What are these triangular divots on top of A320 wing?

The triangular indentations visible on the upper surface of the Airbus A320 wing, located just forward of the wing hoist point, are aerodynamic surface features commonly referred to as vortex generators (VGs) or boundary layer energizers. These small geometric interruptions in the otherwise smooth upper wing skin serve a precise aerodynamic function: they artificially trip the boundary layer from laminar to turbulent flow at a controlled chordwise location. Turbulent boundary layers, counterintuitively, resist flow separation better than laminar ones under adverse pressure gradients — which is exactly what the decelerating airflow on the aft upper wing surface encounters. By inducing transition at a designed point, these features help maintain attached flow over the wing across a wider range of angles of attack and airspeed, contributing to consistent lift characteristics and delaying the onset of buffet.

The placement just ahead of the hoist point is not incidental. On the A320, wing structural hard points — including jacking and hoisting pads — are located at specific spanwise and chordwise stations that correspond to internal rib and stringer intersections. The aerodynamic treatment of the upper surface in this region must account for the slight contour discontinuities introduced by access panels, fairings, and structural reinforcements associated with those hard points. Airbus engineers routinely place vortex generators downstream of any surface irregularity that might otherwise cause premature local flow separation. The triangular geometry, as opposed to the more familiar blade-type VG, minimizes protruding height while still generating the necessary streamwise vorticity to re-energize the boundary layer.

For line pilots operating the A320 family, these features are largely transparent during normal operations but become relevant during preflight walkarounds and post-maintenance checks. Any missing, damaged, or improperly reinstalled vortex generators in this region must be reported, as their absence can subtly alter local wing aerodynamics in ways that affect stall characteristics or buffet onset margins — parameters that Airbus has validated only with the certified surface configuration intact. AMMs (Aircraft Maintenance Manuals) specify exact placement, orientation, and spacing tolerances, and return-to-service after panel work in the area requires inspection confirmation that these features are intact.

In the broader context of narrow-body design, the A320's wing reflects Airbus's use of supercritical airfoil geometry, which squeezes aerodynamic efficiency by maintaining near-sonic flow over a large portion of the upper surface at cruise. The tradeoff is a more sensitive boundary layer that requires careful management via devices like these divots. Boeing's 737 and later designs address similar physics through comparable means. As the A320neo family and the next-generation aircraft programs push cruise efficiency further, surface aerodynamic treatments — including passive devices like VGs and active systems like natural laminar flow sections — are receiving increasing engineering attention. The small triangular divots visible on a ramp walkaround are, in that sense, a quiet but consequential piece of the efficiency envelope that operators depend on for fuel burn and range performance targets.