LARS units and regional QNH
Brize always use the Cotswold RPS rather than their own QNH; at least they do when they hand traffic to adjacent LARS units.
Mode C is transmitted from the aircraft on 1013 but it's displayed on ATC radars based on whatever pressure setting you input, the conversion being done by each individual units processor. I know Lyneham used to input 1013, but other RAF units usually input QFE, whilst civil units input their own QNH.
There is no such thing as the 'London RPS'; Benson should issue their own QNH as the QNH of any airfield under a TMA is deemed to be the same as any other airfield under that TMA.
Mode C is transmitted from the aircraft on 1013 but it's displayed on ATC radars based on whatever pressure setting you input, the conversion being done by each individual units processor. I know Lyneham used to input 1013, but other RAF units usually input QFE, whilst civil units input their own QNH.
There is no such thing as the 'London RPS'; Benson should issue their own QNH as the QNH of any airfield under a TMA is deemed to be the same as any other airfield under that TMA.
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Originally Posted by neilmac
I am guessing the Brize controller wasnt busy so by giving you the Cotswold and not his QNH/QFE to transit his Zone, thus saving you another pressure change on leaving.
In that area I believe you are in the Cotswold RPS?
So at WCO change to Luton and get either their QNH or London RPS.
Bookworm said on this occasion he was able to get the Luton QNH - what if he hadn't been able to? Would the Brize Controller still blindly given the Cotswold or would he have had an attack of common sense in giving what he was actualy asked for?
Its not really an awareness problem whey should a BZN controller worry about your altitude on crossing the Luton CTZ?
In a GA plane WCO to edge of Luton zone is plenty of time to adjust if you give Luton an early call.
Our Mode C readout is always based on 1013
so at least with a/c on QFE its easy to work out internal co-odrination rather then a long winded call right so your on the Cotswold im on QFE .....waiting to work out differerences do I have enough separation when your planes are getting closer!
Cuts down on that nonsensical co-ordination.
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Originally Posted by neilmac
I am guessing the Brize controller wasnt busy so by giving you the Cotswold and not his QNH/QFE to transit his Zone, thus saving you another pressure change on leaving.
So at WCO change to Luton and get either their QNH or London RPS. Its not really an awareness problem why should a BZN controller worry about your altitude on crossing the Luton CTZ?
Don't get me wrong -- I asked just once for the Brize QNH: I certainly could have been more assertive in asking for a real QNH. And I made contact with Luton in good time. But I was specifically aware of the issue on this, a fairly quiet day with not much else to worry about. No hazard in this case, but I wanted to raise awareness of the issue.
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Originally Posted by Il Duce
"...unless you're using it for separation purposes"!!!????
As opposed to, perhaps, using it for cooking purposes or medical purposes?
As opposed to, perhaps, using it for cooking purposes or medical purposes?
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There certainly was a section in MATS part 1 that said the RPS should not be given unless requested by the pilot or words to that effect, haven't checked to see if it is still there.
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I ws amazed that one of my 'intro to the uk' pilots was given the RPS (Portland) by Bournemouth LARS whilst we were in the 'New Forest Tunnel' - the class G between Southampton and Bournemouth with the Solent 2000' cap on it - despite reporting near Beaulieu! (I had already briefed him on RPS with warnings not to use it under CAS, but I'm pretty sure he would still have set it if I hadn't been there to question it.
ps: thanks JS for the pointer to this post from trhe forum atfly on track
ps: thanks JS for the pointer to this post from trhe forum atfly on track
Originally Posted by Standard Noise
IL Duce & 2SHEDS- If I have 2 vfr a/c both on a RIS, I tend not to give them standard separation, only traffic info after all it's an 'information' service. But I will want to know their respective altitudes which I am capable of working out from the pressure setting they are on. Maybe you both spend your time separating everything, personally, I don't!
It is quite evident from all the foregoing correspondence that in the context of most traffic at and below the transition level that is going from one aerodrome-based ATC unit to another for service, use of an RPS is not only a waste of time but confusing and potentially hazardous. It has its uses for low level traffic - military tactical, pipeline patrols etc - apart from that, it is a menace and should be limited to the lumpy bits of Wales and Scotland and the sea areas.
