Landing gear influence on the wake vortex of a large transport aircraft

An experimental investigation on the wake vortex formation and evolution of a four-engine large transport aircraft model in the near field and extended near field has been conducted by means of hot-wire anemometry in a wind tunnel. The half-model used has a scale of 1:19.25 and the tests focus on the high-lift case of a typical landing configuration at a Reynolds number of 0.52 × 10⁶ based on the wing mean aerodynamic chord. The flowfield is investigated up to 4.7 spans downstream of the model, which is investigated with and without landing gear. Based on the measured time-dependent velocity components, the wake flowfield is analyzed by distributions of vorticity, turbulence intensities, and spectral densities. The landing gear consists of a stay and four wheels, which create a bluff-body wake that interferes with the shear layer caused by the wing and wing junction. The landing gear creates a low-energy vortex system and a highly turbulent wake. Due to the landing gear, the main vortex centers are located slightly further outboard and the roll-up process is retarded, especially the inboard movement of the horizontal tail plane vortex. The velocity spectra of the landing gear wake show broadband characteristics with some moderate narrowband energy concentrations in the close near field, which do not enhance inherent wake instabilities. Although the turbulence caused by the landing gear is still present in the extended near field, only a small influence on the overall vortex system of the entire aircraft can be found. The landing gear influence is therefore negligible in the context of reducing minimum aircraft separation distances.