General Aircraft Technical Knowledge Practice Test 2026 – The Complete All-in-One Guide to Master Your Exam!

Induction is the intake stroke, so the inlet valve must be open to admit the air-fuel mixture into the cylinder. As the piston moves downward, the volume increases and the pressure inside drops below atmospheric pressure, drawing the charge in through the open intake port. If the inlet valve were closed during this stage, nothing could enter the cylinder, and the engine wouldn’t fill the cylinder for the next compression stroke. The exhaust valve stays closed during induction to prevent exhaust gases from escaping, and only after induction ends does the intake valve close and the compression stroke begin with both valves shut.