Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

406 MHz ELT

Matronics Email Lists Forum Index -> RV-List

View previous topic :: View next topic

Author Message

dean.psiropoulos(at)veriz
Guest

Posted: Mon Nov 17, 2008 7:45 pm Post subject: 406 MHz ELT

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.

jsflyrv(at)verizon.net
Guest

Posted: Mon Nov 17, 2008 9:02 pm Post subject: 406 MHz ELT

DEAN PSIROPOULOS wrote:



 	  Quote: 	
		  

  




	


 	  Quote: 	
		  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

skylor4(at)yahoo.com
Guest

Posted: Mon Nov 17, 2008 9:37 pm Post subject: 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(at)verizon.net> wrote:

[quote]From: DEAN PSIROPOULOS <dean.psiropoulos(at)verizon.net>

Subject: 406 MHz ELT

To:  rv-list(at)matronics.com

Date: Monday, November 17, 2008, 7:43 PM



[quote]--> RV-List message posted by: "DEAN PSIROPOULOS"

<dean.psiropoulos(at)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           [quote][b]

timb

Joined: 16 Apr 2008
Posts: 77
Location: Frankston, Texas

Posted: Tue Nov 18, 2008 5:54 am Post subject: 406 MHz ELT

I have my antenna mounted just in front of the vertical stabilizer.  My

thinking was in a rollover the stabilizer *might* protect the antenna from

being smashed.  Now I am wondering if the stabilizer causes any shielding of

the signal.  Dean, any thoughts on that?



Tim Bryan

RV-6 Flying

N616TB over 100 hours now



[quote] --

_________________
Tim Bryan
RV-6 Flying
N616TB

gyoung

Joined: 09 Jan 2006
Posts: 211
Location: Republic of Texas

Posted: Tue Nov 18, 2008 9:17 am Post subject: 406 MHz ELT

Regardless of where you choose to mount the antenna and for whatever reason,

consider the routing of the cable from the ELT to the antenna. If you route

it through or near bulkheads or metal edges, it can be severed in a crash.

My ELT was mounted on the keel by the elevator bellcrank in my -6, the

antenna on the seatback cross member and the cable routed under the baggage

floor and thru the rear spar bulkhead. Although my crash was upright, the

cable was severed by the crushed and twisted structure. No signal was ever

detected. I'm keeping the cable for the new one inside the tailcone with the

antenna somewhere back there too.



Regards,

Greg Young

 



[quote] --

timb

Joined: 16 Apr 2008
Posts: 77
Location: Frankston, Texas

Posted: Tue Nov 18, 2008 11:08 am Post subject: 406 MHz ELT

Excellent point Greg!  I mounted my ELT in the baggage compartment up

against the baggage closure and the cable runs through the tail cone but not

through any holes.  It is tie wired to the formers and hopefully that

wouldn't be an issue.  I hadn't thought of that, just did it that way as it

was easy. 



Tim Bryan

RV-6 Flying

N616TB over 100 hours now



[quote] --

_________________
Tim Bryan
RV-6 Flying
N616TB

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Tue Nov 18, 2008 11:34 am Post subject: 406 MHz ELT

Bob Collins asked a question that has not yet been directly answered.

The question I wanted expanded was to clarify for the masses that 121.5

ELTs have been installed without much consideration for intended

function.  Vanity and foolhearty following the builder before you leads

to widely accepted misunderstandings.  "Oh, I did it because twenty

other guys in my EAA chapter have done the same thing and it seemed

okay".



Stein has not answered if he can measure the strength and directional

pattern or who else might.  Bob is still waiting for more clarity.

Several have made excellent posts.  My question remaining is what is the

required polarity needed (Horizontal or Vertical), how will that antenna

installed work in the event the required device is needed as in the case

of Steve Fossett.  Several posters added anecdotes on lives lost because

ELTS don't work as needed (which may often be because of installation

errors).  We should all know those errors.  We should know how effective

our installed antennae are working. We should be protective of the

distance and routing of the coax (Bob's question).  Just because you can

get an annunciation during a test function does not mean that the

aircraft can be located before the battery goes dead from a few thousand

yards away.



Antenna propagation is still on the table.  The idea of a belly mounted

antenna because so many flip over or are stuck nose down is an

interesting one.



John Cox

W7COX

RV builder #40600



--

michele.delsol(at)microsi
Guest

Posted: Tue Nov 18, 2008 12:19 pm Post subject: 406 MHz ELT

I had asked the question - how about two antennas, one top side and one

belly mounted, via a splitter. Is that an option ?



Thanks,

Michèle

-----Message d'origine-----

De : owner-rv-list-server(at)matronics.com

[mailto:owner-rv-list-server(at)matronics.com] De la part de John Cox

Envoyé : mardi 18 novembre 2008 20:34

À : rv-list(at)matronics.com

Objet : RE: 406 MHz ELT






Bob Collins asked a question that has not yet been directly answered.

