Radar vectoring charts and cleared altitudes?
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From: LHR
Radar vectoring charts and cleared altitudes?
Purely as a matter of interest, here's a question for anyone willing to shed light on the following:
(this really needs a picture to explain it, but here goes anyway)
Imagine an airfield with a 4000ft ridge 20 miles away. The radar vectoring chart shows a min alt of 2000ft inside 20 miles, rising to 5000ft outside it. An approaching aircraft is passing 9000ft for 5000ft with high speed towards the airfield.
At what point can you clear the aircraft to 2000ft? Is it when the actual a/c symbol on your radar screen is inside the 2000ft area, or can you employ some anticipation using the likely flightpath of the aircraft, taking its descent rate into consideration?
For instance, if the aircraft has reached 7000ft 25 miles from the airfield, can you clear it to 2000ft -at that point- in anticipation of the fact that (using the 3 x table) it's going to need at least 6 miles to descend another 2000' (before reaching 5000ft), thereby passing the critical 20 mile point at around 5330ft?
thanks in advance - sorry if that's a bit confusing.
(this really needs a picture to explain it, but here goes anyway)
Imagine an airfield with a 4000ft ridge 20 miles away. The radar vectoring chart shows a min alt of 2000ft inside 20 miles, rising to 5000ft outside it. An approaching aircraft is passing 9000ft for 5000ft with high speed towards the airfield.
At what point can you clear the aircraft to 2000ft? Is it when the actual a/c symbol on your radar screen is inside the 2000ft area, or can you employ some anticipation using the likely flightpath of the aircraft, taking its descent rate into consideration?
For instance, if the aircraft has reached 7000ft 25 miles from the airfield, can you clear it to 2000ft -at that point- in anticipation of the fact that (using the 3 x table) it's going to need at least 6 miles to descend another 2000' (before reaching 5000ft), thereby passing the critical 20 mile point at around 5330ft?
thanks in advance - sorry if that's a bit confusing.
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From: where should i be today????
From a UK military point of view, unless it has changed in the last 16 months, it is (was) forbidden to anticipate rates of descent. You are (were) only permitted to issue a descent instruction based on the ACTUAL position of the aircraft with reference to the radar vector chart. Therefore in your example , flying finn, the aircraft would have been descended to 5000ft QFE (as that is what the RVC is based on) or equivalent until the aircraft crosses the 20nm range towards the aerodrome.
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Sorry to disagree with 5mb but there's no way that I will anticipate an aircraft's descent profile. I will clear an aircraft for descent to the level specified in an RVA only when it is within that area or sector.
My reading of the good book (MATS Part 1 that is) supports this - it says that within the Radar Vectoring Area levels allocated must be in accordance with the
information published on the RVA chart. As far as I'm concerned I can't allocate the level until the aircraft is inside the area.
Yes, I may issue a clearance to cross some point not below FL X but it will be for traffic reasons. When vectoring that close to the field that type of clearance is more trouble to work out than it's worth. Clearly 5mb doesn't know me.
FWIW, in my view issuing a clearance on the basis of what the controller anticipates the pilot will do is not just poor practice but is simply asking for the controller to be proved wrong.
Clearly 5mb doesn't know me. Or maybe I've just been doing it for a bit longer and seen it all go wrong too often!
My reading of the good book (MATS Part 1 that is) supports this - it says that within the Radar Vectoring Area levels allocated must be in accordance with the
information published on the RVA chart. As far as I'm concerned I can't allocate the level until the aircraft is inside the area.
Yes, I may issue a clearance to cross some point not below FL X but it will be for traffic reasons. When vectoring that close to the field that type of clearance is more trouble to work out than it's worth. Clearly 5mb doesn't know me.
FWIW, in my view issuing a clearance on the basis of what the controller anticipates the pilot will do is not just poor practice but is simply asking for the controller to be proved wrong.
Clearly 5mb doesn't know me. Or maybe I've just been doing it for a bit longer and seen it all go wrong too often!
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From: where should i be today????
I would be interested to hear the views of the SRG with respect to 5mb's reply. I fully agree that self cancelling restrictions, once readback, are safe enough (not that we tend to do it in the mil) but how can ATC be sure that an ac will maintain its current rate of descent.
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From: Three steps from reality
I feel we can apply a bit of common sense. If the aircraft is near its cleared altitude which happens to be the MVA, and still has a few miles to go to the lower MVA, don't anticipate.
If, using Calgary TCU as an example since it has lots of different MVAs (them Rockies get in the way) and aircraft is in the 13,200 ft MVA (can't remember the exact alts here, but it'll do) and will cross into the 9,200ft MVA in 10 miles, and is now passing FL200 in descent, go right ahead and give descent to 10,000 ft.
If, using Calgary TCU as an example since it has lots of different MVAs (them Rockies get in the way) and aircraft is in the 13,200 ft MVA (can't remember the exact alts here, but it'll do) and will cross into the 9,200ft MVA in 10 miles, and is now passing FL200 in descent, go right ahead and give descent to 10,000 ft.
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From: S coast
I agree with Spitoon & Rej.
It's an absolute that you do not descent below RVA levels (and all radar units in the UK have them).
