Today's Message Index:
----------------------
1. 01:41 AM - Re: ARTEX 406 ELT in a 7A ()
2. 05:18 AM - Re: Re: ARTEX 406 ELT in a 7A (Kelly McMullen)
3. 05:43 AM - Re orig question from Bob C (Charles Heathco)
4. 05:47 AM - Re: Trio Auto Pilot FS (PaulR)
5. 06:35 AM - Re: ARTEX 406 ELT in a 7A (bcollinsmn)
6. 01:06 PM - RV : [ Rob Ray ] : New Email List PhotoShare Available! (Email List PhotoShares)
7. 01:07 PM - RV : [ Al Herron ] : New Email List PhotoShare Available! (Email List PhotoShares)
8. 07:45 PM - 406 MHz ELT (DEAN PSIROPOULOS)
9. 09:02 PM - Re: 406 MHz ELT (Jerry Springer)
10. 09:37 PM - Re: 406 MHz ELT (Skylor Piper)
11. 11:34 PM - Re: 406 MHz ELT and RV8 (=?iso-8859-1?Q?Mich=E8le_W?=)
Message 1
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Subject: | Re: ARTEX 406 ELT in a 7A |
John as a fellow HAM, you know the answer, external, vertical polarization with
a good ground plane. No one has tested these creative internal ELT antenna installations.
It may be fine in a Lancair or Glasair but a all metal RV is not
a good canadate for internal antennas. I can tell you the VHF wing tip com antenna's
are really piss poor. Any one who has one and is honest will tell you.
Some say the wing tip VHF com antenna works. The definition of work is flying
1000' agl towards the airport tower 5 miles infront of you. Forget long distance
omni directional communications at max theoretical range of an airborne 5-10
watt VHF transmitter.
One popular hidden ELT antenna location on RV's is laying the antenna horizontal
in the vertical/horz stab intersection fairing area, under the vertical stabilizer.
It is pretty popular and makes no sense to me from a technical stand
point. I DON'T KNOW OF ANY ONE WHO HAS TESTED IT FORMALLY or INFORMALLY. I personally
think its a bad idea. Hidden use but affective range limited.
The other idea is in the wing but that is a LONG coax run unless you put the
ELT in the wing tip as well. The wing tip is also really terrible for propagation
and practical reasons, like the wing tip rips off. Also access is not great
unless you install an access panel.
The Artex 406 has one antenna for both 406/121.5Mhz about the same dimensions
as current ELT antennas.
The EBC has two antennas, one short 406Mhz antenna and a seperate 121.5 Mhz antenna.
Of course the 406Mhz is very short.
HERE IS SOME FOOD FOR THOUGHT. The DRAG from one typical (20") ELT antenna is
1/8th mph, 0.125 mph penalty (at 200 mph). Is it worth it to hide antennas?
If you are talking about a 406 Mhz only antenna that is a short antenna with
negligible drag. When I raced my RV-4 I took off the Com, VOR antennas for about
1/2 mph to 2/3rds mpg gain. I did put the ELT antenna under the bubble canopy.
Some hide antenna for eye appeal. I think it's not worth it but that is a hard
sale with many builders I consult with.
I think the best NON standard is mounting the antenna or antennas inside the
canopy/cockpit area. The down side is getting a proper ground plane. The old EBC
elts had an internal antenna and the unit was always mounted in the cabin.
The new EBC uses two remote antennas as I mentioned above.
I did a informal survey of RV accidents that where off field and survivable;
many end up on their back, so the belly is not totally a horrible area. That does
not follow the common ELT instructions for mounting the ELT on top of the
aircraft.
Of course any thing that does not follow the ELT's instructions violates the
FAR / STC approved instructions.
Almost all approved ELT installations call for the following:
- Mount ELT as far aft as possible
- Antenna'(s) be mounted close by, no excessive long coaxial run
- Mount the antenna externally.
- Provide maintence access & access after accident
So the approved ideal location is ELT in the tail cone far aft with the antenna'(s)
mounted directly above on the back top, just forward of Vert stabilizer.
