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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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How does washout affect the wing incidence required?

In theory: if I wanted to build an model aircraft with (zero zero) wing/tail incidence, how would washout affect the root incidence required? E.g. if a wing has 2 degrees washout at the tip, would ...
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1answer
140 views

Why are cambered airfoils used for horizontal stabilizers in some designs?

From what I know, usually NACA9/12 or similar symmetrical airfoils are used for the tail. Still some aircrafts use highly cambered airfoils for elevators. What are some advantages and disadvantages ...
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544 views

What is the total wing surface area of the A320?

I was trying to calculate the total area of an A320, and in this link I found the wing area and tail area. But here I read that the wing area is just the 2D projection of the wing. So if I wanted to ...
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1answer
187 views

How do you maximize an electric engines thrust?

I‘ve been recently looking for answers to this question on the internet but the jungle of propellers, fans and electric motors didn‘t quite get me an anwer. How would I have to design an electric ...
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3answers
588 views

Why do the C-141 and C-5 have T-tails?

Both the C-141 Starlifter and C-5 Galaxy have T-tails, where the horizontal stabilizers and elevators are mounted on top of the vertical fin rather than on the sides of the aft fuselage. T-tails are ...
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1answer
162 views

Are same-era military aircraft cockpits designed to be familiar to transitioning pilots?

The wonderful SR-71 ha what looks to me an intimidating cockpit: However, lots of planes of that era have ostensibly-similar cockpits to the layman, take this F-5 for instance: I choose the F-5 as ...
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What happens to the neutral point of a fighter jet during supersonic flight? [duplicate]

I understand that for a fighter aircraft, it would have to be inherently unstable. To do this I believe that the neutral point needs to be aft of the cg. I was told that during supersonic flight this ...
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1answer
171 views

Definition of a Deep Stall

I've been doing some research for a uni assignment and I noticed that the RQ-11B uses a "deep stall landing" to get back onto the ground. What I don't understand though is how this aircraft gets into ...
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3answers
1k views

Have bi-wings been used without creating more drag?

As I understand from answers I've read here 1, 2, 3, biplanes create more lift with less wing span when compared to single wing aircraft, because the combined wings have greater surface area overall. ...
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0answers
129 views

Can be the divergence Mach be greater than 1?

I am wondering if this is possible. I know that by decreasing t/c and increasing the sweep angle it is possible to increase the divergence Mach. Where is the limit? I am calculating the Mach for a ...
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1answer
119 views

Why does operating the rudders in the engine slipstream offer improved rudder authority at low speed?

The above question is usually presented as an advantage for H-tail configurations. How does it help?
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1answer
2k views

Are there any aircraft with powered landing gear?

My student asked me a question this morning. It was: A car drives by turning its wheels against the Earth. An airplane taxis by rolling on its wheels while the engines push against the air. Are ...
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2answers
333 views

Would putting several small propellers on a wing be efficient?

I saw this video that NASA posted, which presents the idea of putting several small propellers on a wing: They claim that by doing this you can force air to blow over the wing more quickly. This ...
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2answers
588 views

What is the 'end plate' effect?

When talking about T-tail configuration, I don't understand the statement that, "The vertical tail can be shorter due to the end plate effect of the horizontal tail." What exactly is the endplate ...
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2answers
107 views

How would gyroscopic effects affect push-pull configuration vs conventional twin engine in the event of engine failure?

This answer, and the Wikipedia article on push-pull configuration both claim that aircraft with push-pull configuration are easier to fly in the event of engine failure, because the thrust provided by ...
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1answer
113 views

Why are the positive points in a V-n diagram associated with pitch maneuvers?

For an aircraft with such flight envelope, the flight conditions in point A, C and D are ...
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0answers
146 views

Will leaving the ducting on the propellers attached to a DIY aircraft give it more thrust? [duplicate]

I'm not sure if its the right place, I have a problem with a flying thingy, and you like flying thingies, don't you? I will be trying to add some means of propulsion to my friend's styrofoam plane (...
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1answer
424 views

Are pressurized passenger aircraft usually completely airtight?

