Regional QNH or 1013

[Driver6452]

Hi there, could anyone advise me on this one, planning a couple of flights above the transition level circa 5000 ft or FL 50, in uncontrolled airspace, and for terrain clearance I`m not sure what altimeter setting to use as were not planning to fly the quadrantal rules, the flights will be conducted VFR, asked some flight instructors and pilots with many more hours than me and the results are equal, also in the Trevor Thom manuals it states that if you have various headings use regional QNH, so any advice would be much appreciated thanks in advance.

[airac]

just watchout for the base of CAS it could be altitude or FL.:ok:
At 5000' I doubt you'll hit any terra firma

[Genghis the Engineer]

Above transition level (certainly above FL50 in the UK), I'd use QNE (1013) for traffic avoidance. Below TL, I'd use RPS (regional pressure setting, commonly but slightly incorrectly called regional QNH) for terrain avoidance.

And talk to ATC and make sure they know what setting you're using.

G

[BackPacker]

Is this a troll?

Above the transition layer you use 1013, below it you use the RPS for FL/altitude reporting. Simple really. The only variable is the altitude of the TL itself. And the RPS of course.

The quadrantal rule (or semi-circular rule) is formulated so that it uses altitudes (thus based on the RPS) below the TL, and uses FLs (thus based on 1013) above. Same goes for the vertical limitations of CAS.

At 5000' I doubt you'll hit any terra firma

I'm searching for an example where there is terrain that extends through the TA into the Flight Levels, and which would make a re-calculation of that terrain altitude to its corresponding FL necessary to stay safe. Does anyone know of such an example?

[englishal]

You don't have to use FL if VFR but I always do because most of the class A airspace (airways etc.) are normally a FL so it ensures you won't bust them. I'd always plan to try and fly at FL50 or above on a reasonably long x/c because you have less traffic to worry about up there and comms / radar are better. I'd always aim to fly a quadrantal level but sometimes that isn't possible due to the weird class A airways in the UK.

The TA is normally choses at an alt above the highest terrain around, so in the USA is is 18,000. IN the UK not much extends above 3000', though I reckon it would be sensible for Europe to have one common TA which is based upon the highest of the Alps.

[BackPacker]

You don't have to use FL if VFR

What you probably mean is "you don't have to fly at a rounded FL according to the quadrantal/semi-circular rule" if VFR.

But as far as I know you have to use flight levels in your reporting to ATC, if you're above the TL. I mean, you don't want to leave the mental arithmatic to the controller, do you?

"G-ABCD report altitude" "6200 feet QNH 1003 G-CD"
"G-DEFG report altitude" "FL65 G-FG"

Now is there a conflict or not? (And what's more important: How many seconds did it take you before you found the answer?)

[IO540]

Worth mentioning that most pilots don't actually care about any of the above, with the main objective being to keep out of controlled airspace ;)

So if flying below CAS whose base is defined as a flight level, you fly on 1013.

If flying below CAS whose base is defined as altitude, you fly on the actual QNH, but that gets a little tricky because the regional pressure setting is no good for staying below CAS. The "proper way" to stay below CAS whose base is defined as an altitude is to obtain the QNH from the ATC unit responsible for that piece of CAS (which you can do by calling it up, or by dialling up its ATIS).

[BackPacker]

Or you do as I do when doing aerobatics between 3000' (below the TA) and FL 55 (above the TL): Leave the altimeter on QNH and use the transponder to see what FL you're at (has to be a mode C or S, obviously).

(My usual aerobatics location has several layers of CAS so I run the risk of busting both below and above.)

[DB6]

Personally I find regional QNH to be fairly useless. If you don't want to use 1013 - and I don't bother if I'm just farting around aka enjoying flying - then I would recommend using the QNH of any airfield near your track (within 25nm if you want to be correct), and I would further recommend using ATIS broadcasts to get them as you don't have to bother making R/T calls then.

[Cusco]

If you're squawking 7000 Mode C (as you do, don't you?) your altitude on the radar controller's screen will be based on FL/1013, so it makes eminent good sense if you're above TL whether you're farting about or not to use FL /1013 on your altimeter.

Cusco

[MFC_Fly]

BackPacker wrote:

But as far as I know you have to use flight levels in your reporting to ATC, if you're above the TL. I mean, you don't want to leave the mental arithmatic to the controller, do you?

