Source of precipitation induced vibration found - antenna

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rdrobson
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Source of precipitation induced vibration found - antenna

Post by rdrobson » Fri Jan 04, 2019 1:40 am

For the past several months whenever I flew through rain or snow I would get an odd vibration in the airplane. Today, the same thing happened but after an hour or so there was a thump and the vibration disappeared. I thought a chunk of ice must have fell off the airplane or something. However, upon landing I was greeted with a broken comm/gps antenna. I was getting occasional static, but overall both radios and the gps were working the entire time.

I’m glad to know the source of the vibration, I just wish it didn’t cost so much!

—Ron
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Steve
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Re: Source of precipitation induced vibration found - antenna

Post by Steve » Fri Jan 04, 2019 4:08 am

Yep, those are pricey (about $1200). If I go with the Garmin GDL-82 solution for ADSB out on my aircraft, I need one of those. That failure doesn't reassure me...

Steve
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rdrobson
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Re: Source of precipitation induced vibration found - antenna

Post by rdrobson » Fri Jan 04, 2019 2:51 pm

Steve wrote:
Fri Jan 04, 2019 4:08 am
That failure doesn't reassure me...
The avionics guy told me it is a good antenna but that it must have been damaged at some point by a bird strike or mishandling on the ground. I’m not aware of anything, but I’m not the one who repositions or washes it.

—Ron
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CFIDave
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Re: Source of precipitation induced vibration found - antenna

Post by CFIDave » Sat Jan 05, 2019 4:29 pm

Wow, good to know you found the vibration source.

I had a similar vibration in icing conditions in my DA42-VI that I could never explain -- but fortunately never had a broken antenna. I haven't flown my DA62 in enough icing yet to experience anything like you observed.

I'd file a new aircraft warranty claim with Diamond for your antenna. FIKI-equipped planes shouldn't have antennas break due to icing.
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rdrobson
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Re: Source of precipitation induced vibration found - antenna

Post by rdrobson » Mon Jan 07, 2019 6:29 pm

CFIDave wrote:
Sat Jan 05, 2019 4:29 pm
I'd file a new aircraft warranty claim with Diamond for your antenna. FIKI-equipped planes shouldn't have antennas break due to icing.
I'm pretty sure the antenna was initially damaged on the ground by someone grabbing it and causing it to crack. This led to the vibration in precipitation (both icing and rain). The day it finally cracked, I had probably been flying in rain and heavy snow for an hour or more with it vibrating off and on before it finally snapped off. It's remarkable that it didn't swing around in the breeze and smack the top of the fuselage after that, but it didn't. I had no idea anything like that happened until we got on the ground.

The antenna is located so that someone getting in on the right wing would have a very easy time grabbing it and I had seen someone reach for it before. I'll make sure to brief anyone from now on to not reach for it.

Thankfully, my destination, KADS, is home to DFW Instruments and they did a great job fixing the issue in very short order! Very pleased with their service.

--Ron
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rdrobson
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Re: Source of precipitation induced vibration found - antenna

Post by rdrobson » Thu Apr 18, 2019 2:40 pm

Update on this item:

I learned that this is a warranty item and that Diamond is in the process of certifying a different antenna. The current one picks up a resonant frequency and eventually fails.

-Ron
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Re: Source of precipitation induced vibration found - antenna

Post by Steve » Thu Apr 18, 2019 3:45 pm

I just bought one of these for my ADS-B installation. I hope that my aircraft resonates at a different frequency! :shock:
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