The old transmitter was only 100mw and now the new 406 ELT's have 5 watt burst,
so that is better regardless of antenna. Still of the antenna is shielded from
the satellites than you are invisible even with 5 watts. We also still need
121.5 Mhz and 100mw for local DF steer to find us. How far can can 100mw get
out with an antenna buried inside of metal structure? I think you are talking
feet not miles in range.
I just can't stand to see such a violation of good antenna installation practices
for the sake of looks and a tenth of a mph.
Cheers George
*************************************************************************************************
Subject: RE: RV-List: Re: ARTEX 406 ELT in a 7A
From: "John Cox" <johnwcox@pacificnw.com>
Bob, I am hoping that this thread actually expands and becomes a Big
Deal, or at least bigger.
I have felt for some time that the location, mount orientation, ground
plane and attempt at concealing the antenna actually leads to an
ineffective or nearly worthless electronic device. That premise was
based on the 121.5 variant not the 406 however, because one build might
have mounted it incorrectly, scores follow suit and then the masses
drink the Kool-Aid. I have always concluded the function might not be
important, only its presence for the DAR signoff.
I have remained curious how many rescues rather than recoveries "after
the fact" are attributed to a properly functioning signal and a
responsible response by the parties that monitor the frequency (either
121.5 or 406.
As a ham (amateur) radio license holder this pursuit of concealing the
antenna has always been fascinating. Do any of the readers have signal
propagation graphs on signal strength radiating from inside the tin
can?
John Cox
Aurora, OR
Message 2
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Subject: | Re: ARTEX 406 ELT in a 7A |
Well just some random musings. I know of TC aircraft with the ELT
antenna bent back under fiberglass ventral fin in otherwise all metal
aircraft..but don't know whether any feds cared about it. I know that my
121 ELT activated on its own in my all metal hangar, and was satellite
detected. Only the weird propagation pattern made it a little difficult
to ascertain it was coming from my hangar and not an ajacent row. So,
not so sure how critical this is, especially at 406 where your radiating
element is approx 1/4 the length of 121 element. Ever look at a police
supervisor car? They often have 5 or 6 UHF antennas around the roof and
trunk, not very far apart. Wonder what issues they have.
gmcjetpilot@yahoo.com wrote:
> John as a fellow HAM, you know the answer, external, vertical
> polarization with a good ground plane. No one has tested these
> creative internal ELT antenna installations. It may be fine in a
> Lancair or Glasair but a all metal RV is not a good canadate for
> internal antennas. I can tell you the VHF wing tip com antenna's are
> really piss poor. Any one who has one and is honest will tell you.
> Some say the wing tip VHF com antenna works. The definition of work is
> flying 1000' agl towards the airport tower 5 miles infront of you.
> Forget long distance omni directional communications at max
> theoretical range of an airborne 5-10 watt VHF transmitter.
>
> One popular hidden ELT antenna location on RV's is laying the antenna
> horizontal in the vertical/horz stab intersection fairing area, under
> the vertical stabilizer. It is pretty popular and makes no sense to me
> from a technical stand point. I DON'T KNOW OF ANY ONE WHO HAS TESTED
> IT FORMALLY or INFORMALLY. I personally think its a bad idea. Hidden
> use but affective range limited.
>
> The other idea is in the wing but that is a LONG coax run unless you
> put the ELT in the wing tip as well. The wing tip is also really
> terrible for propagation and practical reasons, like the wing tip rips
> off. Also access is not great unless you install an access panel.
>
> The Artex 406 has one antenna for both 406/121.5Mhz about the same
> dimensions as current ELT antennas.
>
> The EBC has two antennas, one short 406Mhz antenna and a
> seperate 121.5 Mhz antenna. Of course the 406Mhz is very short.
>
> HERE IS SOME FOOD FOR THOUGHT. The DRAG from one typical (20") ELT
> antenna is 1/8th mph, 0.125 mph penalty (at 200 mph). Is it worth it
> to hide antennas?
