Primarily for general aviation discussion, but other aviation topics are also welcome.
#1859451
So if you’re cleared to leave by descent and to change frequency what happens if you need to change heading due weather whilst still in CAS. I’d make the change and try abs get the new frequency to coordinate with the original CAS frequency. But the implication is that the CAS frequency is accepting the risk of uncontrolled changes?
#1859455
ATC are, in theory anyway, taught to control defensively. If it’s a weather avoidance sort of day I wouldn’t expect one to be released from the airways frequency until a much later point/closer to the airspace boundary than if it’s a CAVOK sort of day.
#1859472
You’d wait till outside CAS if wanting to bimble, you’re still on your IFR flight plan and should route predictably based on that as you descend.

That is…

“GABCD route direct to/route towards XYZ, cleared to leave controlled airspace by descent” = no bimbling.

Or, potentially, and buy your lottery ticket…

“GABCD cleared to leave controlled airspace by descent, bimbling laterally at your pleasure” = bingo!
#1861597
My 2-pennyworth on this is: Don't wear a squawk of a unit you are NOT working. Someone may be trying to coordinate your track on the basis of that squawk.

I was subject to an MOR (MANY moons ago) when Clacton sector 'handed' an aircraft to Eastern Radar (0232 - yes, I remember it THAT well!) as it left CAS at FL160 for Mildenhall - directly on track for the Upper Heyford (in the open FIR, btw) stack ( I said it was many moons ago!), base hold level FL150.

There was one F-111 in the hold at FL150.

I expected Console 3A at Eastern to call to coordinate the track to 1000ft vertical (Eastern 3A had just handed me 2 others inbound to the hold, but I had stopped them at FL 170 and 180 respectively to permit the transit at FL160). In the absence of any coordination from Eastern 3A, my nerve broke first and initiated coord:

"My 6131, in the Heystack at FL 150, maintaining; my 6132 and 6133, joining the Heystack, FLs 170, 180 to maintain, against your 0232 to maintain FL160 until clear of the Heystack, agreed?" The response?

"Sorry 13, not working 0232 yet, still with Clacton sector - can't coordinate." :shock: I'd wasted what little time was available trying to coordinate with the wrong agency. :cry:

The C-130 (for t'was it was) then ploughed through my hold without a bye or leave with my 3 tracks star-bursting around the sky in a (vain) effort to 'get 5' (miles).

The 'kicker' was that the Clacton Sector Controller then MOR'ed me :x for not coordinating with him, even though his track was 'off-route' in the open FIR, where the onus was on the Civ side to initiate coordination with the Mil side, wearing the wrong squawk, whilst transitting through a known active, holding pattern! The paperwork, transcripts, went on for weeks!! And led to more than a few sleepless nights.

I re-iterate guys: NEVER wear a squawk of a unit you are NOT working, especially outside of CAS.

PS - shouldn't it be 'leave CAS by dissent'? :twisted:
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#1861605
Leaving airways by descent for a VFR-only destination in Class G - keep the original squawk because i) in my experience the UK radar unit doesn't instruct you otherwise; ii) changing squawk to 2000/7000 will trigger CAIT if done when still in CAS; iii) you may not become visual and need to divert to an airfield with an IAP. In the case of iii) I prefer to remain with Thames Radar on a traffic service until visual, or if not possible to land make it their job to coordinate the diversion and get me back in the LTMA. Much easier that way than having dumped the Eurocontrol squawk and switched to the A/G frequency.

Same on departure from an A/G airfield in Class G - wear the squawk given to you in the "clearance" from the outset even though you will be on the A/G frequency for a couple of minutes after departure. I understand that the discrete squawk triggers printing of the strip when the aircraft pops up on radar, so to depart on a 7000 squawk is not consistent with system expectations.
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By GrahamB
FLYER Club Member  FLYER Club Member
#1861608
Mark W wrote:Same on departure from an A/G airfield in Class G - wear the squawk given to you in the "clearance" from the outset even though you will be on the A/G frequency for a couple of minutes after departure. I understand that the discrete squawk triggers printing of the strip when the aircraft pops up on radar, so to depart on a 7000 squawk is not consistent with system expectations.


It's my experience when departing from A/G OCAS on an airways flight, and activating it by calling London Info, is that they will give you 0027 (IIRC) as a 'waiting for clearance' squawk. Once the clearance is issued, you change to the airways squawk and call the controlling frequency. Going south or east for me, it may be twenty or more minutes between take-off and changing to that squawk.

