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Questions tagged [aircraft-design]

Questions about the different choices that aircraft designers (typically aerospace engineers) make in order to create an aircraft.

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30 views

What is the reason for forbidding liquids for cooling in drilling on cfrp/Al or cfrp/Ti stacks?

I recently did some research on the effect of cooling on CFRP/Al7075 drilling.But I read somewhere that liquids are forbidden for cooling operations on these multi layer plates !!! , And I wanted to ...
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1answer
70 views

Why have propeller engines never been mounted on the tail?

Recently, Embraer teased this concept. Unlike jet engines, I have never heard of a production airliner or executive aircraft that mounted propellers on the tail like this. From the source: the new ...
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2answers
51 views

Can you have a Hybrid Turboprop-Jet engine?

To start things off I am writing this to gain information for vehicles in a story, so I am more so looking for theoretical possibilities, unless there are real world examples. The background and my ...
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1answer
62 views

What are the effects of increasing Wing Aspect Ratio?

I can think of only 2 effects that is The Induced Dag would Reduce with increasing AR of wing. This goes by the simple formula: $$ C_{d(i)} = \frac{K \times C_l^2}{\pi \times \text{AR}} $$ As drag ...
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1answer
171 views

Charger vs Bronco horizontal stabilizer volume?

While watching this video on the Convair Model 48 Charger, I was surprised by the dimensions of the horizontal stabilizer. Compared to the North American OV-10 Bronco, which is relatively similar in ...
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1answer
189 views

What does account for a high coffin corner of a plane?

The Coffin corner is the altitude at which a plane's stall speed is close to Mach 1, the speed of sound (but still below, at the critical Mach number). What accounts for a coffin corner at higher ...
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1answer
83 views

How does the stick force and behaviour of aircraft relate to the CG locations?

I'm struggling with developing an intuition for flight behaviour and stick force with CG locations. Assuming conventional wing and tail configuration, When the CG is moved from aft to forward, the ...
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4answers
295 views

Countermeasures taken to prevent reverse engineering of military fighter jet technology? [closed]

Inspired from this news - The immediate question after reading the news will arose in the minds of novice people like me that - How the aircraft manufacturers cope with this issue? Which leads to ...
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1answer
99 views

Do aircraft usually fly with CG at 50 percent of chord or do I need to reduce the tail volume?

I'm working on a design having a 3.2-metre wing with a constant chord section in the middle and taper on the sides. With a tail volume of about 0.68, the neutral point is at 60% chord from the leading ...
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1answer
149 views

Why would control-surface balance horns cause problems at transonic speeds?

On many aircraft, control surfaces such as elevators, ailerons, rudders, etc., have "horns" which extend forwards of the surface's hingeline, wrapping around the tip of the wing or ...
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66 views

I don't quite understand the derivative in this vertical wind gust formula

First my english writing skill is still bad so pardon me if i accidentally made any mistake TT-TT. So recently I have learnt about how the vertical gust affect the load factor and the calculation ...
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2answers
108 views

What is the typical wing twist angle at the wing tip for a commercial jet?

I'm trying to find this information for commercial jets. It is nowhere to be found. Does anyone know typical values?
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1answer
185 views

How does the Bell V-280 (a tiltrotor) rotate, bank, and fly sideways? [duplicate]

Here is a video of Bell V-280 Valor. Seems like the old definition of airplane's control is no longer hold for this kind of airplane. If you click the link, it will go directly to the part I want to ...
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1answer
279 views

Is all the extra lift from flaps added upstream where the spars sit?

Flaps can significantly increase the lift for a wing, is all that extra lift added upstream where the spars sit? I ask this question because the flaps in airliners seem to be only connected by a few ...
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33 views

What are typical values for CLmax in clean configuration?

I know typical cruising CL tends to be in the range of 0,5. Maximum CL I'm guessing around 1. Does anyone know typical values?
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2answers
617 views

Can the rudder be considered part of the vertical stabilizer, and the elevator part of the horizontal stabilizer?

