What Causes ELTs to Activate (Besides a Crash)?

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Harold Rutila

Pre-takeoff checklist
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Harold Rutila
I'm vacationing out of state and left my C150 behind. To my knowledge, nobody has rented or trained in it for about 10 days. I just got off the phone with Civil Air Patrol, and apparently my ELT has been going off today for an unknown duration. The airplane is kept inside a covered parking area with tie downs and gust locks installed.

We had some higher winds come through last night, but even when the plane was in uncovered parking in thunderstorms, I never had an issue with the ELT activating. I am going to have the airport check the tapes near my hangar tomorrow to be sure it wasn't some type of vandalism.

CAP reported that mine was the 3rd ELT to go off there today. Apparently they've been really busy with those in north Texas. Has anyone else had any similar experiences? What other things could cause an ELT to go off that I haven't considered?
 
Shock or hitting the switch I think
 
A Bonanza crashed gear-up in Banning Pass (near Palm Springs) a goodly number of years ago. The ELT didn't go off.

They loaded it onto a flatbed trailer and hauled it out of the rough terrain with a 4WD and the ELT didn't go off.

They downloaded it onto a concrete hangar floor and the ELT didn't go off.

They had a Christmas party later that year, somebody slapped the fuselage and the ELT went off.

Go figure.

Jim
 
As an aside, when I took the training to my own Annual Condition Inspections on my Experimental Light Sport, testing the ELT for operation annually involved giving it a good solid whack in the direction of the "forward" arrow on the case. Sometimes it takes quite a hard hit to get it to go off.
 
I have set off my 406 ELT in turbulence around convection. Now, re-setting the ELT after landing was the easy part, re-setting my wifes attitude about family travel by plane was a bit more complicated :redface: .
 
heard one today
dont stats say >90% are not crashes?
Ie
-purposefully turning on for various bad reasons
-inadvertently turning on
-non-crash g-forces including on a bench, in transit
-electronic glitch ie corrosion
 
Let'sgoflying! said:
heard one today
dont stats say >90% are not crashes?
Ie
-purposefully turning on for various bad reasons
-inadvertently turning on
-non-crash g-forces including on a bench, in transit
-electronic glitch ie corrosion
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I have seen corrosion more than once cause the ELT to activate.
 
Chemtrails. Electromagetic pulses. Alien mind melds. And since a 121.5 ELT is nothing more than a POS? Nobody cares much. If you had a real ELT (406) it wouldn't have gone off, and it it did? The Air Force would have called a few minutes after it started.
 
Stewartb said:
Chemtrails. Electromagetic pulses. Alien mind melds. And since a 121.5 ELT is nothing more than a POS? Nobody cares much. If you had a real ELT (406) it wouldn't have gone off, and it it did? The Air Force would have called a few minutes after it started.
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Let's keep it quiet on the chemtrails. Some folks might not like some revelations.
 
Clark, is there any point any more? I feel like it is widely known, and the government is going to at least never deny it; if not outright admit it. Come on, there is so much evidence and pilots are not the best at keeping secrets.
 
Let'sgoflying! said:
Clark, is there any point any more? I feel like it is widely known, and the government is going to at least never deny it; if not outright admit it. Come on, there is so much evidence and pilots are not the best at keeping secrets.
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I was just thinking of the new program but you are undoubtedly right.
 
I have an Airtex 406 mhz ELT. It has gone off twice sitting in a locked hangar without a hand laid on the aircraft for days. First repair was $400, next repair was $125. All within a span of 2 months. Poor customer service, they don't stand behind their repair and they are expensive. Neither I, nor my repair shop will ever purchase anything from them again.
 
The switch has been replaced.

The point is that false activations can happen for a variety of reasons and are therefore somewhat "normal". 406 mhz ELTs were "supposed" to greatly reduce or eliminate false activations that were common in simpler VHF systems. It seems this objective has failed, although now they can identify the offending aircraft and it's location.

False activations still occur, except now it's more expensive to purchase, repair and maintain the ELT.
 