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I'm with Standard Noise on this. If the aircraft are getting a RIS they get information not separation. If the information includes a level based on unverified Mode C then that's what I'll tell the pilot.
Conversion factors, temperature and pressure corrections?? Get real. It's to do with providing the service that I have agreed with the pilot, not overcontrolling and separating every VFR pilot and his dog. And, by the way, just as you say, I take a pride in doing it very professionally.
I get the impression that you are saying that you will accept a level report based on any old setting and make a mental calculation to decide if it is within tolerance. Very professional - what conversion are you using, do you correct it for temperature and pressure, who has authorised that procedure, and what chance is there of you making an error if the Mode C is out of tolerance and you are busy?
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Originally Posted by 2 sheds
I get the impression that you are saying that you will accept a level report based on any old setting and make a mental calculation to decide if it is within tolerance. Very professional - what conversion are you using, do you correct it for temperature and pressure,
who has authorised that procedure,
and what chance is there of you making an error if the Mode C is out of tolerance and you are busy?
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Bookworm,
The Luton QNH is available via their ATIS. The London QNH is broadcast on the Heathrow ATIS frequency and on all of the London area VOR idents, if your NAV box has a voice facility.
We use our second VHF box to keep up to speed on the relevant local QNH via ATIS. We try to have the relevant QNH set before we call the ATC unit to which it belongs, so our altitude is immediately comparable to that of other aircraft they are working. We don't use RPS unless nothing more accurate is available, such as more than 25 nms away from an ATC unit and heading for the hills.
Had you "bust" airspace it is your good self, as the pilot in command, who would be found primarily at fault.
However, a second call to Brize, requesting the London QNH would surely have solved your dilemma?
The Luton QNH is available via their ATIS. The London QNH is broadcast on the Heathrow ATIS frequency and on all of the London area VOR idents, if your NAV box has a voice facility.
We use our second VHF box to keep up to speed on the relevant local QNH via ATIS. We try to have the relevant QNH set before we call the ATC unit to which it belongs, so our altitude is immediately comparable to that of other aircraft they are working. We don't use RPS unless nothing more accurate is available, such as more than 25 nms away from an ATC unit and heading for the hills.
Had you "bust" airspace it is your good self, as the pilot in command, who would be found primarily at fault.
However, a second call to Brize, requesting the London QNH would surely have solved your dilemma?
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UK AIP ENR 1.7
Altimeter Setting Procedures
3.9 Airspace within all Control Zones [ CTRs], and within and below all Terminal Control Areas [TMAs], Control Areas [CTAs] except Airways and the Daventry and Worthing Control Areas, during their notified hours of operation, do not form part of the ASR Regional Pressure Setting system.
3.10 When flying in Airspace belowTMAs and CTAs detailed above, pilots should use the QNH of an adjacent aerodrome when flying below the Transition Altitude. It may be assumed that for aerodromes located beneath such Areas, the differences in the QNH values are insignificant. When flying beneath Airways whose base levels are expressed as Altitudes pilots are recommended to use the QNH of adjacent aerodrome in order to avoid penetrating the base of Controlled Airspace.
Altimeter Setting Procedures
3.9 Airspace within all Control Zones [ CTRs], and within and below all Terminal Control Areas [TMAs], Control Areas [CTAs] except Airways and the Daventry and Worthing Control Areas, during their notified hours of operation, do not form part of the ASR Regional Pressure Setting system.
3.10 When flying in Airspace belowTMAs and CTAs detailed above, pilots should use the QNH of an adjacent aerodrome when flying below the Transition Altitude. It may be assumed that for aerodromes located beneath such Areas, the differences in the QNH values are insignificant. When flying beneath Airways whose base levels are expressed as Altitudes pilots are recommended to use the QNH of adjacent aerodrome in order to avoid penetrating the base of Controlled Airspace.
