View Full Version : Question for controllers - Wx avoidance
12th Apr 2012, 12:13
No doubt this has been asked before (and I am sure there is official regulatory material somewhere on the issue) but I'd like some advice from controllers on Wx avoidance.
Let's say that I am departing / arriving XYZ regional airport in the UK (lets say EDI) on ABC1 SID or STAR. Its a convective wx day with numerous cells around. Understandably this increases the controller workload in a major way, since most arrivals and departures will be asking for revised headings to avoid cells.
My current heading has me on track to penetrate a cell and I am doing my best to get my radio call in to request a heading change. However, due to frequency congestion I am unable to do so. My choices are (therefore) to continue on my cleared heading or revise my heading take avoiding action.
I understand the serious implications of changing heading without clearance. This needs to be balanced with the inherent risk of penetrating a thunderstorm cell. The only way I could think that one may be able to cover oneself legally is to squawk 7700?
Has this ever happened and what is the general opinion of the controller fraternity on such an issue?
Thanks for the feedback :ok:
12th Apr 2012, 12:26
The reality is that aircrafy generally just turn. If there was weather and traffic around as per your above description I would expect most controllers would have a little fat built into their plan expecting this. I would expect if an aircraft was told that their intended diversion was not available and they had to go then they would dial 7700 and go. But to answer the basic question if an Aircraft wont comply with an ATC clearance including doing something because they can't get a word in it is potentially very dangerous so would be an emergency and 7700 should be selected.
12th Apr 2012, 13:30
Hitting the ident may also give the controller an idea that you may want to speak, though not guaranteed to get their attention. 7700 certainly would!
12th Apr 2012, 13:33
7700 Will certainly get someone's attention. It's a good ATCO oral-board scenario. Hopefully there would be some kind of 'Wx reg' on to slow the traffic rates down of the the forecast was so bad.
One Sunday about 6 years ago we had to stop all departures from northern England as the inbound traffic routings were so unpredictable.
12th Apr 2012, 18:12
I would much prefer you select 7700 than turn without permission. The squalking ident idea above if you have that amount of time is a good starting point rather than going in full tilt, but some of the weather recently hasn't been that predictable. If you turn without permission, I definitely want you to get 7700 on, but I'm sure there are many out there that would disagree. All to do with each individuals airspace and their constraints, what works for one may not be best for another.
13th Apr 2012, 08:17
as 5milesbaby says above...
There may well be some airspace around that you can turn without any real worry of hitting another aircraft, but not much of it in the UK.
A colleague had to chastise an aircraft the other day in the LTMA as it had asked for a left turn, was told it could not get it due traffic, so proceeded to turn right, straight into the teeth of yet another aircraft. The controller had asked if a right turn would take the aircraft clear, but had not yet authorised it (they were going to have to move other aircraft out of the way to facilitate it).
Fortunately, because of the ongoing communication, the controller in question happened to be looking at the aircraft at the time it turned and thus prevented an airrpox... quite often they will be looking elsewhere.
If you really need to turn and cannot get on ferquency, squawk 7700, it is an attention getter, but bear in mind the controller may well be concentrating on a piece of airspace 100 miles away.
If you have to do this, file an ASR (obviously you'd do that anyways for an emergency squawk).
In fact if at anytime, even in good weather, you find you cannot get on frequency for an inordinate amount of time, file an ASR; too many controllers (and supervisors) forget that service provision is a key factor; once you get several instances of aircraft stepping on each other, then the sector should be split. If that's not possible, then tactical measures should be put in place to slow the traffic flow.
Remember that TCAS is nowhere near as accurate as ground radar, so turning into what you think is a clear piece of airspace may well be more dangerous than continuing towards the CB.
There are other aircraft in the sky who also may be avoiding weather. An unsolicited turn may well mean that they have to be given avoiding action towards the cell they are trying to avoid!
The only way I could think that one may be able to cover oneself legally is to squawk 7700Turning without permission is not a heinous crime though you need very a good reason to do so. The only legal thing you need to worry about as a pilot is the fact that you are ultimately responsible for the safety of your aircraft.
You can do whatever you want, if you can justify it on safety grounds when you land. Might give us ATCOs a heart attack at the time mind you!
13th Apr 2012, 09:44
Good advice here - thanks for the information chaps. :ok:
13th Apr 2012, 10:03
Squawk Ident is no good. The SSR Ident procedure is abused too much by crews identing when not instructed, especially on departure. Many ATCOs will ignore uncommanded Ident selection.
7700 will convey urgency. That is one of its purposes.
13th Apr 2012, 21:49
If the events of recent days are anything to go by, using 7700 will also get you a personal escort by the RAF's finest. :ooh:
I suppose no-one will notice the sonic boom because of the thunder!
14th Apr 2012, 04:20
while I don't fly in the UK, I will tell you this. by asking the question here on
pprune, you are staying ahead of the plane.
by the same reasoning, you should know before you takeoff that you will have to avoid wx. Advise each controller on initial contact that you will need deviations at pilots discretion and direct to the "X" vor or fix when able.
do this before you need it...that's staying ahead of the game.
I do agree that if you are truly unable to communicate and YOU need to
deviate, selecting 7700 is appropriate...and then you may do as you please to
handle the emergency you just declared. And if you truly can't communicate
you could monitor the assigned freq on one radio and attempt contact on
another freq (last or expected or 121.5).
In the USA, just prior to takeoff (airline, IFR, wx) I advised tower,, be advised
we will deviate as neccesary if we are unable to communitcate with departure
control or center. if they can't handle it...they could deny me takeoff clearance.
14th Apr 2012, 12:18
I advised tower,, be advised we will deviate as neccesary if we are unable to communitcate with departure control or center. if they can't handle it...they could deny me takeoff clearance.
I know a couple of places where the Tower controllers (most of them anyway) would not pass on this info to departures.:ugh::ugh::ugh:
14th Apr 2012, 17:06
One very nasty night I had two 737s inbound EDDH. Initially 15 minutes apart they ended up in formation over, then, East Germany. There was one gap and they ewere both going for it. I could only gave them traffic info, when requested, and let them get on with it.
Air Defence told me to tell them to turn back. Passing the message on only resulted in me being told wherethey could put their SAMs.
Made an entry in the log in case it resulted in an international incident however common sense prevailed and I never heard anything more