I believe London do issue a DEP message under these circumstances, with the airborne time you give them. If the system waited for the first appearance of the airways squawk to do it automatically, would it not screw up the ETA calculation?
#1861614
Mark W wrote:Leaving airways by descent for a VFR-only destination in Class G - keep the original squawk because i) in my experience the UK radar unit doesn't instruct you otherwise; ii) changing squawk to 2000/7000 will trigger CAIT if done when still in CAS; iii) you may not become visual and need to divert to an airfield with an IAP. In the case of iii) I prefer to remain with Thames Radar on a traffic service until visual, or if not possible to land make it their job to coordinate the diversion and get me back in the LTMA. Much easier that way than having dumped the Eurocontrol squawk and switched to the A/G frequency.

Same on departure from an A/G airfield in Class G - wear the squawk given to you in the "clearance" from the outset even though you will be on the A/G frequency for a couple of minutes after departure. I understand that the discrete squawk triggers printing of the strip when the aircraft pops up on radar, so to depart on a 7000 squawk is not consistent with system expectations.


I gather you are talking about the last bit of OCAS flying in IMC? then it’s no brainier to insist on staying high on radar with airways squawk and handover to Luton/Essex/Thames/Southend to cloudbreak than getting dumped somewhere in Kent or Herts with 30nm low run in IMC under LTMA on 1177/2000, but I doubt you could fly IAP at alternate with airways squawk coming from OCAS, my experience at Southend will switch you to their squawks and give fresh IFR clearance to fly IAP if you turn up out of the blue on diversion unless you are first handed to them by LC/Thames, if it’s IMC, I go to Southend IAP first all in CAS before heading to Stapleford (well I had to go back to Southend again once and it was on 4575)

ATC are reluctant to keep Deconfliction Service or Traffic Service when you are heading IFR to some VFR circuit, so they have to cut squawks & services somewhere?

I have no clue about departures, I always set the squawk I get from AG before takeoff and switch to frequency after getting airborne and leaving ATZ but other people would do that call by phone or depart on 7000/2000 and get London Info to help, I doubt it changes anything?
#1861617
The departure process I referred to is where A/G or the pilot phones Terminal Control and obtains the clearance whilst taxying out (the "clearance" being to remain OCAS, on track XXX, next radar frequency and the Eurocontrol squawk). Assuming in an area of good radar coverage you will be picked up within 30 seconds of departure. If not, I am not sure what happens, presumably the radar unit will ask for airborne time in the same way London Info does. Or you can send a DEP message yourself if you have phone data coverage.

The London Info route to getting into the airways is not particularly slick.
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#1861633
Mark W wrote:Assuming in an area of good radar coverage you will be picked up within 30 seconds of departure. If not, I am not sure what happens, presumably the radar unit will ask for airborne time in the same way London Info does. Or you can send a DEP message yourself if you have phone data coverage.

The London Info route to getting into the airways is not particularly slick.


I don’t think there is a timeout or CTOT? LC has tradition to just tactically manage flow and vector left & right anyway, but any idea how long that “clearance is valid” given that you are only cleared to ROCAS under London TMA :D ?

Under Paris TMA, when departing uncontrolled IFR (IFR airport but no ATC), I call ATC by phone to check FPL and get IFR clearance (usually something like “climb FL70 while remain VMC” which is deep in airspace) but you have 10min to pop up on their screen and make RT contact or phone call them again…

It makes sense to call FIS to arrange the clearance if you are joining airspace with 30nm cruise to spare at descent altitude but yes it’s not the sexiest method for quick climb in 1500ft-3500ft TMAs :thumleft:
#1862862
Another data point yesterday, departing UK to France on airways IFR from grass strip
Called by phone before departure, got departure squawk, LC frequency & join CAS at Lydd at FL80

Right after takeoff I called, sent to Heathrow/Thames on Conspicuity squawk who had no clue who I am, pass your message and set me on 7033, 2nd IFR clearance to join CAS in DET and change to another airways squawk again


I was flying F-reg but well used to UK OCAS IFR s***show, but how the heck a non-local pilot can understand all of this? 4 transponder codes & 5 frequencies in barely 10nm !

Most of the times things will work perfectly in a seamless fashion (at least the case on the recent arrival or the previous departure) but on rare one or two occasions they just go south, anyone know why?
#1862931
I can't see any good reason to change squawk unless told to. If the controller meant to tell you and forgot then so be it, it's not going to do anyone any great harm. If you start second guessing then you risk changing it when there was actually a reason you weren't told to in the first place.
#1863126
GrahamB wrote:I believe London do issue a DEP message under these circumstances, with the airborne time you give them. If the system waited for the first appearance of the airways squawk to do it automatically, would it not screw up the ETA calculation?

There's no need to issue a 'DEP' message or airborne time unless you pass an approximate one before you depart (known as 'passing a DM' or departure message); whatever transponder code you are issued with will, when you dial it up, be recognised by the computers at Swanwick/Scottish and will automatically 'trigger' the activation of your FPL , convert the code to a callsign label and activate your FPL for your entire route.
Last edited by chevvron on Thu Aug 05, 2021 6:30 pm, edited 1 time in total.
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