An angle of attack sensor (10, 110) comprising: a vane assembly; a multi-piece faceplate adjacent the vane assembly, the faceplate including: a mounting plate having an opening and an exterior surface; and characterised by a heated chassis (16, 116) with a heater (36, 136) on the heated chassis (16, 116), the heated chassis (16, 116) being positioned adjacent the mounting plate and having a ring portion (50, 150) extending into the opening, the ring portion (50, 150) including: a radially narrow fore portion (54, 154) at a front portion of the ring portion (50, 150) and extending into the opening; a radially wide aft portion (56, 156) at an aft portion of the ring portion (50, 150) and extending into the opening; and an aft-located ramp (58, 158) connected to the radially wide aft portion (56, 156) and extending through the opening above the exterior surface of the mounting plate, the ramp including: an inclined inner surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate. a vane assembly; a multi-piece faceplate adjacent the vane assembly, the faceplate including: a mounting plate having an opening and an exterior surface; and characterised by a heated chassis (16, 116) with a heater (36, 136) on the heated chassis (16, 116), the heated chassis (16, 116) being positioned adjacent the mounting plate and having a ring portion (50, 150) extending into the opening, the ring portion (50, 150) including: a radially narrow fore portion (54, 154) at a front portion of the ring portion (50, 150) and extending into the opening; a radially wide aft portion (56, 156) at an aft portion of the ring portion (50, 150) and extending into the opening; and an aft-located ramp (58, 158) connected to the radially wide aft portion (56, 156) and extending through the opening above the exterior surface of the mounting plate, the ramp including: an inclined inner surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate. a mounting plate having an opening and an exterior surface; and characterised by a heated chassis (16, 116) with a heater (36, 136) on the heated chassis (16, 116), the heated chassis (16, 116) being positioned adjacent the mounting plate and having a ring portion (50, 150) extending into the opening, the ring portion (50, 150) including: a radially narrow fore portion (54, 154) at a front portion of the ring portion (50, 150) and extending into the opening; a radially wide aft portion (56, 156) at an aft portion of the ring portion (50, 150) and extending into the opening; and an aft-located ramp (58, 158) connected to the radially wide aft portion (56, 156) and extending through the opening above the exterior surface of the mounting plate, the ramp including: an inclined inner surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate. a radially narrow fore portion (54, 154) at a front portion of the ring portion (50, 150) and extending into the opening; a radially wide aft portion (56, 156) at an aft portion of the ring portion (50, 150) and extending into the opening; and an aft-located ramp (58, 158) connected to the radially wide aft portion (56, 156) and extending through the opening above the exterior surface of the mounting plate, the ramp including: an inclined inner surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate.