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bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Fri Feb 10, 2006 7:28 am Post subject: antennas

Responding to an AeroElectric-List message previously posted by: "bob noffs" 

<icubob(at)newnorth.net>



2/10/2006



Hello Bob, Dare I post some heresy? Will the gummint sic its watch dogs on 

me? Will the electromagnetic radiation purists on the list rise up in total 

fury to slap me down? Well, I'll take a chance.



Suppose that the gummint, in its infinite wisdom, mandated that every 

aircraft carry 3 pounds of butter and a container of maple syrup just in 

case the survival situation after crashing resulted in a supply of pancakes 

as the available food supply. Would you insist on carrying genuine maple 

syrup or would an imitation be good enough for you?



Maybe an ELT is a little more useful than butter and maple syrup in a crash 

situation, but I sure as hell wouldn't place my entire faith in being found 

and rescued in one of the garden variety ELT's that we are mandated to 

carry. My point is that obsessing over antenna ground plane details is 

wasted time.



Nobody knows exactly what attitude their aircraft will be in when it 

finishes crashing. The ELT antenna could end up pointing directly down at, 

and a few inches from, the surface of the earth. How much difference would a 

perfect ground plane, if one could construct one, make in that situation?



Here is my thinking:



1) To be legal, buy one of the garden variety ELT's that we are mandated to 

carry. Install it securely in the proper location in the proper attitude 

with regard to its deceleration sensor. Fasten on the wire antenna that came 

with the ELT and don't obsess over ground planes or what the antenna's 

attitude will be when you finish crashing. Go fly.



2) If you want to take some truly effective steps for rescue after crashing 

you can, and probably should to the degree that you are concerned and 

considering routes of flight, do some or all of the following.



2A) Always carry a hand held VHF comm radio with a battery supply that you 

KNOW to be capable of extended operation.



2B) Always carry a cell phone with a battery supply that you KNOW to be 

capable of extended operation.



2C) Purchase and carry a PLB http://www.equipped.com/faq_plb/default.asp



2D) Carry a tough plastic container of water -- size your choice. My 

experience with even short time rescued people is that they experienced an 

almost mentally debilitating thirst shortly after crashing.



2E) Carry a knife of enough size and sturdiness to punch through / crack 

your plastic windows and canopy.



I am sure that other posters will add their favorite / essential crash 

survival items, but obsessing over these items falls into the same category 

of time wasting like obsessing over ground planes. Take what you deem to be 

reasonable precautions to be rescued after a survivable crash and then 

proceed to fly worry and guilt free (and legal).



OC



PS: If you have the bank account to afford one of the new 406 Mhz ELT's, go 

for it.



<< hi all, I have several antennas to install. My elt requires a ground 

plane. Tim at b and

c was very helpful with my questions but i question leads to 5 more. Is 

there

any way around a ground plane for the elt? If not, any suggestions on how to

make it in my wood/cloth fuselage? At first i thought numerous strips of 

thin

copper way the way to go but that looks like just more fasteners. Can a very

thin sheet be laid down in the fuse. bottom? It wouldnt exactly be flat with

all the woodworking to go around.....skip.....Thanks in advance, bob noffs>>

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ruebd(at)skymail.csus.edu
Guest

Posted: Fri Feb 10, 2006 9:04 am Post subject: antennas

OC.  



	Well, now on the topic of the Maple syrup that we should carry,

even though my own preference would be for the genuine stuff, the

imitation would be more practical due to storage considerations, now, of

course, we know that refrigeration is required for the genuine after

opening, and is even a good idea with the fake stuff, but who can

guarantee that some hungry passenger, or pilot, would not have violated

the seal and  had a taste before we had our emergency event.  Wow, these

things do get complicated.  Good we have the Gummint working on this for

us. 

	On a serious vein, what is the advantage of the 406 Mhz ones, is

it just the smaller dimensions needed for antenna and ground plane? Or

is there some other factor involved?



Duane Rueb, KF6GYB & PG-12-32627, also Kitfox N24ZM

--

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wjrhamilton(at)optusnet.c
Guest

Posted: Fri Feb 10, 2006 7:01 pm Post subject: antennas

Folks,

In Australia, legislation to mandate fixed ELT in all GA aircraft was 

defeated in the Parliament, after a lobbying campaign by AOPA Australia.



We do have legislation for the mandatory carriage of handheld 

ELT/EPIRB ( your PLB) on all flights over 50 miles from base.



The statistics are stark, in actual crash scenarios, the failure rate 

of fixed ELT is around 95%.

The most common cause of failure is the disruption of the antenna or 

the aerial cable from the box to the antenna, for all the reasons you 

can think of.



