A bypass gas turbine has a mixer nozzle at the turbine outlet with a main body, of lobed cross-section to promote mixing of the turbine gas flow and the bypass flow. For a transition at the forward end of the nozzle from the essentially circular boundary between the two flows preceding the turbine outlet to said lobed form, there is an annular connecting ring fairing a channel section with radially inner and outer flanges to which the forward end of the fabricated main body is secured at the peaks and troughs of its lobes. Fairing elements are secured to the flanges to blend with the lobed form of the nozzle body. Because the nozzle body has a lobed form along its entire length it can be constructed as a single skin fabrication while retaining sufficient stiffness to prevent unacceptable deformations from the pressure forces on it under reverse thrust conditions.
