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  #1  
Old 05-25-2018, 12:01 PM
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madmaveric madmaveric is offline
 
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Default ELT Triggered

I've read a few issues of ELT's being triggered and today mine did it's thing.

I'm not sure yet what caused it yet so I thought I would post the details as someone with more knowledge of these might have some ideas.

My aircraft has only just got it's UK permit and this was the second flight post permit. I flew 2 days ago and again today (briefly), both with an the instructor (I have to re validate my licence due to lack of flying before I get to take her up on my own)

9.20 AM
I got to the airport and cleaned the aircraft. I did notice some static on the cloth while cleaning the outside of the canopy.

10.30AM
I then move the aircraft onto the field to do a run up test as I wanted to check the tick-over as it seemed a little fast on the last flight, (this seemed to be related to the fiction wheel on the throttle being to lose so no adjustments made).

13.40PM
Due to weather it was after lunch before we could attempt any flying.

On getting to the aircraft there was a quiet ticking noise from near the ELT. No other indications of an issue or that it going off was noticed (no light or signal on 121.5) so it wasn't transmitting at this time. I didn't have the manual with me so couldn't perform the test at this point, I made a note to take it with me next time to test the unit again.

I wasn't sure if it was the ELT (turning it off made no difference) or it was just an expansion style ticking you can get from things with temperature changes.

We only did once circuit and decided to call it a day as the cloud base was still around circuit height so we landed and the aircraft put away. At this point there was no noticeable noises from the unit and nothing on 121.5 so it seemed all was well. I should have turned the unit off at this point for further investigation but it all seemed ok at the time.

15.15PM
I left the airfield to drive home.

16.06PM
ELT goes off for 20 minutes until it is turned off by my instructor after the airfield were contacted about it

16.30PM
It was when I got home I received a phone call from the airport saying it had gone off and that my instructor (who was still there luckily) had turned it off. I later realised I also had a missed call while I was driving home from the MCC (UK Distress and Security Beacon Registry).
I contacted the MCC and they said it had gone off at 16.06 for 20 minutes and had now stopped transmitting (presumably when my instructor turned it off)

------

My thoughts on what could have caused it are

1) The quiet ticking was a low battery indication and the unit was set off due to this when the battery run down.
2) There were people in the hangar around the time I left so maybe someone bumped it (unlikely as it would have to be a very hard bump)
3) A new HAM radio antenna was put up on Wednesday close to the hangar, maybe they were testing that out and the RF set it off (I've heard that RF can cause false alarms). The aircraft is pushed right past the antenna to get it onto the field.
4) Was it triggered when I cleaned the outside of the canopy (static apparently can set them off). This one is least likely as this was 6 hours before the first signals were received.

I won't get to investigate this till next week now but any ideas of what it could be or additional tests that I can do would be welcome.
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  #2  
Old 05-25-2018, 12:12 PM
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Default

What make/model of ELT?
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  #3  
Old 05-25-2018, 12:18 PM
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It is an "ACK E-04 ELT" as was supplied by Vans.
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  #4  
Old 05-26-2018, 08:52 AM
John-G John-G is offline
 
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Maveric-

Somewhere here in the forums there was a post about static generated during cleaning of the aircraft setting off the ACK E-04. Apparently ACK was questioned and said to install an in-line static filter on the antenna cable.

Interestingly, my ACK E-04 came with a static filter in the box .... however, there was no information in the Van's plans to install the static filter so I did not install it during the build. After reading that post and ACK's reply, I installed the filter last year when performing the condition inspection in the hopes of preventing an unwanted ELT transmission such as the one you experienced. If the filter came with your unit and you did not install it you may want to consider trying that.

Happy flying,
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  #5  
Old 05-26-2018, 02:18 PM
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I put the static item on as I remembered reading about it but it was several hours before it going off so I'm not sure that could have been a factor. I guess static from putting the canopy cover could be it but that would still be half hour before it sounded.

I can't remember now if the static filter was installed as it was last year sometime, I think it was but will check just to be sure.

I was hoping someone might have come across the 'ticking' sound I heard. Similar to a relay or the noise when a hot car cools down but very quiet.

Either way there everything was apparently ok when I put it away. It was about half hour after I left the airfield that it started transmitting so it all could all just be coincidence.
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  #6  
Old 05-26-2018, 02:19 PM
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BTW the position of the filter is in the manual that comes with the unit if i remember correctly.
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  #7  
Old 05-26-2018, 03:53 PM
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Quote:
Originally Posted by madmaveric View Post
BTW the position of the filter is in the manual that comes with the unit if i remember correctly.
The filter goes directly on the base of the antenna and the co-ax connects to the other end of it.

Neither of my two ELTs came with the filter and it was not mentioned in the FAA approved manual I recieved. I think it got added in the last 2 years or so.
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Last edited by az_gila : 05-26-2018 at 09:29 PM. Reason: timing clarity
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  #8  
Old 05-26-2018, 08:34 PM
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madmaveric madmaveric is offline
 
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The manual I have shows it attached to the aerial as well, so hopefully it was in the parts a I installed.
It would probably better if it isn't in them as that would give me a reason why it triggered but I'll have to wait until next week to check it.
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