Originally Posted by
ATCO Tree
I had not appreciated that an active TRA raised the base of Class C from FL195 to FL245
It doesn't! Active TRAs remain Class C, but they have different rules in order to allow autonomous VFR flight by (mainly) military aircraft.
Originally Posted by
ATCO Tree
It seems that the way in which the AIP and the NATS website describes current airspace classification and structure in the UK is rather disjointed which does not help with the understanding of those flying through it. It’s perhaps no wonder that overseas crews are bemused and confused by the whole thing when flying to/over the UK.
Here's how the AIP describes it, at ENR 1.1 para 5.1.5.1.2:
In complying with the EC Regulation lowering Class C Airspace to FL 195, Temporary Reserved Areas (TRA) between FL 195 and FL 245 have been established to accommodate the various VFR UK airspace users including military autonomous operational requirements above FL 195. TRAs may be used simultaneously by both civil and military aircraft, including aircraft in en-route transit through a TRA. Operations will be conducted in accordance with the Rules of the Air, or as agreed via the Unusual Aerial Activities regulations, and required equipment carriage and operation. Although the background classification between FL 195 and FL 245 within UK airspace is Class C, to avoid operational restrictions, military aircraft may operate autonomously or be in receipt of an ATS from approved ATS units within a TRA. ATS in TRAs will be provided in accordance with the UK Flight Information Services (UK FIS).