The question I wanted expanded was to clarify for the masses that 121.5

ELTs have been installed without much consideration for intended

function.  Vanity and foolhearty following the builder before you leads

to widely accepted misunderstandings.  "Oh, I did it because twenty

other guys in my EAA chapter have done the same thing and it seemed

okay".



Stein has not answered if he can measure the strength and directional

pattern or who else might.  Bob is still waiting for more clarity.

Several have made excellent posts.  My question remaining is what is the

required polarity needed (Horizontal or Vertical), how will that antenna

installed work in the event the required device is needed as in the case

of Steve Fossett.  Several posters added anecdotes on lives lost because

ELTS don't work as needed (which may often be because of installation

errors).  We should all know those errors.  We should know how effective

our installed antennae are working. We should be protective of the

distance and routing of the coax (Bob's question).  Just because you can

get an annunciation during a test function does not mean that the

aircraft can be located before the battery goes dead from a few thousand

yards away.



Antenna propagation is still on the table.  The idea of a belly mounted

antenna because so many flip over or are stuck nose down is an

interesting one.



John Cox

W7COX

RV builder #40600



--

gyoung

Joined: 09 Jan 2006
Posts: 211
Location: Republic of Texas

Posted: Tue Nov 18, 2008 2:28 pm Post subject: 406 MHz ELT

Another reality is access after the crash may not be easy or even possible

if you're thinking you can actually use the portability feature of the ELT.

Fasteners that were normally accessible may be blocked by bent metal or even

bent themselves. I had to cut a hole to get mine out of the salvage. EPLB's

probably make more sense if you want to assure use in the aftermath.



Regards,

Greg Young

 



[quote] --

ronlee(at)pcisys.net
Guest

Posted: Tue Nov 18, 2008 3:01 pm Post subject: 406 MHz ELT

EPLB's > probably make more sense if you want to assure use in the 

aftermath.



PLBs...unless the terms have changed.  EPIRBs are boat units.



Ron Lee

dean.psiropoulos(at)veriz
Guest

Posted: Wed Nov 19, 2008 9:18 pm Post subject: 406 MHz ELT

Just in front of the vertical stab is still a very good location (mine is

about 18 inches forward of the vertical stab).  Since the vertical

stabilizer is quite narrow and parallel to the antenna there will be very

little interference or reflection off of the leading edge.  It's the folks

who have mounted the ELT antenna underneath the fiberglas tail intersection

fairing that are really limiting their usefulness.  In that location the

antenna is mounted horizontally on the aft turtle deck bulkhead (RV-6/7/9)

projecting out into the 90 degree corner created by the intersection of the

vertical and horizontal stabilizers.  That creates an excellent waveguide

effect, blocking the signal from reaching half of the area on the other side

of the aircraft.



Jerry, I understand the thinking about putting the antenna on the bottom and

it's another one of those multitude of "what if" scenarios that we RV

builders run through our heads so many times while we're building.  I guess

to answer that somebody has to do some research on how many downed RVs have

ended up on their backs.  I have heard of several but don't know just what

percentage of ALL RV accidents they actually make up.  If you put it under

the wing and you stay right side up in a crash, you will be attenuating a

good bit of the signal and shortening the range at which you can be

detected.  If you put it between the trailing edge of the wing and the

forward edge of the horizontal stab (top or bottom of fuselage) your range

should be quite good (right side up or upside down).  Then you have to start

thinking about how to keep the antenna from being ripped off in the crash

(Tim Bryan's idea).  And so the thought process goes... sometimes being a

safety analyst makes my brain hurt but, more food for thought.  



Dean Psiropoulos

RV-6A N197DM

[quote] --

t.gummo(at)verizon.net
Guest

Posted: Wed Nov 19, 2008 10:10 pm Post subject: 406 MHz ELT

Dean and all,



I would like to add one more thought about where to put the ELT antenna.

It shouldn't be what percentage land on their backs but ...

If the plane stay upright, there is a great chance that I am relatively OK,

and the ELT will be the least of my problems,

however, if the plane ends up on its back, then the crash was not controlled 

and there will be a good chance that I am NOT OK.

And any help the ELT can be might make all the difference.



Of course, there is no good answer for crashing.  And remember most things 

on the ground are harder than your plane.  



Lets hope no one has need of their ELT.



GummiBear

Air Force Chief of Safety at Incirlik AB, Turkey (many years ago)



---

panamared5(at)brier.net
Guest

Posted: Thu Nov 20, 2008 8:30 am Post subject: 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?  

   

How about in front of the canopy.  On the wing, or on the fuselage side angled up at a 45 degrees.  Recommendation: do what ever you want, it is your airplane.  

   

What I like about this list is we can truly beat a horse to death!  

   

Bob  

RV6 “Wicked Witch of the West”  

       [quote][b]

Display posts from previous:

	Matronics Email Lists Forum Index -> RV-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum