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  #11  
Old 05-16-2023, 06:08 PM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 6,213
Default Loops

Now there's an idea!

Quote:
Originally Posted by Webb View Post
Maybe I’m being cynical but if a crash is sufficient to deform a rear bulkhead and severe a coax cable, then the forward compartment probably could be used for an aluminum coffin.

But to keep in the spirit of things, perhaps a loop in the coax between the bulkheads to provide the “slack” needed to prevent stretching and potential severing of the coax in the event of a crash.
See below. Already planned

Quote:
Originally Posted by wirejock View Post
<snip>
My plan is to leave service loops, aka crash loops secured with self fusing silicone tape. One near the antenna. One at the F707 bulkhead. One at the ELT.
It holds very well and tears under pressure. Normally, I would put a tie of waxed lashing string, but that stuff will cut wire. Not a good idea.

<snip>
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Last edited by wirejock : 05-16-2023 at 06:24 PM.
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  #12  
Old 05-24-2023, 10:27 AM
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dmattmul dmattmul is offline
 
Join Date: Dec 2015
Location: Spring Hill, FL
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Default Snap bushings

Quote:
Originally Posted by Carl Froehlich View Post
If memory serves, this means that all RV-14s built per plans will not pass a DAR.

Carl
Yes, plans call for penetration through 2 bulkheads complete with snap bushings for the 14. I think a "crash loop" would help but that I'm pretty sure was not in the plans.
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  #13  
Old 05-24-2023, 11:11 AM
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Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
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Default

Quote:
Originally Posted by Webb View Post
Maybe Iím being cynical but if a crash is sufficient to deform a rear bulkhead and severe a coax cable, then the forward compartment probably could be used for an aluminum coffin.
Absolutely not! A certain amount of "crush" is designed into many tail cones to relieve pressure on the shoulder harness and avoid back injuries.
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  #14  
Old 05-24-2023, 12:56 PM
Mikeyb Mikeyb is offline
 
Join Date: Nov 2018
Location: Pasadena ca
Posts: 278
Default

Attached is the seminal report on ELT crash performance. Earlier studies showed as many as 15 percent of ELT failures in survivable crashes were due to antenna/cable issues. However during full scale crash tests roughly half resulted in damage to antenna connectors themselves. None were from cable shearing. It also found that many of the cable connectors provided by ELT vendors were not fabricated to MIL-DTL-17 and failed with 1/5th of the mechanical load. The report concluded that the problem could indeed be solved by adding a 10 inch length of cable at both ends using MIL-DTL-17 cable.

https://ntrs.nasa.gov/api/citations/...0170002586.pdf

Mike
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Last edited by Mikeyb : 05-24-2023 at 01:04 PM.
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  #15  
Old 05-24-2023, 01:18 PM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
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Default Misinterpretation?

From the Installation Manual for the ACK ELT-04, page 4:

"...and should avoid crossing aircraft production breaks (i.e. riveted fuselage sections)..."

I don't see how drilling a hole in the webbing of a bulkhead, insulating it with a plastic snap bushing, violates the letter or spirit of the installation guidance.

However, for argument's sake, refer to RV-7 DWGs 21 and 26. Drilling a routing hole in the area where the bulkhead halves overlap and are riveted together, wouldn't be recommended (e.g. Detail B, DWG 21).
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