406 ELT internal antenna

[bmcconnaha]

Hello, I was going some research on adding a 406 ELT to my 1990 J.  I saw there was a service bulletin for this.  My antenna is internal, and I’d like to keep it that way. When I asked about the availability from a service center of the SB, i was told it was no longer available.  My question is, have you added a 406 ELT to your plan e, and kept the antenna internal WITHOUT using the kit called out for in the service bulletin? 
im at a loss at what to do ELT wise. 
 

thank you 

[PaulM]

this issue has been that the part# listed:

110-773 (Rev B )

Should be a standard ARTEX part. 

https://www.acrartex.com/products/110-773-whip-antenna-dual-band/

https://www.cobham.com/media/184642/110-773_rev a_rev b antenna drawing.pdf

so what makes it a magical under the dorsal fin Mooney Antenna?.  

We suppose that the factory has the official answer, but I'm going to say a jig, that bends the antenna to fit, and a piece of paper saying they tested it that way. 

Is the factory the only place that can bend an antenna?.. That would be up to the A&P or avionics shop.   Original mooney jig's aren't required to fix wings, weld landing gear etc and other repairs that affect the airworthiness of the airframe.    This would be a minor alteration. 

Somebody should send a borescope up the tail of a post 2010 Mooney and duplicate the result. 

 

 

[PT20J]

The kit is not available, so you just have to buy the ELT and antenna and fabricate a doubler. Interestingly, the SI says to install the antenna according to the ARTEX manual which says that the antenna has to be vertical. But the SI also permits mounting it in the dorsal fin. One could argue that it is more protected in a crash buried in the dorsal fin and you should be able to use SIM20-116 as authority to do so. Just discuss it with your A&P.

Skip

https://www.mooney.com/wp-content/uploads/2020/12/SIM20-116.pdf

 

[ZuluZulu]

My avionics shop told me they would have to cut into metal to make the antenna internal when I had a 406 MHz ELT from Artex installed.  I HATE the antenna which is mounted left of centerline and thus leans a little to port.  Hate it.

[Guest]

I agree with Skip.  Remove the fibreglass dorsal fairing, build an angled doubler to mount the antenna and reinstall the fairing.  If you’re worried about antenna angle, be sure to crash nose first to keep the antenna vertical.

Clarence

[testwest]

I successfully did this very thing on N201JX and used SIM20-116 as the authority to do it. Tested the installed antenna for VSWR using the internal 406 ELT diagnostics and then ran the tests here: https://www.acrartex.com/406test/ .

I ran about two sweeps as stipulated and the satellites reported back through the 406test system in under two minutes with good results, with the fairing clecoed back in place in case the tests did not work. Note the clecos were omitted in the area of the antenna so as not to corrupt the results. Of course with that caution the tests ran great!

Anyone who says a 406 ELT won't work under a dorsal has no idea what they are talking about.

Here is the dorsal removed and the detail of the ELT mounting hole. Note the diameter of the antenna base on the skin has been propped for electrical bonding and corrosion proofed with an Alodine pen.

 

The ELT tested perfectly again under the new paint:

 

[carusoam]

Inviting @bmcconnaha to stop by to see Norman’s pics above…

-a-

[GeeBee]

If you want the antenna hidden for aesthetics, I get that. If you think it affects your speed it does not. I put a high speed rod with my new 406 unit and it made no detectable difference in performance.

 

[EricJ]

10 hours ago, testwest said:

Anyone who says a 406 ELT won't work under a dorsal has no idea what they are talking about.

I don't think the issue is "won't work" as much as it'll lose performance.   For emergency equipment some feel a loss of performance is not a good tradeoff for aesthetics.

Yours worked under one test condition, which demonstrated that the installation at least doesn't prevent it from working.     The fairing may provide some shear protection during a crash, but that's difficult to anticipate whether that's an advantage or not.

 

[testwest]

I sure do like the aesthetics of the installation. That was the primary motivation to be sure. And the tests have passed correctly each time I did them. It was interesting to see how the satellites picked up all the 406 information including the location and N-number after only about two sweeps which was a transmit time of a couple seconds. The 406test site had all the data. For me, that was a sufficient demonstration of RF performance.

