Turbine Aeroplane Aerodynamics, Structures and Systems
What you must understand
Know the gas turbine cycle and the function of compressor, combustion chamber, turbine and exhaust. Understand the difference between turbojet, turbofan, turboprop and turboshaft, and the meaning of bypass ratio and thrust. Study engine systems: fuel control, ignition, starting, lubrication, cooling and anti-icing, plus indication parameters (N1, N2, EGT, EPR, fuel flow). Understand airframe systems: hydraulic power generation and distribution, pneumatic systems, air conditioning and pressurisation, fuel systems and their venting and refuelling, electrical power generation and distribution, ice and rain protection, and flight controls including powered and fly-by-wire concepts. Know the structure: fuselage, wings, empennage, doors, and the meaning of fail-safe and damage-tolerant design.
Traps in questions
- N1 versus N2: N1 is the fan/low-pressure spool on a turbofan; N2 is the high-pressure spool. Do not swap them.
- Bypass ratio: most thrust in a high-bypass turbofan comes from the bypass flow, not the core.
- Hydraulic system numbering: multiple independent systems exist for redundancy; know that a single failure must not remove all control.
- Pressurisation: cabin altitude and differential pressure are separate limits; exceeding differential pressure is structural.
- Fuel: venting, crossfeed and jettison have distinct purposes; do not conflate them.
Worked example
On a high-bypass turbofan with a bypass ratio of 5:1, roughly five parts of air pass through the bypass duct for each part through the core. Most propulsive thrust comes from the bypass air accelerated by the fan, which is why large fans are efficient.
Rule of thumb
For any system question, ask what the system must do, what provides redundancy, and what indication the crew sees when it fails.