Leave XXX heading....
Thread Starter
Joined: Jul 2007
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From: taking up the hold
Leave XXX heading....
I operate into & out of LHR on a regular basis where we are almost always asked to leave which ever holding fix on a heading. Normally we preselect this heading & when we are directly over the fix heading engages automatically or we engage it manually. The heading change involved is not usually a great deal & of course the TAS & hense the radius of turn is fairly low. ATC seem happy with this technique of turning when we get to the beacon.
However I was recently asked to leave an airway fix on a given heading which involved a turn of about 60 degrees. I used the above technique but with the higher FL & TAS the radius of turn was significantly greater. ATC queried whether we were indeed leaving on the given heading.
In this situation what do ATC expect:
1) Fly to fix then turn.
2) Turn before beacon to leave as if we had flown overhead on that heading.
3) Split the differance.
4) Something else.
However I was recently asked to leave an airway fix on a given heading which involved a turn of about 60 degrees. I used the above technique but with the higher FL & TAS the radius of turn was significantly greater. ATC queried whether we were indeed leaving on the given heading.
In this situation what do ATC expect:
1) Fly to fix then turn.
2) Turn before beacon to leave as if we had flown overhead on that heading.
3) Split the differance.
4) Something else.
Joined: Mar 2007
Posts: 204
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From: UAE
If you treat the fix as a fly-over waypoint, you're not leaving the fix on the given heading; you're leaving a point a few miles away on that heading!
Treat it as a fly-by waypoint, but by all means query that with the controller concerned.
Treat it as a fly-by waypoint, but by all means query that with the controller concerned.
Joined: Jun 2001
Posts: 892
Likes: 6
From: southampton,hampshire,england
Tail-take-off
I'm at LACC Swanwick. Some may consider this [in the en-route scenario] as poor technique....you have identified higher level and airspeed/groundspeed as relevant factors. In addition there are the multiple differences in aircraft flying characteristics and "bank" demand.
Perhaps a literal interpretation is actually impossible as this would necessitate a positioning manoeuvre before the point....this is much less relevant in a low speed/lower level environment. The phrase should perhaps be interpretted as "after xxx turn L/R heading ???" or whatever the R/T "police" mini-brains say is the appropriate book wording.
Next time you get this wiffle/waffle instruction in the en-route phase....ask the controller what he/she expects.....clarity is good for both sides.....and perhaps will be a pick-up point for the training section.
NOTE: in areas of the world where space is plentiful.....no problem...but in dense UK airspace....very relevant.
Perhaps a literal interpretation is actually impossible as this would necessitate a positioning manoeuvre before the point....this is much less relevant in a low speed/lower level environment. The phrase should perhaps be interpretted as "after xxx turn L/R heading ???" or whatever the R/T "police" mini-brains say is the appropriate book wording.
Next time you get this wiffle/waffle instruction in the en-route phase....ask the controller what he/she expects.....clarity is good for both sides.....and perhaps will be a pick-up point for the training section.
NOTE: in areas of the world where space is plentiful.....no problem...but in dense UK airspace....very relevant.
Joined: Feb 2006
Posts: 2,295
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From: Hants
'Leave xxx heading xxx' implies that you will hit the point on the required heading - not pick it up after the point.i.e you manoeuvre before the fix to be in a position to be on the desired heading as you pass over the point.
As 055166K states - if someone said 'After xxx, fly heading xxx", then you initiate the turn as you pass over the point... is you are high and fast then that will mean a bigger radius of turn.
Unlike 0055166K, I work at Swanwick on the TC side (LTMA) - the technique in our work is very relevant as it only involves about a 20 or 30 degree heading change and is applied primarily to aircraft on SIDS in a bid to position them between two stacks to enable climb.
It could be a rather poor technique to employ at higher levels, especially in regions where there are a lot of airways packed into a small space.
The phrase "after xxx fly heading xxx" is much less ambiguous and ope to interpretation than "leave xxx heading" - though to a native English speaker, both should be self explanatory. Unfortunately we get a lot of ATCOs nowadays who have never flown and have a lack of experience of aspects of aviation other than the specific type of controlling they do... they are the ones who need educated as to what the difference is between the two phrases.
If in doubt - safer to ask (though it may cause even more confusion due to the factors in my sentence above)!
As 055166K states - if someone said 'After xxx, fly heading xxx", then you initiate the turn as you pass over the point... is you are high and fast then that will mean a bigger radius of turn.
Unlike 0055166K, I work at Swanwick on the TC side (LTMA) - the technique in our work is very relevant as it only involves about a 20 or 30 degree heading change and is applied primarily to aircraft on SIDS in a bid to position them between two stacks to enable climb.
It could be a rather poor technique to employ at higher levels, especially in regions where there are a lot of airways packed into a small space.
The phrase "after xxx fly heading xxx" is much less ambiguous and ope to interpretation than "leave xxx heading" - though to a native English speaker, both should be self explanatory. Unfortunately we get a lot of ATCOs nowadays who have never flown and have a lack of experience of aspects of aviation other than the specific type of controlling they do... they are the ones who need educated as to what the difference is between the two phrases.
If in doubt - safer to ask (though it may cause even more confusion due to the factors in my sentence above)!
Thread Starter
Joined: Jul 2007
Posts: 829
Likes: 9
From: taking up the hold
Thanks everyone for your comments.
Prior to this occasion I had only ever experinced this in the London TMA so I responded as I had done for years.
In future I will ask for clarification.
Prior to this occasion I had only ever experinced this in the London TMA so I responded as I had done for years.
In future I will ask for clarification.
