Special-category data
Special-category data is the term UK GDPR (and EU GDPR) uses for categories of personal data given heightened protection under Article 9 — racial or ethnic origin, political opinions, religious or philosophical beliefs, trade union membership, genetic data, biometric data for identification, health data, sex life, and sexual orientation. Article 9(1) prohibits processing of any of these unless one of the conditions in Article 9(2) applies.
A pilot’s medical certificate is health data and is therefore special-category data. Syndik8 stores it only on the basis of explicit consent under Article 9(2)(a), and deliberately avoids storing any further special-category detail — the medical class, limitations, clinical commentary, examiner identity, and date of birth are all explicitly out of scope.
In the app: only the medical itself, plus a self-entered expiry date, are stored. See Storage and security for the list of fields Syndik8 keeps and does not keep.