FAA Commercial Pilot Airplane (CAX)Aircraft SystemsMedium
A pilot leaning the mixture on a fuel-injected engine using an EGT gauge wants to establish best power for a climb, rather than best economy for cruise. Compared to peak EGT, where should the mixture be set for best power?
- AExactly at peak EGT
- BFull rich regardless of density altitude
- CSlightly lean of peak EGT
- DSlightly rich of peak EGT
Show answer & explanationAnswer & explanation
Correct answer: D. Slightly rich of peak EGT
Best power mixture is typically achieved by setting the mixture slightly rich of peak EGT (commonly 50-125°F rich of peak, per manufacturer guidance), which provides maximum power output at some sacrifice of fuel efficiency. Best economy, by contrast, is achieved at or slightly lean of peak EGT.
Why the other options are wrong
- A. Peak EGT itself is closer to best economy leaning, not best power.
- B. Full rich wastes fuel and is not the same as the optimized best-power setting.
- C. Lean of peak favors economy/efficiency over maximum power.
Best Power vs Best Economy Mixture
Best power mixture is set slightly rich of peak EGT for maximum power; best economy mixture is set at or slightly lean of peak EGT for maximum fuel efficiency.
- Best power ≈ rich of peak EGT
- Best economy ≈ at or lean of peak EGT
- Fuel injection systems allow more precise mixture control than carburetors
Memory trick: Rich for power, lean for miles — peak splits the two goals.