406 ELT

twotter · Post by **twotter** » Mon Jan 26, 2009 11:20 am

Hey guys/gals.. Has anyone out there done a 406 installation in a 150? I'm trying to figure out what to mount it on as there sure isn't much structure to tie into. I thought someone might have a good idea that might save me trying to reinvent the wheel.

Thanks in advance..

SeptRepair · Post by **SeptRepair** » Mon Jan 26, 2009 11:33 am

Where was the original 121.5 installed? I have been using the existing location and brackets, just modifying the layout of the attach hardware as required.

twotter · Post by **twotter** » Mon Jan 26, 2009 3:05 pm

In most cases with a bit of reinforcing that will work but it is not allowed to be mounted on the skin (RTCA DO-204) and must withstand the 100g load. I've found with the 172 that the old radio rack behind the baggage works with a good doubler but this one has got me scratching my head..

SeptRepair · Post by **SeptRepair** » Mon Jan 26, 2009 4:31 pm

What about bending up a hat section and bridging it between the two stringers you find on most Cessnas. I know the 100G loading sounds like alot at first but remember 100 x1.85 lbs ( weight of ELT approx) is only 185lbs of force. Using 2024-T3 0.040-0.050 with some MS20470-4 rivets would be sufficient. Ill take a pic of a couple of installations showing what I mean and post later.

RDC01 · Post by **RDC01** » Tue Jan 27, 2009 5:24 pm

SeptRepair wrote:What about bending up a hat section and bridging it between the two stringers you find on most Cessnas. I know the 100G loading sounds like alot at first but remember 100 x1.85 lbs ( weight of ELT approx) is only 185lbs of force. Using 2024-T3 0.040-0.050 with some MS20470-4 rivets would be sufficient. Ill take a pic of a couple of installations showing what I mean and post later.

From your personal picture, I wonder where one would find adequate load bearing structure on Hawaii Mars?

RDC

SeptRepair · Post by **SeptRepair** » Tue Jan 27, 2009 10:34 pm

Here is a couple pics I said I would post. I screwed up when I said stringer. I meant former/rib/whatever you wanna call it. If you notice the ELT is mounted to a hat section that is riveted to the skin, as well the ELT is secured to the mount with a strap. The strap is from the ELT manufacturer so it must be rated to 100g's. The second pic is just an idea of something you can bend up and install.

cntrctr · Post by **cntrctr** » Sat Jan 31, 2009 11:11 am

Feel free to correct me if I'm wrong but, I believe that we are not allowed to attach the bracket to the skin. It has to be attached to structure.

twotter · Post by **twotter** » Mon Feb 02, 2009 6:37 pm

cntrctr wrote:Feel free to correct me if I'm wrong but, I believe that we are not allowed to attach the bracket to the skin. It has to be attached to structure.

You are quite correct, the first picture won't cut it.. I ended up having to build a rack in the baggage compartment that tied into the floor structure. There just wasn't anywhere to attach behind the bulkhead..

Cheers..

tiny · Post by **tiny** » Tue Feb 03, 2009 11:38 am

With semi-monocoque structure in a 150 or similar, the skin is part of the primary structure isn't it?

culver10 · Post by **culver10** » Tue Feb 03, 2009 2:10 pm

with semi-monocoque structure in a 150 similar, the skin is part of the primary structure isn't it?

Now, now, we do not want to cloud the issue with facts!

twotter · Post by **twotter** » Wed Feb 04, 2009 3:59 pm

As I stated above, the Kannad install manual specifically says that you cannot mount it on skin. SOL then. The baggage compartment was the only place I could think of. It looks good and if I was a little more computer savvy I would post a pic of the install.

c170b53 · Post by **c170b53** » Wed Feb 04, 2009 8:58 pm

You'll need to tie into a bulkhead, most common way is to fabricate a shelf. Looking at the Canadian requirements your ELT should adhere to the TSO c126 and c142A for the battery. I looked at an advertisement in YPK on a bulletin board for the lightweight Kannad and I could be wrong but I thought it said TSO pending!

twotter · Post by **twotter** » Thu Feb 05, 2009 10:57 am

The Kannad is fully approved and is a nice simple unit to install. I've done lots of them and the 150 is the only one that provided much of a challenge. A shelf was exactly what I did for the 150. If you are out in YPK let me know and I'll show it to you.

c170b53 · Post by **c170b53** » Thu Feb 05, 2009 11:21 am

I was just commenting on the lightweight version not being TSO'd. And I guess their battery is an acceptable installation as it is not a dioxide type?

