Explain the aerodynamics of powered lift systems for STOL/VSTOL aircraft.

Powered lift systems use propulsion to augment aerodynamic lift: Blown flaps use engine bleed air or dedicated compressors to energize flap boundary layer (CL up to 5-6); Upper surface blowing (USB) directs exhaust over wing using Coanda effect; Externally blown flaps (EBF) direct engine flow under triple-slotted flaps; Lift fan systems provide direct vertical thrust; and Vectored thrust rotates engine nozzles. Analysis requires coupled propulsion-aerodynamic modeling including jet-in-crossflow physics, circulation augmentation, and hot gas ingestion. Design challenges include trim changes, asymmetric thrust handling, and transition between powered and conventional lift. Examples include C-17 (EBF), YC-14 (USB), and F-35B (lift fan + vectoring).