"G-ABCD report altitude" "6200 feet QNH 1003 G-CD"
"G-DEFG report altitude" "FL65 G-FG"

Now is there a conflict or not? Well since the controller in your example requested the pilot to report the aircraft ALTITUDE then G-CD responded correctly and G-FG didn't and was therefore the cause of any confusion :ok:

[MFC_Fly]

DB6 wrote:

Personally I find regional QNH to be fairly useless. If you don't want to use 1013 - and I don't bother if I'm just farting around aka enjoying flying - then I would recommend using the QNH of any airfield near your track (within 25nm if you want to be correct), and I would further recommend using ATIS broadcasts to get them as you don't have to bother making R/T calls then.And if there are no other airfields within 25nm of your track and there is high terrain that extends above the 3000' TA? RPS (or Regional QNH as you call it) does have its uses in some UK locations a little further north than where you are.

[Human Factor]

I'm searching for an example where there is terrain that extends through the TA into the Flight Levels, and which would make a re-calculation of that terrain altitude to its corresponding FL necessary to stay safe. Does anyone know of such an example?

Plenty around the world. None in the UK AFAIK.

[reportyourlevel]

The airport I work (UK) at has a transition altitude of 3000' and an MSA of 3200' in one sector - is that what you mean?

[Talkdownman]

Above transition level (certainly above FL50 in the UK), I'd use QNE (1013) for traffic avoidance. Below TL, I'd use RPS (regional pressure setting, commonly but slightly incorrectly called regional QNH) for terrain avoidance.
QNE, slightly incorrectly called 1013...

QNE is not a pressure setting. QNE is the reading in feet on an altimeter with the sub-scale set to 1013.2 mb when the aircraft is at aerodrome or touchdown elevation. During conditions of exceptionally low atmospheric pressure it is not possible to set QFE or QNH on some aircraft altimeters. In these circumstances an aerodrome or runway QNE can be requested.

1013.2 is the Standard Pressure Setting. Flight Levels are measured with reference to the standard pressure setting of 1013.2 mb. In the UK, consecutive Flight Levels above the transition level are separated by pressure intervals corresponding to 500 ft; at and above FL200, by pressure intervals corresponding to 1000 ft.

The Regional Pressure Setting is a forecast of the lowest QNH value within an ASR. The values which are made available hourly for the period H + 1 to H + 2, are given in whole millibars.

UK Altimeter Setting Procedures are here (http://www.ead.eurocontrol.int/eadbasic/pamslight-2C53C9DA382DF1EEB014B000B56E9ED1/7FE5QZZF3FXUS/EN/AIP/ENR/EG_ENR_1_7_en_2010-02-11.pdf).


If you're squawking 7000 Mode C (as you do, don't you?) your altitude on the radar controller's screen will be based on FL/1013, so it makes eminent good sense if you're above TL whether you're farting about or not to use FL /1013 on your altimeter.
The aircraft altitude encoder transmits Mode C data based on Standard Pressure Setting 1013.2. The radar processors will convert the readout to indicate altitude or flight level depending on the Transition Altitude and the QNH entered into the radar data processors.

[mrmum]

I'm searching for an example where there is terrain that extends through the TA into the Flight Levels, and which would make a re-calculation of that terrain altitude to its corresponding FL necessary to stay safe. Does anyone know of such an example?

Plenty around the world. None in the UK AFAIK.

Don't have a chart to hand, but as in UK airspace the transition altitude outside CAS is 3000', doesn't that make a lot of Scotland (outwith the Scottish TMA and Aberdeen CTR/CTA), bits of the Lake district and possibly Wales fit the bill. As for calculating altitude-FL's, isn't that why we have two altimeters in situations when we can't see the ground coming.

[soaringhigh650]

in UK airspace the transition altitude outside CAS is 3000'

What if you're OCAS below a CAS shelf? Is it still 3000 feet?

[Talkdownman]

What if you're OCAS below a CAS shelf? Is it still 3000 feet?
If below a TMA the TA is the TMA TA eg. London TMA TA 6000ft London QNH
Ref in UK AIP somewhere.

[mrmum]

Originally Posted by soaringhigh650
What if you're OCAS below a CAS shelf? Is it still 3000 feet?

Okay, by outside I should have specified outside laterally, not below a shelf

UK AIP (11 Feb 10) ENR 1-7-1 Civil Aviation Authority AMDT 2/10 ENR 1.7 — ALTIMETER SETTING PROCEDURES
1 Notification
1.1 The Selected Transition Altitudes listed in paragraph 4 are notified for the purposes of Rule 34 of the Rules of the Air
Regulations 2007.

3 General Procedures
3.1 The Transition Altitude within the UK is 3000 ft except in, or beneath, that Airspace specified at paragraph 4.1.