>
> If you are talking about a 406 Mhz only antenna that is a short
> antenna with negligible drag. When I raced my RV-4 I took off the Com,
> VOR antennas for about 1/2 mph to 2/3rds mpg gain. I did put the ELT
> antenna under the bubble canopy.
>
> Some hide antenna for eye appeal. I think it's not worth it but that
> is a hard sale with many builders I consult with.
>
> I think the best NON standard is mounting the antenna or antennas
> inside the canopy/cockpit area. The down side is getting a proper
> ground plane. The old EBC elts had an internal antenna and the unit
> was always mounted in the cabin. The new EBC uses two remote antennas
> as I mentioned above.
>
> I did a informal survey of RV accidents that where off field and
> survivable; many end up on their back, so the belly is not totally a
> horrible area. That does not follow the common ELT instructions for
> mounting the ELT on top of the aircraft.
>
> Of course any thing that does not follow the ELT's
> instructions violates the FAR / STC approved instructions.
>
> Almost all approved ELT installations call for the following:
>
> - Mount ELT as far aft as possible
> - Antenna'(s) be mounted close by, no excessive long coaxial run
> - Mount the antenna externally.
> - Provide maintence access & access after accident
>
> So the approved ideal location is ELT in the tail cone far aft with
> the antenna'(s) mounted directly above on the back top, just forward
> of Vert stabilizer.
>
> The old transmitter was only 100mw and now the new 406 ELT's have 5
> watt burst, so that is better regardless of antenna. Still of the
> antenna is shielded from the satellites than you are invisible even
> with 5 watts. We also still need 121.5 Mhz and 100mw for local DF
> steer to find us. How far can can 100mw get out with an antenna buried
> inside of metal structure? I think you are talking feet not miles in
> range.
>
> I just can't stand to see such a violation of good antenna
> installation practices for the sake of looks and a tenth of a mph.
>
> Cheers George
>
>
>
> *************************************************************************************************
> Subject: RE: RV-List: Re: ARTEX 406 ELT in a 7A
> From: "John Cox" <johnwcox@pacificnw.com
> <http://us.f431.mail.yahoo.com/ym/Compose?To=johnwcox@pacificnw.com&YY=17621&y5beta=yes&y5beta=yes&order=down&sort=date&pos=0&view=a&head=b>>
>
>
> Bob, I am hoping that this thread actually expands and becomes a Big
> Deal, or at least bigger.
>
> I have felt for some time that the location, mount orientation, ground
> plane and attempt at concealing the antenna actually leads to an
> ineffective or nearly worthless electronic device. That premise was
> based on the 121.5 variant not the 406 however, because one build might
> have mounted it incorrectly, scores follow suit and then the masses
> drink the Kool-Aid. I have always concluded the function might not be
> important, only its presence for the DAR signoff.
>
> I have remained curious how many rescues rather than recoveries "after
> the fact" are attributed to a properly functioning signal and a
> responsible response by the parties that monitor the frequency (either
> 121.5 or 406.
>
> As a ham (amateur) radio license holder this pursuit of concealing the
> antenna has always been fascinating. Do any of the readers have signal
> propagation graphs on signal strength radiating from inside the tin
> can?
>
> John Cox
> Aurora, OR
>
> *
>
> *
Message 3
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Subject: | Re orig question from Bob C |
I didnt build my plane, but the ELT instal does work well (I have tested
it accidently couple times) Unit is mounted on side of Fusl midway in
baggage far enuf forward to give clearance to remove bulkhead. Thin flex
whip ant mounted just aft of where open canopy rests. Charles H
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Subject: | Re: Trio Auto Pilot FS |
> Would like to know what is the name of the unit etc. never heard of
> golden trio." I am looking for the Altitude Holder....
> thanks for any info
>
Robert,
The "Gold" servo is the ONLY one Trio has. It will work with either axis.
The Trio unit will also work with the old Navaid servos if I'm not mistaken.
I have only the servo and the install kit for sale.
