An airfoil assembly includes an airfoil fairing, a spar, a seal plate, and a seal. The airfoil fairing has a fairing platform and a hollow airfoil section that extends from the fairing platform. The spar has a spar leg that extends in the hollow airfoil section. The spar leg defines a spar leg periphery. The seal plate is secured with the fairing platform. The seal plate has an opening, and the opening has an opening periphery that is complementary to the spar leg periphery. The spar leg extends through the opening. The seal is between the seal plate and the spar leg. The seal seals around the spar leg periphery.