What are the advantages and challenges of geared turbofan engines?

Geared turbofans (GTF) use a reduction gearbox between the low-pressure turbine and fan, allowing each to operate at optimal speed. Advantages: Fan can be larger with slower tip speeds for higher BPR and efficiency, LPT can spin faster with fewer stages (lighter), 15-20% fuel burn reduction vs conventional, and Reduced noise from slower fan tip speeds. Challenges: Gearbox weight and reliability (carrying 30,000+ HP), Heat rejection from gearbox, Maintenance access, and Development cost. The PW1000G series powers A220, A320neo, E-Jets E2 with demonstrated fuel savings. Gearbox uses planetary gear system with sophisticated lubrication and backup systems.