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It sounds very much what you're experiencing is a Phugoid cycle Image License info To put simply, your aircraft is not trimmed correctly. As it descends slightly it gains speed, which increases lift over the wing making it climb. This has the effect of it losing some speed, reducing the lift over the wing causing a descent, increasing the speed - and on it ...


6

Flutter happens when elastic and aerodynamic frequencies converge. Normally, the elastic one is (almost) fixed and the aerodynamic one increases with flight speed. When speed increases further and the frequencies move apart again, flutter will die down. However, with further increasing speed more elastic modes will be encountered with ever smaller gaps ...


6

Air pressure reduces with altitude, so while an individual molecule is striking the the aircraft at 100kt, there are fewer of them. This means there is less pressure placed on whatever surface is being struck. The difference in indicated speed is simply one of a physical limitation with the air speed indicator - air speed indicators rely on dynamic pressure/...


6

If there ever was a pilot who forgot to throttle down on descent Full scale pilots trim their elevator for speed, and use their throttle to climb or descend. "Bobbing or skipping" behavior in cruise is a sign of instability, not surprising for a tailless piece of foam. If this plane has a published CG location, thrust angle and control surface ...


5

It may seem counterintuitive, but by introducing a small amount of turbulence, this interrupts the slower boundary layer which is directly in contact with the wing, thereby delaying local airflow separation and aerodynamic stall. Essentially, at the expense of a small amount of parasitic drag, the stall performance and control effectiveness of the wing can ...


5

The frontal surface is indeed used for the drag coefficient of cars. For airplanes, however, almost* all coefficients use the wing area as their reference. This makes sense exactly because it allows to express L/D as c$_L$/c$_D$. * For the nitpickers: Control surface hinge moment coefficients use the area of their respective control surface, not the wing ...


5

Think of it this way. Your airspeed indicator is not directly measuring the distance traveled of any object, aircraft nor air molecules, over time. Your airspeed indicator is a pressure sensitive device that measures ram air pressure (dynamic pressure) versus static pressure. It converts that measurement into a meaningful value of airspeed. That ram air ...


4

Hot-air Balloons are already made with large holes in them. They are called vents. They can be located in the balloon’s top or sides. They tend to be much much larger than the 4-inch diameter you described in your question. But, their opening and closing are controlled by the pilots. Research the FAA Balloon Flying Handbook. It will give you much more ...


4

To get a deeper understanding beyond the superficial, it helps to break down the forces and moments present on an aircraft that may affect its rigid-body motion: Aerodynamic forces: These are the forces and moments exerted by the airflow on the aircraft Ground forces: These are the forces and moments exerted by the ground on the aircraft, transmitted ...


4

In my experience with model airplanes the bobbing and dipping motion occurs when the center of lift is forward of the center of mass and represents a series of mini-stalls and recoveries that persist and repeat. Since simple model planes generally do not have elevator trim, the solution is to move the wing attach point aft in small increments until the plane ...


3

Thrust is produced mainly in the compressor; as its blades push the air backwards to compress it, a reaction force pushes the blades forwards. These blades are fixed to the shaft. The shaft has a flange on it which pushes against a similar face on the engine mounting, in an arrangement known as a thrust bearing. This in turn transmits the thrust to the ...


2

Resistance is a term used in politics and electric circuits. We here talk of drag. Your induced drag equation uses speed where the lift coefficient belongs: $$c_{Di} = \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$$ What is missing now is the zero-lift drag which is the dominant contributor to overall drag at high speed. From your top speed result this seems to be $...


2

Dynamic pressure is $$ q = ½\varrho v^2 $$ where $q$ is dynamic pressure, $\varrho$ is density and $v$ is velocity (a.k.a. true airspeed). The important bit here is that it is proportional to density and since density and pressure are closely related and pressure decreases with altitude, so does density For the intuition of particles hitting the surface, ...


2

The side slip happens because the lift vector is tilted. Think of a hovering helicopter rotor tilting; the machine drifts to the low side of the rotor disc because the thrust vector of the rotor is tilted. The wings of the plane are just making thrust, but moving forward at the same time. Tilt the thrust line by banking, and a lateral thrust component ...


1

The act of rolling the aircraft creates adverse yaw, which generates sideslip. This is a transient effect which is explained in this answer. In a steady coordinated turn (ball centered), however, sideslip will also be present. This is a steady-state effect. There are a few contributing factors: There is steady-state non-zero rudder, which is necessary to ...


1

Incorrect explanations abound for why an aircraft tends to sideslip when banked, in the absence of any "coordinating" rudder input. Often the fact that the weight or gravity vector has a component pointing towards one wingtip is invoked. See for example the diagram in Martin Simons' "Model Airplane Design". The truth is that this ...


1

TL-DR: IAS is not about speed but about dynamic pressure. You can read it as "This is how fast I would need to fly at sea level standard conditions in order to get the same dynamic pressure" As Jan Hudec pointed out already, indicated airspeed is computed from dynamic pressure. That itself is computed from total (i.e. stagnation) and static ...


1

The most basic and simplest answer is Air gets thicker at the surface. A body moves forward by pushing the air away from its path. Be it a car or a bike. The lower the automobile operates, the more air it needs to disperse to propagate forward. To move forward, a certain amount of energy needs to be expended either on the ground to push itself forward or ...


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