Originally Posted by Spitoon
I'm with Standard Noise on this. If the aircraft are getting a RIS they get information not separation. If the information includes a level based on unverified Mode C then that's what I'll tell the pilot. Conversion factors, temperature and pressure corrections?? Get real. It's to do with providing the service that I have agreed with the pilot, not overcontrolling and separating every VFR pilot and his dog. And, by the way, just as you say, I take a pride in doing it very professionally.
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You can request and should receive any pressures the unit has. However, you should have been flying on the RPS not the Brize qnh. The controller probably thought that you meant to ask for the RPS.
2 Sheds- at my unit SRG insist that if you issue a discrete transponder code to an aircraft to identify it, you MUST verify any associated mode C.
Towering Cu- it could be that RAF units don't even have access to local QNH as they tend to use QFE below TA and 1013 above it, hence for crossing the Brize Zone you would normally be asked to set Brize QFE, and outside the zone below TA you would be given the Cotswold regional; hopefully someone from Brize will pick this up and either confirm or refute!
I would personally suggest that if flying in class G below TA and NOT talking to ATC, you use RPS; if talking to ATC you use the observed QNH they give you.(But be warned some tower only ATC units plus FISO units with no qualified met observer may only be able to issue QFE!)
Towering Cu- it could be that RAF units don't even have access to local QNH as they tend to use QFE below TA and 1013 above it, hence for crossing the Brize Zone you would normally be asked to set Brize QFE, and outside the zone below TA you would be given the Cotswold regional; hopefully someone from Brize will pick this up and either confirm or refute!
I would personally suggest that if flying in class G below TA and NOT talking to ATC, you use RPS; if talking to ATC you use the observed QNH they give you.(But be warned some tower only ATC units plus FISO units with no qualified met observer may only be able to issue QFE!)
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Originally Posted by chevvron
I would personally suggest that if flying in class G below TA and NOT talking to ATC, you use RPS; if talking to ATC you use the observed QNH they give you.(But be warned some tower only ATC units plus FISO units with no qualified met observer may only be able to issue QFE!)
Originally Posted by 2 sheds
I don't know how the subjects of separation or over-controlling or type of service came into the disussion! Are you now saying that you would identify an aircraft with a discrete Mode A code but leave the Mode C unverified?
Going back to bookworm's original question - I was under the impression (please feel free to alter that impression) that a pilot could request any pressure setting he wished but set whatever the controller told him to depending on the aircraft's proximity to MATZs, active radar patterns, CAS etc etc.
I'm all for letting the flying fraternity getting on with what they want to do without overdoing it with altimeter changes every 2 minutes. Overcontrolling - no thanks, I don't get paid enough for the amount of controlling I do now so I'm not going to provide unpaid overtime as well!
Last edited by Il Duce; 14th Jun 2006 at 11:42.
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Applying separation under RIS... there is of course one ocassion when the Controller should take standard separation into account, and that's when vectoring a/c under RIS. The pilot would be quite entitled to be pissed off if the Controller's vector placed the aircraft into confliction, unless the pilot had been visual beforehand. An opinion that is IIRC backed up by several Airprox Reports?
But I digress?
But I digress?
Originally Posted by chevvron
2 Sheds- at my unit SRG insist that if you issue a discrete transponder code to an aircraft to identify it, you MUST verify any associated mode C.
The other point:
MATS Pt 1:
Controllers are to verify the accuracy of Mode C data, once the aircraft has been identified and the Mode A validated, by checking that the readout indicates 200 feet or less from the level reported by the pilot.
"Readout", not a rapid rough calculation because the pilot is reporting on a different subscale setting.
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Can't be bothered to read all of the posts as it is getting rather silly... however (and their are some exceptions to the rules, both individuals and units).... the majority of NATS controllers do not know how to effectively apply RAS/RIS - and the college instructors are amongst the worst.....
Maybe this lack of knowledge (or ignorance to use the word in its proper definition) is one of the reasons why military and civil do not always understand each other...
I will now step back from the fuse I have lit, but suffice to say, I have extensive knowledge of both sides of the operation..
Maybe this lack of knowledge (or ignorance to use the word in its proper definition) is one of the reasons why military and civil do not always understand each other...
I will now step back from the fuse I have lit, but suffice to say, I have extensive knowledge of both sides of the operation..