scrap regional pressures

[BigEndBob]

Would it be a good idea to scrap regional pressure settings and up the transition altitudes to a common level.

There are enough airfields to get up to date QNH's and have a better idea how far we are above ground should we have an engine failure. We would be on an appropriate setting for transiting around, under or through mainly class 'D' airspace.

Make transition altitude 6000, this might give faster aircraft crews more time for after takeoff checks and prevent level busts.
Flying at FL35 in the UK you wouldn't have to worry about flying into high ground during low pressures, because FL35 wouldn't exist. Half the traffic above 3000' now isn't flying quadrantals because its general handling, climbing or descending.

Regional pressures are just as good as say subtracting 500' to any aerodrome QNH we may have set as a safety factor.

Introduce a Welsh and Scottish QNH for remote areas.

[eagerbeaver]

i have often thought this too, i hardly ever use the regional unless i am miles from anywhere, but it is the lowest forecast pressure and so as long as you remember that and keep thinking ahead its the safest option some of the time. (I have never seen a huge diference between a qnh and the regional)
I have always found (with regards to terrain clearance and on QNH) that a lot of people always forget to account for the height of the ground and always over-read the altimeter (eg pfl's) so it all goes fuzzy anyhow as they are reading the alt incorrectly.

or is that just rubbish?

good topic though......

[StrateandLevel]

I made the same point some years ago but was advised by the chaps at DAP that the regional pressure was very useful. So far I have not discovered what its useful for! Its origins are no doubt centered around Coastal Command Sunderlands and Shackletons flying IFR below 3000 feet.

[RobinHood]

BigEndBob

I'm glad I'm not the only one to see that Regional Pressures are about as useful as cholcolate fireguards.

All day long I hear people requesting the Barnsley and Cotswolds, getting all flustered and confused over 1 millibar, reading them back incorrectly, and then not using them anyway!

And whats the need for regional pressures anyway???

The purists will say "ah, its so you can guarantee terrain clearance!" What difference has a couple of millibars ever made to a CFIT accident? I can't ever recall a situation where an aircraft struck high ground because he had a QNH set instead of the regional pressure. We're generally only talking a few millibars here, so if a few millibars is what makes the difference between hitting the ground and not hitting it, I think its fair to say the aircraft would be flying too close to terra firma anyway!

Interestingly, the terrain clearance argument works both ways. How many pilots have unwittingly flown just under the base of a CTA with regional QNH set, only to discover that when they set the aerodrome QNH they are inside controlled airspace!

It is my understanding that the other purpose of regional QNH is that it gets aircraft flying outside controlled airspace on the same altimeter setting. To me this is exactly what we don't want - every man and his dog buzzing around at 2000 feet on a Sunday afternoon on the same setting.

I personally think it is more prudent to set the QNH of aerodromes en-route, updating the altimeter as you go. This way your looking at an accurate indication of altitude, which to me is much more useful and reassuring than confusing the situation and flying an altitude which is anything but true.

I can't see why we need to bother with a bunch of altimeter settings we don't need. If it was up to me I would ditch QFE as well, but thats another debate!

Cheers all

[Tinstaafl]

Aerodrome QNH last night: 1018
Regional QNH last night: 1005.

That made RQNH about as useful as tits on a bull to me on an IFR flight at night into an aerodrome in a valley without an instrument approach. I want to know my actual terrain separation thanks. Nearly as bad is having to use a plethora of aerodrome QNHs while travelling from A --> B. I'd rather see an area QNH that isn't the lowest but is within (say) 3mb of the area's aerodrome QNHs ie ~100' of max. deviation.

Oz uses 5mb ie the area QNH has a max deviation of 5mb from the actual QNH anywhere within that area. That gives a 150' margin of error. Still acceptable I think. If there is a greater deviation then the area is subdivided as necessary. Works well and elimates the UK problem of the artificially low Regional QNH setting putting you inside a CTA step. All aircraft outside the circuit use the AQNH, circuit/approach traffic use the AD QNH.

This allows en-route traffic to utilise a common QNH for comparison & separation AND allows flight past airstrips/aerodromes/CTA without being too far different from local.

Not having a/c on a common QNH is worse. How can you have a meaningful comparison of altitude eg climbing/descending/crossing a/c, if your reference points are arbitrarily different?

[RobinHood]

"Not having a/c on a common QNH is worse. How can you have a meaningful comparison of altitude eg climbing/descending/crossing a/c, if your reference points are arbitrarily different?"

My point here is that in reality a large percentage of the traffic in any given area is using an aerodrome QNH or QFE i.e. it is departing or arriving an aerodrome in that area. So what you've got is a mish-mash of traffic on all different settings regardless of whether they are using regional QNH. So even if you can compare altitude of traffic using the regional QNH, how do you account for the other traffic in the area which is using aerodrome QNH/QFE???

[slim_slag]

Where do the ATC guys get the pressure when calculating lowest usable flight levels? Must be regional to some extent, closest reporting station within 100 miles?? If you don't get the lowest usable flight levels right then you can have conflict between an aircraft flying at the transition altitude using 29.92, and one flying just below using reported pressure.

[FormationFlyer]

With regard to transition altitude.....

if I am general handling ifr or vfr my heading changes sooo much that I am less worried about a/c separataion than I am terrain clearance - nearest a/d qnh is far far more important to me in this scenario...

[Tinstaafl]

I think there's a terminology misunderstanding. UK uses a regional QNH. Oz uses an area QNH. On the surface they seem the same however there's fundamental difference between them.

UK regional QNH: The lowest forecast QNH for the whole region/area
Oz area QNH: The QNH accurate to within 5 Hpa (Mb) of all QNHs for the area. The predefined AQNH regions/areas are subdivided as necessary to maintain not more than 5Hpa difference.

The upshot is that there is only 150' max difference for a/c on a local/aerodrome QNH vs. area QNH. Accurate enough for traffic comparison. This is not the case for the UK regional QNH. The tolerance is considered sufficient to be acceptable for CTA step penetration avoidance

An area QNH is great for cross country flights because it reduces the number of QNHs that must be sought & set and keeps all the cross country traffic on a common reference. All a/c apart from local/aerodrome traffic use the single AQNH but are still no more than only 150'/5Mb different from the local traffic.

My preference would be for a 100'/3Mb tolerance. Easily do-able in the UK