Deviations - when to ask

[+TSRA]

Hey controller folk,

A search shows many conversations about asking for deviations but not to as technical an answer I'm looking for to answer a question from a conversation I was having last night.

We were deviating around occasional CBs, TCUs and ACCs. None required any more than about a two mile deviation from track centreline as we were already on the edge of the clouds.

The question posed was at what point should we actually ask for deviations considering the protected airspace generated around the aircraft? I've always asked for any deviation, no matter how small based on the idea that we share the airspace and I may not know whose coming around the other side.

But...the counter argument was if we are being protected by a set number of miles either side of track, would the controller necessarily care if we were forced to deviate within that protected airspace, especially considering deviations are normally lateral and not vertical. In other words his argumen is we should only ask for deviations if we will exit the protected airspace being generated for the track centreline.

I thought it was interesting enough to not discount the idea and ask the question, even though I don't necessarily agree.

Thanks!

[cloverm]

"But...the counter argument was if we are being protected by a set number of miles either side of track, would the controller necessarily care if we were forced to deviate within that protected airspace, especially considering deviations are normally lateral and not vertical. In other words his argument is we should only ask for deviations if we will exit the protected airspace being generated for the track centreline."

In a radar controlled airspace(Radar Identified) you should always ask

[samotnik]

Ask for each and every deviation unless you are granted an open clearance (i.e. "avoiding to the right approved"). Your 2NM deviation may cause separation loss with other traffic or prohibited areas, and potentially some further headache to the ATC if not spotted by the ATCo and dealt with on time.

[HEATHROW DIRECTOR]

When a pilot said to me, "Can we turn ten degrees left to avoid" I would tell him a radar heading to fly to achieve that. That way we both knew what was happening.

[Chesty Morgan]

That's because we are supposed to ask for an actual heading not left or right XX degrees.

[HEATHROW DIRECTOR]

I never heard that but I have been out of it for a long time.

[NZScion]

In New Zealand, there are words in the AIP to the effect that pilots must maintain the centreline of track as much and as accurately as practicable. Any deviation from this (including weather) requires an ATC clearance inside controlled airspace.

[mbucholski]

How do unapproved deviations relate to P-RNAV, RNP, PBN and all that stuff?

[+TSRA]

Thanks for the replies all. It's all pretty much in line with what I was thinking.

And then, while a couple of miles may not matter, does three, four, six? And you'll find different views from different controllers about what 'own navigation' means in terms of track-keeping performance.

LookingForAJob, this generates another question open to everyone. Consider a deviation from track centreline that will be more than a minor one - say, 30 miles or more - would it be better for all involved to ask for a reroute via a fix that is in the clear rather than asking for deviations? Does that make your lives easier or harder?

[zonoma]

In a London Control area sector it will make little difference requesting a reroute as the computer is good enough to provide all the controllers your details to ensure safe passage. If you are significantly off course then there is the possibility that London have already rerouted you themselves to get the next sector/centre the correct details too, however this isn't an official reroute as such and pilots are rarely informed.

Your profile doesn't say where you are based +TSRA, however if you can ever get to Swanwick, Southampton then the TRUCE program (about to be renamed as ABES SIM), which is the controller annual check, always welcomes pilots to attend. This year there is a piece about severe weather avoiding......... You can find details and who to contact here in the Rumours & News forum.

Edited to insert the link to the TRUCE thread in Rumours & News.

[Una Due Tfc]

Originally Posted by +TSRA

Thanks for the replies all. It's all pretty much in line with what I was thinking.



LookingForAJob, this generates another question open to everyone. Consider a deviation from track centreline that will be more than a minor one - say, 30 miles or more - would it be better for all involved to ask for a reroute via a fix that is in the clear rather than asking for deviations? Does that make your lives easier or harder?

I like to be kept in the loop with deviations just so I have situational awareness and can give a heads up to other traffic, but then we don't have airways anymore. I'm normally clearing you direct x, so any deviation in that situation would require approval.

As regards routing after a big deviation, it all depends where you are. If you're near an adjacent FIR boundary and were say flight planned to take a turn on the boundary, I'll try and get you direct to a waypoint further inside that FIR if it looks like it will suit you more.