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Efficiency is the (often measurable) ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without waste.
216 questions
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Why aren't egg-shaped laminar flow fuselages more common?
I came across this beautiful Phantom 3500 egg-shaped fuselage jet design.
(source)
I've been hearing for a while about laminar flow and how it can significantly increase efficiency with more ...
- 7,483
5
votes
3
answers
1k
views
Can the elevator propellers of an eVTOL be retractable?
A lift-cruise eVTOL (without variable thrust) requires elevator propellers for vertical flight and cruise propellers for forward flight. However, when one set is in use, the other remains inactive, ...
- 137
3
votes
3
answers
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How close can supersonic airplanes get to subsonic fuel efficiencies?
I was struck by this sentence in @therac's excellent answer for why quieter supersonic planes don't offer efficiency gains.
Supersonic L/D will always be lower than subsonic, like a best-case of 7:1 ...
9
votes
2
answers
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Are there efficiency gains with quiet supersonic technology?
I was reading about the Nasa X-59 a low supersonic noise test aircraft which is nearing the start of flight testing, and it occurred to me that I don't understand the relationship between sonic boom ...
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9
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Why is it inefficient to expel high speed gas?
I'm reading the wikipedia page on turbofans, where it says turbojets are inefficient at low speeds because:
energy is wasted as the propelling jet is going much faster rearwards than the aircraft is ...
- 511
1
vote
1
answer
264
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Most Efficient Commercial Aircraft Design? [closed]
What was the most efficient aircraft design (based on factors such as lift, drag, and fuel consumption) but not developed or scrapped due to issues with long term viability and maintenance, operations ...
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vote
1
answer
283
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Determining Required Fuel from Payload/Range Diagram
I would like to determine the amount of fuel required for a flight at a given range/payload combination - ideally from the payload/range-diagram [1] of the corresponding aircraft alone.
I know that ...
- 1,976
3
votes
1
answer
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Max Range Relationship to Altitude for Propeller-Driven Aircraft
Chapter 11 of the PHAK states, "If a change in altitude causes identical changes in speed and power required, the proportion of speed to power required would be unchanged. The fact implies that ...
- 629
1
vote
0
answers
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Are Runway Profile Descent charts available to non-121 carriers? If so, where can I find them?
AIM 5-4-2(c) says:
When crossing altitudes and speed restrictions are issued verbally or are depicted on a chart, ATC will expect the pilot to descend first to the crossing altitude and then reduce ...
- 23.3k
17
votes
2
answers
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Why did Airbus mix "colored light means ON" and "colored light means OFF" in the overhead panel?
Disclaimer: I don't have a real Airbus A330 at hand, nor am I a pilot.
After having crashed twice due to icing in rainy weather (not to talk about that here) with an Airbus A330 in X-Plane 12 ...
- 468
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6
answers
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Function of the compressor in a gas turbine engine
I am trying to understand the importance of having compressed air in the combustion chamber of a gas turbine engine. As far as I understand it, the reasons are twofold.
Firstly, the compressor is ...
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4
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Which engine is more financially economical to operate, a turboprop or gasoline engine?
I've seen a discussion about this somewhere before. I'm aware that there's no real way to calculate this. So rather then comparing weight and volume for efficiency, let's compare prices. Which engine ...
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3
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Why is a dedicated compressor more efficient than using bleed air to pressurize the cabin?
Bleed air is air "stolen" from the compressor of the jet engine and has traditionally been used to pressurize the cabin. The alternative is to use a separate compressor just to provide cabin ...
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4
votes
1
answer
755
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Does Oswald Efficiency make a significant difference on RC-aircraft?
As we know, Oswald Efficiency ($\epsilon$) is caused by change in downwash over the span of the wing, thus causing a change in effective angle of attack over the wing and therefore induced drag ...
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0
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1
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324
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How to calculate boundary layer thickness?
So I have a flat plate with a surface of 7sqm and an aspect ratio of 12 with air blowing straight at it (like a wing) at a speed of 50km/h. I would like to manually calculate the thickness of the ...
- 143