Vane arc segment formed of fiber-reinforced composite

A gas turbine engine comprising:

• a compressor section;
• a combustor in fluid communication with the compressor section;
• and
• a turbine section in fluid communication with the combustor, the turbine section having vane arc segments disposed about a central axis of the gas turbine engine, each of the vane arc segments includes
• an airfoil fairing having a fairing platform and a hollow airfoil section extending there from, the hollow airfoil section defining an airfoil profile and surrounding an internal cavity, the fairing platform defining a gaspath side and a non-gaspath side,
• the airfoil fairing being formed of a fiber-reinforced composite comprised of fiber plies, the fiber plies including at least one cavity fiber ply that is arranged as a tube that circumscribes the internal cavity,
• the at least one cavity fiber ply extending through the fairing platform and defining at least a portion of an upstanding collar on the non-gaspath side of the fairing platform, the upstanding collar defining a collar profile, and
• the tube necking down through a neck portion such that at least a portion of the collar profile is narrower than the airfoil profile.