Gas turbine engine nacelle

A nacelle for a gas turbine engine, made in accordance with the steps of:

• defining an initial geometry for a nacelle, the initial geometry providing an intake at the an upstream end of the nacelle and an exhaust at a downstream end of the nacelle, wherein the intake has, in flow series, an intake lip and a diffuser, the intake lip having a highlight defining a boundary between inner and outer surfaces of the intake lip, and on all longitudinal sections through the nacelle that contain a longitudinal axis of the nacelle (i) said inner and outer surfaces having their tangents coincident at the highlight, and (ii) said inner and outer surfaces having their maximum curvatures at the highlight;
• pivoting, at each of one or more positions on the highlight and in a plane of the respective longitudinal section, an upstream portion of the intake lip lying in the respective longitudinal section about the highlight;
• and
• adjusting surfaces of the intake neighbouring the pivoted upstream portion to smoothly blend surfaces of the pivoted upstream portion to unadjusted surfaces of the intake further removed from the pivoted upstream portion to obtain an altered geometry for the nacelle.

A method of designing a nacelle for a gas turbine engine including the steps of:

• providing an intake portion at an upstream end of the nacelle, the intake portion having in flow series:
• an intake lip, and
• a diffuser;
• providing an exhaust portion at a downstream end of the nacelle, wherein
• the intake lip has a highlight which is a closed loop defining a boundary between an inner surface of the intake lip and an outer surface of the intake lip, at which a tangent to the inner surface is coincident with a tangent to the outer surface;
• configuring the highlight to lie in a highlight surface which is either planar or curved in only one principal direction;
• and
• configuring one portion of the intake lip, such that at each of one or more, but not all, positions on the highlight, and in a respective longitudinal section through the nacelle, the one portion of the intake lip crosses a tangent to the highlight surface at that position on the highlight and surfaces of the intake lip neighbouring the one portion of the intake lip are adjusted to provide smoothly blended surfaces.