What is vibration in helicopter?

What is vibration in helicopter?

A helicopter main rotor is capable of producing vibrations in both the vertical and lateral planes. A vertical vibration is a result of unequal lift produced by the main rotor blades. This vibration is a result of the airframe rolling with the mass effect caused by the unequal vertical lift component.

What is vibration amplitude?

Amplitude, in physics, the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path. When the amplitude of a wave steadily decreases because its energy is being lost, it is said to be damped.

What is the frequency of a helicopter?

Helicopter vibration has a peak power at frequencies around 5 Hz, which is within the range that the human upper body presents resonance frequency.

What is the formula of amplitude of vibration?

Therefore, the amplitude of a wave is dimensionally represented as [M0 L1 T0].

How do you increase the amplitude of a vibration?

Increasing amplitude without changing frequency requires that a vibrating object travel with more speed to travel from one extreme of its excursion to the other. Acceleration from moving in one direction to moving in the other must also increase.

What normally causes a low frequency helicopter vibration?

Low-frequency vibrations are often caused by disturbances in rotor revolution, while medium-frequency vibrations can typically be attributed to loose components that affect the rotor system.

What is the range of frequencies of vibration in a helicopter?

The highest main rotor vibration peak occurs at 60 Hz, five times the main rotor Blade Passing Frequency. There are still noticeable 12 Hz peaks at up to 300 Hz sound frequency = 270 Hz frame vibration frequency. EDIT. This presentation shows vibration measurements taken off of an unnamed helicopter.

How do you reduce vibration in a helicopter?

To minimize vibration, a pendulous dampener in the nose of a Bell 222 dampens the main rotor. Tuning is done by adding or subtracting weights. Jim Fackler Dynamics Rotor track and balance (RT&B) smoothes and reduces vibrations in helicopters caused by the rotor system.

What causes vibration in the tail of a helicopter?

“Other sources of vibration can be bearing defects, insufficient lubrication and dirt entrapment between moving/rotating surfaces. Excessive vibration of main and tail rotors can cause the tail section of helicopters to be physically ripped from the main structural assembly, and result in catastrophe.

Which is rotor has the biggest vibration amplitude?

“By far the biggest vibration amplitude is seen in the main rotor N-per-revolution (RPM x number of blades) which increases with density altitude, airspeed and weight,” says Jim Fackler, sole proprietor of Jim Fackler Dynamics of Duarte, Calif. “Being an aerodynamic phenomena, its severity is logarithmic with airspeed.