Shaggy1505... In addition to 3DDave's comments...
The following 'Duhhhh lesson learned' is an important element in aircraft vibration...
In the 1980s I worked on several propeller driven Vietnam era aircraft. We were constantly dispositioning repairs for odd/annoying cracks, chafing/galling, etc.
During the examination of one aircraft [OV-10A] for a 'slow climb-rate problem' it became evident that the variable pitch prop-blade pitch settings [for each blade] and blade-tip-tracks were out-of-tolerance. The defective prop assys were replaced and the 'newly overhauled assys' were precision evaluated/re-adjusted for matching-everything: blade pitch, variable pitch synchronization, blade-tip-track and [Duhhhh] dynamic [on-engine] balance.
We also discretely 'sanded'* the top-coat paint finish on the spinners, wings, booms and stabilizers to attain a much smoother appearance... since the paint was noticeably grainy/rough all-over [to the touch]. Although the sanded aircraft looked 'odd' [to say the lest] the results were a much 'smoother' skin surface texture.
[* using jitter-bug sander with fine-weave Scotch-Brite pads and a ‘light-touch by the mechanics’... HOWEVER, we didn’t touch the paint on balanced control surfaces]
The results of this evaluation, adjustments and maintenance actions were like a lightning-bolt hitting us engineers and the maintenance team squarely in the brain!
Critical attention to these static/dynamic elements made for [instantly] one of the 'smoothest-running-fastest-climbing aircraft' in the fleet. It was more than evident that attention to these 'small static/dynamic details' had an amazing effect on the entire aircraft: performance and vibration-wise.
We took this lesson to heart. All fleets of prop aircraft were re-examined in-light-of-these lessons-learned on this one aircraft. The maintainers and flight crews noted a vast reduction in damage/discomfort and an improvement in the quality of ‘everything else’: flight-performance improvements, reduced noise/vibration, diminished structures/systems problems, etc.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
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