A Thr
⚙️ Autothrottle (A/T) vs Autothrust (A/THR)
| Feature | Autothrottle (A/T) | Autothrust (A/THR) |
|---|---|---|
| Typical aircraft | Boeing and older types | Airbus and newer European aircraft |
| System type | Mechanical — physically moves the thrust levers to control engine power | Electronic — thrust levers stay fixed in detents; power is adjusted by computer commands |
| Operation | The system automatically moves the thrust levers forward/back to maintain selected airspeed or thrust | The system keeps levers in a fixed detent (e.g. CLIMB), and computers vary engine thrust electronically |
| Control input | Throttle lever servomotors | FADEC (Full Authority Digital Engine Control) |
| Pilot interaction | Pilot sees and feels lever movement | Pilot sees thrust changes on engine instruments, levers stay still |
| Purpose | Maintain selected speed or thrust automatically | Maintain selected speed or thrust automatically (same function, different design) |
✈️ In Simple Terms
Autothrottle (A/T) physically moves the thrust levers to control power (used in Boeing). Autothrust (A/THR) adjusts engine thrust electronically, with levers left in fixed detents (used in Airbus).
Both systems have the same job — to automatically control engine power for speed and thrust management — but the mechanical design and pilot interface differ.
🧭 Autopilot vs Autothrottle / Autothrust
The autopilot and autothrottle (or autothrust) are separate systems, each controlling different parts of the aircraft — but they work together for full flight automation.
⚙️ Key Difference
| System | Controls | Example Functions |
|---|---|---|
| Autopilot (A/P) | The aircraft’s attitude and flight path — pitch, roll, and heading. | Holds altitude, flies LNAV/VNAV, tracks ILS. |
| Autothrottle / Autothrust (A/T or A/THR) | The engine thrust — controls airspeed or thrust setting. | Maintains target speed, limits thrust, manages climb/descent power. |
✈️ How They Work Together
- The autopilot controls where the aircraft goes (path).
- The autothrottle controls how fast it goes (speed).
- Both systems receive target commands from the Flight Management System (FMS) or Flight Control Unit (FCU/MCP) and coordinate automatically.
But:
The autopilot does not command or move the autothrottle — they are independent systems, each with its own computer and servos.
✅ In short:
The autopilot flies the aircraft’s path, and the autothrottle/autothrust manages its speed. They work in parallel, not in hierarchy — the autopilot does not control the autothrottle.