Or is it strictly correct to say these are separate elements, and you can't call the whole a "stabilizer"?
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1answer
86 views

What are typical CLmaxTO and CLmaxL values for modern aircraft?

Roskam gives these values for typical ranges: However several of his tables are off (for example he estimates typical cruising L/D at 13-15 when many planes are above that). Does anyone know typical ...
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1answer
206 views

What would be the advantage of a Puller vs. Pusher configuration on Embraer's new Turboprop?

Embraer recently teased a turboprop aircraft with aft-mounted, open rotor engines. Why would this aircraft not use a pusher configuration? The reasons that are frequently stated as a benefit for a ...
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1answer
110 views

How can my CD0 estimation be improved?

In this question (link) @PeterKämpf asked me to give a basis for my results. I will share my method for estimation here to see if you guys agree it is correct and how I can improve on it. Note that I ...
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1answer
109 views

What are typical values of CD0 for commercial high-subsonic jets?

Torenbeek (engineer famous for his book on aircraft design) indicates 0.014-0.020. However I've been estimating values for typical planes like the B737/A319 and I'm getting values of 0.026-0.027. I'm ...
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0answers
47 views

How is a design cruise altitude picked? [duplicate]

Different planes have different design cruise altitudes, given by the manufacturer. You can find these in their Airport Planning Manuals or in Jane's All the World's Aircraft. I know that the first ...
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1answer
241 views

What are engineers trying to maximize when they design for takeoff at MTOW? (It seems to me the only free variable is the OEW.)

For a commercial flight, the payload it carries is the weight of passengers and their baggage. Therefore fixed by seat configuration. Fuel weight is determined by the range of the flight. MTOW or ...
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3answers
716 views

How to correct the design of an aircraft that is not speed-stable during approach?

I was just wondering if an aircraft is found to NOT be speed stable during the approach flight phase, what might a designer be able to do to stabilize the aircraft without adversely impacting its ...
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1answer
310 views

Would an oval fuselage fly as well as a round one?

I was looking at various planes, and was wondering why we don't have oval shaped fuselages instead of only round ones. Is there a reason? Perhaps aerodynamics, or stresses?
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2answers
454 views

Use of a solenoid valve over a selector valve

When designing a low-wing light aircraft with two integral tanks at the wings and a collector tank in between, what type of valve should be used to allow the pilot to select the integral tank which ...
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99 views

Why doesn't the -30% SFC fully account for the dramatic reduction in fuel consumption compared to the 1960s?

In looking at the specific fuel consumption (SFC) of some aero engines I find that for example, the Rolls Royce Conway turbofan engine had typical cruise SFC of 0.874 lb/(h lbf) whilst the most modern ...
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0answers
164 views

Why don't I see this kind of split ailerons on aircraft?

Why don't I see split ailerons that work like spoilers going up and like normal ailerons going down? Isn't that a good way to get rid of adverse yaw?
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5answers
677 views

What is the principle behind flight of airplanes? [duplicate]

What is the principle behind flight of airplanes? Need a simple answer for grade 7 student. Thank you
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1answer
63 views

Angle of Attack influence on Adverse Yaw

we are analyzing an aircraft's lateral-directional control characteristics with self-made code. We have observed that the aileron's influence on the body axis yaw moment is quite sensitive to the ...
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2answers
137 views

How are cabin pressure and oxygen level maintained inside the airplane? [duplicate]

How are cabin pressure and oxygen level maintained inside the airplane?
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42 views

What's this outlet on the wing of Eurofighter Typhoon EF2000 for? [duplicate]

I was seeing this image and saw this outlet. It's not the outlet of an APU, is it?
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1answer
126 views

What is the dihedral angle of the A380?

It is understood that the A380 has a sweepback angle of 33.5 degrees and a taper ratio is approximately 0.3. However, what is the dihedral angle of this aircraft?
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108 views

Why was the minimum turbulence intensity that commercial airliners have to withstand increased?

From 50 fps turbulence intensity at VC to 90-100 fps turbulence intensity at VC. The amended FAR design criteria was introduced in 1980 or 1981 for commercial airliners. What prompted this change?
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1answer
182 views

What trailing edge flap design does the A350 use? Is it similar to the A380?