--------
Paul Rose
N417PR (res)
RV-9A
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=214659#214659
Message 5
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Subject: | Re: ARTEX 406 ELT in a 7A |
[quote="stein(at)steinair.com"]The do not archive was because this was to settle
my personal curiosity more
than anything else. I didn't have anything to add to the technical part of
the discussion, so I guess I just didn't want my weird question filling up
the already bloated archives
do not archive (just to make Bob shake his fist at me) !!!
> --
Your personal curiosity is our enlightenment, fella! (g) When you ask a question....
it makes me think it's an answer I NEED!
Do not archive
--------
Bob Collins
St. Paul, Minn.
RV-7A (#&^ fiberglass!)
http://rvbuildershotline.com
Day job: http://minnesota.publicradio.org/collections/special/columns/news_cut/
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=214665#214665
Message 6
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Subject: | RV : [ Rob Ray ] : New Email List PhotoShare Available! |
A new Email List PhotoShare is available:
Poster: Rob Ray <smokyray@rocketmail.com>
Lists: RV-List,Rocket-List,RV4-List,RV8-List
Subject: Vets Day Fly-By...
http://www.matronics.com/photoshare/smokyray@rocketmail.com.11.17.2008
----------------------------------------------------------
o Main PhotoShare Index
http://www.matronics.com/photoshare
o Submitting a PhotoShare
If you wish to submit a PhotoShare of your own, please include the
following information along with your email message and files:
1) Email List or Lists that they are related to:
2) Your Full Name:
3) Your Email Address:
4) One line Subject description:
5) Multi-line, multi-paragraph description of topic:
6) One-line Description of each photo or file:
Email the information above and your files and photos to:
pictures@matronics.com
----------------------------------------------------------
Message 7
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Subject: | RV : [ Al Herron ] : New Email List PhotoShare Available! |
A new Email List PhotoShare is available:
Poster: Al Herron <herronpvf@sbcglobal.net>
Lists: RV-List
Subject: Canopy Slide Seal Lanyard
http://www.matronics.com/photoshare/herronpvf@sbcglobal.net.11.17.2008
----------------------------------------------------------
o Main PhotoShare Index
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o Submitting a PhotoShare
If you wish to submit a PhotoShare of your own, please include the
following information along with your email message and files:
1) Email List or Lists that they are related to:
2) Your Full Name:
3) Your Email Address:
4) One line Subject description:
5) Multi-line, multi-paragraph description of topic:
6) One-line Description of each photo or file:
Email the information above and your files and photos to:
pictures@matronics.com
----------------------------------------------------------
Message 8
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|
When I was flying missions with Civil Air Patrol in the State of Oregon we
had far more 121.5 ELT false alarms than real activations but...we responded
to every one of them and learned some lessons along the way. Most of the
missions I was associated with were production spam cans who had their
antennas mounted on top of the fuselage behind the cockpit. Yes it's ugly
but they put them there for a reason. When the ELT IS activated in a crash,
these installations have the BEST chance of being located by search and
rescue (SAR).
Scott's waveguide premise is correct, the cockpit does make a great one and
NO that is not helpful in getting one located and rescued in a timely
manner. If you land (crash) right side up that waveguide will direct the ELT
signal upward where the satellites will receive it. But, once the 121.5 ELT
is heard by the satellite and a SAR aircraft dispatched, the area to be
searched is still quite large. The SAR aircraft has to be able to "hear" the
ELT in order to pinpoint you. If your installation is in the cockpit then
this waveguide effect means that the SAR aircraft's direction finding (DF)
equipment needs to be A LOT closer to you to pick up the signal. That takes
more time in the grid and eats up precious time getting help to a stricken
pilot who may be badly injured.
This waveguide effect was brought home to me quite vividly on one CAP
practice mission where our incident commander placed the ELT inside a metal
garbage can and then tipped the can on its side with the open end facing a
mountain peak. We spent hours with the direction finder pointed at the
mountain listening to the reflected signal from the garbage can waveguide
and searched all over that mountain but never located the "stricken"
aircraft. A frustrating exercise but very eye opening.