Sharp eyes will notice there are no antennas on this airplane forward of the baggage compartment. The accumulated drag reduction is noticeable, not so much for speed as for going the same speed on a little less fuel. A few little drag reduction mods do add up, even though they may not be individually discernible without an instrumented airplane and very stable atmospheric conditions.

Again, I did have some people (not here) say that the under-dorsal installation would not work at all. Mooney's certified installations and my experience suggest otherwise!

So, to directly answer the OP's original question: "have you added a 406 ELT to your plane", the answer is yes, yes I did!

"And kept the antenna internal WITHOUT using the kit called out for in the service bulletin?" yes, to that too, and as a bonus the installation was signed off with no problems whatsoever, and the installation passes its operational and continued airworthiness tests.

The pictures and cited SI show exactly how it was done and should be able to be duplicated by an A&P or even a motivated and sufficiently skilled owner-operator under A&P supervision. Note I did not build an angled doubler, just mounted the base to the skin and bent the antenna forward under the dorsal, it does come up vertically for a short bit before the bend.

 

 

[bmcconnaha]

On 3/18/2022 at 7:17 AM, GeeBee said:

If you want the antenna hidden for aesthetics, I get that. If you think it affects your speed it does not. I put a high speed rod with my new 406 unit and it made no detectable difference in performance.

 

I’m not too worried about the speed loss, however minuscule it is.  There isn’t a great spot on my plane to put it that keeps it centerline and not not canting left or right.  It’s much cleaner for now.  
 

seems to be a moot point anyways, the avionics shop doesn’t want to do it, so I had them run wire in preparation.  I’ll get to it at some point down the road, before I paint the plane.  

[A64Pilot]

I installed a Garmin chart plotter with Radar etc in my Center Console boat one time and worried that I would have to have an external antenna as the T-top was aluminum tubing.

Well after installation I turned it on and is was tracking maybe ten satellites with good reception, after realizing the boat was parked inside of a metal building with the doors closed I didn't worry anymore.

More than a couple of times we had the avionics shop across the field install avionics for a foreign customer only for me to get a call that the ELT was going off (foreign ELT’s have to be ordered pre-programmed) and for some reason they gave out my number to be called, but point is these ELT’s were again in a closed up metal building.

Sure we don’t want to attenuate a signal if we can help it, but these things meaning I guess the Satellite are better than we think.

Me, I just have the literally worthless 121.5 ELT that no one listens for anymore.

Edited March 19, 2022 by A64Pilot

[bmcconnaha]

43 minutes ago, A64Pilot said:

I installed a Garmin chart plotter with Radar etc in my Center Console boat one time and worried that I would have to have an external antenna as the T-top was aluminum tubing.

Well after installation I turned it on and is was tracking maybe ten satellites with good reception, after realizing the boat was parked inside of a metal building with the doors closed I didn't worry anymore.

More than a couple of times we had the avionics shop across the field install avionics for a foreign customer only for me to get a call that the ELT was going off (foreign ELT’s have to be ordered pre-programmed) and for some reason they gave out my number to be called, but point is these ELT’s were again in a closed up metal building.

Sure we don’t want to attenuate a signal if we can help it, but these things meaning I guess the Satellite are better than we think.

Me, I just have the literally worthless 121.5 ELT that no one listens for anymore.

I’m trying to determine the value of the 406elt.  Aviation consumer did an article a little while ago on the.  In the title “reduce expectations”.  Now, if I was flying without being on an IFR flight plan, or without flight following on the regular, i would think different.  Aviation consumer seems to think PLBs are a better choice, but of course the don’t automatically activate 

 

[bmcconnaha]

On 3/18/2022 at 10:29 AM, testwest said:

I sure do like the aesthetics of the installation. That was the primary motivation to be sure. And the tests have passed correctly each time I did them. It was interesting to see how the satellites picked up all the 406 information including the location and N-number after only about two sweeps which was a transmit time of a couple seconds. The 406test site had all the data. For me, that was a sufficient demonstration of RF performance.