Various sources on the internet indicate that the passenger cabins on pressurised airplanes are not 100% airtight. I'm not talking about ventilation/pressure valves/cabin pressurisation system, but ...
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2answers
189 views

Is it possible to power a very small jet using batteries? [duplicate]

I have read a lot of answers on batteries powering large commercial jets, and how it won't work. However, for a small jet like the Honda jet, would it be possible for it to be powered completely by ...
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1answer
122 views

How to determine the maximum servo torque required for a nose gear?

It's pretty much it. I know how to calculate the friction force on the nose gear for a three-point landing condition using the method set forth in ...
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3answers
13k views

Could a Dyson fan scale up to be used as a bladeless aircraft engine?

Dyson has been making bladeless fans for a few years now that accelerate a consistent stream of air without exposed blades. If this concept were applied to aircraft engines, it could potentially ...
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2answers
142 views

Can lift be equated to how much air is moved?

The explanation for lift that I find easiest to visualize is that air is deflected downward by the wing. This downward action causes an equal and opposite reaction of an upward force against the plane,...
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4answers
2k views

Are there any hybrid electric planes?

Are there any hybrid planes (planned), or would this be impossible because we don't have big enough batteries?
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185 views

What aerodynamic phenomenae can decrease the pressure gradient in Boundary Layer Ingestion?

I'm exploring a question concerning whether or not boundary layer airflow presents physical limitations that are too great for current technologies to overcome (I'm holding the position that it is in ...
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1answer
216 views

Why have helicopter top speeds not increased much over time?

With advancements in technology why there isn't much increment in helicopter top speeds from what they were in the 1980s? We have newer designs like the Eurocopter X3 which is a hybrid, but the speed ...
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2answers
754 views

Is 1 propeller always more efficient than 2?

Based on other answers I've read here (1) (2) (3), a single large blade propeller is the most efficient type of thrust you can get. There are 2 reasons for this (as I understand it). Firstly, ...
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1answer
361 views

Why is the Boeing 757 undercarriage so high?

Compared to other wide bodies the 757 seems to stand on very tall landing gear. Considering strength, weight, cost, stowage space and ease of ground servicing you would want the shortest possible ...
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1answer
493 views

How to calculate the Gust Envelope?

I am trying to draw the V-n Diagram for a small aircraft I built, but I am stuck in the gust envelope part. I know how it is supposed to look. However, I am having a hard time calculating it. I would ...
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3answers
472 views

Does “pendulum effect” apply to hang gliders or any aircraft?

In discussion of aircraft roll stability in FAA paragraph on dihedral effect and in keel effect and in Why are high wing aircraft more stable the question of pendulum effect arises. This is usually ...
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1answer
474 views

What‘s the thrust of two stacked propellers?

Let‘s say that you have two identical propellers and each is powered by their own motor and together they produce a thrust of 1 kN. How does the thrust change if instead of operating them side on side ...
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1answer
271 views

How does a Hawk jet avoid pitching down when its air brake is applied

Some aircraft have air brakes in an aerodynamically neutral position with respect to rotational forces on the airframe (e.g. F-15)... source ... more often, others have brakes that are ...
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5answers
7k views

Why do most biplanes have their top wing slightly forward of the lower wing?

In most of the biplanes, the top wing is located a little forward of the lower wing. What is the use of this? Also, how does this affect stability of the aircraft.
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2answers
198 views

Are high lift wings bad for faster speeds

I notice a trend in many aircraft designs. If the aircraft was designed to go slowly but have shorter takeoffs/landings they use airfoils with a high lift. However for long endurance flights they use ...
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1answer
168 views

How much extra weight is added by strengthening a piston-prop fighter for carrier landings?

To land on a carrier, an aircraft must be strong enough to withstand sudden deceleration by the tail hook catching the arresting wire. I think it also requires strengthening the undercarriage to ...
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0answers
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How can I find the Local Section Moment Coefficient?

