FL 55 or 5500' ?
 

Query from today. Flying in Class G on 010R from the LYD VOR, and climbing to 5000', with Class A above at 5500' (alt). This was a simple IMC training Ex. and I am FE/FI at Lydd. QNH 1000hps.
Contacted Manston for a basic service, stating that we would remain "outside controlled airspace". The plan was to carry out a procedure turn at LYD 12D,and set a monitored descent back towards the LYD VOR. (We were VMC). Manston reminded me that there was a "stub" airway involving SANDY, at FL 55. Given the QNH, we descended and completed the exercise.
Checking my Low level IFR chart, I see that N57, WIZAD to DET has low FL of FL 55, in an area marked on the 1/2 mill VFR chart as Class A at 5500'. I also note that on the IFR chart (euronautical) the "Worthing" Class A starts at FL 55, not 5500', as on the VFR chart. Can anyone explain this potential conflict. (Many thanks JT)

Transition altitude under the LTMA is 6000ft; outside the LTMA it's 3000ft.

Hardly surprising that there is such confusion with inconsistent TAs at different places, at adjacent locations, at different times of the day and some being non-terrain-safe.

The sooner we have a harmonised terrain-safe TA in the UK the safer and simpler for all. It is a pity that the wheels have to grind so slowly...

Why don't they change to 6000ft everywhere while they're deliberating about whether to have 10,000/12,000/18,000 ?

PS to the above, last night I found my (Aerad/Navtech) London area chart and this airspace seems to be crossed by numerous airways, with a base of FL 55. Eg. L10, N57, M140,Y47 and Y803. Is it correct to say the first 500' of the airway base is not used and therefore is not a conflict if the Class G below is defined as a FL?

There was a change last year in this area where by the whole of the Worthing CTA now is subject to a transition altitude of 6000'.

I believe the rules are that it is permissible to cross an airway at its base level at right angles, I'm not sure that is possible with the mix of airways in that area all going in different directions. If that is true, then you would have to remain 500' clear, which with a QNH of 1000 would mean 4'600ft maximum give or take.

From UK IAIP ENR 1.1-2 Para 1.4.1.5.1

Aircraft may ALSO, without ATC clearance, fly at the base of ANY controlled airspace in ANY direction when the lower limit is defined in ANY way [except, of course, GND].

By ICAO definition, the boundary between airspace of two different classes is the lower of the two classes, so the base level of an airway above the open FIR is Class G.

Although doing so is probably bad airmanship considering climbing by 1 ft would result in an infringement.

To answer Pembroke's question: This looks like an error to me. No airway should be defined with a FL base below the TA. This airway section is within the London TMA (TA 6000ft), so a FL55 base is wrong. Also, a TMA and a CTA should encompass all airways within there lateral boundaries below their top level, although I am not sure that this is a hard and fast rule.

I have an idea how that might have happened: That part of the airway is NOW within the London TMA, but until recently it was part of the Worthing CTA, where the TA is 3000ft. That part of the CTA was redesignated to London TMA in 2012, I believe, but someone forgot to change the base levels of the airways within that chunk. Evidence? the AIP entry for airway N57 at SANDY actually says

Except that this is now the level change between Worthing CTA and London TMA, where the TMA base is 5,500ft.

Hence the VFR chart and the IFR charts disagree, the VFR chart only shows the LTMA, the IFR chart shows the airway base, both using different sections of the AIP as equally authoritative source...

Might be worth mentioning to the CAA...

I have sent an e mail to NATMAC, and hope it gets sent to the relevant department.

The current system of transition altitudes (TA) is a total mess. The TA varies between 3,000ft and 6,000ft, with some areas of airspace having different TAs at different times of the day.

Surely it must be a matter of priority to introduce a common terrain safe TA within the UK , and then decide whether a higher TA (10,000ft; 12,000ft or 18,000ft) should be introduce throughout Europe?

Who do you suggest does the work for that?

Directorate of Airspace Policy.

I've been trying to find out a few better answers but not quite finding the final answer.

In those parts of the Worthing CTA where the airway bases are FL65 and FL75, London ATC have procedures when the QNH falls below certain values, the lowest available flight level rises. Basically, under those segments, the transition altitude of 6000' is always outside CAS and always available, the airway loses levels to provide separation. I cannot find any entry at the moment that relates to the FL55 segment but will post back when I do.

Sounds like the procedures for the holds in the TMA. ATC has a chart showing which FLs are available in the holds to provide 1000ft separation above the TA of 6000 ft.

It's exactly that HD, but still can't find anything about the bit of the airway inside TC's control with FL55 as the base. I've checked the Air Pilot and that also states the base as FL55 which I do agree, is a little strange. I'm sure separation is provided and that Pembroke doesn't have to avoid this airway, just can't find the definitive answer that confirms this!

Consultation - Transition Altitude | Consultations and Responses | About the CAA

The CAA has been consulting on the transition level - 18000 was proposed. details in the URL above.

<<transition level - 18000>>

Someone else who is confused?

The highest elevation in the UK FIRs is Ben Nevis, 4,409' amsl.
Therefore there is no requirement for an 18,000' transition altitude. 6000' would work well in UK/FAB airspace. It works in the LTMA, some of the busiest and most professionally controlled airspace in the world.
OK, you could possibly argue for 8000' over Scotland if the pressure was really low. I don't know why the Irish want 18,000 as Lugnaquilla is over 1000' lower than Ben Nevis.

Forget transition-levels also, and the transition-layer for that matter.

What matters is the lowest flight level providing a MINIMUM separation of 1000' from aircraft operating at the Transition altitude of 6000'. It's often called 'Minimum Stack level'.
"Separation standards are minima".

Much of the en-route sector structure involves interfaces at FL195, therefore major engineering would be required, by organisations which seem to be focussed on reducing costs.

Wise words Zooker...