Another common reason is that the aircraft is in the water , 100% of 

ELT's do not work under water. Post accident fire, prior internal 

failure etc, are common additional causes.



In contrast, in survivable accidents, 100% of hand held ELT have 

worked. In non-survivable accidents, all you are talking about is 

saving search costs. Given what little information is available in 

the US ( I did a lot of work jointly with the Civil Air Patrol on the 

subject) the 95% + failure rate holds good in the US ---- As you 

might expect, given the causes of failure are inherent in the 

design/installation of fixed ELT.



Remember that the US legislation to mandate ELT bypassed all the 

usual consultation, cost benefit analysis etc, it was a knee jerk 

political reaction to the loss of an aircraft in Alaska, I don't 

recall if it was a Congressman or Senator that was lost. There is 

absolutely NO evidence to show that the outcome of that accident 

would have  been any different had the aircraft been fitted with an 

ELT, statistically there was a better than 95% failure probability. 

Given actual accident, the failure probability was closer to 100%.



In view of phasing out the COSPAR/SARSAT on 121.5/243, in accord with 

the latest specifications for new generation ELT, commodity priced 

400 mcs GPS/ELT are now available.



Interestingly, because of the low cost of an ELT, their use is 

widespread, even Forest Service type organisations ( the name varies 

state by state) rent ELT to hikers who do not have their own, most 4 

Wheel Drivers carry one now, if they are in a remote area.



In short, fixed ELT are a total waste on money.



Even in three airline accidents ( all Airbus) that we could track 

down, where the tail mounted ELT survived in-tact in a largely intact 

tail section, all three ELT failed to transmit a useable signal.



Cheers,

Bill Hamilton.





At 21:28 10/02/2006, you wrote:

 	  Quote: 	
		  



Responding to an AeroElectric-List message previously posted by: "bob noffs"

<icubob(at)newnorth.net>



2/10/2006



Hello Bob, Dare I post some heresy? Will the gummint sic its watch dogs on

me? Will the electromagnetic radiation purists on the list rise up in total

fury to slap me down? Well, I'll take a chance.



Suppose that the gummint, in its infinite wisdom, mandated that every

aircraft carry 3 pounds of butter and a container of maple syrup just in

case the survival situation after crashing resulted in a supply of pancakes

as the available food supply. Would you insist on carrying genuine maple

syrup or would an imitation be good enough for you?



Maybe an ELT is a little more useful than butter and maple syrup in a crash

situation, but I sure as hell wouldn't place my entire faith in being found

and rescued in one of the garden variety ELT's that we are mandated to

carry. My point is that obsessing over antenna ground plane details is

wasted time.



Nobody knows exactly what attitude their aircraft will be in when it

finishes crashing. The ELT antenna could end up pointing directly down at,

and a few inches from, the surface of the earth. How much difference would a

perfect ground plane, if one could construct one, make in that situation?



Here is my thinking:



1) To be legal, buy one of the garden variety ELT's that we are mandated to

carry. Install it securely in the proper location in the proper attitude

with regard to its deceleration sensor. Fasten on the wire antenna that came

with the ELT and don't obsess over ground planes or what the antenna's

attitude will be when you finish crashing. Go fly.



2) If you want to take some truly effective steps for rescue after crashing

you can, and probably should to the degree that you are concerned and

considering routes of flight, do some or all of the following.



2A) Always carry a hand held VHF comm radio with a battery supply that you

KNOW to be capable of extended operation.



2B) Always carry a cell phone with a battery supply that you KNOW to be

capable of extended operation.



2C) Purchase and carry a PLB http://www.equipped.com/faq_plb/default.asp



2D) Carry a tough plastic container of water -- size your choice. My

experience with even short time rescued people is that they experienced an

almost mentally debilitating thirst shortly after crashing.



2E) Carry a knife of enough size and sturdiness to punch through / crack

your plastic windows and canopy.



I am sure that other posters will add their favorite / essential crash

survival items, but obsessing over these items falls into the same category

of time wasting like obsessing over ground planes. Take what you deem to be

reasonable precautions to be rescued after a survivable crash and then

proceed to fly worry and guilt free (and legal).



OC



PS: If you have the bank account to afford one of the new 406 Mhz ELT's, go

for it.



<< hi all, I have several antennas to install. My elt requires a ground

plane. Tim at b and

c was very helpful with my questions but i question leads to 5 more. Is

there

any way around a ground plane for the elt? If not, any suggestions on how to

make it in my wood/cloth fuselage? At first i thought numerous strips of

thin

copper way the way to go but that looks like just more fasteners. Can a very

thin sheet be laid down in the fuse. bottom? It wouldnt exactly be flat with

all the woodworking to go around.....skip.....Thanks in advance, bob noffs>>






	




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