ELT installation questions

[Norm G]

I'm at the point in my restoration where it's time to install a ELT in my 1941 BC12-65.The question of what brand ELT should I buy and where. Location of mounting hardware and where would be the best location for the unit and antenna are the kind of feedback that would really help.

Thanks,
Norm G

[flyguy]

Re: ELT installation questions

A little searching here should bring up some information. At least 2 of my planes have had the Narco ELT and I have not had any problems as I remember. You do have to pop, every 2 years, for a $25 battery that just consists of some alkaline D cells potted in a case. That is a a rip off.
See the thread here about the 406 MHz issue if you don't know about it.
It is on page 2.
Darryl

[astjp2]

Re: ELT installation questions

Let your A&P install it, there are several load testing requirments that need to be met on new installations that most owners dont need to deal with. I have a feeling a 406 Mhz will become mandatory next year, there is no ruling for it yet, but I do see it coming....

[Ray36048]

Re: ELT installation questions

ACK E01 I think is the best for the money. It uses flashlight batteries. You do not need to replace them until the battery expiration date. If you prefer, you can replace them every 2 years and put the ones from the ELT in your flash light.

[Ian Norgrove]

Re: ELT installation questions

Hi Norm, I'm an avionic tech,among other things.... installing ELT's. When you buy a new ELT it now has stringent requirements for the strength of the mounting. The manufacturer's installation guide lists how strong it needs to be. It usually requires mounting to a substantial part of the airframe that does not flex and can be tested with a spring scale to withstand eg. X lbs of force without deflecting more than .10" with reference to an adjacent part of the structure. These figures can vary depending on the manufacturer, but you can get the general idea.
For a typical Cessna type, that usually means having the mount attached to at least a bulkhead and some stringers, as the usual attachment to the outer skin is nowhere near strong enough.
For a tube steel fuselage mount you could fabricate a flat 2024-T3 aluminum plate, maybe .125", and secure it to a tube cluster with at least three or four 'adel' clamps to obtain the necessary firmness, then mount the ELT clamp or plastic base to that. Mount it as far back behind the baggage compartment as you can reach ( has more surviveability back there) and then mount your antenna as close as you can while still maintaining a ground plane for it.

Don't take any shortcuts with this stuff, I'm sure Steve Forsett wished his ELT had worked as planned. Some aircraft ( depending on category) require a remote switch in the cockpit to be installed when a new ELT is installed so the pilot can turn on the ELT if he feels the aircraft is in danger of crashing, and that means it doesn't depend on the 'G' switch to activate it. In my aircraft I will be fitting that switch whether its a requirement or not, it's nice to know that someones going to be looking for you.
Just a note for the ELT's that use the 'D' size batteries....they are a great idea, but you must use batteries that all have the same USE BY date to be legal, so check the dates before you buy.
I Hope this helps......Ian

[flyguy]

Re: ELT installation questions

Ian, Is that a mandatory retrofit on the solid mounting? Seems like a pretty good idea considering how useless a smashed ELT is. Mine is in pretty solid, but probably not good enough. Since it is a Narco **10 it would make more sense if it had the heavy battery pack forward as most planes don't crash going backwards. Duh. Mine is the other way around. I did not do it.
Darryl

[Ian Norgrove]

Re: ELT installation questions

Hi Darryl, My understanding is that you only need to worry about your mount if you are replacing the the ELT with a new one, and it's then that you must comply with the mounting instruction/ remote switch etc.
From the way you described it, I'm not sure which way yours is mounted, make sure you look at it and ensure that the arrow that indicates direction of flight is pointing forward, if not, the 'G' switch will not work with any sudden impact. There are some really poor installations out there, it would be a shame to be killed by your own ELT as it breaks loose.
You shouldn't need to make a box, just make sure the holding clip is in good condition and that the plate it's mounted to can't break loose.

Ian

[astjp2]

Re: ELT installation questions

Well if you have an EBC 102, you can replace it with another EBC 102, but if you have an EBC 102 and you replace it with an EBC 502, you will have to do the mount installation, which includes enough structrual integrity so the structure of the aircraft will not allow the mount move more than .100" in any direction with something like 200# of force applied to the mount. There is an AC on the Installation if I remember right. Adel clamps will allow the mount to move with this much force, they bend too much. Tim

[flyguy]

Re: ELT installation questions

Two hundred lbs figures out to be about 60 G's for my unit. The way mine is mounted the battery pack would smash the little fragile looking electronics package that is mounted on the end of the battery pack. The electronics is in front of the heavy part.

Checked my old battery pack, yep that is the way the arrow points, it is installed correctly for the G trigger. So in a crash, if it came loose, the control switch, the antenna connector, and the electronics package would be what takes the brunt of the impact. Have a 50/50 chance, if the switch was hit, that it would turn the unit OFF. Great little design.

DC

[astjp2]

Re: ELT installation questions

The issue is with the mounting, not the ELT its self, if the mounting flexes, it will not allow the elt to get the correct shock loading to trip the g switch. That is why it also needs to be as far back as possible in the airframe, to protect the structure of the mount, if its mounted up front and the engine gets pushed back into the passenger area, and the elt is located there, it may get destroyed instead of surviving the impact. Tim

Two hundred lbs figures out to be about 60 G's for my unit. The way mine is mounted the battery pack would smash the little fragile looking electronics package that is mounted on the end of the battery pack. The electronics is in front of the heavy part.

Checked my old battery pack, yep that is the way the arrow points, it is installed correctly for the G trigger. So in a crash, if it came loose, the control switch, the antenna connector, and the electronics package would be what takes the brunt of the impact. Have a 50/50 chance, if the switch was hit, that it would turn the unit OFF. Great little design.

DC

[Norm G]

Re: ELT installation questions

Ian, Thank you for your help. The information you provided is just what I wes looking for. Now I believe the best place will be behind the bagage area between a bottom tubing cluster using a strong mounting plate just as you suggested.
Thanks again,
Norm G

[flyguy]

Re: ELT installation questions

My narco ELT can be set off by slapping the unit with your hand. That isn't much of a crash. My comment on the stupidity of the design was assuming that the mount I have, even though it looks pretty solid, would probably allow the ELT to break loose in a severe crash. The design of the ELT itself is still a fragile, poorly thought out, piece of crap.
If the designer had protected the electronics, connections, and switch and if it was installed with a service loop in the antenna cable there would be a good chance of continued operation even if it did break loose.
Add a strong mount to that and you have at least those two things going for you.
DC