I am working on coding the Lifting Line Method, which uses horseshoe vortices to get the dimensionless force and moment vector for parts of a wing. C_mi is a term that means the local section moment ...
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2answers
247 views

What is the purpose of thinner airfoils used near wing tips?

I know that a thicker airfoil at root will strengthen the root spar but what is the reason behind using thinner airfoils at the tip? Is it because thinner airfoils have higher stalling angles of ...
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0answers
179 views

Will the new Boeing NMA be 'more electric' than the current B787?

I understand that the B787 is the 'most electric' aircraft to date, however there have been many issues with the plane, and I'm interested in knowing if the latest Boeing New Midsize Aircraft (NMA) - ...
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3answers
292 views

Why is extreme cold weather a challenge at airports, since jets operate at extreme cold conditions in flight?

Wondering what specifically the issues are. Obviously, taking off and landing have more 'moving parts' but more curious about the actual extreme cold. I assume the operating temperatures at cruise ...
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3answers
257 views

How the fuel in the wings is managed in case of an engine failure?

Consider an aircraft has fuel tanks only in wings (No central tank). Will the fuel for the respective engines will be consumed from the respective wings? In case of a single engine failure, if the ...
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4answers
361 views

Why do we not see propellers on swept wings or jet engines on straight wings? [closed]

Why are these configurations not observed often? The only time I see propellers are on straight wings or on the nose, while jet engines are always on swept wings or the tail. Why?
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1answer
224 views

In a jet, are Vy and Vx achieved at a constant AOA at all altitudes?

It is known that in terms of IAS, Vx (best climb angle speed) rises with altitude, and Vy (best climb rate speed) decreases with altitude, until they converge at the plane's absolute ceiling. http://...
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1answer
344 views

Can you escape an aircraft through the lavatory?

In his book "Catch me if you Can", Frank Abagnale claims he evaded arrest by removing a panel in the lavatory of a VC10, climbing through it and hence escaping out of the (taxiing) aircraft through a ...
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4answers
581 views

What drives the shape of an engine's intake on a fighter jet?

Rectangular intakes have more corners which might increase subsonic pressure losses and would weigh larger than a pitot (Semi-circular) type intake. Are the designer drivers solely based on supersonic ...
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4k views

What is this F-18 Hornet “air intake” for?

I think I read once that they served to cool the on-board computer systems, but I'm not sure.
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3answers
293 views

What are the drawbacks for manufacturing a large airliner capable of water landing?

Emergencies are rare but still occur. Apart from weight and extra fuel costs, What are the drawbacks for manufacturing a large airliner capable of water landing in case of an emergency? Assuming the ...
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2answers
166 views

Windowless VS windowed aircrafts [duplicate]

While Emirates was showing off its triple seven's ability to provide crystal-clear viewing from virtual windows, it mentioned: "that could be a step to windowless aircrafts", and I felt like it meant ...
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2answers
151 views

How can larger wingspan decrease the strength of wingtip vortices?

In the last paragraph from the link below, it states that Vortex Strength is inversely proportional to Wingspan. Why is this? http://avstop.com/ac/flighttrainghandbook/wingtipvortices.html EDIT: ...
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484 views

Could an aircraft be tied down, then throttle up and release for takeoff in order to use a shorter runway?

Could airplanes, in theory, be designed to takeoff by first tying the tail to a post, throttling the motors to full power, and then letting loose? Could it even take off while tied, if the cable is ...
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2answers
260 views

What is the airplane with the best flying characteristics? [closed]

I'm reading Stick and Rudder by Wolfgang Langewiesche, and in Chapter 7 titled, "What the Airplane Wants to Do" he discusses stability. In discussing it, he says that no plane yet built is completely "...
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289 views

What aircraft has the highest critical Mach number?

What aircraft has the highest critical Mach number? The highest I heard of was BAC/English Electric Lightning at Mach 0.95. Are there planes with higher Mcrit. and is it plausible to go higher than ...