ELT location

[learaviator]

I searched the Hangar forum for ELT and it says there is no suitable matches. Sorry if I am bringing up something that has been discussed. I am installing a new ELT and was wondering where people put theirs. Currently mine is in the baggage compartment, right side just ahead of the float kit fitting.

[flyboy122]

I put mine in the back corner of the baggage shelf. Reasonably sturdy and in the same section of the aircraft as the antenna. I can physically see it to make sure it's armed, and don't have to worry about baggage getting banged into it. Finally, in the event of an accident I can quickly and easily remove it if for some reason I elect to leave the crash site (my ELT came with a rubber ducky antenna for out of aircraft use). More importantly, I can instruct pretty much any un-aviation educated person on how to retrieve it in the event that I can't.

You are installing a 406MHz ELT, correct?

DEM

[learaviator]

I put mine in the back corner of the baggage shelf. Reasonably sturdy and in the same section of the aircraft as the antenna. I can physically see it to make sure it's armed, and don't have to worry about baggage getting banged into it. Finally, in the event of an accident I can quickly and easily remove it if for some reason I elect to leave the crash site (my ELT came with a rubber ducky antenna for out of aircraft use). More importantly, I can instruct pretty much any un-aviation educated person on how to retrieve it in the event that I can't.

You are installing a 406MHz ELT, correct?

DEM

Thanks for the reply!
Yes 406, a Kannad AF Integra with internal GPS. I have my baggage shelf out so I think I am going to put it on the right rear baggage floor and put a guard over it.

[rnealon1]

Mine is located in the tail just aft of the baggage compartment wall.

Bob

[GAHorn]

If I were making a new installation I think I’d consider beneath the rear seat, near the left rear doorpost, so it’d be accessible yet protected from baggage and inadvertent tampering.

[n2582d]

At last year's IA renewal seminar I asked Josh Cawthra, an NTSB accident investigator who gave a presentation, this very question. Specifically, since he had seen a lot of bent metal, what's the best place to install an ELT from a survivability standpoint? He basically said that if the accident is survivable the ELT is generally found intact. When the ELT is destroyed it doesn't matter as the occupants won't have survived either. That being said, I'd want to tie the hat section that forms your ELT mount onto an existing stringer or bulkhead.

Considering you have a 180 hp engine with a constant speed wouldn't it help your CG to install the ELT as far aft as reasonably possible? This is what the FAA recommends in 7.2.4 of AC 91-44A and what Airtex calls for in their installation instructions. Over the years Cessna has come out with numerous Service Bulletins/Kits regarding ELT installation. Here's just one of many. To access the ELT back in the tail cone you could use the battery access door assembly from a C-175.

C-175 Battery Access Panel

Screen Shot 2020-04-14 at 10.16.24 PM.png (22.74 KiB) Viewed 18329 times

The most recent ELT installation information for S.E. Cessnas I find is SK182-116C / SEB97-03. Here's a screen shot from SK182-116C:

[learaviator]

At last year's IA renewal seminar I asked Josh Cawthra, an NTSB accident investigator who gave a presentation this very question. Specifically, since he had seen a lot of bent metal, what's the best place to install an ELT from a survivability standpoint? He basically said that if the accident is survivable the ELT is generally found intact. When the ELT is destroyed it doesn't matter as the occupants won't have survived either. That being said, I'd want to tie the hat section that forms your ELT mount onto an existing stringer or bulkhead.

Considering you have a 180 hp engine with a constant speed wouldn't it help your CG to install the ELT as far aft as reasonably possible? This is what the FAA recommends in 7.2.4 of AC 91-44A. Over the years Cessna has come out with numerous Service Bulletins/Kits regarding ELT installation. Here's just one of many. To access the ELT back in the tail cone you could use the battery access door assembly from a C-175.

Screen Shot 2020-04-14 at 10.16.24 PM.png

The most recent ELT installation information for S.E. Cessnas I find is SK182-116C / SEB97-03. Here's a screen shot from SK182-116C:

Screen Shot 2020-04-15 at 7.22.50 AM.png

Wow! Lots of good info there...I really appreciate all of it!!!

