ELT's Which one. ?

Well, here it is Friday Night, and no words of wisdom from Cessna.
 
Well, golly, how on earth can it be installed then? o_O
 
Tom-D said:
Well, here it is Friday Night, and no words of wisdom from Cessna.
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Won't likely get anything of value. If they had to respond to every mechanic that wanted to intall a 406 in some old Cessna, they'd need a few hundred more technical advisors. Ain't gonna happen.

A mechanic can often find himself overthinking some of this stuff. Just make a stiffener or two and install the ELT and be done with it.
 
Dan Thomas said:
Won't likely get anything of value. If they had to respond to every mechanic that wanted to intall a 406 in some old Cessna, they'd need a few hundred more technical advisors. Ain't gonna happen.

A mechanic can often find himself overthinking some of this stuff. Just make a stiffener or two and install the ELT and be done with it.
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Why make two stiffeners when what you have is good enough?
 
Dan Thomas said:
Why be bothering Cessna when what you have is good enough?
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Cessna should know if it is good enough. After all they have the engineers that design and build these A/C.
And why would you believe that it is unreasonable to ask?
 
Why do you have to make it a drama? Borrow a pull scale and test the mount for movement. That’s the ultimate pass-fail regardless of what Cessna or anyone else says.

Since you bank your rep on what Cessna says, you must be a real advocate for SID inspections?
 
Stewartb said:
Why do you have to make it a drama? Borrow a pull scale and test the mount for movement. That’s the ultimate pass-fail regardless of what Cessna or anyone else says.
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That there. Easy to do. A lot faster than waiting for Cessna. And I bet they don't have the data on deflection of that equipment shelf anyway.
 
Stewartb said:
Why do you have to make it a drama? Borrow a pull scale and test the mount for movement. That’s the ultimate pass-fail regardless of what Cessna or anyone else says.

Since you bank your rep on what Cessna says, you must be a real advocate for SID inspections?
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Don't you think that was a bit over the top?
Since when it is bad to ask the manufacturer their opinion?
 
At the end of the day, Tom will do what ever he thinks right, regardless what anyone else thinks. And he is welcome to own it.

I wish him luck.
 
Tom-D said:
Why make two stiffeners when what you have is good enough?
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It's easier to check the load deflection yourself. I doubt Cessna will give you any useful info.

I put in two 406s this year and 2 last year. None where interfaced to gps. The owners were satisfied with the 1-3 mile non-gps accuracy vs 100 yard accuracy for gps enabled. One install required a major alteration to structure for mount deflection limit but only because of where he wanted it mounted due to his rod holder/cargo mod in the tailboom.

FYI: they revised ac91-44a last Feb which puts all relevant info in one place but mfgr docs are usually good enough.
 
Question, the installation for the ACK E-04 states to locate the ELT as far aft as possible. My current ELT is located in the aft fuselage in front of the stabilator. I have not tested that mount yet. It would be very easy to relocate the ELT behind the rear seat next to the battery. Should I consider that as a viable location or mount it as far aft as the instillation instructions state.

SECTION 2 ELT INSTALLATION


Several problems associated with previous TSO C-91, and C-91a ELT installations, is the

result of poorly chosen mounting locations. Generally the most suitable location for fixed

wing aircraft, is to position the ELT transmitter in the fuselage as far aft as possible.
 
AKBill said:
Question, the installation for the ACK E-04 states to locate the ELT as far aft as possible. My current ELT is located in the aft fuselage in front of the stabilator. I have not tested that mount yet. It would be very easy to relocate the ELT behind the rear seat next to the battery. Should I consider that as a viable location or mount it as far aft as the instillation instructions state.

SECTION 2 ELT INSTALLATION


Several problems associated with previous TSO C-91, and C-91a ELT installations, is the

result of poorly chosen mounting locations. Generally the most suitable location for fixed

wing aircraft, is to position the ELT transmitter in the fuselage as far aft as possible.
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Read the manual. The ELT and antenna need to be in the same section of structure so that the antenna cable doesn't cross rivet lines where sections join. If it does, the manual wants a steel cable between the ELT and antennae to take the strain if the section pulls apart so that the antenna cable doesn't rip. That there is a pile of work. And if the ELT is right ahead of the stabilator, that means the antenna, wihout a steel cable, has to be close to the vertical fin, which messes up the transmission pattern of the antenna.

Lots of fun getting things so they will work when they need to. ELTs only work about 50% of the time; we don't need that number to get any worse. Sometimes I wonder if much of the 50% failure rate is due to lousy installation.
 
Any reports to back that 50% claim up? Please limit it to 406 since we've known for decades that 121.5 is worthless.

Any reference to the manual that requires a steel cable? My two planes use different brands of 406s and neither manual says anything like that. The only thing I've seen referenced regarding cable failures is velcro straps on the ELT mount.
 
AKBill said:
the installation for the ACK E-04 states to locate the ELT as far aft as possible.
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Most aft location is standard FAA guidance, but it gives the disclaimer "as possible." The updated FAA guidance actually states "as far aft as practicable." Antenna location, ELT maintenance, the ability to manually turn off, as well as clear of cargo storage or pax ingress are other considerations in deciding location. The important item is the ELT mount location must meet/exceed the deflection limits.

For example, I relocated an ACK from an aft location to a more forward location due to the install of a fish rod/cargo modification in the tail boom. Unfortunately, the ELT mount also required a Major Alteration to the existing structure to meet the deflection limit. But this install was an exception more than the norm.

Dan Thomas said:
the manual wants a steel cable between the ELT and antennae
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I believe the recommendation of a coax tether across structure breaks or rivet lines is only referenced in the ARTEX manuals. However, the language used does not make it a required item.
 