John is correct, the practical value of "hiding" the ELT antenna along the
roll bar or under the tail fairing is ZILCH!!! I just finished my RV-6A and
mounted the ELT antenna on the top of the fuselage behind the sliding
canopy. Yup it's ugly sticking up there but...if I do go down and the unit
is activated, that location gives me the best chance of being found as fast
as possible. Yes I know the activation rate is not that great but...you
spent good money on and are installing a tool that could save your life in
an emergency so why not give yourself the best chance of having it do some
good.
Since 406 MHz ELTs still use radio waves to perform their magic, everything
I just mentioned applies. There will be a lot fewer false alarms on the 406
ELTs IF AND ONLY IF all you aviators out there fill out your registration
cards and mail them in. Then, when the USAF search and rescue center gets
your signal they can phone you right away and find out whether it's just a
false alarm or a real emergency. The good news is, if it's a real emergency
the satellites will pick up your 406 MHz signal quicker and locate you
within a smaller radius of area. The only down side is for the SAR team,
the 406 ELTs send out a burst of data every so often as opposed to the
continuous transmission of the 121.5 units. This makes DF tracking a little
more difficult but you should still be found much more quickly than before.
Recommendation: read the instructions that come with your unit and mount the
antenna where they say to do so. If no instruction, mount on top of the wing
or fuselage in an open area with the least potential for reflections. And
PLEASE PLEASE register your unit. I live in Florida now where boaters have
had 406 MHz EPIRBs for a long time. Problem is, there are still lots of
false alarms because boaters have a dismal record of registering their
units!! Fill out that card and send it in.
Dean Psiropoulos
RV-6A N197DM
First flight scheduled for this Saturday.
Message 9
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DEAN PSIROPOULOS wrote:
>
>
>I just finished my RV-6A and
>mounted the ELT antenna on the top of the fuselage behind the sliding
>canopy. Yup it's ugly sticking up there but...if I do go down and the unit
>is activated, that location gives me the best chance of being found as fast
>as possible.
>
>Dean Psiropoulos
>RV-6A N197DM
>First flight scheduled for this Saturday.
>
>
>
>
Of course it well not do much good if you are inverted and the antenna
is bent over
against the fuselage or is broken off.
I am one of those people that mounted mine inside under the roll over
frame on a tip up, it
has just as much chance of working there as anywhere else.
Jerry
do not archive
Message 10
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All of this discussion regarding mounting of the ELT antenna is very intere
sting and eye opening, but we -8 builders have one issue:- There is simpl
y no place on top of the fuselage to mount the antenna because the canopy o
n the -8 slides all they way back to the vertical stabilizer when it's open
!- As far as I can tell, this leaves only the options of mounting the ant
enna in the cockpit, or underneath the empennage fairing as others have don
e.- Anyone have any other suggestions?
Skylor
RV-8 under construction (getting close)
--- On Mon, 11/17/08, DEAN PSIROPOULOS <dean.psiropoulos@verizon.net> wrote
:
From: DEAN PSIROPOULOS <dean.psiropoulos@verizon.net>
Subject: RV-List: 406 MHz ELT
<dean.psiropoulos@verizon.net>
When I was flying missions with Civil Air Patrol in the State of Oregon we
had far more 121.5 ELT false alarms than real activations but...we responde
d
to every one of them and learned some lessons along the way. Most of the
missions I was associated with were production spam cans who had their
antennas mounted on top of the fuselage behind the cockpit. Yes it's ugly
but they put them there for a reason. When the ELT IS activated in a crash,
these installations have the BEST chance of being located by search and
rescue (SAR).
