I would think that the gear doors rumbling would be far more musical than listening to AC-DC.

Cheers

Dom

VH-CZJ

Gerard,
   I had the same problem. Whenever the airspeed started moving past 210 knots a buzz would start and then turn into a rumble as the plane went faster. If the aircraft was decelerated......to a speed around 205 knots, the rumbling and buzzing would disappear but would reappear if the aircraft accelerated back above 210 knots. I was certain it was the nose gear door (made from fiberglass) so I took the advice in archive and fabricated a much stiffer aluminum door. To my surprise the buzzing and rumbling problem was still there over certain speeds.!!!!???!!!! Fortunately for me, I live at at a place where we formation fly to breakfast every Saturday and I usually fly with the SX-300 guys. One of these friends volunteered to go up with me and formate under me to see if the problem could be observed. Apparently, the main gear doors trailing edges are being sucked out into the slipstream at certain airspeeds. We repeated the speed runs (accelerate/decelerate) and proble! m was clear.
   My plane does have a difference with yours which is, even though I have the outback gear, I decided to use the original cutout doors thinking they would create less drag. Don't know whether they do or not but have been unable after many different attempts to keep the doors closed at high speed. In January I will be racing and afterwards plan on doing a major condition inspection (demating wings, removing all control surfaces, etc) and at that time will fit the original outback gear doors from the option kit. They do appear to be stiffer (I hope they don't generate more drag). I hope that this cures my problem. Some of the Reno racers have recommended stiffening gear doors because this is a common problem for them while racing. If you find a magic bullet to correct the problem, please post it. 

Mark Quinn
Lancair 360
Spruce Creek Fly-in, Florida


-----Original Message-----
From: gerardoconnell@optusnet.com.au
To: lml@lancaironline.net
Sent: Wed, 3 Dec 2008 9:15 pm
Subject: [LML] outback gear doors-vibration is back

Hi Ian and those whom have had gear door problems

-Gerard from Down Under/Up Over has gremlins again

Hope you're going well and enjoying you're flying. I'm just writing a quick note 

both on and off list as we've been over this ground before. 

Do you recall discussing the buzzing noise I had some time back which I resolved 

both by removing the nose gear door and overlapping the main and inboard gear 

doors to get better "purchase" and stop vibration.

Well guess what?   Thhe noise is now starting to return-I initially thought I 

had the bass turned up too much whilst listening to AC -DC but even with the 

radio off I can appreciate the buzz from outside the aircraft. 

Perhaps I need to listen to Robbie Williams instead?

I originally spent thousands of $ trying various solutions to this problem and 

the final fix has worked for about 200 hours. I understand that some have also 

extended the door hinge/bracket to address this problem.

In short, my question is this-did you have this buzzing/vibration problem and 

what methods did you employ before removing the inner gear doors altogether? Is 

this my best short cut to making the problem go away once and for all?

Your thoughts would be appreciated including and issues you mar or may nopt have 

experienced after removing the inner doors.

Cheers,

Gerard

--

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