30

Asymmetric thrust means now you have more thrust on one side than the other. A yawing moment results. You want to balance this yawing moment in order to still fly straight. This means the airplane needs to produce an opposing yawing moment somewhere else. The most suitable part to do so is the vertical tail surface, which will do this by producing a side ...


14

User Sidestick_n_Rudder posted on PPRuNe (emphasis mine): Vs1g is the lowest speed, at which the airplane can maintain 1g, i.e. level flight. It corresponds to the Cl max Vs is the lowest speed attained during stall testing of the airplane. The pilots were able to reach this speed lower than Vs1g, but the plane was already losing altitude. The way I ...


13

In a turn you have two opposing effects: In order to tighten the turn, more of the lift needs to be tilted sideways for the needed centripetal force. At the same time, you want to fly slowly so the turn rate and with it the centripetal force stays manageable. Starting with the equation for the turn radius: $$R = \frac{2{\cdot}m}{\frac{\rho}2{\cdot}c_{L}{\...


11

The windmilling prop extracts energy from the mass flow through the propeller disk area. An 8-bladed prop can extract more energy from the mass flow, and does this at lower RPM than the 2-bladed prop. The extra energy it can harvest is due to lower tip losses. Pic above is from Principles of Helicopter Aerodynamics by J. Gordon Leishman, and shows results ...


7

No, it does not. It does not change even if the actual wing area does e.g. by extending Fowler flaps. Lift is only very roughly proportional to wing area. It depends on the span and the chord and the profile in complex ways. By referencing to the wing area you are just getting a number that is of the same order for different wings so you can more easily see ...


7

This generally means a short wingspan with an extra-strong wing spar structure (to take the lift and G loads), a wing with either high-lift devices that deploy in the turn or a relatively thick wing profile, no fuel tanks or excess mass in the wing itself (to minimize the axial moment of inertia of the airframe), big ailerons (to generate a large rolling ...


7

First of all, any radiator thrust is limited by the amount of ram pressure which can be achieved at the radiator entry. This is just 1.4 times ambient pressure at Mach 0.8, and then very little flow speed remains (which is good, because that limits internal losses in the radiator). Next, the heat exchanger should cause as little drag as possible. A blunt ...


6

Aerodynamics science is not a standalone discipline and involves many other aspects that are peculiar to it. In particular, only to cite some: Fluid mechanics : fluid mechanics research is very extended, starting from experimental, until the numerical one. Related to it we have all the research related to math (Fluid dynamic equations' nature, specific ...


5

The idea that the plane was unable to leave ground effect is not quite right, in fact it's the opposite. Ground effect results in the plane having slightly more lift (and less drag) at very low altitudes close to the ground, and it typically comes into play when your altitude is less than the wingspan of the aircraft, this is why it is sometimes described as ...


5

No that has no benefits for aviation at all, except for the marketing department. A large amount of losses funnelling the airflow from motor to a small strip, from which it is propelled at high velocity. As stated in many places on this site, thrust T = $\dot m \cdot \Delta V$, while the energy expelled E$_{kin}$ = $½ \cdot \dot m \Delta V^2$. So thrust ...


4

After the stall is reached the airfoil still generates lift, but less than before the stall. Plus drag has greatly increased due to the separated boundary layer on top of the wing, which causes pressure drag. Image source Figure above shows why the boundary layer separates: the airflow close to the skin is slowed down by friction, and does not have enough ...


4

Research in aerodynamics has not stopped. Just in the first ten days of 2022, over a thousand papers have been published.


4

The Navier Stokes cannot be solved analytically, they can however be computed numerically. Which is the technology behind flight simulation, using a determined time interval to compute all dynamic (differential) equations, then use the result as input into the next time interval equation. Real-time digital computation. The technology is quite mature, as ...


4

What is aerodynamic reason why turbine with 8 blades will rotate slower then with 2 blades? It won't, all else being equal. The speed of the turbine is governed by the aerodynamic forces on the blades and the resistance in the turbine. (By resistance I mean non-aerodynamic forces like drag in the bearings and the actual generator.) In a two-bladed turbine (...


4

(Note: the first two paragraphs of this answer were aimed at the original title of this question, which was "Why does the ball no longer point straight down in a multi-engine airplane with inoperable engine?") First let's address a misconception that some readers may take from your title. In linear, constant-heading flight in any aircraft, "...