Scott's waveguide premise is correct, the cockpit does make a great one and
NO that is not helpful in getting one located and rescued in a timely
manner. If you land (crash) right side up that waveguide will direct the EL
T
signal upward where the satellites will receive it. But, once the 121.5 ELT
is heard by the satellite and a SAR aircraft dispatched, the area to be
searched is still quite large. The SAR aircraft has to be able to
"hear" the
ELT in order to pinpoint you. If your installation is in the cockpit then
this waveguide effect means that the SAR aircraft's direction finding (DF)
equipment needs to be A LOT closer to you to pick up the signal. That take
s
more time in the grid and eats up precious time getting help to a stricken
pilot who may be badly injured.
This waveguide effect was brought home to me quite vividly on one CAP
practice mission where our incident commander placed the ELT inside a metal
garbage can and then tipped the can on its side with the open end facing a
mountain peak. We spent hours with the direction finder pointed at the
mountain listening to the reflected signal from the garbage can waveguide
and searched all over that mountain but never located the "stricken"
aircraft. A frustrating exercise but very eye opening.
John is correct, the practical value of "hiding" the ELT antenna
along the
roll bar or under the tail fairing is ZILCH!!! I just finished my RV-6A an
d
mounted the ELT antenna on the top of the fuselage behind the sliding
canopy. Yup it's ugly sticking up there but...if I do go down and the unit
is activated, that location gives me the best chance of being found as fast
as possible. Yes I know the activation rate is not that great but...you
spent good money on and are installing a tool that could save your life in
an emergency so why not give yourself the best chance of having it do some
good.
Since 406 MHz ELTs still use radio waves to perform their magic, everything
I just mentioned applies. There will be a lot fewer false alarms on the 40
6
ELTs IF AND ONLY IF all you aviators out there fill out your registration
cards and mail them in. Then, when the USAF search and rescue center gets
your signal they can phone you right away and find out whether it's just a
false alarm or a real emergency. The good news is, if it's a real
emergency
the satellites will pick up your 406 MHz signal quicker and locate you
within a smaller radius of area. The only down side is for the SAR team,
the 406 ELTs send out a burst of data every so often as opposed to the
continuous transmission of the 121.5 units. This makes DF tracking a littl
e
more difficult but you should still be found much more quickly than before.
Recommendation: read the instructions that come with your unit and mount th
e
antenna where they say to do so. If no instruction, mount on top of the win
g
or fuselage in an open area with the least potential for reflections. And
PLEASE PLEASE register your unit. I live in Florida now where boaters have
had 406 MHz EPIRBs for a long time. Problem is, there are still lots of
false alarms because boaters have a dismal record of registering their
units!! Fill out that card and send it in.
Dean Psiropoulos
RV-6A N197DM
First flight scheduled for this Saturday.
=0A=0A=0A
Message 11
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|
Subject: | 406 MHz ELT and RV8 |
I changed the subject because I feel that there is a definite issue as
to
ELT mounting on RV8s as Skylor mentioned.
The canopy slides back all the way against the vertical stabilizer
fairing '
so that leaves no room on the back deck. On the premise that the antenna
must be vertical, this leaves the following areas on the outside:
=B7 On top of the vertical stabilizer
=B7 Forward of the wind shield
=B7 On top of one of the wings ' certainly feasible but so
ugly!!!
=B7 On the rear of the canopy fairing ' ground plane issue ?
Furthermore would require that the antenna cable move back and forth
with
the canopy.
Inside of the cockpit would seem to be a bad compromise as it would not
be
vertical and would be close to metal, hence serious concerns as to its
transmission capabilities.
As to mounting it under the vertical stabilizer, horizontally, probably
a
bad compromise as the antenna is horizontal and masked by a fair amount
of
metal.
Then there is another issue. If the plane tips over during the crash,
then
all the topside locations are rendered useless.
Question : Is it OK to place two antennas on one line via a splitter or
are
splitters good only for receiving antennas such as VOR + ILS. If that
were
the case, then it would be possible to have two ELT antennas, one on top
and
one on the belly. The down side would be that if the belly antenna were
zapped during the crash, it might ground the cable and render the top
antenna useless.
Any thoughts ?
