Re:Rolls-Royce concludes testing of plane technology to brea...
by sandworm101 on Tuesday September 29, 2020 @02:28PM
(#24631267)
>> fuel-powered aircraft will shed half their takeoff weight during flight.
While that is true of jets optimized for altitude, small piston aircraft (cessnas) do not burn nearly that much fuel on takeoff. Small aircraft can generally do a dozen or more takeoff/landing cycles on a single tank.
Re:Rolls-Royce concludes testing of plane technology to brea...
by nickff on Tuesday September 29, 2020 @02:37PM
(#24631367)
Fuel is burned throughout the flight, not just take-off (and initial climb to altitude), which is why airliners flying long-haul routes usually gain altitude as they progress. The Cessna 172 seems to have a fuel fraction of around 20% (an order of magnitude higher than a car), and airliners are much higher (~40%).[1][2]
Re:Rolls-Royce concludes testing of plane technology to brea...
by dredmorbius on Tuesday September 29, 2020 @03:02PM
(#24631626)
A 2020 Toyota Camry --- a typical 4-door sedan --- has a curb weight of 3,340 lb and a 15.8 gallon fuel tank (95 lb), for a fuel-to-weight ratio of 2.8%.
Range is ~615 miles at 39 mpg highway.
Passenger and cargo capacity is another 1,500 lb on top of this, give or take.
This is far lower than any conventional aircraft, though a few ultralights might compare.
Re:Rolls-Royce concludes testing of plane technology to brea...
by TylerE on Tuesday September 29, 2020 @04:10PM
(#24632369)
Even on a tiny little Cessna fuel is 1/8th of the weight, and fuel burn per hour in cruise is approx. 50lbs/hr.
Re:Rolls-Royce concludes testing of plane technology to brea...
by dredmorbius on Wednesday September 30, 2020 @12:49PM
(#24640778)
And again with my Camry example, assuming 60 mph and 39 mpg, that's about 9 lb/hr fuel consumption.
The Cesna has a 140 mph cruise, a bit over double that of the Camry on highway, but that still means 20 lb at equivalent distance for the car, less than half the light plane.
Aircraft are fuel burners.
(Agreeing, just giving land-travel equivalent.)
Long-haul alt-energy aircraft utilise very low airspeed (low drag), extreme mass budgets (they're wonders of materials and structural engineering), and altitude profiles (potential energy0 to manage overall energy budgets and use.