[n2582d]

I've looked at the installation instructions for various ELT's. One thing they all seem to have in common is that they reference two RTCA (Radio Technical Commission for Aeronautics) documents. The first is DO-204A, § 3.1.8:

a) The ELT unit shall be mounted to primary aircraft load-carrying structures, such as trusses, bulkheads, longerons, spars, or floor beams (not aircraft skin) or a structure that meets the requirements of the following test: b) The mounts shall have a maximum static local deflection no greater than 2.5 mm (0.10") when a force of 450 newtons (100 lbf) is applied to the mount in the most flexible direction. Deflection measurements shall be made with reference to another part of the aircraft not less than 0.3 meters (1 ft.) nor more than 1.0 meters (39.4") from the mounting location.

I think this stringent requirement rules out installing the ELT on the hat shelf.

The second is DO-182, § 6.2.2.b:

a) To maximize the probability of the ELT transmitting a detectable signal after a crash, all ELT system components, which must survive a crash intact, e.g. transmitter and external antenna, should be attached to the airframe in such a manner that the attachment system can support a 100 g load, (ELT weight x 100, ELT antenna weight x 100, etc.) applied through the center of gravity of the component (ELT, antenna, etc.) in the plus and minus directions of the three principal axes of the aircraft. b) Post-crash critical components of the ELT system, e.g. transmitter and external antenna, should be mounted as close to each other as possible. c) The antenna coax cable should not cross any production breaks, e.g., major structure sections, such that the ELT and antenna are in the same section of the aircraft and as close together as possible. d) If the ELT and external antenna are on opposite sides of an airframe production break, the components should be secured to each other by a tether that can support a 100 g load (ELT weight x 100). The interconnecting antenna-to-ELT coax cable should have sufficient slack on both ends that it will not be subjected to any tensile load and should be tied loosely to the tether.

I'd like to use the C-175 battery access panel idea but place it further aft in the tail cone. The main challenge to this of course is getting a DER to sign off on it. I'm sure that could get expensive.

[c170b53]

I created a shelf just above the floor between the two frames just aft of thr hat shelf. It has a 1 inch flange running its length to give it rigidity its attached to the frames and to the side of the skin and on the bottom of the skin by standoffs. Its definitely overkill but as Gary pointed out, its built to comply with the ELT mounting deflection rule. I can’t remember, the thickness, but its at least .060.. Again overkill but up north, its easy to get lost and just as easy to remain lost, so ELT’s come under a fair amount of scrutiny by the aviation community, hence I felt I had to comply with the rules.

[c170b53]

Something like this has worked for me

[n2582d]

Very nice work Jim!

[c170b53]

Thanks Gary, likely you’ve noticed thats an ACK 406 ELT. Its on its last legs, as the FAA has deemed them illegal. Too bad, tested it today and this unit like its predecessor 121.5 ACK, has worked flawlessly, zero issues.
Looking at the kannad as its replacement, anybody have it installed ? Any for or against recommendations on that unit?

[n2582d]

Thanks Gary, likely you’ve noticed thats an ACK 406 ELT. Its on its last legs, as the FAA has deemed them illegal. ... .

. Jim, I’m unaware of any FAA action against ACK ELTs. In fact they boast, “The aviation products are in use worldwide and have never been subject to any Airworthiness Directives or have had any safety related recalls or service bulletins issued.” Perhaps you’re thinking of Ameri-king’s AD 2017-16-01?

Looking at the kannad as its replacement, anybody have it installed ? Any for or against recommendations on that unit?

There are a lot of reviews on various ELTs online. Obviously one needs to not just look at initial cost but also cost of replacing batteries. Kannad doesn’t allow the owner/operator to change the battery. I was surprised to see that Kannad uses a Velcro strap to install their ELT. According to SAIB HQ-12-32 the FAA frowns on hook-and-loop fasteners. Kannad’s Service Bulletin to this issue is found here. Kannad allows 3 minutes to comply with this 16 page Service Bulletin. They clearly read and work a lot faster than I do!