Besides, using Finn's example, if the boundary to drop out of 5000ft is 20 n.m from the airfield, why is there any rush for further descent?
By my calculation, using a CDA (see other thread) passing 6000ft for an airfield 20 n.m away would be sufficient to get the height off....better still if the airfield has any significant elevation.
Tori
It's an absolute that you do not descent below RVA levels (and all radar units in the UK have them).
Besides, using Finn's example, if the boundary to drop out of 5000ft is 20 n.m from the airfield, why is there any rush for further descent?
By my calculation, using a CDA (see other thread) passing 6000ft for an airfield 20 n.m away would be sufficient to get the height off....better still if the airfield has any significant elevation.
Tori
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From: LHR
Cheers for the replies. The example was purely a fictional one for the sake of argument, and in fact a more realistic case is the one in Lock n' Load's reply.
It's not an issue in the UK as such as there is no significant terrain, but what prompted my question was going into say the major towns of N. Italy, ie just beyond the Alps. There, like in Calgary's case, I'm pretty sure you get a descent clearance to a lower altitude when you're still in the higher vectoring area, but it is of course obvious that you are not going to hit any mountains as they're behind you at this stage.
The kind of anticipation I was talking about was precisely the type described by L'nL - but are the rules different in the UK vs in more hilly countries?
The example I'm thinking of is the arrival on to 23 in GLA where you get held at 3000ft on base because of the hill on the northern side of the extended CL. You only get descent to 2300ft (?) when you're on the final intercept heading and presumably in the lower vectoring area. This approach leaves you momentarily above the glide - which is not a problem, but requires a tiny bit of forethought when considering your speed and config particularly in the case of a tailwind.
As the a/c commander (or his 'assistant', in my case) is the one legally responsible for terrain clearance even when under positive radar control, I just wanted to get a bit of clarification as to what the rules are for you guys - for the next time when we're descending in IMC!
p.s. The Spaniards get round the problem by asking "are you in visual contact with the ground" when descending you into Barcelona. Again, fair enough.
It's not an issue in the UK as such as there is no significant terrain, but what prompted my question was going into say the major towns of N. Italy, ie just beyond the Alps. There, like in Calgary's case, I'm pretty sure you get a descent clearance to a lower altitude when you're still in the higher vectoring area, but it is of course obvious that you are not going to hit any mountains as they're behind you at this stage.
The kind of anticipation I was talking about was precisely the type described by L'nL - but are the rules different in the UK vs in more hilly countries?
The example I'm thinking of is the arrival on to 23 in GLA where you get held at 3000ft on base because of the hill on the northern side of the extended CL. You only get descent to 2300ft (?) when you're on the final intercept heading and presumably in the lower vectoring area. This approach leaves you momentarily above the glide - which is not a problem, but requires a tiny bit of forethought when considering your speed and config particularly in the case of a tailwind.
As the a/c commander (or his 'assistant', in my case) is the one legally responsible for terrain clearance even when under positive radar control, I just wanted to get a bit of clarification as to what the rules are for you guys - for the next time when we're descending in IMC!
p.s. The Spaniards get round the problem by asking "are you in visual contact with the ground" when descending you into Barcelona. Again, fair enough.
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From: S coast
In the specific case of rwy 23 @ GLA, it's my understanding - never having worked there - that the original levels flown whilst providing terrain clearance from the ridge caused certain Ac types GPWS to go off because of rate of closure to the ground albeit stopping descent at a terrain-safe level.
Therefore a higher level to accomodate one A/c type became 'standard' for everyone. Without having an RVA chart to hand, I suspect the actual RVA level is lower than 3000ft, but that is the practical level used until late into the ILS closure to prevent unwanted GPWS-induced go-arounds.
I'm sure I'll be corrected by someone in the 'know' if I've got this wrong
Tori
Therefore a higher level to accomodate one A/c type became 'standard' for everyone. Without having an RVA chart to hand, I suspect the actual RVA level is lower than 3000ft, but that is the practical level used until late into the ILS closure to prevent unwanted GPWS-induced go-arounds.
I'm sure I'll be corrected by someone in the 'know' if I've got this wrong
Tori
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From: the far side of the moon
Working North of the border, where there are some quite large lumbs, our RVC looks like a demented childs jigsaw puzzle. In all cases however descent instruction are not given until an ac crosses the line into the next sector. This may be a Mil thing, as some of the ac can quite literally point themselves at the floor, or it is a civil interpretation as well, I can not tell you. However, descent instructions for civil ac are given in the same way. without it I would imagine you would have to give a conditional descent profile ie 1000ft per mile and a point to be level at in order to counter lost comms. All in all a bit time and effort consuming if you are busy. Far better to say descent report level abc, advise approaching for further.
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From: Three steps from reality
The Glasgow point reminds me of a rule in the Edinburgh MATS Pt2. Aircraft from the west/south west being vectored for r/w 24 are not to be given descent to below 4,000 ft till past the r/w 30 approach course. They're well into the 3,000 ft area of the RVA by then, but the rule is there to stop GPWS events based on rate of closure with terrain rather than proximity with terrain. The high ground there tops out at 1,900 ft.
