Mailing List flyrotary@lancaironline.net Message #50916
From: David Staten <david.staten@gmail.com>
Subject: Re: [FlyRotary] Weird sound during descent
Date: Thu, 15 Apr 2010 13:02:05 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Is there any free play in the control surfaces that could cause a fluttering of the surface that you dont hear when power/noice is higher?

On Thu, Apr 15, 2010 at 10:13 AM, Jeff Whaley <jwhaley@datacast.com> wrote:

I have been hearing a weird buzzing sound usually detectable on base leg at low power settings.  It is hard to describe in text but is repeatedly as zzuuzz, zzuuzz, zzuuzz .

I thought it was wind noise escaping between the fuselage and gear legs, as there are no fairings between the fuselage and top of the cub-style gear.

Last night it was bit bumpy and during one descent there was a good bump that lifted me against the seat belts -- the noise stopped.

Tracy had cautioned me against low power steeps descents, something about thrust bearing and/or snubber – maybe refresh me on that one Tracy?

However, an approach speed of 500 fpm, 80 mph, 3000 rpm, mp <10”, is not what I’d consider steep.

 

Anyone care to give me a clue as to what I might be hearing?

If I get a chance to fly this weekend, I’ll experiment to see if I can stop/change the noise with speed or attitude adjustments.

Jeff



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