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 below TMAs 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 an adjacent aerodrome in order to avoid penetrating the base of Controlled Airspace.

4 Selected Transition Altitudes
4.1 The following Transition Altitudes apply to flights within or beneath the following Airspace:

Aberdeen CTR/CTA 6000 ft
Belfast CTR/TMA 6000 ft
Birmingham CTR/CTA 4000 ft
Bristol CTR/CTA 6000 ft
Cardiff CTR/CTA 6000 ft
Doncaster Sheffield CTR/CTA 5000 ft
Durham Tees Valley CTR/CTA 6000 ft †
East Midlands CTR/CTA 4000 ft
Edinburgh CTR/CTA 6000 ft
Glasgow CTR/CTA 6000 ft
Leeds Bradford CTR/CTA 5000 ft †
London TMA 6000 ft
Manchester TMA 5000 ft
Newcastle CTR/CTA 6000 ft
Scottish TMA 6000 ft
Solent CTA 6000 ft †
Sumburgh CTR/CTA 6000 ft †

† Note: Outside the notified hours of operation the Transition Altitude is 3000 ft.

[soaringhigh650]

This is horribly complicated and potentially dangerous too. :uhoh:

There needs to be a common TA.

[englishal]

What you probably mean is "you don't have to fly at a rounded FL according to the quadrantal/semi-circular rule" if VFR.
No I mean (in the UK) you can set the local altimeter setting and fly around at an altitude. For example if I am VFR from X to Y I can call up ATC and request something and report my altitude as Altitude 7000 on QNH 1002 for example. There is no requirement to set 1013 above the TA for VFR flight.

However it is wise to. I heard some chap on the radio on his way to the Channel Islands the other day at 4000' QNH. The controller advised him that he may infringe Q41 which has a base of FL35 to which he replied that on that altimeter setting he should be below FL35...."shouldn't he?". Then the controller responded that she'd get back to him after she had calculated it. Would have been a lot easier for him to just set 1013 on the altimeter and remain below FL35.

Of course around the LTMA the airspace is delimited by altitude (London QNH), elsewhere it might be flight level. It does get horribly complicated especially when you get say an airway which is defined as "FL65 (Minimum altitude 5500')".

[cats_five]

<snip>
In the UK not much extends above 3000', though I reckon it would be sensible for Europe to have one common TA which is based upon the highest of the Alps.

Lots of points (and ridges) above 4,000' in Scotland, and the highest of the Alps is almost 5,000m so a common TA looks rather unlikely to me.

[mrmum]

This is horribly complicated and potentially dangerous too.

Yes it is, I think we should just have a UK (or Europe) wide TA of say 10,000' - just to pick a nice round easy number. That would leave most light aircraft operations where we wouldn't have to bother with it, or the completely pointless system of quadrantal FL's. The base levels/altitudes of some CAS would have to be redefined, but how hard's that.

It's rubbish that being at the appropriate quadrantal gives any kind of protection from a collision with other aircraft in class G airspace. What it does do, is make being terrain safe and staying out of airframe icing conditions unnecessarily tricky other than in summer.

For example;

MSA of 4,600'
Freezing level of 6,000'
TRK(M) of 300*

to keep it simple, let's say the QNH is 1013mb, assuming we are IFR in cloud, we are obliged to be at an even+500 FL, FL45 is below MSA so can't be used, FL65 will put us in known icing, so that's no good either. If we didn't have to use a low TA and FL's, we could simply pick any convenient altitude between 4,600' and 6,000'

[bad bear]

This is horribly complicated and potentially dangerous too.

There needs to be a common TA.

I totally agree soaringhigh650, what would your prefer, 10,000' or 18,000'?

It would solve so many problems
bb

[soaringhigh650]

what would your prefer, 10,000' or 18,000'?
18,000'. But I think the UK is moving towards 6,000 now. I'm not sure what the rest of Europe is doing.

[bad bear]

I hear that inside CAS it will be 6,000' in the Uk and that several airports are working to have the change in place for early next year, but, still 3,000' outside. I hope we see 18,000' in UK very soon both inside and outside CAS
bb

[2high2fastagain]

A higher TA certainly sounds sensible to me. I've always thought that it should be set at a safe height so that if you're flying above the TA, you know you won't hit anything (even in very low pressure areas). I guess the question is whether this works for you chaps flying in Nepal?

[Mickey Kaye]

dito 18,000 feet, Scrap RPS and QFE.

[IO540]

18000ft has no meaning in the UK or Europe.

The USA has picked it because above 17999ft is a uniform layer of Class A (to 59999ft I believe, above which it is Class E).

