Upper VS Uniform (for letter U)

[Tango23]

Hello everybody

Many times when the ATC clears us for an airway they would say for eg. (clear Upper Alpha 1 1 2) for UA112 and not Uniform Alpha.

Any Idea what's the reason behind this?
Or maybe it's a regional thing and not global:hmm:

[Up North Like]

You could have UA112 or perhaps LA112. U meaning Upper Airway and L meaning Lower Airway :)

[Tango23]

Thanks UNL for the reply

Okay, but in that case what about the airways that start with W or N for example?

and why don't they call L Lower instead of Lima?

Thanks for the reply again

[chevvron]

The 'split' depends on what the particular country you are flying though classes as 'upper' and 'lower' airspace. In the UK it is now FL195 as it is in most of Europe but previously it was FL245. An upper air route may be slightly different from its lower airway in spite of the numerical value being the same as the airway in lower airspace may need to deviate slightly to avoid (say) a danger area which might not extend into the upper airspace..

[zonoma]

Airways were just the single letter (no U or L beforehand) and numbers and denoted the airspace within 5nm of the centreline with a specific classification when in Lower Airspace. "Upper Air" starts at a defined FL (FL195+ in the UK) where all the airspace is designated Class C. The U was added to Upper air routes which is just a single centreline and aircraft within 5nm of the centreline are classed as "on-route" within that Class C airspace.

It's all historic now as slowly all the "U"s are being withdrawn and everything is being classed as an air route so expect no "U"s anywhere in a few years time!

[Little One]

ICAO Annex 11 Appendix 1

4. Use of designators in communications
4.1 In printed communications, the designator shall be expressed at all times by not less than two and not more than
six characters.
4.2 In voice communications, the basic letter of a designator shall be spoken in accordance with the ICAO spelling
alphabet.
4.3 Where the prefixes K, U or S specified in 2.3 are used, they shall, in voice communications, be spoken as follows:
K — KOPTER
U — UPPER
S — SUPERSONIC
The word “kopter” shall be pronounced as in the word “helicopter” and the words “upper” and “supersonic” as in the English
language.
4.4 Where the letters “F” or “G” specified in 2.4 are used, the flight crew should not be required to use them in voice
communications.

So they should be spoken as Upper and not Uniform

[Tango23]

chevvron
zonoma
Little one

Thank you very much guys, now it started to make much more sense
I'll pay closer attention to the future flight plan routes that I'll fly to connect all the dots.

Grazie

[Little One]

There was a question about why certain letters like N and Q were used but seems that Question has been deleted. For those still looking for the answer its also in Annex 11

2. Composition of designator
2.1 The ATS route designator shall consist ofa basic designator supplemented, if necessary, by:
a) one prefix as prescribed in 2.3; and
b) one additional letter as prescribed in 2.4.
2.1.1 The number of characters required to compose the designator shall not exceed six characters.
2.1.2 The number of characters required to compose the designator should, whenever possible, be kept to a maximum
of five characters.
2.2 The basic designator shall consist of one letter of the alphabet followed by a number from 1 to 999.
2.2.1 Selection of the letter shall be made from those listed hereunder:
a) A, B, G, R for routes which form part of the regional networks of ATS routes and are not area navigation routes;
b) L, M, N, P for area navigation routes which form part of the regional networks of ATS routes;
c) H, J, V, W for routes which do not form part of the regional networks of ATS routes and are not area navigation
routes;
d) Q, T, Y, Z for area navigation routes which do notform part of the regional networks of ATS routes.
2.3 Where applicable, one supplementary letter shall be added as a prefix to the basic designator in accordance with
the following:
a) K to indicate a low-level route established for use primarily by helicopters;
b) U to indicate that the route or portion thereof is established in the upper airspace;
c) S to indicate a route established exclusively for use by supersonic aircraft during acceleration, deceleration and
while in supersonic flight.
2.4 When prescribed by the appropriate ATS authority or on the basis of regional air navigation agreements, a
supplementary letter may be added after the basic designator of the ATS route in question in order to indicate the type of
service provided in accordance with the following:
a) the letter F to indicate that on the route or portion thereof advisory service only is provided;
b) the letter G to indicate that on the route or portion thereof flight information service only is provided.

[Tango23]

Little One, You ROCK!