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Why do most commercial aircraft have the Center of Gravity before the Aerodynamic Center?

The reason for placing the CoG in front of the neutral point is the behaviour when the Angle of Attack increases: for passive stability, we want gravity to provide a nose-down moment: $dC_L/d\alpha$ ...
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1 vote

Why do most commercial aircraft have the Center of Gravity before the Aerodynamic Center?

Actually, the diagrams are sort of a "tongue in cheek" way of saying we don't fly staticly stable planes because we want to save fuel costs "your winnings, sir" Over the life of ...
• 17.7k
1 vote

Why do most commercial aircraft have the Center of Gravity before the Aerodynamic Center?

I'm shocked - shocked! - to see this inaccuracy from Airbus. Or am I? Of course the bold statement is utter nonsense, but is repeated over and over. Which doesn't make it true, but very hard to dispel....
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Why do most commercial aircraft have the Center of Gravity before the Aerodynamic Center?

It is this way so the aircraft will be stable. Think about a dart -- the CG (the heavy brass weight) is far forward, while the aerodynamic center (the fins) are very far aft. The dart can not trim -- ...
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What is the typical drag percentage of air intakes on a commercial airliner

The legendary Fluid Dynamic Drag by Sighard Hoerner contains all the numbers you need. Chapter 9-E should be what you're looking for.
• 6,119
1 vote
Accepted

RAT Deployment and Stowage

The RAT is typically deployed using a spring loaded lever and cannot be stowed in flight. See this question for more details on deployment: How do Ram Air Turbines get deployed? There is no ...
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1 vote

Can someone help me understand this aerofoil?

This is a rotorcraft airfoil. Item 206 is the rear wing spar. All the information you need is provided in the actual patent application. US Patent Application for COMPLIANT STRUCTURE DESIGN FOR ...
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1 vote

Is there an aerodynamic benefit of covering the underside of wings?

There most certainly is, early hang gliders we’re single-surface, then more advanced designs adopted a small under-surface just behind the leading edge, and the extend of the lower surface increased ...
• 1,434
Accepted

Is there an aerodynamic benefit of covering the underside of wings?

Lift is a function of velocity squared. As more powerful engines became available, higher airspeeds allowed designers to choose the airfoil shape that provided the least amount of drag for a given ...
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Why do some Caravelles have a full outboard wing fence, and some only a partial outboard fence?

Every square inch of skin surface adds to induced drag, so nothing is going to be bigger than it absolutely needs to be. Whether through math or empirical testing (or some of both), it was determined ...
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Aircraft progress: Evolution or design?

The main driving forces behind airplane progress have been 1) better materials to make them out of and 2) better engines to power them with. Better materials mean greater strength and safety. Better ...
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Is Ducted fan or Propeller better to maximize forward speed of RC aircraft with a given power?

Like turbo fans, the idea of EDFs is to have higher air speed in a smaller dimeter compared to a propeller. The problem is you need 4x the air speed when halving the diameter to produce the same ...
Accepted

XFLR5 vs AVL vs DATCOM vs OpenVSP

It depends on what you want from the calculations. First, I'll assume that you are mainly interested in calculating the pitch stability of the aircraft to help you determine where to locate the CG. ...
• 1,416
Accepted

Why is the A330/A340's alpha-floor protection disabled above mach 0.53?

Try to see it this way: ALPHA FLOOR is a protection function of the AUTO THRUST SYSTEM, and it protects the aircraft from excessive speed decay. It does not primarily protect the aircraft from ...
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What is the purpose of the fin at the Boeing 787 APU exhaust?

StackExchange is so funny sometimes! It is to simply keep fuel from the body drain tubes out of the APU exhaust.
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Is there any significance to the flap design on some Cessna citations?

If you look at the flap track system carefully on the Latitude, you can see the track system being used occupies the space between the panels when retracted, and that particular configuration required ...
• 118k
Accepted

Why would older jets and turbo props use electric gyros vs vacuum driven?

Electric gyroscopic systems provide redundancy to vacuum powered instruments. "Older" (and modern) jets and turboprops are required to fly in all kinds of weather, including iceing ...
• 17.7k
Accepted

What is the difference between position and navigation lights on light training aircraft?

Position lights, sometimes called Navigation lights, are the same thing. In the U.S., 14 CFR Part 91.205 (c)(2) refers to these lights as "position" lights.
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Why do autopilot controllers use $\theta$ as the input signal rather than $\gamma$?

You are right, your input should be $\gamma$. However the control of $\theta$ is important. To combine both variables, typically a nested control structure is adopted. For this, two control loops, an ...
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