Chapter 22 - Section 8C

Emergency Locator Transmitter (ELT)

 

Choosing the ELT

There are several ELT on the market for the experimental aircrafts. For our composite plane, we must add a ground plane under the center antenna. That's somewhat of a hassle and most builders dread it - me included. An ELT (Ameri-King 451) claimed to have TSO approved antenna that does not require a ground plane. I downloaded their installation manual and found that it’s rather straight forward. Its installation procedures mirror other popular brands as well. It has a GPS hook up which will download every 5 seconds. In the event of an accident that warrants the activation of the ELT, the GPS location will be transmitted concurrently - reducing the search and rescue time from hours to minutes. The only concern I have is that this ELT uses its own battery power throughout its operational period (~5 years). Seems to me, that's quite a constant draw on a battery. Regardless, so far so good...until I found out more from customer reviews. According to the reviews, there were many complaints of early battery failures and poor repair support. I also found an article relating to employee complaints of poor quality parts being used for the ELT and that FAA was getting involved. Hmm...

 

I finally decided to go with a different brand - the ACK-E04 instead. I checked around for competitive prices for the ELT and found they are pretty much the same from various sources. I decided to buy it from Aircraft Spruce which is only 6 miles from the Chino Airport. I purchased the complete installation kit. The ACK-E04 requires a ground plane, 12V power from the electrical system, a ground line and a RS232 for GPS input. It happens that Tim Andres has the same unit. That's even better, I can learn from him!  2 days after I purchased the ACK unit, I heard that FAA shut down the Ameri-King ELT product line. Talk about ducking the bullet.

 

Mounting the ELT

The ACK-E04 consists of a main transmitter/battery, a remote control unit, a horn, and a whip antenna. I decided to mount the transmitter under the pilot seat, the control unit at the IP and the whip antenna along the back side of the pilot seat - attached to the center seat support structure. The reason for mounting the ELT unit directly under the pilot seat is that it is accessible during flight.

 

 

 

 

 

 

 

 

Mounting Tray

ACK provides a mounting/retaining tray and straps for securing the transmitter/battery body. To secure the tray/strap onto the floor, I used 4 Tee nuts as shown (left). I drilled out 4 holes (just through the top glass layer + foam. Applied ample flox onto the Tee nuts, then imbeded them into the pre-drilled holes. Allow to cure. 

 

 

 

 

 

 

 

 

Ground Plane

Per ACK-E04 installation manual, the ground plane for the ELT does not have to be a solid sheet of metal (as most builders assume). At minimum, it needs 4 wires/copper ribbons, with minimum length of 12" long, radiating outwards, from the center vertical whip antenna (provided).

 

 

 

 

Once installed, I followed all the test procedures per ELT manual. All tested well as specified. For a dry run, I waited till top of the hour and flip on the "ARM" switch, while monitoring Frequency 121.5 with my hand held. The distinct "whooping" noise was music to my ears! Once completed, flip the power switch on the ELT to "ARM" position. All is well. No phone call from FAA and no unexpected "whooping" transmission from my ELT.

 

Installation Problems

I went flying the next day. While ELT installation was still fresh in my mind, I decided to switch on Freq. 121.5 shortly after take-off - just for fun...

"Whoop, whoop, whoop..." followed!  What the hell? That couldn't be me, right???? Who's that idiot testing their ELT during the wrong time of the hour - I thought to myself.

Just to confirm, I un-buckled my safety belts, reached down under my seat, and switched my ELT to off... the Whooping stopped immediately!  Ok, time to get a phone call from Mr. FAA - never did.

 

Just to be sure, I took a second flight with Doug Pitzer flying his plane ahead of me. We coordinated my turning on/off my ELT in flight. Sure enough, he picked up my distress signal from my ELT the moment I turned it on...rats! The tower was wondering if Doug can hear it louder over Corona Airport. Well, he won't be able to get it louder anywhere else...I was flying right behind him!

 

Through the process of elimination, I was able to trace the culprit to my TT31 transponder located at the front of the nose. Whenever the transponder comes online, it will trigger the ELT to go off! I was never able to figure out the theory behind that. My intuition tells me that the ELT should be triggered by its forward/backward G forces and not by RF signals around its vicinity. It turned out that my intuition was wrong. I posted my problem to the Cozy Forum, and was pointed out to me that extra RF shielding around the ELT cables may solve the problem.

 

I bought a set of torrids and mounted one around every entry and exit point of all the cables between the ELT unit, antenna and remote control - problem solved!

 

The good news about this whole experience is that my ELT antenna is working just fine!