Sharp eyes will notice there are no antennas on this airplane forward of the baggage compartment. The accumulated drag reduction is noticeable, not so much for speed as for going the same speed on a little less fuel. A few little drag reduction mods do add up, even though they may not be individually discernible without an instrumented airplane and very stable atmospheric conditions.

Again, I did have some people (not here) say that the under-dorsal installation would not work at all. Mooney's certified installations and my experience suggest otherwise!

So, to directly answer the OP's original question: "have you added a 406 ELT to your plane", the answer is yes, yes I did!

"And kept the antenna internal WITHOUT using the kit called out for in the service bulletin?" yes, to that too, and as a bonus the installation was signed off with no problems whatsoever, and the installation passes its operational and continued airworthiness tests.

The pictures and cited SI show exactly how it was done and should be able to be duplicated by an A&P or even a motivated and sufficiently skilled owner-operator under A&P supervision. Note I did not build an angled doubler, just mounted the base to the skin and bent the antenna forward under the dorsal, it does come up vertically for a short bit before the bend.

 

 

Thank you.  Ill most likely do that when I get home.  The avionics shop will let me know what ELT I have now, I might be able to add the switch now, and run the wire, so when I am ready to do it, there wont be any interior work, just pulling the dorsal fin and mounting a new antenna 

[A64Pilot]

1 hour ago, bmcconnaha said:

I’m trying to determine the value of the 406elt.  Aviation consumer did an article a little while ago on the.  In the title “reduce expectations”.  Now, if I was flying without being on an IFR flight plan, or without flight following on the regular, i would think different.  Aviation consumer seems to think PLBs are a better choice, but of course the don’t automatically activate 

 

Coming from the boating world they are called EPIRBS but pretty much the same device, many want a Garmin Inreach or SPOT and think they are best as they can message, but the really big difference in an ELT or EPIRB for that matter is they auto activate, and in an EPIRB and I assume an ELT they are higher power and the battery will xmit for a much longer time., but really the automatic part is what can be a lifesaver.

So it’s my opinion that if your out playing bush pilot especially meaning your not talking to anyone because there is no one to talk to, that a SPOT or Inreach and or PLB is an excellent back-up device, but does not replace the ELT or EPIRB.

If your IFR on Radar talking to center, then that’s different, just my opinion.

The 121.5 ones like I have are worthless and it’s stupid that we have to maintain them, another opinion. You know the history of why we even have them? Congress not the FAA is why, because a Congressman went down in Ak and was never found.

A GPS 406 is a wonderful device, it not only tells the RCC where you are exactly, but also who you are. the 121.5 one goes “beep”

On edit if you have a PLB and rely on it, keep it close by and turn the thing on before an accident if possible. Military we wore survival vests with survival equipment in it of course, when playing bush pilot in my Maule I wore one, I’ve been told a fishing vest works well, but its a good place to put your PLB etc.

Maybe this one in red?

https://www.amazon.com/Zhusheng-Pockets-Photography-Breathable-Waistcoat/dp/B08C7KJQP7/?_encoding=UTF8&pd_rd_w=JuRZm&pf_rd_p=6571d503-3939-4d29-87b5-6a8ea95c783b&pf_rd_r=NSZR50JDF8SBXQ2TZ3EF&pd_rd_r=c00ae7d7-5204-4478-8be3-44218ca360f5&pd_rd_wg=BvlXW&ref_=pd_gw_ci_mcx_mi&th=1&psc=1

Even if your in your Mooney the Canadian NWT is a great place to fly in Summer, a vest might be a good idea, and $26 is dirt cheap

Picture of the kids in the Inuvik airport almost 20 years ago. I never went anywhere in the NWT including Tuktoyoktuk that I wouldn’t take a Mooney.

‘She is 22 now and getting married this year

 

Edited March 19, 2022 by A64Pilot

[OR75]

On 3/17/2022 at 10:19 PM, testwest said:

I successfully did this very thing on N201JX and used SIM20-116 as the authority to do it. Tested the installed antenna for VSWR using the internal 406 ELT diagnostics and then ran the tests here: https://www.acrartex.com/406test/ .

