Re Build of N94978 BC12-d

[dalijohn]

Re: Re Build of N94978 BC12-d

Did it have documented ELT installation previously?

[astjp2]

Re: Re Build of N94978 BC12-d

There is an advisory circular on mounting, they changed the requirements, the big thing is no zip ties or Velcro or Adel clamps. I bought an EBC406 and its mounted in my baggage compartment using aluminum blocks and a thick aluminum plate. Tim

[3Dreaming]

Re: Re Build of N94978 BC12-d

There is an advisory circular on mounting, they changed the requirements, the big thing is no zip ties or Velcro or Adel clamps. I bought an EBC406 and its mounted in my baggage compartment using aluminum blocks and a thick aluminum plate. Tim

Would you mind providing a link to that AC. I found one that said no Velcro as the sole means of mounting, but there was no mention of not using Adel clamps.

[PA1195]

Re: Re Build of N94978 BC12-d

A NTSB report of an ELT, fastened via velcro, that departed its mount during a crash. Tore off the antenna coax. See pages 38-40 with pictures.

http://www.ntsb.gov/investigations/AccidentReports/Reports/AAR1103.pdf

I'd be interested to see the no-Adel Circular.

Gary

[Leenicklas]

Re: Re Build of N94978 BC12-d

Never had an ELT

[astjp2]

Re: Re Build of N94978 BC12-d

It was an interpretation of 91-44a para 6a, that the shock requirements necessary require hard mounting per ac43-13.2b which precludes using adel clamps since they are used to isolate vibrations (which is part of the shock requirement), they also interpreted something that says it cant be mounted to the outside skin incase the skin buckles, not allowing the appropriate shock condition (think Cessna skins). This was addressed in an IA seminar in Anchorage in 2009. It was news to me too. Now I just make billet aluminum blocks that bolt to the tubes with a plate. Not real expensive compared to what could be out there. Tim

http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_91-44A.pdf

[astjp2]

Re: Re Build of N94978 BC12-d

I found another requirement, adel clamps would exceed the .100 movement,

The ELT shall be mounted to primary 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 2.5mm (0.1 inch) when a force of 450 newton's (100lbs.) 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 meter (1 foot) nor more than 1.0 meter (3 feet) from the mounting location

http://www.supercub.org/forum/showthread.php?44660-Practical-mounting-of-406-ELT-in-Supercubs&

[Guest]

Re: Re Build of N94978 BC12-d

Doesn't AC43.13-2b show a clamp being used for mounting in figure 2-10?

It's an AN742 clamp not an Adel but I suspect that is of little consequence, we can get Adels with or without rubber and in various metals (steel, SS, aluminum) as I recall.

What am I missing?

Dave

[astjp2]

Re: Re Build of N94978 BC12-d

that clamp is for mounting something like a plywood floor board in a cub, still does not meet the .100 at 100 lb requirement for an elt

[PA1195]

Re: Re Build of N94978 BC12-d

The link Tim provided is worth a read...some unpleasantness awaits those whose ELT goes off w/o reasonable cause and the Administrator gets involved in its installation.

I have an ACK 406 that was previously installed, and sits aft of the extended baggage's metal bulkhead mounted to a horizontal metal plate. Don't recall the hardware used...it's too tight for me to crawl back in that hole. Its remote control and audio alarm are on/behind the instrument panel. Non-shielded (?) wiring (looks like phone telcom cabling) connects the aft and forward components. RF ingress may eventually be a problem as noted in the link.

Any way after 40+ years of self contained EBC 102A 121.5 mHz units that I "might" be able to activate and/or remove from the wreck, now there's an ELT hidden where I can't get to, can't retrieve without cutting the fabric, and is subject to loss of the coax connections and antenna in an upset. That's what happened in the Senator Ted Stevens wreck I linked above...no signal after impact.

A Delorme Inreach or SPOT unit sitting on the console top might be a better option if alerting help and portability is the goal.

Gary

[Garry Crookham]

Re: Re Build of N94978 BC12-d

I found another requirement, adel clamps would exceed the .100 movement,

The mounts shall have a maximum static local deflection no greater than 2.5mm (0.1 inch) when a force of 450 newton's (100lbs.) 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 meter (1 foot) nor more than 1.0 meter (3 feet) from the mounting location

http://www.supercub.org/forum/showth...-in-Supercubs&

This quote is from an ACK ELT manual. If you're installing some other mfg of ELT it doesn't apply. AC43.13 2B Chapter 1 Structural Data and Chapter 2 Com, Nav, and ELT installations lay it out very nicely.
And to muddy the waters even more, in a legal interpretation by the FAA Office of the Chief Counsel: The Aircraft Maintenance Division (AFS-300) in the Office of Flight Standards Office has expressed the view that the installation of a TSO ELT in a small airplane using methods, techniques, and practices contained in AC 43.13-2B would not constitute a major alteration to the aircraft. In view of the definition of a major alteration, we concur with that determination. Accordingly completion of an FAA Form 337 would not be required." You can retrieve the legal interpretation from the FAA website.

Garry

[Guest]

Re: Re Build of N94978 BC12-d

that clamp is for mounting something like a plywood floor board in a cub, still does not meet the .100 at 100 lb requirement for an elt

No not so, its for other than floorboards, here is the text description from AC43.13-2b "FIGURE 2-10. TYPICAL ATTACHMENT OF SUPPORT STRUCTURE TO TUBULAR FRAME OTHER THAN STRUCTURE TO FLOOR"

[Guest]

Re: Re Build of N94978 BC12-d

This quote is from an ACK ELT manual. If you're installing some other mfg of ELT it doesn't apply. AC43.13 2B Chapter 1 Structural Data and Chapter 2 Com, Nav, and ELT installations lay it out very nicely.
And to muddy the waters even more, in a legal interpretation by the FAA Office of the Chief Counsel: The Aircraft Maintenance Division (AFS-300) in the Office of Flight Standards Office has expressed the view that the installation of a TSO ELT in a small airplane using methods, techniques, and practices contained in AC 43.13-2B would not constitute a major alteration to the aircraft. In view of the definition of a major alteration, we concur with that determination. Accordingly completion of an FAA Form 337 would not be required." You can retrieve the legal interpretation from the FAA website.

Garry

What's a major alt? Yeah that's a debate isn't it.

There have been some FSDO folks and others saying that items listed in the TCDS can be major alt's and require a 337. I asked for an interpretation and the chief counsel says anything in the TCDS item list is not ever a major alt. No surprise I think.

So twice now I like the chief counsel's statement. Usually we complain that the FAA makes no sense. Two cases here where they do.

Dave

[astjp2]

Re: Re Build of N94978 BC12-d

Every ELT requires the same load check requirements....some just tell you what they are.

[astjp2]

Re: Re Build of N94978 BC12-d

So what uses plywood (shown in figure 2-10) besides a floor? I think its passing through the plywood floor and attaching to the structural tubing....but it still does not qualify the elt mounting requirements.

No not so, its for other than floorboards, here is the text description from AC43.13-2b "FIGURE 2-10. TYPICAL ATTACHMENT OF SUPPORT STRUCTURE TO TUBULAR FRAME OTHER THAN STRUCTURE TO FLOOR"