An angle of attack sensor 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; a chassis, the chassis being positioned adjacent the mounting plate and having a ring portion extending through the opening, the ring portion defining a ring-shaped deflector that surrounds the vane assembly and extends above the exterior surface of the mounting plate, wherein the deflector includes: a fore ramp at an upstream portion of the deflector; and an aft ramp at a downstream portion of the deflector, wherein the fore ramp including an inclined outer surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate; characterised by: the aft ramp including an inclined inner surface extending with an incline in the aft direction to a height above the exterior surface of the mounting plate; and wherein the chassis is a heated chassis with a heater positioned on, or embedded in, the heated chassis. a vane assembly; a multi-piece faceplate adjacent the vane assembly, the faceplate including: a mounting plate having an opening and an exterior surface; a chassis, the chassis being positioned adjacent the mounting plate and having a ring portion extending through the opening, the ring portion defining a ring-shaped deflector that surrounds the vane assembly and extends above the exterior surface of the mounting plate, wherein the deflector includes: a fore ramp at an upstream portion of the deflector; and an aft ramp at a downstream portion of the deflector, wherein the fore ramp including an inclined outer surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate; characterised by: the aft ramp including an inclined inner surface extending with an incline in the aft direction to a height above the exterior surface of the mounting plate; and wherein the chassis is a heated chassis with a heater positioned on, or embedded in, the heated chassis. a mounting plate having an opening and an exterior surface; a chassis, the chassis being positioned adjacent the mounting plate and having a ring portion extending through the opening, the ring portion defining a ring-shaped deflector that surrounds the vane assembly and extends above the exterior surface of the mounting plate, wherein the deflector includes: a fore ramp at an upstream portion of the deflector; and an aft ramp at a downstream portion of the deflector, a fore ramp at an upstream portion of the deflector; and an aft ramp at a downstream portion of the deflector, wherein the fore ramp including an inclined outer surface extending with an incline in an aft direction to a height above the exterior surface of the mounting plate; characterised by: the aft ramp including an inclined inner surface extending with an incline in the aft direction to a height above the exterior surface of the mounting plate; and wherein the chassis is a heated chassis with a heater positioned on, or embedded in, the heated chassis. the aft ramp including an inclined inner surface extending with an incline in the aft direction to a height above the exterior surface of the mounting plate; and wherein the chassis is a heated chassis with a heater positioned on, or embedded in, the heated chassis.