Document Details

SnazzyDystopia5099

Uploaded by SnazzyDystopia5099

Fanshawe College, London, Ontario

Tags

rotorcraft helicopter design rotor blade aerodynamics

Summary

This document reviews various rotor blade designs, focusing on symmetrical and asymmetrical approaches. It explores different construction methods like bonded and multi-pocket constructions, along with the role of trim tabs and balance weights in flight control. Key concepts like aerodynamic efficiency and rotor blade performance are also discussed.

Full Transcript

Two rotor blade designs Symmetrical and asymmetrical -symmetrical has a better aerodynamic pitch characteristic Asymmetrical produces greater lift for the same surface area. Asymmetrical has higher camber on one side than the other. -engineers get the same pitching characters from an asymmetrical bl...

Two rotor blade designs Symmetrical and asymmetrical -symmetrical has a better aerodynamic pitch characteristic Asymmetrical produces greater lift for the same surface area. Asymmetrical has higher camber on one side than the other. -engineers get the same pitching characters from an asymmetrical blade by sweeping the edges 3 degrees upwards To gain aerodynamic stability. -symmetrical are the most common design, because of the unstable aerodynamic characteristic of the asymmetrical. -two different planforms Parallel (uniform) and tapered. Uniform is when the leading and trailing edge run parallel to each other. Uniforms will create greater lift, because of the chord line. Uniform blades have the Tapered is when the leading and trailing edge converge towards the edge and the chord length decreases. Manufacturers prefer to produce 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. Ribs have to change on tapered, due to uneven chord length. -Tapered produces lift more equal, because it accounts for the variation of speed. Negative Twist blade 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 (uniform planform) Different types of construction -we use bonded construction because it is stronger, and has no drilling holes. When we form a blade aft of the spar. Single pocket is quicker for the manufacturer to build, because it uses one big skin. With a multi pocket, they have to ensure that ribs are in the right spot. Multi pocket is easier to repair than a single pocket. -single pocket would get thrown out if damaged. We can not move the chord line mass balance weight, only time acceptable to move it is during repair Two trim balance weights, one in tip of rotor blade If weight is added forward, it will cause the blade to fly lower in its plane of rotation -if added aft, it will travel higher in its plane of rotation. -feature common to all leading edges of rotor blades, they will all have stainless steel capping (erosion protection) erosion is caused by small dust particles in the air when the helicopter is flying. The bottom of rotor blades is painted matte black to prevent glare in the pilots vision Required static discharge abilities are composite blades. Rotor blades can be made of composite, metal, and wood, If inspecting composite rotor blades, tap testing is one of the primary inspection methods. Multi pocket is more expensive to build. We might find additional double plates, at the root of the tip, they increase structural strength without increasing blade weight, or additional stiffness to the span of the blade. Balance weights Spanwise balance weights, at the blade tip in the center on the spanline. Chordwise mass balance weight located in the leading edge of the blade 30-50 percent of the span Tracking weights, located one in the leading edge forward of the span line and one is the trailing edge of the spanline. Weight added to the leading edge would make the helicopter fly lower in the plane of rotation, adding in the trailing edge 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. Bend trim tab higher to fly lower, bend lower to fly higher. -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. Collective always gets rigged first on a helicopter, collective can often be connected to throttle, connected by correlator, or auto throttle. One end connects to the collective, and the other end connects to the throttle. Before connecting them together, make sure that the throttle is rigged correctly (rig throttle, and collective independently) After rigging is complete, the helicopter is tested by ground run, then hover, then full flight, the autorotational check which is completed with the helicopter at minimum gross weight. 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. Main servo flap reduces the need for hydraulics. It also has infinite life And simplify the hub, and removal of hydraulic systems are simpler. These blades create less vibration, and these blades and quieter, Allows tracking on the ground and in flight. More time to react for auto rotation.

Use Quizgecko on...
Browser
Browser