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There are several answers, depending on what precisely your idea of zero fuel means. The first is the simplest: We use a regular aircraft and simply assume that it takes off with zero fuel and still flies as if its tanks are full. Now the answer depends on the range: Longer flights need disproportionally more fuel. The linked answer gives 3.88% of landing ...


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...how much more efficient would an airliner be? Answer: $$ \frac {\text{fuel weight percentage at TO - fuel weight percentage at touchdown}}{2}$$ This answer computes the saving in fuel consumption due to a saving in empty weight - 10% less empty weight results in a fuel saving of 10%. That is empty weight. In a traditional, fuel burning aeroplane, total ...


2

Short answer is about twice as efficient for a mid range route,(3000 nautical miles) when based on fuel used per ton of cargo per mile traveled. Explanation: I will use the 737-400 as an example because I have an operational manual for it. First we need to define terms. I assume we are talking about fuel burn per something: per mile, per hour, or per ...


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It depend whether the airliner is propeller driven or jet powered. Propellers are most efficient at low altitudes, but air resistance decreases with pressure as you go higher, enabling the same thrust to push the plane faster. Propellers are at their most economical (very roughly) around 10-20,000 ft. Jets are most efficient at moderately high altitudes, ...


2

It's important to note that an airliner cruising at 50000 ft (I assume that's what you meant, and that's actually business aircraft territory; airliners are generally below the low 40s). Is going pretty slow from an indicated airspeed perspective. At 50000 ft an airplane is going roughly twice its indicated airspeed (it's actual speed through 3D space is ...


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Could an airliner ever be as efficient at 15 or so meters using ground effect as it is at 50,000 km even if it has to go slower and be shaped differently? Yes it can. The most efficient shape for an airliner is no shape at all, so that the passengers have to get out and walk. (On 15-meter-tall stilts of course.) Alternatively, consider attaching ...


2

Airliners can typically carry about 40-45% of their maximum total weight as fuel. If they didn't need to, they could theoretically carry that much extra payload instead, or they could fly lighter and burn 40-45% less fuel (because fuel burn rate is closely related to the total weight). Obviously it's not quite that simple. Planes usually only carry as much ...


1

If all current aviation engines could run by burning external fuel (let's say it's able to magically extract sufficient amount of hydrogen from atmospheric water vapor, even when relative humidity is very low) and mix it with atmospheric oxygen, then these engines would have unlimited autonomy, or limited by maintenance cycles only. If these engines exhibit ...


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Current science does not support the concept of perpetual motion. You can not extract energy out of nowhere. Sailing ships, including wind turbine powered ones, can sail against the wind, but they do so by extracting energy from the interface between wind and water - transferring wind's energy to water and using some of it for propulsion. There is no ...


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This is a perpetual motion scheme, and no that would not work as it does violate the second law of thermodynamics. Said wind turbine scheme like that could generate electricity, but would add additional drag on to the airframe which would have to be compensated for by additional thrust (energy is conserved). In a perfect world the total drag force on those ...


2

The simple reason this isn't in use is it won't and can't work. Under no circumstances can you obtain even as much energy from your array of Ram Air Turbines as they will sap from the aircraft's motion -- it'll be like trying to save fuel by deploying a drag brake. Why? Because of what gets lumped together as "losses." A windmill turbine is less than 100%...


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As some of the comments above (which are really on the money) suggest it's a complicated question to answer because it is a case of "horses for courses" and that is even if we focus purely on straight-forward fuel efficiency. But given the programs that have been attempted (or are still ongoing) and also various studies it seems that ekranoplans seem to work ...


2

Do planes depreciate like cars? Planes do not really depreciate like cars per say but aircraft engines kind of do! Planes are a bit different than cars due to the certification process being far more verbose. Year to year changes tend to be non-existent or come down to trim/paint options. As such a well maintained old aircraft with a fresh/low time engine ...


2

You are basically describing an ejector pump. This would not be very efficient, I'm afraid (I'll try to dig up some comparative figures). The arrangement in this case would be a jet engine used to accelerate an amount of air inside a duct. With a long enough duct, the end result would be a single airmass exiting at (somewhat) uniform speed. Unfortunately, ...


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