Mich=E8le
RV8
De : owner-rv-list-server@matronics.com
[mailto:owner-rv-list-server@matronics.com] De la part de Skylor Piper
Envoy=E9 : mardi 18 novembre 2008 06:32
=C0 : rv-list@matronics.com
Objet : Re: RV-List: 406 MHz ELT
All of this discussion regarding mounting of the ELT antenna is very
interesting and eye opening, but we -8 builders have one issue: There
is
simply no place on top of the fuselage to mount the antenna because the
canopy on the -8 slides all they way back to the vertical stabilizer
when
it's open! As far as I can tell, this leaves only the options of
mounting
the antenna in the cockpit, or underneath the empennage fairing as
others
have done. Anyone have any other suggestions?
Skylor
RV-8 under construction (getting close)
--- On Mon, 11/17/08, DEAN PSIROPOULOS <dean.psiropoulos@verizon.net>
wrote:
From: DEAN PSIROPOULOS <dean.psiropoulos@verizon.net>
Subject: RV-List: 406 MHz ELT
<dean.psiropoulos@verizon.net>
When I was flying missions with Civil Air Patrol in the State of Oregon
we
had far more 121.5 ELT false alarms than real activations but...we
responded
to every one of them and learned some lessons along the way. Most of
the
missions I was associated with were production spam cans who had their
antennas mounted on top of the fuselage behind the cockpit. Yes it's
ugly
but they put them there for a reason. When the ELT IS activated in a
crash,
these installations have the BEST chance of being located by search and
rescue (SAR).
Scott's waveguide premise is correct, the cockpit does make a great one
and
NO that is not helpful in getting one located and rescued in a timely
manner. If you land (crash) right side up that waveguide will direct the
ELT
signal upward where the satellites will receive it. But, once the 121.5
ELT
is heard by the satellite and a SAR aircraft dispatched, the area to be
searched is still quite large. The SAR aircraft has to be able to
"hear" the
ELT in order to pinpoint you. If your installation is in the cockpit
then
this waveguide effect means that the SAR aircraft's direction finding
(DF)
equipment needs to be A LOT closer to you to pick up the signal. That
takes
more time in the grid and eats up precious time getting help to a
stricken
pilot who may be badly injured.
This waveguide effect was brought home to me quite vividly on one CAP
practice mission where our incident commander placed the ELT inside a
metal
garbage can and then tipped the can on its side with the open end facing
a
mountain peak. We spent hours with the direction finder pointed at the
mountain listening to the reflected signal from the garbage can
waveguide
and searched all over that mountain but never located the "stricken"
aircraft. A frustrating exercise but very eye opening.
John is correct, the practical value of "hiding" the ELT antenna
along the
roll bar or under the tail fairing is ZILCH!!! I just finished my RV-6A
and
mounted the ELT antenna on the top of the fuselage behind the sliding
canopy. Yup it's ugly sticking up there but...if I do go down and the
unit
is activated, that location gives me the best chance of being found as
fast
as possible. Yes I know the activation rate is not that great but...you
spent good money on and are installing a tool that could save your life
in
an emergency so why not give yourself the best chance of having it do
some
good.
Since 406 MHz ELTs still use radio waves to perform their magic,
everything
I just mentioned applies. There will be a lot fewer false alarms on the
406
ELTs IF AND ONLY IF
all you aviators out there fill out your registration
cards and mail them in. Then, when the USAF search and rescue center
gets
your signal they can phone you right away and find out whether it's just
a
false alarm or a real emergency. The good news is, if it's a real
emergency
the satellites will pick up your 406 MHz signal quicker and locate you
within a smaller radius of area. The only down side is for the SAR
team,
the 406 ELTs send out a burst of data every so often as opposed to the
continuous transmission of the 121.5 units. This makes DF tracking a
little
more difficult but you should still be found much more quickly than
before.
Recommendation: read the instructions that come with your unit and mount
the
antenna where they say to do so. If no instruction, mount on top of the
wing
or fuselage in an open area with the least potential for reflections.
And
PLEASE PLEASE register your unit. I live
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