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Mã học phần TE3891, với thời gian thi 60 phút, đề trắc nghiệm áp dụng cho sinh viên chuyên ngành hàng không Trong máy bay có cánh cố định vật thể khí động học để tạo lực nâng là đôi cánh của máy bay được gắn cố định vào thân. Vận tốc ngang của máy bay (cũng đồng nghĩa với vận tốc dòng chảy bao máy bay nếu xét trong hệ quy chiếu gắn với máy bay) có được nhờ lực tác động ngang sinh ra nhờ động cơ (có thể thông qua cánh quạt hoặc dòng khí phản lực). Động cơ quay cánh quạt (hoặc phụt dòng khí phản lực) sẽ tạo phản lực đẩy máy bay chuyển động tương đối với không khí về phía trước, khi chuyển động tương đối như vậy cánh máy bay sẽ bị dòng khí chảy bao bọc xung quanh và tạo hiệu ứng lực nâng khí động lực học tác động từ dưới lên, khi vận tốc máy bay đạt đến giá trị nào đó lực nâng sẽ đủ lớn để thắng trọng lực và máy bay sẽ bay được. Còn đối với máy bay trực thăng cánh nâng là cánh quạt nâng nằm ngang ở trên phần thân (hoặc trên hai cánh), nó đồng thời còn để tạo lực đẩy ngang làm trực thăng chuyển động ngang.
BỘ MÔN KỸ THUẬT HÀNG KHÔNG & VŨ TRỤ ĐỀ THI QUÁ TRÌNH – HỌC KỲ - NĂM HỌC 2020-2021 Học phần: Cánh quạt máy bay Mã học phần : TE3891 Mã lớp Mã lớp thi : 124533 Ngày thi : 07/05/2020 : QT124533 Thời gian thi: 60 phút TRƯỞNG BỘ MƠN GIẢNG VIÊN PGS TS Vũ Đình Q TS Đinh Công Trường CÂU HỎI: High speed propellers are designed to A operate at supersonic tip speeds B operate at high forward speeds C rotate at high RPM A left-handed propeller is one that A rotates clockwise when viewed from the rear B is fitted to an engine on the left side of the aircraft C rotates clockwise when viewed from the front Forces acting on a propeller are A torque, thrust and centrifugal B centrifugal, twisting, and bending C torsion, tension and thrust The blade angle at the root is A same from tip to root B less than the tip C greater than the tip The purpose of propeller twist is A to maintain Blade Angle along the blade B coarsen the blade angle at the root C to maintain Angle of Attack at the same value along the blade The forces acting on a propeller blade are A thrust, aerodynamic and tension B C bending, twisting and centrifugal thrust and torque Blade angle at the root is A low B master blade angle C high Blade angle is taken from the chord and A propeller shaft B plane of rotation C relative airflow What forces act on a propeller blade? A Thrust and torque B Bending, CTM and ATM Where CTM: Centrifugal Twisting Moment; ATM: Aerodynamic Twisting Moment C Bending, thrust, torque 10 CTM will A try to bend the blade away from the engine B cause the tips to rotate at supersonic speeds C turn the blade about the lateral axis 11 When in reverse pitch, CTM will tend to move the propeller blades towards A a positive pitch B a negative pitch C a position depending on rpm 12 As a propeller blade moves through the air, forces are produced, which are known as A lift and torque B thrust and torque C lift and drag 13 A rotating propeller imparts rearwards motion to a A large mass of air at low velocity B small mass of air at high velocity C small mass of air at low velocity 14 Propeller efficiency is A the ratio of output speed to input propeller speed B the ratio of the useful work done by the propeller to work done by the engine on the propeller C the ratio of the work applied to the geometric pitch to useful work on the C.S.U 15 Geometric Pitch is the distance moved A in one revolution B C in one revolution when slip is maximum in one revolution without slip 16 As propeller rotation speed increases the centrifugal turning moment on the blades will A decrease B increase C remain constant through RPM range 17 Propeller torque is the resistance offered by the propeller to A feathering B rotation C changing pitch 18 The angle between the resultant airflow direction and the propeller blade plane of rotation is known as A angle of attack B helix angle or angle of advance C blade angle 19 Aerodynamic Twisting Moment A turns the blades to high pitch B turns the blade to windmill 20 Propeller blade angle A is constant along the blade length B increases from root to tip C decreases from root to tip 21 Coarse pitch is used for A take off and climb B landing and power checks C maximum economical cruise in level flight 22 Effective pitch is A geometric pitch plus slip B distance moved in one revolution C pitch measured at the master station 23 Torque acts A in the same direction as the plane of rotation B in opposition to the direction of rotation C at right angles to the plane of rotation 24 The purpose of blade twist is to A reduce angle of attack at the blade root B to even out thrust distribution across the propeller C to ensure that tip speed does not go faster than Mach 25 Thrust is greatest A at 70 to 80% of propeller length B the same all along the length C in the first 50% 26 Changes the pitch of a blade A bending forward B about its twisting axis C towards the feather plane 27 High speed aerofoils are employed at A the master station B the root C the tips 28 A right hand propeller A rotates clockwise when viewed from the front B is always fitted to the starboard engine C rotates clockwise when viewed from the rear 29 The chord line of a propeller is A a line joining the tip to the root of the blade B a line joining the leading and trailing edges C a line joining the tips of the blades 30 The plane of rotation is defined as A the plane in which the propeller rotates B the plane in which thrust force acts C the angle at which the blade strikes the airflow 31 A windmilling Propeller has A a small positive blade angle B pitch measured at the master station C geometric pitch plus slip 32 A windmilling Propeller has A a small positive angle of attack B a small negative angle of attack C a small positive blade angle 33 Windmilling causes A maximum propeller drag B Centrifugal Twisting Moment C propeller underspeeding 34 The primary purpose of a feathering propeller is to A prevent further engine damage when an engine fails in flight B C eliminate the drag created by a windmilling propeller when an engine fails in flight prevent propeller damage when an engine fails in flight 35 The primary purpose of propeller is to A provide static and dynamic stability to aircraft B change engine horsepower to thrust C create lift on the fixed aerofoils of an aircraft