Stewartb said:
Any reports to back that 50% claim up? Please limit it to 406 since we've known for decades that 121.5 is worthless.

Any reference to the manual that requires a steel cable? My two planes use different brands of 406s and neither manual says anything like that. The only thing I've seen referenced regarding cable failures is velcro straps on the ELT mount.
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Here's the Artex ME406 manual, which quotes the RTCA requirements on page 43: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=2ahUKEwjwo5fqw6ndAhWTHjQIHZo0CdEQFjACegQICBAC&url=https://avsport.org/acft/Artex/ME406_manual.pdf&usg=AOvVaw2MLNv2NSqnqB24vRxaRetn

An exerpt:
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.

And just for kicks, the following page says this:

CAUTION: MANY ORIGINAL ELT INSTALLATIONS ARE INADEQUATE AS FAR AS UNIT LOCATION AND
SURFACE RIGIDITY ARE CONCERNED. BECAUSE OF THE CRITICAL FUNCTION AN ELT
PERFORMS, IT IS IMPORTANT THE INSTALLATION FOLLOWS THE INSTRUCTIONS AND
RECOMMENDATIONS HEREIN.
CAUTION: THE MOUNTING SURFACE MUST BE EXTREMELY RIGID; THEREFORE, MOUNTING AN ELT
DIRECTLY TO THE AIRCRAFT SKIN IS UNACCEPTABLE. MOUNTING THE ELT DIRECTLY TO
THE AIRCRAFT SKIN INDUCES “CRASH HIDING” VIBRATIONS AND PROVIDES A VERY
POOR MOUNTING SURFACE.

As far as failure rates go, the TSO C91 (121.5) was awful indeed. As much as an 88% failure rate for crash-induced activations: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&ved=2ahUKEwii3crkxandAhXmIDQIHZwDDxw4ChAWMAB6BAgBEAI&url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19910001651.pdf&usg=AOvVaw1cGzc6wgnuR-eAz_oJFDXP

For the TSO 126a (406) units, the 50% figure has been tossed around quite a bit, and finding the authoritative source is difficult. The Canadian Owners and pilots Association (COPA) has been opposing mandatory 406 installation for GA, citing the failure factors for C91 units that would also apply to the C126. AN example: https://copanational.org/fr/2016/12/08/elt-update-transport-canada-effectively-mandates-406-elts/

Excerpt:

The COPA letter of dissent also pointed out that while perhaps there may be some improvement with the more robust specification for 406 ELTs, the fundamental causes of failure will continue because the device, cabling and antenna must still survive the accident, and there is no evidence that the tighter specification will significantly reduce the failures.

And another good article from the Australians regarding failures of both types of ELTs: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=2ahUKEwjJhIKizKndAhXZHzQIHb5oDVwQFjAJegQIAhAC&url=https://www.atsb.gov.au/media/4126629/ar-2012-128_final.pdf&usg=AOvVaw1h0m7FcTfxchVRmv5WjCxb

An excerpt:

Observation
There are many cases like this one where there is simply no explanation as to why an ELT failed to activate during a high g-force impact. In this case, the ELT was found by the ATSB to be intact after the impact; the mounting was intact, the unit itself undamaged, and the co-axial antenna cable still attached. Both the switch on the ELT, as well as the remote switch on the instrument panel where found to be in the correct setting, and a functional test of the ELT unit after being removed from the aircraft confirmed that it operated as expected.

The rest of the article deals with obvious reasons why the ELT failed to activate: Fire, submerging, G-forces tearing everything apart, and so on. Poor installation was a significant factor.

A 406 is built to a higher standard than the 121.5, so it should be more reliable. But if the installer cheaps out on the installation, he's wasting the customer's money. The RTCA guidelines are in the installation manuals for good reason: they are addressing factors that have caused failures in the past.
The G-switches of both types of ELTs have been troublesome. The Ameri-King ELTs were really bad, but the Artex and others still have failures.
 
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I thought the 406s use accelerometers instead of G switches? Testing my ACK switch is super simple. Act like I'm throwing it per the manual. No more taking the unit apart and exercising the G switch.
 
bluerooster said:
I just installed one in May. Best one for the price IMO.
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Back ordered, no expected delivery date.
They might be the best and most wonderful, but if you can't get them.
 
Tom-D said:
Back ordered, no expected delivery date.
They might be the best and most wonderful, but if you can't get them.
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AS expects Sept 7, according to their website.
 
SkyGeek has them. So does Gulf Coast, either direct or on Amazon.
 
Wag Aero shows it in stock, and less than AS.
 
Stewartb said:
I thought the 406s use accelerometers instead of G switches? Testing my ACK switch is super simple. Act like I'm throwing it per the manual. No more taking the unit apart and exercising the G switch.
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I think it's still a simple switch. The ones I've seen are a tiny thing about the size of a half-watt resistor. An accelerometer, at least the sort used in your cellphone, needs constant current to drive it, and the ELT battery can't afford that.
 
Tom-D said:
Well, here it is Friday Night, and no words of wisdom from Cessna.
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Tom, it's been over a month since you asked for Cessna's guidance. Did you ever hear back from them? What guidance did they give?
 
bkspero said:
Tom, it's been over a month since you asked for Cessna's guidance. Did you ever hear back from them? What guidance did they give?
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nope, nothing.
 
Tom-D said:
nope, nothing.
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Bummer. I guess it was always a long shot, but I was hoping to be pleasantly surprised by an answer...any answer. Even one where they just said they could not answer the question.
 
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