Canadian_JOY
Well Known Member
Hi Folks,
Seems that ELT's are a hotly debated topic around here. The intent of this topic is not to add fuel to the fire, but rather to share some factual information that I hope will help folks who are going to purchase an ELT. A recent thread on a "cheap 406MHz ELT" contained some information which might be misleading and could potentially lead to one of us not getting what we expected in a purchase transaction. Since nobody needs this kind of hassle in their lives I thought I'd get some of the facts out on the table in hopes ELT buyers will become better educated consumers.
Firstly, let's talk TSO's (technical standards orders). A piece of avionics gear that meets a particular TSO in fact meets a specific set of design and performance characteristics, as defined in the TSO document. In the case of ELT's there are three TSO's that commonly apply:
1) TSO C91
2) TSO C91a
3) TSO C126
Of these TSO's, C91 is the oldest, the original. I don't know about other jurisdictions but I do know in Canada it is no longer legal to do a new installation of a C91 ELT, so even if you were to purchase a used one it would be illegal to install it in your spanky new RV.
After it became evident that TSO C91 wasn't providing the operation performance that was originally intended, a revision was issued in the form of TSO C91a. This spec featured improved performance requirements, including advances in crashworthiness, reliability of operation, and frequency stability. The marketplace is currently well populated with TSO C91a units made by a variety of manufacturers - these are what we commonly refer to as 121.5/243.0MHz ELTs.
TSO C126 is the newest spec for ELTs, and in fact is the TSO which deals with 406MHz ELT's. Neither C91 or C91a units emit on 406MHz, period. This was the bit of factual information that was incorrect in a previous thread. If you want a 406MHz ELT, it MUST meet TSO C-126. All TSO C126 MHz ELT's also broadcast on 121.5MHz so that SAR resources and overflying commercial flights can still use this signal to home in upon.
Now for another little bit of info... The TSO certification process requires the manufacturer to certify their equipment as an operational group. That means that certification testing is carried out with a specific ELT, external "buzzer" (if necessary), antenna(s) and cockpit control unit. For us on the buying/installing side of the equation, what this means is that we can't "mix and match" compenents. That means no home-brew antennas, no re-use of your existing cockpit controller (unless the manufacturer specifically indicates in their installation manual that the part number you have is approved for use with the new C126 ELT). It also means that you need to install the new ELT in accordance with its approved installation manual - re-use of "existing" installation components may not meet the TSO requirement. While those of us who are building/flying "experimentals" don't necessarily need to meet TSO like the "certificated" boys do, it is a very wise idea to stick to the TSO requirements when it comes to this piece of life-saving gear.
Here's the final tidbit of data that is vital to those intent on purchasing a 406MHz ELT. These things are not cookie cutter "one size fits all" like the old TSO C91 and C91a units. Each jurisdiction dictates how the C126 ELT should be programmed. Some of the variables include country coding, whether the unit needs to transmit tail number or 24-bit ICAO code (Mode S address), or any one or combination of a few other choices. This being the case the TSO C126 ELT is essentially a device dedicated to a single aircraft ( for instance, my 406MHz ELT needed to be coded with my ICAO code for use in Canada). When purchasing an ELT you will need to understand what your unique national requirements are and be able to provide the ELT vendor with the appropriate information so as to ensure the ELT is properly coded prior to its delivery to you. Additionally, many jurisdictions mandate specific certification requirements, so while a vendor may offer a TSO C126 ELT for sale, it may not be approved for use in your particular jurisdiction, so caveat emptor!
I hope the info relayed here will be of help to those who are ELT shopping. Once again I will stress this isn't intended to be fuel for any kind of debate about the usefulness or need for ELT's, but rather is intended solely as a communication of facts to help ELT buyers become more educated and thus avoid some common pitfalls.
Seems that ELT's are a hotly debated topic around here. The intent of this topic is not to add fuel to the fire, but rather to share some factual information that I hope will help folks who are going to purchase an ELT. A recent thread on a "cheap 406MHz ELT" contained some information which might be misleading and could potentially lead to one of us not getting what we expected in a purchase transaction. Since nobody needs this kind of hassle in their lives I thought I'd get some of the facts out on the table in hopes ELT buyers will become better educated consumers.
Firstly, let's talk TSO's (technical standards orders). A piece of avionics gear that meets a particular TSO in fact meets a specific set of design and performance characteristics, as defined in the TSO document. In the case of ELT's there are three TSO's that commonly apply:
1) TSO C91
2) TSO C91a
3) TSO C126
Of these TSO's, C91 is the oldest, the original. I don't know about other jurisdictions but I do know in Canada it is no longer legal to do a new installation of a C91 ELT, so even if you were to purchase a used one it would be illegal to install it in your spanky new RV.
After it became evident that TSO C91 wasn't providing the operation performance that was originally intended, a revision was issued in the form of TSO C91a. This spec featured improved performance requirements, including advances in crashworthiness, reliability of operation, and frequency stability. The marketplace is currently well populated with TSO C91a units made by a variety of manufacturers - these are what we commonly refer to as 121.5/243.0MHz ELTs.
TSO C126 is the newest spec for ELTs, and in fact is the TSO which deals with 406MHz ELT's. Neither C91 or C91a units emit on 406MHz, period. This was the bit of factual information that was incorrect in a previous thread. If you want a 406MHz ELT, it MUST meet TSO C-126. All TSO C126 MHz ELT's also broadcast on 121.5MHz so that SAR resources and overflying commercial flights can still use this signal to home in upon.
Now for another little bit of info... The TSO certification process requires the manufacturer to certify their equipment as an operational group. That means that certification testing is carried out with a specific ELT, external "buzzer" (if necessary), antenna(s) and cockpit control unit. For us on the buying/installing side of the equation, what this means is that we can't "mix and match" compenents. That means no home-brew antennas, no re-use of your existing cockpit controller (unless the manufacturer specifically indicates in their installation manual that the part number you have is approved for use with the new C126 ELT). It also means that you need to install the new ELT in accordance with its approved installation manual - re-use of "existing" installation components may not meet the TSO requirement. While those of us who are building/flying "experimentals" don't necessarily need to meet TSO like the "certificated" boys do, it is a very wise idea to stick to the TSO requirements when it comes to this piece of life-saving gear.
Here's the final tidbit of data that is vital to those intent on purchasing a 406MHz ELT. These things are not cookie cutter "one size fits all" like the old TSO C91 and C91a units. Each jurisdiction dictates how the C126 ELT should be programmed. Some of the variables include country coding, whether the unit needs to transmit tail number or 24-bit ICAO code (Mode S address), or any one or combination of a few other choices. This being the case the TSO C126 ELT is essentially a device dedicated to a single aircraft ( for instance, my 406MHz ELT needed to be coded with my ICAO code for use in Canada). When purchasing an ELT you will need to understand what your unique national requirements are and be able to provide the ELT vendor with the appropriate information so as to ensure the ELT is properly coded prior to its delivery to you. Additionally, many jurisdictions mandate specific certification requirements, so while a vendor may offer a TSO C126 ELT for sale, it may not be approved for use in your particular jurisdiction, so caveat emptor!
I hope the info relayed here will be of help to those who are ELT shopping. Once again I will stress this isn't intended to be fuel for any kind of debate about the usefulness or need for ELT's, but rather is intended solely as a communication of facts to help ELT buyers become more educated and thus avoid some common pitfalls.