Large aircraft that fly fixed routes and smaller aircraft that take on additional passengers and fuel en route. A futuristic image, certainly, yet a consortium, led by the National Aerospace Laboratory (NLR), recently received a European research commission to seriously study the potential of such ‘cruiser-feeder’ operations for civilian aircraft.
The concept involves a ‘cruiser’ flying at cruising attitude above mainports, such as Amsterdam Airport Schiphol. Smaller aircraft , the ‘feeders’ , pick up passenger modules and place them on board the ‘cruiser’. At the same time, fuel, baggage, supplies and waste are exchanged between the ‘cruiser’ and the ‘feeder’. The cruiser then continues flying for thousands of kilometres more, with this procedure being repeated along the way.

The expectation is that, in the distant future, a form of this cruiser-feeder operation will result in substantial fuel savings. This scenario is already rendered plausible when, in special cases, only fuel is exchanged between a cruiser and feeder. In such cases, fuel savings of 31 percent are achieved based on flights of 6000 nautical miles (approximately 11,000 km) that carry 250 passengers, with one refuelling procedure undertaken en route. Compared to all the other technologies aimed at rendering aircraft more fuel-efficient, this particular operation offers huge potential savings.

The research is thus far focusing on two key bottlenecks. Which cruiser-feeder concepts are possible? What exactly is required in order for the cruiser-feeder concept to fully meet the airworthiness standards that apply to civil aviation? How significant are the potential benefits? In order to answer these questions, a design study was conducted for the cruiser and the feeder. In addition, research will focus on the automation of the berthing, a key requirement for guaranteeing safety. Finally, flight simulation experiments will be conducted to study the cruiser-feeder concept.

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Photo: an artist’s impression of the ‘cruiser-feeder’ concept