Both Airbuses have similar flap deployment based on some YouTube videos I have watched, just wondering if they both have the same flap design being "Single-Slotted Fowler Flaps".
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1k views

What flap design does the A380 use? Is it Fowler flaps, slotted flaps or a combination?

I have looked at maintenance manuals, the Airbus website, and Wikipedia but still could not find a definite answer as to what trailing edge flaps the Airbus A380 uses.
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3answers
171 views

Why should Mach wave angle be less than wing sweep angle?

This is from my lecture notes: I see that this is so you can have subsonic flow over the wing planform, but why is this desirable? And are there more reasons? I can think of heat being an issue if ...
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3answers
171 views

Ground effect and Lift coefficient

Is there a correlation between the lift coefficient and the proximity between the wing and the ground? I know that the lift coefficient is dependent on angle of attack; However, based on experiments ...
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1answer
146 views

When the F 16 landing the flaperons are used for rolling due to the functionality as ailerons, but after touching the ground it is the same?

In landing gains the flaperons are down 20 degrees. If you have to do corrections of the bank angle on approach then you move upward only one of the flaperons. But after touching the runaway it is ...
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3answers
203 views

How can I make a serious wind tunnel?

I am looking for specifics of building and the operation of low speed wind tunnels, but most diy wind tunnels on internet are improved versions of science fair projects at best. What would I need to ...
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1answer
112 views

What causes air flow towards fuselage near the winglet?

I am trying to understand how winglets are beneficial in reducing induced drag and I came across this article; https://www.boldmethod.com/learn-to-fly/aerodynamics/how-winglets-work-to-reduce-drag-and-...
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2answers
104 views

How can I calculate the tail area required to achieve longitudinal static stability?

I've got a longitudinal stability question. I've not attempted this question yet as I didn't know where to start from, also my lecturer hasn't explained static stability to us clearly and I needed a ...
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1answer
381 views

Are the emergency exits on a Boeing 747-400 plug doors?

Rossiya Airlines flight FV5625 to Antalya suffered an incident at the gate when a passenger opened an emergency exit (seems to be the L3 door, from what I can tell) "because they felt too hot&...
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3answers
112 views

Is the classical definition of induced drag merely a mathematical construct?

I understand that the presence of vortices at the wing tip cause part of wing to see a higher angle of attack and cause more drag. But the explanation that lift vector tilts backwards seems like a ...
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3answers
272 views

Can any helicopters use negative collective to descend rapidly?

On a helicopter, the collective is used to adjust the attack angle of all the main-rotor blades in the same direction by the same amount, causing the amount of lift generated to increase or decrease ...
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1answer
75 views

When, and how to calculate this, you can expect too much Wing Dihedral generates Dutch Roll, increases in Drag? [closed]

The question comes from the Arup designs, and the engineer who turned it into blueprints, Hoffmann, ('A Novel All Wing Airplane', Raoul J Hoffman, Popular Aviation, March 1935, pp 163 and 196), they ...
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1answer
130 views

Why is sweep angle measured at the 25% chord?

If you look at wing planforms of e.g. the Spitfire, you can see that the sweep measured at the 25% chord line is 0°. However, the leading edge is rounded/slightly swept and therefore induces spanwise ...
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0answers
63 views

Do high wings aircraft create an additional vortex in the middle?

At the same time, the air on the upper surface has a tendency to flow in toward the fuselage and off the trailing edge. This air current forms a similar vortex at the inboard portion of the trailing ...
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2answers
1k views

Why does a Cessna 172 have dihedral wings if it has high wings?

"Dihedral goes hand in hand with low wing aircraft, and anhedral goes with high wing". This is what I assumed till now. But when I see a Cessna 172, the wings are a little dihedral. So why ...
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2answers
6k views

Why was the C-5 considered the largest plane possible?

We started to build the C-5 and wanted to build the biggest thing we could https://en.wikipedia.org/wiki/Lockheed_C-5_Galaxy The An-225 is 50% larger and has a shorter life. Did they mean the C-5 was ...

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