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34 votes
Accepted

Why did Airbus mix "colored light means ON" and "colored light means OFF" in the overhead panel?

The logic for illumination of buttons on the overhead panel is called the dark cockpit concept, previously also called the Forward-Facing Crew Cockpit. It was originally developed by Airbus for the ...
Bianfable's user avatar
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24 votes

Why is a dedicated compressor more efficient than using bleed air to pressurize the cabin?

The other answer is on the right track, but doesn't emphasize the real difference (IMO). Let's say it takes 100 hp (or kW if you prefer) to compress the amount of air you need for a given purpose. ...
Rob McDonald's user avatar
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23 votes
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Why is it inefficient to expel high speed gas?

It depends on what you call efficient. In principle, the force imparted on the airplane is equal to the momentum expelled backwards: $$F=\frac{\Delta m}{\Delta t} \cdot v$$ The power requirement to ...
Sanchises's user avatar
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21 votes

Which engine is more financially economical to operate, a turboprop or gasoline engine?

Piston engines are significantly less expensive to operate, as long as the aircraft's performance and reliability requirements can be satisfied by a piston engine. It's not just the fuel, it's the ...
Therac's user avatar
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17 votes

Why is a dedicated compressor more efficient than using bleed air to pressurize the cabin?

Using bleed air isn't free. In order to produce the same amount of power as an engine with no bleed air taken out, the engine needs to compress more air. This takes energy, and means more fuel used ...
Chris's user avatar
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12 votes

Why did Airbus mix "colored light means ON" and "colored light means OFF" in the overhead panel?

I think this gets into Human Factors and other usability issues, but as an interface designer as part of my job I can say how I would approach this... I don't have (and I don't think it is published) ...
Ron Beyer's user avatar
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12 votes

Function of the compressor in a gas turbine engine

The reason is thermodynamics: without the compressor, the power output of a gas turbine would be exactly zero. It's not about being "more efficient" but about fundamentally being able to ...
Sanchises's user avatar
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12 votes

Which engine is more financially economical to operate, a turboprop or gasoline engine?

From a fuel burn perspective, these ballpark numbers can be useful to remember: Specific Fuel Consumption, Expressed as LBS/HP/HR: Turboprops - .5 to.7 lbs traditionally, mid .4s to .5 for newer ...
John K's user avatar
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11 votes
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Why is a dedicated compressor more efficient than using bleed air to pressurize the cabin?

Given all this extra hardware why is a "bleedless" design more efficient per passenger-km? Flexibility and adaptation But this can only be understood not focusing on the engines only rather ...
sophit's user avatar
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9 votes

Which engine is more financially economical to operate, a turboprop or gasoline engine?

Up to about 450 horsepower, piston engines are more economical for the typical use model (short hops, slow speeds, unpressurized aircraft, low gross weights). Above 450 horsepower, turbines are more ...
niels nielsen's user avatar
8 votes

Function of the compressor in a gas turbine engine

The compressor raises the pressure and temperature at which the fuel is burned, thereby increasing the thermodynamic efficiency of the cycle (Brayton) on which the jet operates. Second, without the ...
niels nielsen's user avatar
8 votes
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Function of the compressor in a gas turbine engine

You don't. A (sc)ramjet doesn't have a compressor, as the forward velocity of the jet provides the necessary pressure. Most thermal engines do work by expanding a gas. In many cases, this gas expands ...
Lawnmower Man's user avatar
5 votes

Why is it inefficient to expel high speed gas?

seems to me like attempting to "capture" the expelled air is akin to putting an air-powered generator behind a turboprop propeller to turn another propeller You're close, but why not put ...
Robert DiGiovanni's user avatar
5 votes

Does Oswald Efficiency make a significant difference on RC-aircraft?

Yes and no. All the physics still hold. The absolute distance from wingtip to fuselage doesn't matter -- flow structures scale down to match the aircraft. However, most R/C aircraft are not flown ...
Rob McDonald's user avatar
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4 votes

Function of the compressor in a gas turbine engine

In order for a jet to create thrust, pressure must be created so the difference in pressure from the inside of the engine to the outside air will create a flow of a certain mass at a certain velocity. ...
Robert DiGiovanni's user avatar
3 votes

Function of the compressor in a gas turbine engine

Would a jet engine need the compressor? All heat engines require a compression step, only in turbomachinery the part involved is called compressor. But other engines also compress a medium as part of ...
Peter Kämpf's user avatar
3 votes

Most Efficient Commercial Aircraft Design?

The most efficient designs, based on lift, drag and fuel consumption, for heavier than air craft, were the ones that could fly slowly enough and still have sufficient Reynolds numbers to generate lift ...
Robert DiGiovanni's user avatar
3 votes
Accepted

Determining Required Fuel from Payload/Range Diagram

The gradient between points A and B of your diagram is determined by the overall efficiency of the airplane. It depends on the amount of fuel needed to fly a bit further by trading payload for fuel ...
Peter Kämpf's user avatar
2 votes

Max Range Relationship to Altitude for Propeller-Driven Aircraft

A change in altitude doesn't cause identical changes in speed and power required. Assuming that the drag is dominated by parasitic drag (typically true at cruise speed), the drag force is proportional ...
Chris's user avatar
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2 votes
Accepted

What is the difference in performance between variable pitch prop and two fixed propellers for take-off and cruise speeds?

The Voyager aircraft was a push-pull twin with different engines/props. The front engine is a 130 hp air cooled 240 ci engine. The rear engine is a 110 hp liquid cooled 200 ci engine. Both engines ...
Rob McDonald's user avatar
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2 votes

Function of the compressor in a gas turbine engine

I think that both a practical and a thermodynamic answer can be given. As far as I understand it, the reasons are twofold. Correct From a practical point of view, compressing the air before the ...
sophit's user avatar
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1 vote
Accepted

Which engine is more financially economical to operate, a turboprop or gasoline engine?

One-for-one is a rather poor comparison here, the whole package must be considered for efficacy. It would be more appropriate to compare the economics of operating two 2000shaft hp turbines to four ...
Max Power's user avatar
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