Civil Aviation Rules
Where the rules sit
The Civil Aviation Act 1990 gives the CAA power to make ordinary rules. For IFR, the key Parts are Part 1 (definitions), Part 61 (pilot licences and ratings), Part 91 (general operating and flight rules), Part 67 (medical standards), and Parts 71 and 172 (airspace and air traffic services). Part 61 sets licence and rating requirements and privileges; Part 91 sets the flight rules you apply daily. A rating is not a licence: a PPL, CPL or ATPL is the licence, and the instrument rating extends its privileges to IFR.
What the instrument rating authorises
Within the limits of the rating and aircraft type, an instrument-rated pilot may fly under IFR and in IMC. The pilot must still meet medical, recency, aircraft equipment, and route or airspace requirements. Part 91 requires an IFR flight plan and ATC clearance in controlled airspace, an alternate unless specific conditions allow, and appropriate take-off and landing minima.
Worked example
A CPL(A) holder wants to fly a twin IFR at night. Licence: CPL. Rating: instrument aeroplane. Medical: Class 1 current. Recency: instrument experience valid. Aircraft: IFR-equipped and maintained. Route: controlled airspace; file IFR, obtain clearance, nominate an alternate. If any item fails, the flight cannot proceed IFR.
Traps
Do not treat an instrument rating as a licence. Do not assume a PPL is barred from IFR. Keep currency separate from recency. Check the exact Part 91 minima; commercial operations may add Part 125 or 135 requirements.