Thread: Need ELT help
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Old 01-23-2012, 11:18 PM
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Flyin'Bryan Flyin'Bryan is offline
Join Date: Nov 2009
Location: Littleton, Colorado
Posts: 272
Default Maybe and maybe not - some food for thought

Originally Posted by dbuds2
Got my ACK-406 from Van's and after lots of reading and searching like you're doing, I'm mounting both the ELT and the anntennae on the outboard rib of my right wing. The stiffness from the skin and spar satisfied me for the mount of the ELT and the anntennae should always have visiablity to the sky thru the fiberglass wing tip.

Originally Posted by flyenforfun View Post
The antenna will function fine without pointing vertical
Hello all. I periodically see posts about ELT and/or antenna placement , and I thoroughly appreciate the fact that I will also one day have to figure out where to install mine when the time comes. What continues to bother me, however, is how some of you are choosing to install the ELT antenna in one wing or the other.

At this point I have to put on my hat of 26-years of experience with the Colorado Wing Civil Air Patrol as a check pilot, instructor pilot, and search and rescue mission pilot. As such, I have devoted years to training Colorado search and rescue pilots and aircrews in the art of electronic direction finding, and I would like to enlighten everyone about some things in hopes that you will find a different location to place your antennas other than the wings. My intent is not to hijack this thread, but to provide information in the interest of safety, and to ensure the best possible outcome should the unlikely event occur where you need to rely on the ELT to save your life or that of your passengers.

Basically, the most common accidents that occur are stall/spin accidents close to the ground. I have unfortunately seen with my own eyes the kind of destruction that occurs to the airframe when this happens. One wing or the other is typically completely demolished depending on several factors, including the direction of rotation of the spin. The opposite wing is usually thrown clear of the wreckage and is also very badly damaged due to impact. In almost all of these cases some part of the tail is the least impacted part of the airframe, so this is the logical location that you should attempt to install both the ELT and the antenna.

I realize that the sliding canopy of the RV-3, 4, and 8 aircraft presents a challenge in trying to accomplish this. But there is a reason why this installation is always toward the rear of the airplane in production aircraft, and is also the reason why the black boxes are located in the tail sections of commercial airliners.

Lastly, just to provide some insight into the training that CAP aircrews engage in with respect to ELT direction finding techniques, here are some of the training scenarios that they engage in to ensure that they can locate the signal in the shortest amount of time possible:
1. Full system direction finding (both audio and carrier signal of the ELT are fully functioning)
2. Partial ELT operation, including
a. Carrier signal but no audio (Carrier only)
b. Audio but no carrier signal
c. Antenna not vertical (i.e. practice beacons and the antenna are placed sideways or even upside down)
d. Simulated broken antenna or weak battery
e. Antenna covered by metal or snow, etc.
f. Reflective signals

And that is just a few of the scenarios that are utilized for training purposes. The folks that are proficient in these skills are quite excellent at tracking down an actual ELT location to within a few feet or less. In fact, in Colorado, if a fully functioning ELT is being heard, the average amount of time it takes to locate the ELT is about 3 hours. If your antenna and/or ELT is damaged, or the battery is weak, it may take much longer to track you down.

So I guess the moral to my story is that if you have the ELT antenna installed in one of your wings, please get it out of there, and endeavor to relocate it as far aft in the airframe as possible. I am intrigued by some of the pics of the side mounts inside the fuselage, and I think that this is a much better installation location than in the wings. Just my 2 cents.
Be safe.
Bryan Raley
Building RV8
EAA Chapter 301
SportAir Workshop Graduate x 4: Sheet Metal, RV Building, Electrical, and Composite classes.
Tail Wheel Endorsement Completed
Empennage done, Wings in progress, N462AK reserved.

Last edited by Flyin'Bryan : 01-23-2012 at 11:32 PM.
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