EPST, the developer of COMPASS, publishes an official nine-subtest list on its own site, but the exact line-up still varies by operator (the last two subtests are optional, and the Advanced battery swaps several modules), so treat any named module list you find elsewhere online with caution. What can be said with confidence is which task families candidates consistently describe — and the cognitive half of the test centres on mental arithmetic, memory, spatial orientation and technical comprehension.
The task families
Mental arithmetic: candidates describe rapid calculation without a calculator, often under tight time pressure — including fractions, decimals, percentages and speed–distance–time style questions.
Memory: short-term recall tasks, reported to involve remembering sequences of items or instructions and reproducing them after a delay.
Spatial orientation: reasoning about position and heading, such as relating instrument indications or map views to an aircraft's orientation in space.
Technical comprehension: physics-flavoured questions about mechanical principles — levers, gears, pulleys, forces and basic aerodynamic intuition.
Verbal reasoning in English: the test is administered in English, and candidates report language comprehension being assessed alongside the numerical work.
How to prepare
Each family has a direct counterpart on the practice page. Use Mental Math for the arithmetic — start with the full mix, then drill the focused fractions, decimals, percentage and time modes wherever your score trend is flattest — and add the Speed, Distance & Time game, which mirrors the COMPASS maths module's signature word problems at its real pace of 24 questions in 18 minutes. Spatial Awareness and the three-dial Spatial Orientation exercise target the orientation tasks, Technical Reasoning covers the mechanical-comprehension questions, Aviation English keeps the test's working language sharp, and Sequences keeps your pattern-spotting quick under a clock. Short daily sessions across all of them beat a long binge on your favourite.