I ran about two sweeps as stipulated and the satellites reported back through the 406test system in under two minutes with good results, with the fairing clecoed back in place in case the tests did not work. Note the clecos were omitted in the area of the antenna so as not to corrupt the results. Of course with that caution the tests ran great!

 

Anyone who says a 406 ELT won't work under a dorsal has no idea what they are talking about.

Here is the dorsal removed and the detail of the ELT mounting hole. Note the diameter of the antenna base on the skin has been propped for electrical bonding and corrosion proofed with an Alodine pen.

The ELT tested perfectly again under the new paint

 

I must be blind ... but where is the antenna ?

[OR75]

1 hour ago, bmcconnaha said:

I’m trying to determine the value of the 406elt.  Aviation consumer did an article a little while ago on the.  In the title “reduce expectations”.  Now, if I was flying without being on an IFR flight plan, or without flight following on the regular, i would think different.  Aviation consumer seems to think PLBs are a better choice, but of course the don’t automatically activate 

 

I think the main value of the 406 is that the install imposes that you have an activation switch in the cockpit.  It should be part of the pre-ditching checklist instead of waiting for a shock activation.   

[testwest]

Sorry! I did not get a picture of that, but the antenna installs in the prepped hole and bends forward under the dorsal. It's generally in the area where there were no clecos in the test fit-up photo.

[Guest]

The other day we accidentally triggered an Artex ME406 in the shop.  Cirrus installs the antenna in the fuselage, the signal made it through the skin, through the hangar’s steel roof and to the satellite in seconds.  SAR called the owner who laughed and said it was in my shop.  They called me for an explanation.  They do work well.

If you’re flying with an old 121.5 you may as well leave it in the hangar.

Clarence

[Jerry 5TJ]

Missing GA aircraft have been located from cell tower data, too. There’s almost always a cell phone on board, often one per passenger.  If there’s no post-crash fire the cell phones frequently survive and operate for a day or two. 

[carusoam]

The extra value of 406mhz and WAAS GPS….

Is when you are flying over the middle of nowhere… and have a problem…

One burst let’s the world know exactly where you are…

Often, cell towers cover a lot of American highways… but not very well as you get away from population centers…

 

There has been one lost Mooney (non-mser) that didn’t get found until the snow melted months later… West end of Canada…

Plane went down, close to, next to, the highway…

file that under modern safety devices that are installed for a reason…

North of Boston gets kinda woodsy…

PP thoughts only, not an avionics guy…

Best regards,

-a-

[philiplane]

Antennas work fine under fiberglass, which is invisible to radio or GPS signals. The key is to have the tip of the antenna as vertical as possible. Transmitting antennas use the rod to radiate the signal, like a light bulb radiates light equally in all directions, and the base needs to be a good reflector to achieve that pattern. That's why an optimum antenna is a rod tuned to the transmitting frequency, and the rod will be perpendicular to the base. The base will also have a minimum diameter to serve as a good reflector of the radio energy. The top of a fuselage works well as a reflector. 

The problem with inclined antennas is that they don't radiate in an equal pattern. When you crash and shear off a wing, and the plane is now on its' side, the antenna may, or may not, be in position to give a good signal. Or you overrun the runway and go down an embankment, and the incline puts the antenna in the shadow of the vertical fin.  

Satellite coverage depends on line of sight, and the satellites are rarely directly overhead. Most times, they are low on the horizon, and if your antenna has a blind spot in that direction, the satellite won't see the transmission. Signal bounce helps offset some of this, but it is not something you want to rely upon in an emergency.

So I would recommend going for functionality first, and cosmetics a distant second, when setting up your potentially life saving 406 ELT. It should work well without question, and if you can hide the antenna, well, that is a bonus. I don't see how bending the antenna tip forward, under the fin, will give a radiation pattern you can bet your life on. This Mooney SB is for conversion of a 121.5 ELT to the 406 ELT, and it allows bending the antenna, when ARTEX only approved a straight rod antenna, or the whip antenna, as part of their STC kit. We've asked them to use an angled blade style antenna instead, and they said no. More importantly, the ARTEX installation manual says the antenna must be installed within 15 degrees of vertical.

