Thursday, October 26, 2017

Emergency Locator Transmitter – Yep, It Works! “Eyes In The Sky” Found Me

Not long ago I read a few posts on the forums indicating there have been instances where the ACK E-04 Emergency Locator Transmitter was accidentally triggered while cleaning the aircraft. Apparently, the static charge generated by cleaning cloths or dusters next to the antenna have triggered the ELT to transmit. After contacting ACK about the anomaly, the builders were instructed by ACK to install a static suppressor in line with the antenna's coax cable. The Van’s assembly instructions for the RV-12 do not show or mention the use of the static suppressor. As I understand it, early shipments of the ACK E-04 may not have included the static suppressor … so this may explain why the suppressor is not shown or mentioned in Van’s drawings even though a static suppressor is now included in the ACK E-04 ELT box. Anyway, did not install the static suppressor during the build because it was not mentioned in the instructions or shown on the drawing. However, after reading the reports of others accidentally triggering the ELT while cleaning and ACK suggesting instillation of the static suppressor, decided it can’t hurt to install the static suppressor while performing the condition inspection … after all, the suppressor was included in the box from ACK.

One thing that has bothered me is the way the RV-12 assembly instructions show wrapping the excess antenna coax cable for the ACK E-04 ELT in a loop and using wire ties to flatten out the loop and secure the excess coax to the side of the ELT. This is done because the antenna cable from ACK is 5' long and the antenna is within inches of the ELT. Seriously, this is NOT the way a coax cable feeding an antenna should be treated.
Van’s assembly instructions direct the builder to coil the ACK E-04 ELT’s excess black coax antenna cable as shown here. This is not a good practice for coax cable being run to a transmitting antenna.

Decided since the ELT needs to be removed from it's mounting tray to comply with the requirement of testing the internal G switch annually, this would be the perfect time to do something about all the excess coax cable. Referring to the ACK E-04 instillation manual, ACK states the coax antenna cable can be as short as 2' … perfect, so headed over to the local avionics shop on the field and had them fabricate a 2' cable made from higher quality double shielded coax cable.

After removing the ELT from the mounting tray and completing the test procedure for testing the G switch (all successful), the ELT unit was placed back in the mounting tray and the new 2' antenna cable and static suppressor was installed. The new shorter coax cable was routed around the back of the ELT’s mounting tray, down under the ELT and back up to the ELT’s antenna. This will eliminate the coiled mess shown in the photo above.  The static suppressor was installed on the base of the ELT antenna between the antenna and the coax cable coming from the ELT, as can be seen in one of the photos below. So far so good.
The new 2' ELT coax antenna cable (copper looking) is routed behind the ELT’s mounting tray and loops under the ELT and up to the ELT’s antenna. I feel this a much better instillation as opposed to coiling the excess coax and using wire ties to secure 4 1/2' of coiled coax cable to the side of the ELT.
The static suppressor supplied in the box with the ACK E-04 ELT can be seen on the top right … it is the silver cylinder attached to the base of the ELT's antenna. The shorter copper looking coax antenna cable from the ELT is attached to the static suppressor.

I can assure readers the 2' coax cable connected to the static suppressor works great! How do I know? Well, I accidentally activated the ELT after performing the required testing of the G switch. The main reason for this admission of guilt is to reinforce the fact one should not  perform tasks on an aircraft when in a hurry. During construction of the DOG Aviation RV-12, extra effort was made to insure work sessions were not hurried or rushed so complete attention could be given to the task at hand. Being pressed for time and rushing is a recipe for errors, especially if the work environment throws in mitigating factors as I’m about to share with you.

Admittedly, I was somewhat in a hurry to finish up working on the ELT as to not be late for an appointment. After testing, the ELT was placed back in the mounting tray and wire ties were used to secure the audio alert indicator and associated wiring to the side of the ELT. This where it all went downhill, the mistake(s) made were threefold … instead of flipping the toggle switch on the ELT to the “ARM” position, the toggle switch was inadvertently flipped to “ON” … mistake one. When the ELT audio alert indicator began beeping, I quickly reached across the cockpit to slap the remote panel indicator mounted on the instrument panel. Thinking I pressed the reset button when in fact I must have slapped the “EMERGENCY ON” button … mistake two. At this point, I quickly walked away to make a log book entry documenting the testing and changing of the antenna cable ... mistake three. Next the environmental contributors came into play as it was raining moderately outside so the noise level inside the hangar was high. ( For those who have never been inside an all metal hangar during a rain .... light rain is noisy, moderate rain is very loud and a heavy rain is literally defining to the point ear protection is needed).  Between the music playing in the hangar at the time and the increased noise level caused by a steady rain hitting the all metal roof, it created a very noisy environment … so much so, I did not hear the occasional beeps coming from the ELT until between songs when the beeping finally caught my attention as the rain eased up a bit … OH CRAP!!!!  I quickly raced over and flipped the toggle switch on the ELT to OFF … and just then noticed I had initially flipped the toggle to “ON” by mistake. DUH!

As a side note for those readers not familiar with how the new dual frequency ELT’s work … when first activated, the ELT transmits on the FAA’s emergency frequency of 121.5 MHz. Typically, the 121.5 MHz  frequency is monitored with a handheld or aircraft radio during testing the ELT’s functionality. The testing should be performed between on the hour to 5 minutes after the hour ... this is so brief transmissions seen during this timeframe can be ignored as testing . Once activated for testing or accidentally, the ACK E-04 ELT needs to be reset immediately within 30 seconds or so … if the ELT has not been reset or powered off before 50 seconds has passed, the ACK E-04 ELT will begin transmitting on a second frequency of 406 MHz to the COSPOS/SARSAT satellites high overhead. The 406 MHz transmission to the satellites also includes the last GPS coordinates received by the ACK E-04 ELT from the aircraft’s avionics.

Apparently, I did not power off the ELT in time ... because 5 minutes or so later, I received a call from home where Jan said she just received a call from a government agency and they needed to talk to me. Of course, I called the monitoring agency back immediately and apologized profusely for setting off a false alarm for them to chase down. The woman I spoke with was very kind and said it happens all the time … nice to hear, but it did not make me feel any less of a dumb ass! We had a chat about how extremely sensitive the satellites really are because I was truly astonished that the satellite had picked up the signal and that they knew my exact location … given it was raining outside and I was in a totally enclosed all metal hangar with both hangar and access doors closed due to the rain. We joked about now knowing the ELT really works and actually transmits accurate GPS coordinates … still did not make me feel any less of a dumb ass!!! By the way, if desired, there is a form that can be submitted to the SAR agency in advance for scheduling an actual test of the ability of the E-04 ELT to transmit on the 406 MHz frequency.

Already have plans for the 5' of coax cable removed from the ELT antenna. The plan is to keep the coax cable in the map box as an emergency insurance policy. Should the Garmin GTR 200 radio ever fail in flight, my plan is to connect the coax cable to the handheld radio I always carry. The rubber duck antenna on the handheld radio will be removed and the 5' coax will be used to temporarily connect the handheld radio to the ELT’s antenna. The BNC connector on the ELT's antenna is within easy reach and should significantly extend the communication range of the handheld. Of course, this assumes there no other issues with the aircraft, just a broken radio. I’m not condoning this practice … but if the radio fails …there is a com antenna within easy reach … just sayin'.