Primarily for general aviation discussion, but other aviation topics are also welcome.
... and if I don't, then presumably there are others that also don't know.....

Spurred on by the TMZ - is mode S required or not threads and wondering where the requirement for TMZs are specified has got me wondering......

Looking more generally than TMZs, there is EU law (part FCL, Part med Part NCO etc.) , there is UK law (mainly the ANO).... There is also the Rules of the air (Part SERA and the UK add-on (ROTA regs))

Then there is the AIP, CAP documents, ORS documents and maybe others.

What decides what goes in a CAP, what goes in the AIP and what goes in an ORS(4) (are there other ORS other than 4?)

What legal status do they have?
As I've got to keep an eye on some damp paint at the moment I don't have the time to go through all of those regulations, but do any of them mandate mode S (for, I assume you mean, a private flight in a small aeroplane)?

If not then I'd suggest mode S is not generally mandatory at our end of the flying world.

EASA Air Operations rules do mandate mode S for bigger, hairier, aircraft as do some of the equipment schedules in the ANO.
Regarding the specific question of TMZs it’s SERA.6005 which says

All flights operating in airspace designated by the competent authority as a transponder mandatory zone (TMZ) shall carry and operate SSR transponders capable of operating on Modes A and C or on Mode S, unless in compliance with alternative provisions prescribed for that particular airspace by the ANSP.

The other regs you mention are about carriage of mode s for certain classes of aircraft all the time aren’t they?

The next para for 6005 says

Airspaces designated as radio mandatory zone and/or transponder mandatory zone shall be duly promulgated in the aeronautical information publications

It seems to be spread over multiple places in the U.K. AIP

Going back to the more general question, Statute, AIP, CAP, ORS? what are the rules about what goes where and who decides?
CAP just stands for ‘CAA Publication’ - pretty much every significant document ever produced by the CAA since the current numbering series started (I’d guess some time in 1980s) has a CAP number. I think they are somewhere in the 1500 - 1600 series at the moment.

There are no rules as such about the status of the contents - it could be anything from the CAA’s own formatted consolidation of the ANO (393) or other regulations (such as 804), to airworthiness regulations (such as 747), which have a sort of delegated legal status from the ANO, to the Skyway Code, which is a mixture of rules referenced from regulations and pure guidance.

ORS4 is just the dumping ground for general exemptions, derogations and permissions that are made against and/or under the ANO or other European legislation, so everything there generally has legal status.

The structure of the AIP is set by ICAO. AICs seem to have gone out of fashion a bit recently, but they are yet another way of the CAA issuing information.
PaulB liked this
So is it all a random mess? I was hoping for some logic, so that when you're looking for something, you'd be able to hazard a reasonable guess as to whether it was in statute, the AIP, a CAP/ORS* or even s standards document.

* Is there an ORS 1, 2 & 3?
As Ed said, the format and structure of the AIP is set by ICAO and is the mechanism by which pilots from other states can brief themselves on arrangements in the UK.

Originally, the purpose of CAPs was to transpose ICAO SARPS and PANS into the UKs rules, because those ICAO requirements are not directly applicable to the UK. This has become blurred somewhat with EU law which is directly applicable to the UK and does not have to be duplicated in CAPs but sometimes has been.
I'd recently read the discussions here about the removal or the SERA class D exemption, the 500' rule and the Farnborough airspace and was thinking does it all have to be as complicated as this?

Surely, it should be easy to find accurate up to date information that's clear and concise. If we can't find it, how would someone visiting the UK find it (especially if English was not their mother tongue)?

I've just seen this on Twitter so am wondering is the current system complicated or complex (or perhaps made over-complicated or over-complex) and how we could make it simple(r)


From here

G-JWTP liked this
Point of note, but would have thought only Mode C or Mode S transponders appropriate (for use in TMZ) as Mode A only transmits identifying code only. Mode C equipment enables the ATCO to see the aircraft altitude or flight level automatically. Mode S equipment has altitude capability and also permits data exchange. Stand to be corrected, but cannot see how Mode A transponder-equipped aircraft can go into the TMZ? Whole point is for controller to see who you are and where you are?
Mode C is not sufficient for a TMZ, it must be Mode S.
GEN 1.5
5.3 Carriage of SSR Transponder Equipment
5.3.1 The requirements for the carriage of Secondary Surveillance Radar (SSR) transponder equipment are hereby notified for the purposes of the UK Air Navigation Order. Aircraft shall carry SSR Mode S transponder equipment as prescribed in sub-paragraphs (a) to (g) below. Sub-paragraphs (a) and (b) detail the requirements in notified Mode S Enhanced Surveillance Airspace, and sub-paragraphs (c) to (g) detail the requirements in all other UK airspace. For the purposes of the UK Air Navigation Order, EU-OPS aeroplanes shall also be equipped in accordance with these requirements.
(f) All aircraft within United Kingdom airspace notified as a ‘Transponder Mandatory Zone’.
Note: Applies to Airspace Classes D, E, F and G as appropriate .
Requiremeent = Mode S Elementary Surveillance
ak7274 liked this
TMZs (and RMZs) are an example of something that is made un-necessarily complex. SERA requires that national details are promulgated in the AIP so naturally one might look for an AIP section on TMZ/RMZ.

Wrong..... it's scattered all over the place and even the general requirements (for TMZs) are hidden in a section on general transponder carrying requirements.

It's just asking for people to get it wrong/misunderstand etc as borne out by pages and pages of discussions on here about it and similar subjects.
patowalker wrote:Mode C is not sufficient for a TMZ, it must be Mode S.
GEN 1.5

xtophe wrote:But if you read the other thread, you'll see that ENR2.1 is not consistent with GEN1.5 and that some TMZ are not listed in GEN 1.5

Agreed. With reference to your post about Farnborough CTA 8 on the other thread, here is further 'clarification'. :)

3.2 Class E+ TMZ Controlled Airspace
3.2.1 Although it is recognised that pilots are to be always aware of the classification of the airspace in which they operate, unlike with other CAS classifications and pilot requirements, VFR activities within Class E airspace are uncontrolled. Farnborough CAS CTA-8 and CTA-9 are ‘Class E plus conspicuity’ airspace. 2 These Class E+TMZ CTAs thereby require VFR transit aircraft to fly in accordance with the conditions detailed at SERA. 13001. Section 13 (Operation of an SSR transponder).

2 ... 128_en.pdf
(SERA 13001 requires a pilot to operate a transponder at all times, if installed.)