Linked Questions

10
votes
5answers
11k views

What determines the best glide speed?

I found the best glide speed of cessna 152 is 60 kts. My question is why it is not more or less than 60 kts? What are the factors upon which the best gliding speed is determined?
16
votes
2answers
7k views

Why would maximum fly-time (endurance) not coincide with max L/D operating point?

This question is motivated by another SE Aviation answer where @Peter Kampf writes the following two useful bits of information: Aircraft like to fly near their optimum L/D ratio, where drag ...
2
votes
1answer
140 views

Solutions to improve the aerodynamic behavior of a UAV

So I'm working at a project of a UAV with the follow characteristics: Rectangular planform Conventional tail The fuselage is just a metal/aluminum rod So we need to improve its aerodynamic behavior/...
5
votes
1answer
470 views

How do I obtain the max endurance altitude?

There are excellent explanations of the physics that determine maximum endurance speed here, here, and here. I was thinking of aircraft that have to be "on station" without an indicated altitude and ...
6
votes
1answer
363 views

Does one-engine cruise consume less fuel than two-engine cruise?

Scenario 1. A two-engine airliner experiences rapid depressurization and makes an emergency descent to 10,000 ft, and diverts to the nearest airport. Scenario 2. The same two-engine airliner ...
16
votes
2answers
22k views

Why do military turbofan engines use a low bypass ratio?

I know that the most civilian engines use a high bypass ratio which is good for fuel economy and noise reduction. What prevents military engines from using the same technology instead of opting for ...
15
votes
4answers
11k views

What is the propeller efficiency, $μ_p$, of modern propellers for light sport aircraft?

Roskam's book on preliminary design gives a value of 0.7 for "homebuilt" aircraft and 0.8 for general aviation. What explains this difference in propeller efficiency? The content of Roskam's book is ...
0
votes
1answer
1k views

Which portion of combustion energy is used to spin the compressor of a pure jet engine?

In level flight at constant speed, it is correct to assume that the quantity of energy created by fuel combustion (FE) is exactly extracted by the turbine section (ME) and is used solely to spin the ...
3
votes
4answers
4k views

How can I find the optimum chord wing length for this wing?

This Aviation SE forum looks the perfect place to ask this question: people here usually make maths the root of most solutions and I think this may solve my aerodynamic optimization problem! I am ...
6
votes
2answers
7k views

How to pick a good airfoil based on Cl and Cd

Let's assume I have 10 different airfoils graphs of Cl x Aoa, Cd x Aoa and Cl/Cd x Aoa. How do I pick the best one that will give me the most efficiency (the longest flight time)? I understand the ...
0
votes
1answer
460 views

Is it possible to create a direct supersonic airflow to a turbofan's afterburner in order to enhance the performance or reduce the fuel consumption?

so I found out that SR-71 Blackbird is using what's called "turboramjet" and I find the idea a bit appealing since they say with such engine, the Blackbird is more fuel efficient at it's top speed. I ...
24
votes
6answers
7k views

In what way are the Concorde's engines considered efficient?

The Concorde is powered by a bunch of Rolls-Royce/Snecma Olympus 593 turbojet engines. Much has been said about how efficient they are at speed, and the fact that they allow long-range cruise at Mach ...
9
votes
1answer
1k views

How does the efficiency of a turbofan compare between take off speeds and optimal conditions?

I know turbofans are less efficient than propellers due to accelerating a smaller mass of air faster. So my question here is not comparing turbofans vs other engines, but compare how inefficient is a ...
14
votes
2answers
5k views

Which commercial aircraft can stay in the air the longest?

Which commercial aircraft, when fully loaded with fuel (and passengers and luggage up to its max takeoff weight), could stay in the air the longest without landing, and how long could it stay in the ...
6
votes
3answers
4k views

Why are the top speeds for jet engines higher than for propellers?

I realize turbines are more efficient than piston engines, but if that were true, then why don't turbo-props reach jet speeds?

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