406 ACK ELT

[Eric Rehm]

Does anyone know if the original ELT antennae located on the underside aft fuselage on a M20J is compatible with the new ACK 406 ELT?  I am trying to avoid cutting a hole in the fuselage to add the ACK antennae.

Thanks

[Boilermonkey]

Nope, but thereSIM20-116 M20M ELT retrofit.pdf is a Mooney Service Bulletin to allow a retrofit of the new antenna either under the dorsal fin or outside the dorsal fin.  

[Guest]

ELT antennae are mounted on top of the fuselage or under the dorsal fairing.

Clarence

[RobertGary1]

  On 4/6/2021 at 8:34 PM, Eric Rehm said:

Does anyone know if the original ELT antennae located on the underside aft fuselage on a M20J is compatible with the new ACK 406 ELT?  I am trying to avoid cutting a hole in the fuselage to add the ACK antennae.

Thanks

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What purpose does an elt antenna under the plane serve?

[carusoam]

  On 4/6/2021 at 10:59 PM, RobertGary1 said:

What purpose does an elt antenna under the plane serve?

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Serve as a disappointment when it gets cleaved off during the off-field landing...  

Under the plastic dorsal fin is a nice way to allow it to broadcast, and stay protected...

Welcome aboard Eric.

Best regards,

-a-

[PT20J]

  On 4/6/2021 at 8:34 PM, Eric Rehm said:

Does anyone know if the original ELT antennae located on the underside aft fuselage on a M20J is compatible with the new ACK 406 ELT?  I am trying to avoid cutting a hole in the fuselage to add the ACK antennae.

Thanks

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That's probably the com 2 antenna.

[PT20J]

406 MHz ELT signals are vertically polarized. This means that the antenna is most efficient when vertical. The ACK E-04 installation manual requires the antenna to be within 30 deg. of vertical. The Mooney SB cited above allows an ARTEX ME406 SARSET ELT 406 MHz whip antenna  (P/N 110-773) to be installed in the dorsal fin as was the 121.5 MHz antenna. In order to make it fit in the dorsal fin, the antenna will need to be deflected horizontally which will decrease it's effectiveness. The SB also says installation should be in accordance with the manufacturer's installation instructions ARTEX Manual 570--1600 (attached). Within that document you will find the following statement for the 110-773 antenna:

The antenna must be mounted on the top of the aircraft to assure maximum ‘visibility’ of satellites (406 MHz). The best location is the upper aft portion of the fuselage. It should be mounted vertically and away from projections such as a propeller, tail surfaces, or the shadow of larger antennas. (emphasis mine).

This is an emergency device. If it were me, I would mount the antenna vertically for best performance and in accordance with the ELT manufacturer's recommendations.

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ELT-Cobham-570-I-CALD.pdfFetching info...

[201Mooniac]

It is a shame those antennas are so ugly.  I've been looking for a good 406 antenna solution and have yet to find one that isn't ugly or 5x the cost of the ELT.

[Jerry 5TJ]

  On 4/6/2021 at 10:59 PM, RobertGary1 said:

What purpose does an elt antenna under the plane serve?

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“Because I was inverted.”

[Jerry 5TJ]

A diversity transponder is more useful than an ELT. In my opinion, of course.

If your plane goes missing Aireon will look for the historical records of your ADS-B transmissions as observed from the 66+ Iridium satellites.   

if your transponder has diversity, meaning it has both top and bottom antennas, the satellites will see your track down to the last transmission.   

Then your ELT may be triggered, or maybe not.   

You still have to install the ELT even if you have diversity Mode S, naturally. 

 

[ZuluZulu]

  On 4/7/2021 at 1:45 AM, 201Mooniac said:

It is a shame those antennas are so ugly.  I've been looking for a good 406 antenna solution and have yet to find one that isn't ugly or 5x the cost of the ELT.

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My plane grew a new antenna for a 406 upgrade and I haaaaaaate it. Every time I see it, it irritates me greatly. Damn thing better work if I crash!

[EricJ]

  On 4/7/2021 at 2:14 AM, Jerry 5TJ said:

A diversity transponder is more useful than an ELT. In my opinion, of course.

If your plane goes missing Aireon will look for the historical records of your ADS-B transmissions as observed from the 66+ Iridium satellites.   

if your transponder has diversity, meaning it has both top and bottom antennas, the satellites will see your track down to the last transmission.   

