Helicopter track and balance is the process of adjusting the rotor blades to reduce the aircraft vibration and the track spread of the rotor blades.
What is the purpose of blade tracking?
The purpose of tracking the main rotor blades is to obtain a smooth ride. This is accomplished by adjusting the blade track to reduce vibration. An out-of-track condition will produce a vibration, usually a one-per rev which is felt as a vertical vibration.
What is helicopter blade flapping?
Blade Flapping is the up and down movement of a rotor blade, which, in conjunction with cyclic feathering, causes Dissymmetry of Lift to be eliminated. … The resulting larger angle of attack retains the lift that would have been lost because of the reduced airspeed.
What is helicopter blade sailing?
Blade sailing is an aeroelastic phenomenon affecting helicopter rotors when rotating at low speeds in high wind conditions. This is a potentially dangerous blade motion and the excessive flapwise tip deflections generated endanger the airframe, the flight crew and any personnel working close to the aircraft.What are the 4 types of helicopter vibration?
- High gross weight.
- Low RPM.
- High density altitude.
- Steep or abrupt turns.
- Turbulent air.
What is helicopter ground resonance?
ground resonance. A resonance that manifests itself as a violent rocking of the helicopter when it is on the ground. This phenomenon is most evident when the helicopter is on hard surfaces that do not absorb vibration. It is caused by the resonance between the skid and the rotor system.
What is helicopter vibration?
Helicopter vibration can be a serious safety concern and cause mechanical issues. Vibration in aircraft occurs when spinning objects become unbalanced, meaning one side is heavier than the other. The extra weight on one side throws off the center balance, making the rotation lopsided.
What is feathering in helicopter?
Feathering. The action that changes the pitch angle of the rotor blades by rotating them around their feathering (spanwise) axis. Feathering axis. The axis about which the pitch angle of a rotor blade is varied. Sometimes referred to as the spanwise axis.How do helicopters fly forward?
This kind of directional flight is achieved by tilting the swash plate assembly with the cyclic, which alters the pitch of each blade as it rotates. As a result, every blade produces maximum lift at a particular point. … The unbalanced lift causes the helicopter to tip forward and move in that direction.
What is hovering in helicopter?Hovering is when the helicopter is flown so that it maintains a constant position over the ground. It is the main capability which differentiates helicopters from airplanes.
Article first time published onDo helicopter blades change speed?
Usually no. Helicopter throttle changes can cause rapid changes, not just to lift, but also torque, which in turn requires adjusting the tail rotor. Generally speaking, helicopter blades are able to tilt to adjust lift without changing the amount of torque being applied.
What is a flapping hinge?
The horizontal hinge, called the flapping hinge, allows the blade to move up and down. This movement is called flapping and is designed to compensate for dissymmetry of lift. The flapping hinge may be located at varying distances from the rotor hub, and there may be more than one hinge.
What are the levels of vibration in a helicopter?
While helicopter design has vastly improved over recent years, the current levels of vibration average between . 05g and . 1g. These levels are significantly higher than those in a jet-engine aircraft, which are typically below .
Do helicopters vibrate?
Helicopters have many rotating parts and vibrations are inevitable. But sudden increased or new vibrations can lead to catastrophic failure of components. Helicopter vibrations can be broken down into the following by frequency: Low.
What causes high frequency vibrations in helicopters?
High frequency vibrations are associated with the engine bearings, cooling blower fan blades, the tail rotor driveshaft, or any other component spinning at high revolutionary speeds. Main rotors rotate at close to 360 revolutions per minutes (r.p.m.), with tail rotors generally spinning six times faster than that.
How does a helicopter main rotor work?
A helicopter main rotor or rotor system is the combination of several rotary wings (rotor blades) and a control system that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight.
What is the pitch link in helicopter?
The pitch link is the vertical — or nearly vertical — member that connects the blade pitch horn to the rotating swashplate (Figure 50-1). Its sole function is to make sure the blade responds to the collective and cyclic control commands corresponding to the swashplate’s position.
What is propeller track?
Blade track is the ability of one blade to follow the other in the same plane of rotation. If your propeller has been bumped or compromised, check the tracking. A change in tracking can be unnoticeable or cause severe vibrations.
Where is the hand throttle of a helicopter located?
The throttles on some turbine helicopters are mounted on the overhead panel or on the floor in the cockpit. between the pilot’s knees or on a teetering bar from a single cyclic located in the center of the helicopter. The cyclic can pivot in all directions.
What does the vertical stabilizer do?
The stabilizers’ job is to provide stability for the aircraft, to keep it flying straight. The vertical stabilizer keeps the nose of the plane from swinging from side to side, which is called yaw. The horizontal stabilizer prevents an up-and-down motion of the nose, which is called pitch.
How do helicopters avoid ground resonance?
It starts when the blades “bunch up” on one side of the rotor disc where they generate an unbalanced centrifical force that gets in phase with the natural frequency of the aircraft rocking on it’s landing gear. Modern helicopters avoid this by using dampers on the blades and on the gear (shock absorbed struts).
How does a helicopter lift upwards off the ground?
Unlike airplanes, helicopters feature spinning wings called blades or rotors on top. As a helicopter’s blades spin, they create a force called lift that allows the helicopter to rise into the air. A helicopter’s rotors perform the same function as an airplane’s wings.
Why do helicopter blades lead and lag?
Due to dissymmetry of lift, flapping up and down occurs. Since angular momentum has to be conserved, the speed of blade increases/decreases during flapping up/down motion. To compensate for this blade leads front by a certain degree in the rotor plane, in advancing half and lags by a certain degree in retreating half.
Can a helicopter fly in the rain?
Helicopters can fly just fine in the rain, and in conditions way worse than prevailed in Paris on November 10. First, about helicopters and weather. … There is nothing special about the rain-worthiness of the helicopter any president normally uses. In principle, any helicopter can fly in clouds or rain.
Can a helicopter fly in reverse?
Unlike an airplane, a helicopter can fly backwards or sideways. It also can hover in one spot in the air without moving. This makes helicopters ideal for things an airplane cannot do.
How does a helicopter differ from an airplane?
The primary difference between a helicopter and an airplane is the way that the mechanics are designed to generate lift. Helicopters use their rapidly spinning rotors to create the momentum required to lift the aircraft. These rotors can be adjusted to perform maneuvers such as turning or hovering.
Why do helicopter blades flap?
Flapping is the vertical movement of a blade up or down to increase or decrease lift in order to compensate for dissymmetry of lift. To equalize lift across the rotor disc, the advancing blade flaps up and the retreating blade flaps down.
What does feathering a blade mean?
Feathering. Feathering the blades of a propeller means to increase their angle of pitch by turning the blades to be parallel to the airflow. This minimizes drag from a stopped propeller following an engine failure in flight.
What are the 3 types of helicopter tail rotor?
There are three basic classifications: semirigid, rigid, or fully articulated. Some modern rotor systems, such as the bearingless rotor system, use an engineered combination of these types. the feathering hinge enables the pitch angle of the blades to change.
Why is a helicopter hovering over my house?
Violent crimes in progress, pursuits, property crimes, traffic stops, and perimeters are the most common reasons why you might hear a helicopter flying overhead. … Search and rescue operations are another common reason why you might see and hear a helicopter flying over residential areas.
How long can a helicopter hover in one spot?
Generally, though, a helicopter can hover anywhere between 2- 5 hours on average before it needs to be refueled. The length of time depends on the type of helicopter, the efficiency of the engines and main rotor system, as well as the kind of hover a pilot wants to hold.
