We present a non-intrusive in situ measuring method to obtain the mean coefficient of friction (COF) in a common edge contact of complex shape. The significance of COF on computed contact stresses, and thus on predicted lifetime compels us to develop an accurate derivation method. A dovetail specimen, accounting for the blade/disk interface of gas turbine engines, is subjected to static uniaxial tension, and displacements fields are measured on the lateral face, near contact, with Digital Image Correlation. A Finite Element Method Updating identification is employed to identify the mean COF at any loading cycle operating within the full-slip regime. The numerical model is first validated through a series of virtual tests. Application to a Low-Cycle Fatigue test shows an increase of the COF with the number of cycles. The study also brings to light the high sensibility of the specimen to geometrical positioning.\GRAPHIACAL ABSTRACT\