HELI

Introduction to Rotary Wing Aircraft, Vorlesung an der ZHAW SoE, Studiengang Aviatik

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Kartei Details

Karten	246
Sprache	English
Kategorie	Technik
Stufe	Universität
Erstellt / Aktualisiert	13.06.2018 / 20.06.2018
Lizenzierung	Keine Angabe
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Flip-Modus

Why is the generation of an induced velocity a consequence of the generation of lift (by a heli rotor)?A. Because of the conservation of momentum B. Because of the conservation of energy C. Because of air viscosity D. Because of rotation speed Omega

A. Because of the conservation of momentum

In hover, induced velocity is inversely proportional to rotor area. This means, with respect to a reference radius: A. That a rotor with a smaller radius will generate a higher induced velocity but will have the same efficiency – while generating the same thrust force B. That a rotor with a smaller radius will generate a smaller induced velocity – while generating the same thrust force C. That a rotor with a smaller radius will generate the same induced velocity – while generating the same thrust force D. That a rotor with a smaller radius will generate a higher induced velocity – while generating the same thrust force

D. That a rotor with a smaller radius will generate a higher induced velocity – while generating the same thrust force

Induced velocity in autorotation is: A. Zero B. Equal to descent velocity, without considering the final flare C. Smaller than descent velocity, without considering the final flare D. Larger than descent velocity, without considering the final flare

C. Smaller than descent velocity, without considering the final flare

Induced velocity in autogyrus / gyroplanes is: A. Zero because the rotor is windmilling B. Non-zero because the rotor does generate lift C. Zero because the rotor is not driven by the engine D. Non-zero because the rotor turns

B. Non-zero because the rotor does generate lift

What is normally meant by “vortex ring”? A. A working state of a rotor characterized by stable re-circulation through rotor disc B. A working state of a rotor characterized by a strong wake C. A working state of a rotor characterized by circulation D. A working state of a rotor characterized by unstable re-circulation through rotor disc

D. A working state of a rotor characterized by unstable re-circulation through rotor disc

What is meant with the term windmilling? A. Windmilling is the working state of a rotor in which the flow gives energy to the rotor system – i.e it is the state in which wind turbines work when they generate power B. Windmilling is the working state of a rotor in which the rotor accelerates its rotation speed C. Windmilling is the working state of a rotor in which the rotor system gives energy to the flow- i.e it is the state in which wind turbines work when they generatie power D. WIndmilling is the working state of a rotor in which the flow gives energy to the rotor system – i.e it is the state in which helicopter rotors work

A. Windmilling is the working state of a rotor in which the flow gives energy to the rotor system – i.e it is the state in which wind turbines work when they generate power

Why is a rotor less efficient than a wing in forward flight at high speed, at an advance ratio mü=V/(Omega x R) = 0.40 for instance? A. Because the flow around the retreating blade is disturbed by compressibility effects and the advancing blade experiences inverse flow or very high angle of attack B. Because the flow around the blades is disturbed by compressibility effects C. Because the flow around the advancing blade is disturbed by compressibility effects and the retreating blade experiences inverse flow or very high angle of attack D. Because wing increase their efficiency as speed increases

C. Because the flow around the advancing blade is disturbed by compressibility effects and the retreating blade experiences inverse flow or very high angle of attack

What is the physical phenomenon at the origin of ground effect? A. While flying close to the ground a high-pressure cushion appears between rotor and ground B. While flying close to the ground a high-pressure cushion appears above the rotor C. While flying close to the ground a high-pressure cushion appears between rotor and ground D. While flying close to the ground a high-pressure cushion appears above the rotor

A. While flying close to the ground a high-pressure cushion appears between rotor and ground