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34 votes

Does flying slower actually save fuel?

Yes it saves fuel, unless you get really slow (well below cruise speed - more later.) Since drag (and thus power required) increases with the square of velocity it will save fuel for the total flight. ...
Gerry's user avatar
  • 20k
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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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
Accepted

What would be the range of a cargo 777 full of usable fuel up to MTOW?

First, go to the Boeing Airport Planning documents website. This includes a wealth of information about most Boeing commercial aircraft. Choose the document that matches the aircraft you're ...
Rob McDonald'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

What would be the range of a cargo 777 full of usable fuel up to MTOW?

First cut numbers, working from Wikipedia's B-777 page, and using the 777-200LR, since that seems to be the longest-ranged of the models: Max Takeoff Weight (aircraft + passengers + cargo + fuel) = ...
Ralph J's user avatar
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6 votes
Accepted

How does the Boeing TTBW reduce fuel consumption?

We have a question here concerning the Boeing TTBW study from the time it was called Sugar VOLT. In my answer I speculated that the cruise Mach number of that design is 0.75 or lower. You are correct ...
Peter Kämpf's user avatar
5 votes

What are the standard numbers for fuel consumption (kg), kg/NM, and kg/h, of Boeing 737-300?

There are charts out there, but the rule of thumb is 5,000 lbs per hour average for a flight. The first hour is more given the higher fuel flow at takeoff & initial climb, but as an average that's ...
Ralph J's user avatar
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4 votes

What would the effect be of flap deployment on a UAV such as the Reaper or Predator?

the climb performance is usually worse with flaps extended That depends which parameter needs to be maximized. If you want to climb as steeply as possible, flaps will definitely help. If, however, ...
Peter Kämpf's user avatar
4 votes

Airliner sharp wing tip vs elleptical

Airliners have some boundary conditions which make elliptical wings less preferable. Wing sweep. A swept, elliptical wing suffers lift loss at its center and will easily see its tips stall first at ...
Peter Kämpf's user avatar
3 votes

Airliner sharp wing tip vs elleptical

An elliptical lift distribution is optimal in terms of induced drag. It can be achieved by an elliptical planform (with a straight span and un-cambered airfoils and no twist), or by twisting a more ...
Rob McDonald's user avatar
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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
3 votes

What are the standard numbers for fuel consumption (kg), kg/NM, and kg/h, of Boeing 737-300?

You can look at the appropriate airport planning document. Airline manufacturers make them available. It contains a ton of information, you'll want to check out the payload-range diagram. For the -...
Rob McDonald's user avatar
  • 13.2k
2 votes

Why does fuel consumption decrease with increasing aircraft altitude?

I was trying to solve the same question of this topic and I arrived here, I see that this is an old post but but maybe I can contribute a little. Let's work in the formula quoted by Jose: Then, ...
Daniel Gonzales's user avatar
2 votes

Does flying slower actually save fuel?

There is an optimal speed for whatever you are trying to do -- for example, and optimal speed to cover the most distance per unit of fuel is probably what you are thinking of. However, if you were ...
Rob McDonald's user avatar
  • 13.2k
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
  • 16k
2 votes
Accepted

How the EFD system of F18e shows the fuel in tanks of the fighter?

Fuel qty is displayed in 1000s of pounds. The Fuel Qty Indication System measures fuel quantities from the individual internal and external tanks and displays them on the Engine Fuel Display in 1000s ...
Romeo_4808N's user avatar
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2 votes
Accepted

How much fuel can be saved in a half full of passengers plane?

The most can be saved with short range planes on long trips. When passenger load is around 10% (as it is for very long range airliners), reducing that to 5% will not make much of a difference. But we ...
Peter Kämpf's user avatar
2 votes

AirBus A380 and Boeing 747 - fuel consumption while taking off?

This video shows the A380 engine instruments during takeoff. There are differences between engines but they average about 8700 kg/hr per engine, or 34,800 kg/hr total (9.7 kg/s, or 12.1 L/s, or 3.2 ...
fooot's user avatar
  • 73.4k
1 vote

AirBus A380 and Boeing 747 - fuel consumption while taking off?

With a quite good approximation it can be shown that a jetliner typically consumes fuel for around 3% of its MTOW during warmup, taxing and take off. This percentage corresponds to around 17'250kg for ...
sophit's user avatar
  • 13.6k
1 vote

How much fuel can be saved in a half full of passengers plane?

The answer is heavily dependent on the exact airliner. As a general rule, the practical answer is "not enough". Reducing the airliner's weight saves fuel during takeoff (slightly), climb (...
Therac's user avatar
  • 27.6k
1 vote

How to calculate fuel burn rate in Model BK117 helicopter

Given the fuel quantity and the fuel flow, it should be quite trivial to calculate endurance. Consider the following: Fuel flow simply states the amount of fuel consumed during a given timespan. For ...
U_flow's user avatar
  • 3,840
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
  • 2,604

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