c170b53 · Post by **c170b53** » Tue Feb 24, 2009 12:01 pm

Called around yesterday to MOT with the question, What type of ELT will be required for a US based aircraft flying to Alaska this summer? I don't call that often and now I know why I don't need to call in the future. I just wonder how many other departments of our Federal government operate the same way?

conehead · Post by **conehead** » Tue Feb 24, 2009 2:52 pm

Did you reach someone in Mumbai?

azimuthaviation · Post by **azimuthaviation** » Sun Mar 15, 2009 3:47 pm

which manual does it say you cant attach to the skin?

cntrctr · Post by **cntrctr** » Mon Mar 16, 2009 4:30 pm

I'm not overly computer savy so I hope this cut and paste works the way I want it to but it is the specification mentioned above.
TSO-C126 406 MHz Emergency Locator Transmitter (ELT)
Applicable Minimum Operational Performance Standards (MOPS)
RTCA DO-204 (Hardware)
2.1.13 Automatic Fixed (AF) Equipment
Requires means to detect the occurrence of a crash and automatically activate the transmitter, aural and visual indication to the flight crew of activation, controls available from the pilot's position, and means to rigidly mount the equipment to the aircraft structure.
2.1.14 Automatic Portable (AP) Equipment
Must meet all requirements of AF equipment plus include an auxiliary antenna and tether or an antenna directly attached to the ELT. Must be able to be removed from aircraft and operated without the use of tools.
Appendix A Beacon Coding: Defines coding protocols for 406 MHz digital message
Table A-1 Aviation User Protocol
Table A-2 Serialized Aviation User Protocol
3.1.8 ELT Mounting
"The ELT shall be mounted to primary aircraft load carrying structures such as trusses, bulkheads, longerons, spars or floor beams (not aircraft skin). The mounts shall have a maximum static local deflection no greater than 2.5 mm (0.1 in) 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 airframe not less than 0.3 m (one foot) or more than 1.0 m (three feet) from the mounting location."

mag check · Post by **mag check** » Mon Mar 16, 2009 4:45 pm

3.1.8 ELT Mounting
"The ELT shall be mounted to primary aircraft load carrying structures such as trusses, bulkheads, longerons, spars or floor beams (not aircraft skin). The mounts shall have a maximum static local deflection no greater than 2.5 mm (0.1 in) 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 airframe not less than 0.3 m (one foot) or more than 1.0 m (three feet) from the mounting location."

So, if it needs to be mounted to the "primary aircraft load carryimg structure" then I guess all existing radio trays are no good?
And if you have a homebuilt monocoque composite a/c, then you can't mount it at all.

cntrctr · Post by **cntrctr** » Mon Mar 16, 2009 6:09 pm

I could be wrong, but I expect that the reason that the ELT's have to be mounted to structure is because of the G-switch. If what ever its mounted to would just fold up or tear up (ie. skin) without first reaching enough G's to activate the switch then the whole thing is pretty useless. So following that reasoning then this requirement wouldn't necessarily need to apply to the radio rack or anything else like that.

mag check · Post by **mag check** » Mon Mar 16, 2009 6:17 pm

cntrctr wrote:I could be wrong, but I expect that the reason that the ELT's have to be mounted to structure is because of the G-switch. If what ever its mounted to would just fold up or tear up (ie. skin) without first reaching enough G's to activate the switch then the whole thing is pretty useless. So following that reasoning then this requirement wouldn't necessarily need to apply to the radio rack or anything else like that.

"reasoning"??? We are talking about transport here!!!
If it says "primary aircraft load carrying structure", then how can it mean anything else?
I don't think an existing radio tray will cut it, as this would not be carrying aircraft loads.

azimuthaviation · Post by **azimuthaviation** » Tue Mar 17, 2009 6:28 am

ok thanks

NeverBlue · Post by **NeverBlue** » Mon Mar 23, 2009 5:34 pm

...shouldn't you be doing it to an STC? ...and if you're not then you should be doing an STC. An ELT instal is a Major Modification no?

Who signed out that installation in the first picture?
You'll be real happy if you crash and instead of your ELT going off it goes flying past your head with it's tray and everything else.

You guys should read CAR's or something.

Nobody should be putting in an ELT that has to ask for advice through a forum like this.

Twotter! I'm not surprised...

Hornblower · Post by **Hornblower** » Mon Mar 23, 2009 6:23 pm

NeverBlue wrote:...shouldn't you be doing it to an STC? ...and if you're not then you should be doing an STC. An ELT instal is a Major Modification no?

No

Unit 969 · Post by **Unit 969** » Tue Mar 24, 2009 1:35 pm

viewtopic.php?f=27&t=36769&p=360024&hil ... ax#p360024

And apparently you can just slap a SkyTrax on as well.

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