The Real Reason Why The World's Largest Commercial Aircraft Only Has Reverse Thrust On 2 Engines

Airbus chose a distinctive configuration for the A380: it has four engines, but reverse thrust is fitted only on the two inboard units (numbers 2 and 3). The outer engines lack thrust reversers after landing, largely because of their position under the aircraft’s enormous 80-meter wingspan and near the runway edge. That placement would make it more likely they could disturb or ingest gravel, dirt and other debris from unpaved areas, increasing the risk of foreign object damage to engines, wings and the fuselage. The article adds that each thrust reverser adds weight, structural complexity and maintenance needs. It also notes the A380 is certified to stop using brakes and spoilers alone, with the two inboard reversers mainly adding braking performance on wet or slippery runways.