Questions tagged [vibration]

Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.

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What is the difference between buffeting and wake galloping?

I am interested in flow-induced vibration and confused between buffeting and wake galloping. As far as I have studied, both phenomena are the vibration of an object with another object in front of it. ...
3 votes
2 answers

Why in a CFM56-3 is vibration measured in displacement for N1 and in velocity for N2?

N1 is measured in mils (thousandth of an inch) and N2 is measured in IPS (inches per second). Why are different methods used?
12 votes
7 answers

How much do propellers stutter?

A photo in EAA's monthly magazine shows one propeller blade as a dozen distinct images rather than the usual smooth motion blur. One explanation (this answer appears to have been deleted) for this is ...
4 votes
1 answer

Why this inertial regulator of dragonfly wing pitch reduces self-excited coupled flapping and feathering vibrations and improves gliding flight speed

The pterostigma of insect wings an inertial regulator of wing pitch is linked in this answer to Why do dragonflies have these special little spots on their wings? (open access copy here) The Summary ...
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1 vote
0 answers

What are the expected vibration frequencies in a co-axial rotor system with contra-rotating propellers?

I am trying to understand the frequency spectrum of a co-axial rotor system. Form now i have a RC helicopter with two sets of three gear systems arranged in parallel, The number of teeth are 7,23,27) ...
5 votes
1 answer

What could cause lower torque than normal during cruise in a King Air 300?

At approx FL200 in our King Air 300 we experience a vibration and notice the torque drop for both engines. The torque stays about 10% lower than normal in cruise. The vibration is intermittent and ...
9 votes
5 answers

Do aircraft cabins have suspension?

On cars, we have 'shock absorber' suspension that decouples the passengers and loads from the road vibrations, bumps etc. On planes do we have any form of suspension that decouples the passengers &...
1 vote
2 answers

Main structural (and any other) impact of hard landing

I was reading this question related to the parts suffering the most G forces. Reflecting about that question I question myself about hard landing, which is not a normal operation. So, my especific ...
3 votes
3 answers

Is there any alternative to isolating the vibration of an ultralight engine other than using engine mounts?

Is there any alternative to isolating the vibration of an ultralight engine other than using engine mounts?
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8 votes
1 answer

What is the range of frequencies of vibration in a helicopter due to the main rotor alone?

Vibration in helicopter can be caused by many different reasons. I am interested to know what is the range of frequencies of vibration due to the main rotor alone? I understand that it would depend ...
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56 votes
6 answers

Why do most radial engines use an odd number of cylinders?

To help suppress vibration, most 'V' and 'horizontal' engines use an even number of cylinders as closely opposed as possible. Radial engines are well known for excessive vibration. For some reason ...
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3 votes
2 answers

How is vibration isolation achieved in helicopters?

In many helicopters, they say they have reduced the vibrations significantly, but how is this isolation being achieved?
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