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JLang

Loud Periodic Creak While Taxiing

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When taxiing, or even rolling the plane with the engine off, there is a loud, periodic creak that I have been unable to locate.  It seems to come from fuselage, where the main gear enters, and is dependent on rolling speed.  In other words, a loud sharp creak every few feet across the ground, even when pulling the plane out of the hangar.  I thought it might be a wheel bearing going out, and the noise reverberating up the gear, but the wheels seem to turn normally (same amount of slop as before, spins freely) when raised off the ground.  I can't see any loose gear attachment, and I don't understand how loose gear would make a noise like this, anyway.  What would be rotating or moving, other than the wheels?  Anybody had something similar?  Thanks in advance.

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An acquaintance of mine had this with his ctsw and it was the gear leg fairing rubbing on the fuse fairing where it enters. the gear leg fairing is held by small brackets which can be adjusted a bit by bending.

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My CTSW is pretty loud when rolling, there is some squeaking, rattling, clanking, and other odd noises.  It's very apparent when I taxi with my noise canceling headset off.  But after nearly 500 hours I've learned to ignore it, the CTs (at least the ones with the older style gear) are just noisy in ground ops.

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The squeaking is the brakes. The rattling and creaking is the fairings or the doors. The clanking is the rotors if you have the old marc ingegno brake system.

You should never hear cracking or crinkling though. That's the sound of something bad, and that's fibers breaking and delamination. Think of wood fibers breaking or bending. Like these:

 

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I've gotten in the habit of having first time flyers stand next to the gear while I rock the wing in the hangar and explain to them that the fairing squeaks on the gear leg sometimes. I do it because it can be a bit disconcerting the first time you hear it.

My OCD has caused me to think up all sorts of possible solutions but ultimately I just decided to turn on the noise cancelling headsets and ignore it.

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BTW I switched to Matco brakes and they rattle as well.  I think it's just vibration in the play on the caliper guide pins.  If I touch the brakes the noise instantly stops as the pads grab and take up the play.  They do seem less noisy then the Marc units though.

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I had the rattling brakes as well. Arian at FDUSA changed them out (not sure which type) and now they’re very quiet. 

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Since my initial post I have only been able to fly twice, due to a long string of terrible (but unfortunately typical) flying weather, but I was still unable to pinpoint the loud creak.  Again, it only happens when rolling, and is dependent on speed/wheel rotation.  This would seem to point to brakes.  But the noise comes from the gear/fuselage attach area, which would point to fairings.  However, adding foam to the fairing joint had no effect, nor did grabbing/moving the fairing while pushing the plane.  It seems to be the gear attach, but I can't find exactly where, nor do I understand why it would be tied to wheel rotation.  It's like a (very) bad bearing, only if the bearings were at the fuselage.  Which, um, they are not.  The wife, who is already convinced the wings and other helpful parts are about to fall off, is not happy about this noise...

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The fuselage is a sounding box, just like the body of a guitar. The gear leg is solid aluminum, and will transmit any wheel noise to the sounding box, exaggerating any noise. Also any movement in the gear saddle will also resonate throughout the airplane. More than likely when the airplane rolls, the gear leg is moving in the saddle causing the noise. The sound is amplified because of what I described above. I have heard creaking noises from several CTSW's that I have worked on over the years.

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When you apply a small amount of brakes, does the rattle immediately stop? That’s what I had. Annoying, but I lived with it until Arian put a stop to the issue. 

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1 hour ago, KentWien said:

When you apply a small amount of brakes, does the rattle immediately stop? That’s what I had. Annoying, but I lived with it until Arian put a stop to the issue. 

The sounds that I was referring to is not rattling brakes.

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2 hours ago, KentWien said:

When you apply a small amount of brakes, does the rattle immediately stop? That’s what I had. Annoying, but I lived with it until Arian put a stop to the issue. 

A small or normal brake application has no effect in my situation.

 

7 hours ago, Tom Baker said:

The fuselage is a sounding box, just like the body of a guitar. The gear leg is solid aluminum, and will transmit any wheel noise to the sounding box, exaggerating any noise. Also any movement in the gear saddle will also resonate throughout the airplane. More than likely when the airplane rolls, the gear leg is moving in the saddle causing the noise. The sound is amplified because of what I described above. I have heard creaking noises from several CTSW's that I have worked on over the years.

I think this must be the right track.  Both tires are visibly out of round --- not severe, but noticeable when spinning with the wheel lifted off the ground -- so my current theory is that when rolling, that regularly shifts the weight just enough to move the gear against the saddle, as you put it.  And although it clearly is not coming from inside the cabin, it does seem louder there than when outside.

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I had popping noises while taxiing, turned out to be a bad main wheel bearing. Went to Matco's which are way better wheels.

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56 minutes ago, JLang said:

Original Marcs

You said the tires are out of round. A little out of round after sitting is normal, but I have seen tires not centered on the Marc rims before. It takes special care to make sure they are centered when mounting.

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15 hours ago, Tom Baker said:

You said the tires are out of round. A little out of round after sitting is normal, but I have seen tires not centered on the Marc rims before. It takes special care to make sure they are centered when mounting.

I changed tires and tubes about 4mo ago, and since it was my first time it's entirely possible that special care was not taken.  You mean centered laterally, with a section of the bead too far up or down the rim?  Would raising the wheel, deflating the tire, and incrementally reinflating while checking position or "roundness" make sense?

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1 hour ago, JLang said:

I changed tires and tubes about 4mo ago, and since it was my first time it's entirely possible that special care was not taken.  You mean centered laterally, with a section of the bead too far up or down the rim?  Would raising the wheel, deflating the tire, and incrementally reinflating while checking position or "roundness" make sense?

Yes. The issue I am thinking about may have been with the old Sava tires, but it is still worth checking. There is a ring molded in the tire that you should be able to see. It should be centered on the rim.

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There is one thing I recommend people do though regarding fairings.

Run tape around the areas where the fairing touches the fuselage between the fairing and fuselage to act like a sacrificial layer. My CT, after 3000 hours, has worn through the paint and started on the carbon fiber when I noticed how far it was getting and coated it with epoxy.

Unless you fly a lot, you're not really going to see this issue, but it's an extra long term care tip if you intend to keep the plane for a long time.

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For the wheel pants, I noticed it was rubbing into the paint on the gear legs.  I took some clear fuel line, cut it down the length of the hose, and put it around the upper edge of the wheel pant to create that barrier as well as tightening any wobbling between the leg and the wheel pants.

Danny

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52 minutes ago, Fly Boss said:

For the wheel pants, I noticed it was rubbing into the paint on the gear legs.  I took some clear fuel line, cut it down the length of the hose, and put it around the upper edge of the wheel pant to create that barrier as well as tightening any wobbling between the leg and the wheel pants.

Danny

That sounds like a good idea.

I will try that tomorrow. Thank you.

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On 3/1/2018 at 9:37 PM, Fly Boss said:

For the wheel pants, I noticed it was rubbing into the paint on the gear legs.  I took some clear fuel line, cut it down the length of the hose, and put it around the upper edge of the wheel pant to create that barrier as well as tightening any wobbling between the leg and the wheel pants.

Danny

Weather stripping works excellent for this.

That said, if it's resting against the pant while sitting on the ground, you need to adjust the pant. When you land, the gear WILL flex enough to move the pant, an in time, it WILL crack. Adjust it so that while the aircraft is jacked, it almost touches the bottom of the pant. OR: trim the pant back some.

Speaking from experience in a rental environment.

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