Rotor Wing Review - Week 3 PDF

What are the Two rotor blade designs? -Symmetrical and asymmetrical Which blade design has a better aerodynamic pitch characteristic? -symmetrical Which blade design produces greater lift for the same surface area? -Asymmetrical Which blade design has higher camber on one side than the other. -As...

What are the Two rotor blade designs? -Symmetrical and asymmetrical Which blade design has a better aerodynamic pitch characteristic? -symmetrical Which blade design produces greater lift for the same surface area? -Asymmetrical Which blade design has higher camber on one side than the other. -Asymmetrical How do engineers get the same pitching characteristic from an asymmetrical blade? -by sweeping the edges 3 degrees upwards To gain aerodynamic stability. What is the most common blade design, and why? -symmetrical are the most common design, because of the unstable aerodynamic characteristic of the asymmetrical. -What are the two different planforms? -Parallel (uniform) and tapered. What planform has the leading and trailing edge run parallel to each other? -Uniform What platform will create greater lift, and why? -Uniforms will create greater lift, because of the chord line. What planform has a converging leading and trailing edge and decreasing chord length towards the blade root? -Tapered What platforms do manufacturers prefer to produce and why? - uniforms because it is more cost effective, because only one machine stamping out ribs because the chord line does not change and only use one rib part number. Which blade planform has to use a different rib number for each rib and why? -Ribs have to change on tapered, due to uneven chord length. Which blade planform produces more equal lift and why? -Tapered , because it accounts for the variation of speed. Why do parallel blades have a negative twist? -To have higher AOA at the root to produce the same amount of lift from the root and the tip, the twist goes from root to tip, higher angle where the for blade is spinning slower. Why do we use bonded construction? -Because it is stronger, and has no drilling holes. What skin configuration is quicker to build and why? -Single pocket, because it uses one big skin, and With a multi pocket, they have to ensure that ribs are in the right spot. What skin configuration is easier to repair? -Multi pocket, because we can replace the one damaged skin, but a single pocket only has one skin. What would we do if single pocket skin configuration is damaged? -It would get thrown out if damaged. Can we move the chord line mass balance weight? -We can not move the chord line mass balance weight, only time acceptable to move it is during repair How much trim balance weights do we use? -Two trim balance weights, one in tip of rotor blade What will happen If weight is added forward to the trim tab? -it will cause the blade to fly lower in its plane of rotation. What will happen if weight is added aft of the trim tabs The blade will travel higher in its plane of rotation. -what will the leading edges of all rotor blades have and why? stainless steel capping (erosion protection) erosion is caused by small dust particles in the air when the helicopter is flying? Why are the bottom of rotor blades painted flat black? -To prevent glare in the pilots vision What blades are required to have static discharge abilities? -Composite blades. What are the most common materials rotor blades can be made of? -Composite, metal, and wood, What is the primary inspection method used for composite rotor blades? -Tap testing What blade skin configuration is more expensive to build? -Multi pockets are more expensive to build. What do additional double plates at the root of the tip of the blade do? -They increase structural strength without increasing blade weight, or additional stiffness to the span of the blade. Where are spanwise balance weights located -at the blade tip in the center on the spanline. Where are chordwise mass balance weights located? -in the leading edge of the blade 30-50 percent of the span Where are tracking balance weights located? -One located in the leading edge forward of the span line and one is the trailing edge of the spanline. What would weight added to the leading edge of the rotor blade do? would make the helicopter fly lower in the plane of rotation. What would adding weight in the trailing edge of the rotor blade do? It would make the helicopter fly higher in the plane of rotation? -Trim tabs are easier to have than tracking weights and will be in the trailing edge, approx 75 percent of span, and relies on velocity of airflow to achieve aerodynamic effect. What way would you bend the trim tab to make the rotor blade fly higher in its plane of rotation? -Bend the trim tab lower What way would you bend the trim tab to make the rotor blade fly lower in its plane of rotation? Bend the trim tab higher? What do we do before rigging? -Turn off hydraulics before rigging and ensure that all residual hydraulic pressure has been removed from the system, move controls a couple of times to consume remaining hydraulic power. What gets rigged first on a helicopter? -Collective always gets rigged first on a helicopter. How does the correlator connect the collective to the throttle? -One end connects to the collective, and the other end connects to the throttle. What do we do before connecting the collective and throttle together? -Make sure that the throttle is rigged correctly (rig throttle, and collective independently) After rigging is complete, what testing on the helicopter is done? -The helicopter is tested by ground run, then hover, then full flight, then autorotational check which is completed with the helicopter at minimum gross weight. What is the servo tab? The servo flap is a small airfoil located at about 75 percent span of the rotor blade, situated on the trailing edge of each rotor blade it is located there to get the greatest aerodynamic reaction to the servo tabs action. What does the main servo flap do? Main servo flap removes the need for hydraulics. It also has infinite life. What are the benefits of the servo flap? Simplifies the hub, removes the need for hydraulic systems, they create less vibration, are quieter, allows tracking in flight and on the ground, and allows more time to react for autorotation And reduces the amount of force required for pitch change. (makes it pounds of force and not 100 pounds of force) What is the correct order that we rig the flight controls in? -Collective, then the cyclic, then the anti-torque pedals. What system is more complex, droop compensator or correlator? -Droop compensator What does the droop compensator do? The droop compensator is a mechanical linkage that auto inputs commands to the governor so the system doesn't lag too much when you pull or reduce power. What is the correlator? Correlator is a mechanical linkage between the collective and the throttle that connects them? What are theTwo different vibration absorbing devices? Bifilar vibration absorber, and Hub vibration absorber. What vibration absorbing devices have two four arm disks? -Bifilar vibration absorber  Which vibration absorbing device hasWeighted drum supported by three springs? -Hub vibration absorber. In force trim system device what returns the cyclic to its previous position? The gradient spring? -If all flight control systems have force trim how many gradient actuators there are, there are 4 gradient actuators, 2 for cyclic, and 1 for collective, and one for anti-torque. If a helicopter has a fixed elevator what type of airfoil will it be? - It will be an inverted airfoil directing lift in downwards direction. What does the elevator do? -Elevator provides a more level flight attitude, more comfortable flight. What will the elevator do with the cyclic moved forward? -Elevator will move with cyclic forward to maintain a level attitude. What vibration system has moveable weights on the ends of its arms? -Bifilar. Can pop out floats take off on water? -No. Why is Overspeed a concerning situation? -because it allows uncontrolled amounts of centrifugal force to be generated on the helicopter. Where would you find a chordwise mass balance weight? -on the leading edge between 35-55 percent of the span, It is placed by the manufacturer and only repair stations can adjust it. Where can tracking weights be found? -Before and aft of the spanline, are the tracking weights. Irreversible prevents force feedback from controls, and in event of hydraulic failure, will lock fluid in the hydraulic actuator, allowing pilots to have manual control of the hydraulic systems. Why do manufacturers prefer bonded construction with no mechanical fasteners? -because drilling holes through bond lines with mechanical fasteners weakens the strength of the bond. What Special inspection is required after autorotation? -hard landing inspection.