A pivotal year for urban air mobility when Airbus will fly its alpha prototype of the City Airbus demonstrator to address associated risks and prove flight dynamics challenges can be overcome .

We will see small fleets of experimental vehicles flying in a city environment . Not fully certified products but vehicles that are safe and will start testing the appetite for cities for this new type of transport .

Urban air taxis will be in service .

Pure electric one-hour flights will be in their infancy with 19 or 10 seat vehicles transporting passengers on short missions .

Expect to see the first single aisle A320- sized hybrid aircraft featuring a gas turbine with integrated electric energy storage . carry too much weight in battery to have any room for passengers . Until that goal is reached , Cousin believes larger , longer range aircraft will follow a hybrid model . “ Initially we ’ ll see a large generator ( 2MW ) installed between the thrust-producing fan and the gas turbine , and that motor / generator will be used throughout flight to either inject or extract power depending on the phase of flight you ’ re in ,” he predicts .

When taxiing along the runaway , planes could operate purely electrically and during take-off would use the energy storage as back up . Then , if an engine failed during ascent , power could be injected into the other good engine to boost its thrustproducing capability . Gains could also be made at the top of a climb to deliver extra thrust to reach cruise altitude .

“ We ’ re seeing efficiencies of over 50 % which is as good as the best diesel engines ,” adds Cousin . “ However , they are horribly inefficient when they ’ re operating in off-design points . For example , in descent when you ’ re idling the engine so it ’ s ready to give power within eight seconds if the pilot pushes the throttles forward – it ’ s burning a lot of fuel to produce

46 March 2018