3

The key to getting out of Ground Effect is having sufficient amount of thrust to overcome the increase in Induced Drag as you start to move away from the ground. If you don't have the sufficient amount of thrust to overcome the increase in induced drag you will never leave ground effect and that is indeed what happened in the video. A few observations about ...


3

If I understand the details of your question (the first part), the center of pressure should never be completely behind every part of the aircraft structure. That would not be possible. However to answer the question as you pose it in the last sentence, the CP does not have to be on a part of the design where there is actual aircraft structure. If the ...


3

The reference area is arbitrary, i.e. you can choose what your reference area is. But the idea of a reference area is that it is constant, and the influence of e.g. angle of attack on lift is reflected in the coefficient of lift. Some form of projected wing area is just the most common choice for airplanes (and there are certainly some good engineering ...


3

W = F*d Where W is the energy needed to apply a force F over a given distance d. Power is energy divided by time and also equivalent to Force applied for a given velocity. F x v = F x d/t = W/t For an airplane and straight and level flight at constant true airspeed, the force of drag is equal to the force of thrust. Fd = Ft Since the force of drag is ...


3

The difference is due to the different systems of how they produce their upwards lift and is not necessarily linked to the size. On most small helicopters (like the one you have in the lower picture) you have a so called "fixed-pitch" system. The rotor blades always have the same curvature (pitch) and how much lift they produce is controlled by the ...


3

As other answers have said, manned and large drone helicopters have twisted rotor blades. RC helicopters almost all have zero-camber (symmetrical), zero-twist rotor blades. These are almost comically inefficient (the center half of the disk produces almost no lift), leading to typical flight times of five minutes or so. They have the benefit of working ...


3

The equations solved for the most of the CFD software are the Navier-Stokes equations (let's stay in the general case of compressible ones). The Problem of Navier Stokes equations solution existence means that (only in case of the 3D problem) the solution of Navier-Stokes equations is not proven to "exist and be unique" alias the Lax-Millgram lemma ...


3

The answer start by understanding how are aerodynamic forces generated. The aerodynamic forces are a result of the pressure distribution around the airfoil and of the shear forces due to the viscosity (look at the wikipedia definition, without entering too much into details). Starting from this, we can have a look to a simple case (NACA0012) in which we ...


2

The absolute MTOW is a limit imposed by structural considerations, not altitude limitations. At every point on earth, a max allowable TO weight must be established by the pilots based on runway length, pressure altitude, climb performance etc. The service ceiling can be reached at structural MTOW: it is defined as the altitude where the maximum rate of climb ...


2

A simple and arguably easy to understand answer is that the wing does not produce separate forces called Lift and Drag. It produces force at every point of the wing *, pointed in a direction normal (perpendicular) to the surface of the wing at each point. Lift is just the sum of the the components of all these forces that are normal or perpendicular to the ...


1

Given that the video did not mention anything being wrong with the aircraft, my money is on the shift in winds being the primary cause for the apparent reduction in airplane performance. I would also blame the pilot for rotating before he had the indicated airspeed for a climb. The time to reject a takeoff is before the wheels leave the ground. The pilots ...


1

In a coordinated turn, this is purely a geometry question. Let's call the distance from centerline to engine $d$. The plane must bank to allow for centripetal acceleration $a=v^2/r$ with $v$ true airspeed and $r$ turn radius. This places the engines at a lateral distance of $$d^*=\frac{d}{\sqrt{1+\frac{a^2}{g^2}}}$$ from the centerline with $g$ acceleration ...


1

Firstly, your hypothetical situation ("is it possible...") would represent an over-constrained problem. It would never be possible that an a/c has enough thrust to overcome drag at speed Y, but doesn't have enough power to overcome drag at the same speed Y. That's a fundamental contradiction, indicating a misunderstanding about the basic ...


1

At airfoiltools.com you can examine many relationships of lift and drag without worrying about the "right" answer on a test. In one particular course of study, "approaching stall" may be the warning buffet of airflow separation from the trailing edge of the wing. With a magnifying glass, you may see lift begin to decrease here as drag ...


1

Imagine a propeller being turned by an engine suddenly losing power. How to make it a good generator as well as a good propeller? Probably a more symmetric airfoil. As seen here, a good airfoil shape will help create more lift/thrust from the relative wind. Interference will play a role in rotation speed. This is why more blades have a lower maximum ...


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