation otherwise ATC won't release him/her IFR.

Not only do you have to separate aircraft from terrain, you also need to separate from aircraft. Controller need to protect the airspace of a non-radar departure from other IFR aircraft until you have a radar contact with the aircraft. For example, if you had aircraft A flying over a VOR that was part of a DP or ODP of your departure airport (for aircraft B), you cannot assign aircraft B an altitude that would cause a loss of separation with aircraft A if you lost comms with both aircraft before you had radar contact. Put another way, if aircraft A is at 8,000 the highest altitude you could give B would be 7,000. If you lost comms with both aircraft, you know they will have positive separation.

So, thats the background on non-radar departures. Im going to guess that there was another aircraft somewhere along the flightplan of the departure possibly either at 17,000 or 18,000' which would cause the controller to hold him down until he could get radar and then separation standards reduce some what and he could be climbed higher.

[Jonathan_tcu]

Can we say that 2 aircrafts that are 100 nm apart for both of their departures, heading to the same destination, the ODP and MSA is taken into fact, but the the aircraft closest to the destination after departure would be assigned a lower altitude, right?  And the the other aircraft further away or right behind him, would get the higher altitude.  Here from Timmins airport, there have been instances where 3 aircrafts departed within say 5 or 10 minutest of each other and assigned departure radials.  Example, departures southbound to Toronto Pearson Airport, departs rwy 21 direct to Mans VOR, he would intercept the 209 degree radial, and  a Bearskin flight, same rwy21 departure to Sudbury CYSB would be asked to interecept the 179 degrees radial (V5 airway) and the 3rd aircraft would be asked to climb VFR if able, until the first 2 guys are radar identified at 10 000 feet for separation rules.  If aircraft # 3 could not climb VFR, he would be asked to climb VFR, and not above 4000, or his departure woud actually be delayed altogether.  Let me know how this sounds.