Trans alt/level (Ireland & UK)

[genius-747]

Hello, a quick question about Transition altitude and level.

I know in Ireland the transition altitude is set at 5000' within the Shannon FIR, meaning that every a/c once climbing through 4999' on the regional QNH must then set 1013HPa (QNE) in the altimeter subscale.

However in the UK I know the transition altitude is different in places, but I think it is mainly 3000'... am I correct?
And I can only persume that if the trans alt is 3000ft then everything above that is expressed on R/T as flight levels...FL35, FL40 etc...

Here is where the confusion lies for me.

Take for example a short hop from Dublin (EIDW) to The Isle of Man (EGNS) in a C-172 VFR.

Because you are heading between 000 and 180 and VFR you should cruise at odd+500 ie. 35, 55, 75 etc..

If, when you tune the Dublin ATIS and you here that the Trans Level is FL60... does this mean that you cannot cruise at FL55 and indeed the next available cruising level for the little cessna is FL75 (which may be out of reach of the climb performance if max weight!!)

Am I correct in saying if the Transition level is FL60, NOTHING may cruise between 5000' and FL60 no matter what?
Like wise if the Transition level if FL70 NOTHING may cruise between 5000' and FL70 (2000')...is that correct?

Finally if say you decide to plan the trip at 3500', when in the Shannon FIR you will be using the regional QNH in the subscale, but when you then enter the Scottish FIR/London FIR and their trans alt is 3000' are you expected to immediatly change to 1013 once you cross the FIR boundry?

If so how does this effect your cruising height if maby their trans level is higher than FL35?



I know there is a lot there to deal with, but I would really appreciate any help because I am PPL holder that wants to make some trips from Ireland to the UK and this really bothers me at the moment.

Thanks people!

[Aussie Andy]

G'day genius-747 - you may be getting a couple of things mixed up. I'm a bit pressed for time so will be brief (and apologise in advance if this is unclear):

1) Transition Altitude - this relates only to pressure setting for your altimeter subscale. In the UK it is generally 3,000' but in some areas it is 6,000' or some other setting and if non-standard (i.e. where not 3,000') this will be advised either on the approach plate or by ATC via ATIS etc. In the US its 18,000' I believe!

2) Cruising level - In the UK we use the quadrantlal rule, not the ICAO standard semi-circular rule (more's the pity!), but lets not get hung up on that at this stage: lets stick to the semi-circular rule example you have used here for arguments sake. If the rule says "odd + 5" then you set QNH and fly 3,500' or 5,500' or 7,500' or 9,500' etc. as long as below the transition altitude, BUT once you are above the transition level (whatever it may be - whether FL030 or FL180) you fly the equivalent flight levels (i.e. set to 1013.2mB) and fly e.g. FL035, FL055, FL075 or FL095 etc. as appropriate.

Make sense!?

Andy

P.S. Quadrantal rule (when in UK FIRs):
Mag Track 000-089 - ODD FL
Mag Track 090-179 - ODD FL + 500'
Mag Track 180-269 - EVEN FL
Mag Track 270-359 - EVEN FL + 500'Also:
When descending from FL to altitude: vertical position is given as altitude.
When climbing from altitude to FL: vertical position is given as FL.

I think! :bored:

[FlyingForFun]

Also, you specified that this is a VFR flight. For VFR, the quadrantal rule is recommended above 3000', but not mandatory. It is only mandatory for IFR flights. I assume that this is similar to Ireland, but I don't know.

FFF
--------------

[Aussie Andy]

Good point FFF - but g-747 its worth bearing in mind that if you cross the next FIR boundary from UK into France then you are back on the semi-circular rule and (for some reason I don't understand) ATC there expect you to be on a "VFR semi-circular" level and will tell you off if you report otherwise!

Personally, I feel a bit safer if +/- 100' or 200' from these levels.. but then again, it seems everyone else thinks so too! Ultimately of course, under VFR, we have to see and avoid!!!

Andy :O

[Lucifer]

Take a look on the plates for your destination at IOM, and it will tell you what the TA is for that area.

[Chilli Monster]

If, when you tune the Dublin ATIS and you here that the Trans Level is FL60... does this mean that you cannot cruise at FL55 and indeed the next available cruising level for the little cessna is FL75 (which may be out of reach of the climb performance if max weight!!)

It's probably worth pointing out here some basic altimetry, as what you've written doesn't actually happen.

Transition LEVEL is a function of Transition Altitude and QNH. It doesn't mean, as you say in your examples, that you can't fly in the levels that are between Transition Altitude and the Transition Level - what it means is those levels don't actually exist!

Example: QNH is 977mb, Standard is 1013. That's a 36mb difference or, another way to look at it is 1080feet (30ft / mb).

5000ft + 1080ft is 6080ft or FL60.8.

So - 5000ft QNH equals FL60.8

First available FL (Transition Level) is therefore FL65 (you always round up).

Conversely - go the other way:

QNH is 1037, difference from 1013 = 24mb or 720ft

5000ft minus 720ft equals 4280. Round it up, transition level equals FL45, which is 220ft above 5000ft on the QNH.

So - you can fly at any level you like up to 5000ft - (or whatever your local Transition Altitude is - for those of us in the UK mainly 3000ft but there are local differences for certain Control Zones and TMA's) but above that it's time to do some mental maths.

Rule 1 - don't fly at Transition level. Depending on Pressure it can be close to the Transition Altitude. First available in the UK is normally 500ft above TL. That guarantees you at least 500ft separation as provided by the quadrantal rule in the UK.

[Whipping Boy's SATCO]

Rule 2 - Flying at TL+500 (MFL) doesn't necessarily guarantee terrain clearance. If IFR, you need to calculate the Minimum Safe FL.

[dublinpilot]

fff,

I could be wrong, but I believe that flying on the semi-circle rule above 3000 in Ireland, if mandatory for VFR flights too.

Leglisation says "Shall", which I take to mean is compulsory.

dp

[FlyFreeWbe]

Following on from Chilli Monster
Transition Level is a flight level (IE FL45, FL60 etc) and Transition Altitude is a "height" (in speech marks due to the books use of height, level and altitude). To me, this means that if an aircraft was climbing, 1013 would be set on the altimeter once through 3000'; on descending, regional QNH would be set once through FL45. (as Aussie Andy alluded to)

The pressure in the UK rarely goes below (or near) 950 millibars, or above (or even close to) 1050 millibars. The usage of those altitudes therefore allows for 1,500 feet

1013-950 = 63
1050-1013= 37

At 30 feet per millibar, that'll give 1890 feet tops. 1500 is good enough as we don't often see those extremes.
FFW

[Chilli Monster]

FlyFreeWbe

What the F:mad:k are you talking about? If ever a post was full of confusing, meaningless twaddle that was it.

Also Transition Altitude is just that, an Altitude. Height is vertical distance derived above a specific point or datum at ground level.

[FlyFreeWbe]

I did ask you to forgive me, No need to swear.. Basically saying how two peeps flying @ 3000' and FL45 respectively won't ever collide. I got confused reading the first posts, and thought this was relevant. Hopefully no harm done.

[Chilli Monster]

Basically saying how two peeps flying @ 3000' and FL45 respectively won't ever collide.
Not necessarily.

3000' on a QNH of 963mb equates to FL45. I have worked in an area where the Regional Pressure Setting at one time was approaching 950mb - and people were still flying (Northern North Sea).