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Iridium can only see 1090ES ADS-B out.   The UAT folks will need to phone a friend or something.

[Guest]

  On 4/7/2021 at 1:45 AM, 201Mooniac said:

It is a shame those antennas are so ugly.  I've been looking for a good 406 antenna solution and have yet to find one that isn't ugly or 5x the cost of the ELT.

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The antenna can be installed under the composite dorsal fairing following the S/I posted above.  It’s a trade off between an externally mounted antenna (ugly) and drilling out the rivets holding the fairing on and touching up the paint.

Clarence

[Hank]

  On 4/7/2021 at 10:54 AM, M20Doc said:

The antenna can be installed under the composite dorsal fairing following the S/I posted above.  It’s a trade off between an externally mounted antenna (ugly) and drilling out the rivets holding the fairing on and touching up the paint.

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Because nothing in aviation is simple, easy or straightforward . . . .

[Ragsf15e]

While ugly, I like the ability to activate the 406mhz elt from a button up front to ensure it’s activated before any off field landing.  Especially in remote areas, you want there to be no doubt someone has a good idea where you are.  That button helps me get over the ugly antenna.

[Hank]

  On 4/7/2021 at 3:46 PM, Ragsf15e said:

While ugly, I like the ability to activate the 406mhz elt from a button up front to ensure it’s activated before any off field landing.  Especially in remote areas, you want there to be no doubt someone has a good idea where you are.  That button helps me get over the ugly antenna.

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Even my old 121.5 ELT had a panel switch. I also wouldn't feel good without one.

[Ragsf15e]

  On 4/7/2021 at 5:23 PM, Hank said:

Even my old 121.5 ELT had a panel switch. I also wouldn't feel good without one.

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Ahh, I didn’t know some of the old ones had the cockpit switch.  All the same, it’s a good feeling to be able to turn it on and send gps coords directly to the satellites and the rescue coordination center vs just making a lot of noise on guard.

[bradp]

  On 4/7/2021 at 12:46 AM, PT20J said:

That's probably the com 2 antenna.

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LORAN antennas also are bent whip style.  

[Hank]

  On 4/7/2021 at 6:36 PM, Ragsf15e said:

Ahh, I didn’t know some of the old ones had the cockpit switch.  All the same, it’s a good feeling to be able to turn it on and send gps coords directly to the satellites and the rescue coordination center vs just making a lot of noise on guard.

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Don't have a good photo, but it's over here:

[carusoam]

Panel mounted switch...

Better than waiting for deceleration due to hard things...   

Best regards,

-a-

[A64Pilot]

121.5 and 243.0 ELT’s are worthless, no one even monitors the frequencies anymore, but you have to have something, Congress said so.

[Guest]

  On 4/7/2021 at 5:23 PM, Hank said:

Even my old 121.5 ELT had a panel switch. I also wouldn't feel good without one.

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The only issue with old 121.5 ELT’s is that no one is listening for them.  How many people fly with their second radio monitoring the frequency?

Clarence

[Ragsf15e]

  On 4/7/2021 at 10:05 PM, M20Doc said:

The only issue with old 121.5 ELT’s is that no one is listening for them.  How many people fly with their second radio monitoring the frequency?

Clarence

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We should.  I do.  Well, when I remember to.  If you fly ifr, it’s worth it as a way to potentially save yourself grief from the faa if you end up on the wrong freq and lose contact.  However, Even if you hear an elt, locating it isn’t gonna happen fast or maybe at all.  How long do we think it will be before a real search is started and how long to triangulate that 121.5 elt?  The 406mhz has much better odds as they know exactly who’s airplane is sending it out and where (if you’ve registered your code).

[Guest]

I find it amazing the number of pilots who will buy LED everything’s for their plane but still don’t have a 406 ELT.  Here in Canada our national pilots organization fought Transport Canada on the 406 issue.

Clarence

[PT20J]

  On 4/7/2021 at 10:05 PM, M20Doc said:

The only issue with old 121.5 ELT’s is that no one is listening for them.  How many people fly with their second radio monitoring the frequency?

Clarence

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I thought a lot of airlines monitor guard. Perhaps some of our airline pilots can tell us.

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