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The phone wire is the comm cable between ELT and panel switch. Artex makes a switch that requires ship's power and an "ACE" version that uses a lithium battery. Both require a ground in the system, either at ELT or at the switch. Most guys I know ground at the switch. The Artex manual states that if the switch wires are severed the ELT will still function but if there's any short in the comm wire the ELT may be activated. Cheap phone wires and end plugs would be a good place to look for inadvertent ELT activation issues.

http://www.aeroclubrieti.it/w/wp-content/uploads/2014/01/ELT-Cobham-570-I-CALD.pdf
 
I hunted one down in a USPS train car once. Apparently train rides are bumpy, even packed in styrofoam and that rubber stuff. The postal inspector was ticked that the Sheriff made him roll out at midnight to open the car.
 
When I was renting a 172 in Australia, I found it was missing the ELT. When asked about it, I was told the owner had removed it because he kept setting it off during hard landings. Man, I've done some hard landings in a 172, but I haven't ever set off the ELT.

It takes fairly little to trip the ELT if you slap it in the right direction. Part of the annual test is to just snap it in a whip-like fashion.
 
AKBill said:
I have seen corrosion more than once cause the ELT to activate.
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This.

I have seen battery acid leak on the ELT wiring that was placed below the battery resulting in corroded insulation, corroded wire, and a short circuit that set it off.

I have also seen Ameri-King ELTs fail in various modes (including transmitting and indicating that they were transmitting) for no apparent reason other than crappy equipment.
 
Harold Rutila said:
What Causes ELTs to Activate (Besides a Crash)?
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A fat-fingered mechanic during annual.
Don't ask how I know.
After it going off for 3 days, nobody bothered calling. I went to apologize to the tower afterwards and only received puzzled looks.
I now believe the nay-sayers who claim that that nobody listens. No kidding.

Harold, glad to hear that somebody cared enough to call you, that shows nice initiative.
 
wsuffa said:
I have also seen Ameri-King ELTs fail in various modes (including transmitting and indicating that they were transmitting) for no apparent reason other than crappy equipment.
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Yep, if the battery in the AK remote goes dead the thing starts transmitting.
 
I set one off due to nosewheel shimmey, (rented 172) The damper got fixed in the next day or so. Recently I set mine off by whacking it on the palm of my hand, The case broke, but it passed annual inspection. ;) I'll have a new one before next annual, (I hope).
 
BigBadLou said:
A fat-fingered mechanic during annual.
Don't ask how I know.
After it going off for 3 days, nobody bothered calling. I went to apologize to the tower afterwards and only received puzzled looks.
I now believe the nay-sayers who claim that that nobody listens. No kidding.

Harold, glad to hear that somebody cared enough to call you, that shows nice initiative.
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CAP does that to teach their cadets.
 
I aborted a takeoff when I noticed my ASI not reading. While I was under the panel looking a chap came up to me and informed me my ELT was going off.
 
As it turns out, I received another follow-up from the CAP representative a few hours after I made this post. They sent another group out to the airport after I gave them permission to enter my airplane and discovered that it was not my airplane emitting an ELT signal after all. It sounded like one of my neighboring aircraft had one going off.
 
denverpilot said:
I hunted one down in a USPS train car once. Apparently train rides are bumpy, even packed in styrofoam and that rubber stuff. The postal inspector was ticked that the Sheriff made him roll out at midnight to open the car.
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Many, many, many moons ago, we found one in a third floor file cabinet of a bank building. Guy put his brand new, still in the box ELT in the office cabinet before leaving work on Friday. Secretary later slammed it shut. Spent the entire weekend trying to track down an intermittent signal...
 
FlyingElvii said:
Many, many, many moons ago, we found one in a third floor file cabinet of a bank building. Guy put his brand new, still in the box ELT in the office cabinet before leaving work on Friday. Secretary later slammed it shut. Spent the entire weekend trying to track down an intermittent signal...
Click to expand...

LOL. And inside a metal box.

Friends shared this one from last week here...

PLB activation with GPS coordinates.
Drive right to the guy's house.
He sees the antennas on the car and knows what they're looking for. He yells from his front porch...
"It's not mine! The batteries are dead in it!"

LOL. It was his. He had been playing with it because he thought it was dead.
 
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