VFR cannot go into Class A, and they have mountains reaching about 16000ft, so it was logical for them to do it this way.

In the UK, 18k would mean nothing. There is Class C at FL195 I think but that's about it.

France is closer to the US model, with Class D at FL115 and Class A at FL195. But the UK is just a mess.

Equally, the 3000ft TA is meaningless. It should be a lot higher, because "flight levels" that low down cannot be flown while respecting MSA, in many places.

[honda cbx]

If your flying VFR, you use Regional QNH, and you dont use the Quadrant rule. Even if your above the TL.

[BackPacker]

PS the US could conversely benefit from adopting millibars for altimeters - easier to remember.

No, you will not want to do that. If you're changing subscales, you need to go all the way and adopt hectopascals. Otherwise you've got another conversion process on your hands in a few years time anyway.:=

[englishal]

If your flying VFR, you use Regional QNH, and you dont use the Quadrant rule. Even if your above the TL.
I don't. I fly at FL and try and fly quadrantals. The reason for this is two fold - 1) most upper airspace is defined by FL (i.e. airways) and this ensures I don't bust them, and 2) If I happen to meet IMC conditions en-route I can continue IFR with minimal fuss.

Altimeter subscales are just numbers. It doesn't matter whether it is 2992 or 1013 you just twist the relevant number in. Same as if your ASI is marked in knots, MPH or KMH, you just fly the numbers and don't even bother trying to convert them, so no big deal.

I think a TA of 18k would be good because it would bring Europe in line with the USA and it would ensure clearance of all of Europe's highest mountain peaks. I'd then suggest that the UK drops the Class C from FL195 to FL180, just so we know where we stand with regards to upper airspace.

[honda cbx]

Englishal, i can't belive if your flying at say 4000ft (TL 3000ft) you would use FL's or the quadrant rule for VFR flying!!. Also, changing to IFR flight rules if you happen to meet cloud is ok if your qualified, best way is if your VFR, stay VFR, or dont fly.

[CJ Driver]

Why do you all keep banging on about regional pressure settings? Regional pressure settings are primarily intended for non-radio traffic, either because you don't have a radio, or are flying out of radio contact of a nearby facility. They are intended as a last resort - if you lose contact with an ACTUAL source of pressure setting information (a nearby ATIS, an airfield, whatever), you can resort to the RPS. Converserly however you should NEVER set the RPS if you have access to better and more current actual pressure information. Which, in the UK anywhere South of Dundee, and North of the Channel, is pretty much all the time. (Except for those of you who do actually fly NORDO).

[englishal]

Englishal, i can't belive if your flying at say 4000ft (TL 3000ft) you would use FL's or the quadrant rule for VFR flying!!. Also, changing to IFR flight rules if you happen to meet cloud is ok if your qualified, best way is if your VFR, stay VFR, or dont fly.
Why not? Why not fly at FL40 in that case, or 45, 50, 55, 60, 65, 70, 75, 80, etc.... for that matter if you can? if I was coming down across Wales I'd climb to FL75 rather than at 7500' I might even try FL195 VFR ;)

FL will ensure you don't bust airspace as they will be marked in FL. How do you know, for example that 6500' Regional will keep you clear of the airway North of exeter which is FL65?

PS If you fly to France or go to the USA you HAVE to fly semi-circular rules when VFR (odd+500, even+500), no choice. So may as well get into the habit. It might also seperate you from IFR traffic.

[Maoraigh1]

"Why do you all keep banging on about regional pressure settings? Regional pressure settings are primarily intended for non-radio traffic, either because you don't have a radio, or are flying out of radio contact of a nearby facility"
I'm happy to fly on whatever altimeter setting an air traffic facility give to me, eg QFE for Lossie Approach. It never occurred to me that Inverness and Scottish sometimes give me Portree, Orkney, occasionally Belfast, expect a readback, but don't want me to set it on the altimeter.

[IO540]

GPS altitude?

;)

[madlandrover]

It never occurred to me that Inverness and Scottish sometimes give me Portree, Orkney, occasionally Belfast, expect a readback, but don't want me to set it on the altimeter.

As ATS providers they're required to give you any information to affect the safety of your flight - but it's down to you to decide what to do with that information. I had a good example flying with a student the other day, when a military LARS provider insisted that the airway in front of us was defined on a RPS rather than (in this particular case) a local airfield QNH. Wasn't an issue for us because we were descending well below it anyway, but it would have been quite possible for them to push someone into an infringement due to incorrect altimetry.

[sunday driver]

Well I'm now completely confused

There's only one thing for it ...

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