Yes, you may pass a test in perfect conditions on the ramp, but how will it work out in the woods, or in the mountains, when the plane is damaged and you need the ELT the most?

Edited March 20, 2022 by philiplane

[EricJ]

40 minutes ago, philiplane said:

Antennas work fine under fiberglass, which is invisible to radio or GPS signals.

Only E-glass is mostly transparent to RF energy, and typically only radomes are made from that.    Other types have varying degrees of atennuation, and it is not difficult to make a composite material that is completely opaque to RF energy.    I wouldn't assume what the characteristics are of a fin that wasn't specifically made of E-glass or materials selected to minimize signal attenuation.

Even E-glass attenuates the signal, it's just minimized for the application.

Edit:   I should clarify, by E-glass I mean the composites used specifically for RF transparency.   The actual materials have changed over the years.   Not all fiberglass minimizes RF attenuation.

 

40 minutes ago, philiplane said:

The key is to have the tip of the antenna as vertical as possible. Transmitting antennas use the rod to radiate the signal, like a light bulb radiates light equally in all directions, and the base needs to be a good reflector to achieve that pattern. That's why an optimum antenna is a rod tuned to the transmitting frequency, and the rod will be perpendicular to the base. The base will also have a minimum diameter to serve as a good reflector of the radio energy. The top of a fuselage works well as a reflector. 

The problem with inclined antennas is that they don't radiate in an equal pattern. When you crash and shear off a wing, and the plane is now on its' side, the antenna may, or may not, be in position to give a good signal. Or you overrun the runway and go down an embankment, and the incline puts the antenna in the shadow of the vertical fin.  

Satellite coverage depends on line of sight, and the satellites are rarely directly overhead. Most times, they are low on the horizon, and if your antenna has a blind spot in that direction, the satellite won't see the transmission. Signal bounce helps offset some of this, but it is not something you want to rely upon in an emergency.

So I would recommend going for functionality first, and cosmetics a distant second, when setting up your potentially life saving 406 ELT. It should work well without question, and if you can hide the antenna, well, that is a bonus. I don't see how bending the antenna tip forward, under the fin, will give a radiation pattern you can bet your life on. This Mooney SB is for conversion of a 121.5 ELT to the 406 ELT, and it allows bending the antenna, when ARTEX only approved a straight rod antenna, or the whip antenna, as part of their STC kit. We've asked them to use an angled blade style antenna instead, and they said no. More importantly, the ARTEX installation manual says the antenna must be installed within 15 degrees of vertical.

Yes, you may pass a test in perfect conditions on the ramp, but how will it work out in the woods, or in the mountains, when the plane is damaged and you need the ELT the most?

Agreed, and this is what I was hinting at earlier.   Passing a few ground tests is not indicative of performance in the field, and will not reveal how much link margin has been  lost due to the installation.   Reducing the performance of emergency equipment should be done with great caution.

Edited March 20, 2022 by EricJ

[GeeBee]

Some discouraging statistics

 

[EricJ]

3 hours ago, GeeBee said:

Some discouraging statistics

 

That's a pretty common misuse or misinterpretation of statistics that happens a lot with safety equipment.    Seatbelts are rarely called on to do their job, nor are helmets or fire extinguishers, or most safety equipment for that matter.   But, for the rare (but anticipatable) occurrence where they make a big difference, you need them there.    If we always knew the characteristics or timing of a crash before hand, we could do a lot better job of engineering and selecting the safety equipment that we need. 

Aviation is full of stuff like this.   How many times have you sumped fuel without detecting water or a misfuel or contaminants?   How many times in a row do you have to sump with no contaminants before you call the system good and stop doing it?   

I have a 406 ELT and a PLB, the same ACR shown in the vid.   Sometimes I take the PLB flying with me if I'm going to be over very remote terrain, because it is anticipatable that there could be a crash that I survive, but the ELT doesn't function.

We all have our own risk tolerance and experiences.  It is very sad when there's a bad outcome that could have been saved with straightforward application of existing technology.