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ENG 1 & 2 RUNNING

System study · Engines

FADEC, Start Logic & Thrust Ratings

Two dual-channel FADECs run the whole show — start sequencing, thrust limits, and protection logic. Click through the diagram, then quiz yourself on start logic and thrust settings.

Engine control & indication click a component

Simplified — not for operational use. Click a FADEC channel, spool, or the thrust levers.
FADEC 1 CHANNEL A / B ENGINE 1 N1 / N2 / EGT THRUST REVERSER 1 FADEC 2 CHANNEL A / B ENGINE 2 N1 / N2 / EGT THRUST REVERSER 2 THRUST LEVERS TLA POSITION ENGINE START SELECTOR / LOGIC FIRE LOOPS / BOTTLES
Click any component above to see what it does →

Start sequence — the short version

BLEED AIR
SPINS THE START

Bleed air — from the APU, a ground cart, or the opposite engine via cross-bleed — spins the starter, which rotates the core (N2). Once N2 reaches a set threshold, FADEC introduces fuel and ignition fires. As the engine accelerates and stabilizes, the starter automatically cuts out and the FADEC hands off to normal running logic — no need for the crew to manually time any of these steps.

Quick reference

FADEC

  • Full Authority Digital Engine Control
  • Two independent channels (A/B) per engine
  • Controls start logic, fuel scheduling, and thrust limits
  • Protects against overspeed and over-temperature automatically

THRUST RATINGS

  • Idle, Climb, Max Continuous, and Takeoff (TOGA)
  • Flex/derated thrust reduces takeoff thrust on long runways to save engine life
  • FADEC enforces the limit for whichever rating is selected

THRUST REVERSERS

  • Only deployable on the ground
  • Redirect exhaust forward to aid deceleration after landing
  • Locked out in flight by multiple independent safeguards

Check yourself

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