What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

IF YOU USE DURACELLS

I replace them at every annual, both the ELT proper and the remote.
It's cheap insurance.
 
I just had an annual done a few months ago on the PulsarXP I recently owned. The A&P I/A did the typical ELT tests which all passed. He then opened the ELT and looked at the Duracell batteries inside. The expiration date was March of 2008 (my annual was being done in May). He said to change them before the next annual, but they were technically "good" up until then.
 
I just removed the Duracell batteries that were dated 2010 and installed new ones that were dated 2014! The removed batteries had a 1% loss over the new ones. 9.675 volts and 9.505 volts total.

Are we allowed to go to the date on a Duracell battery? WOW! thats seven years. I would be pleased with two years.
 
I just looked at the manual for the ACK ELT and all of the batteries must be date coded and all must have the same date. After the ELT has been run for a cumulative 1 hour all cells must be replaced. Otherwise you can leave them in until their expiration. Of course the log book must be updated with the batteries. With this in mind I still change them at the annual condition inspection. Like the first response above, cheap insurance.
 
Bryan Wood said:
After the ELT has been run for a cumulative 1 hour all cells must be replaced. Otherwise you can leave them in until their expiration.

I believe the FAR states, in addition to the 1 hour rule, that they must be replaced after 50% of their useful life. (91.207 (C)(2)).
 
As said, cheap insurance. I woundn't mind change them every year whatever dates there are stamped. You can use them in some non-critical (non-aviation) application after they have been one year in your ELT. So no need to throw them away...
 
Why replace perfectly good batteries?

No need to replace them either... A stated in a previous post, the TSO'd ACK ELT is approved for use with batteries that have not reached their expiry date, provided they have not been used for an accumulated time of one hour.

If you have not used your ELT (beyond an occasional quick check), replacing the batteries every year doesn't increase reliability by a measureable amount.

Incurring a cost with no benifit is not "cheap insurance".
 
Last edited:
Why change them? Just open up the ELT and make sure none have leaked or corroded and maybe check the voltage to be safe. I would not replace yearly.
 
Here is a link to an interesting article that help explain the ELT battery replacement issue. The one thing is that the 50% life of the battery requires that that if the batteries are good for say 4 years then they will need to be replaced every 2 years. so if the experation date is say 2011 then they will need to be replaced in 2009.

http://www.avionicswest.com/articles/eltupdate.htm
 
useful life = expiration date?

c177tx said:
Here is a link to an interesting article that help explain the ELT battery replacement issue. The one thing is that the 50% life of the battery requires that that if the batteries are good for say 4 years then they will need to be replaced every 2 years. so if the experation date is say 2011 then they will need to be replaced in 2009.

http://www.avionicswest.com/articles/eltupdate.htm


i have a real problem with this interpretation -- that somehow the expiration date defines the "useful life" of the battery. i'll try to enumerate my objections below for discussion:

1. it seems self-evident to me that the "useful life" of a battery is the length of time that that battery can be used to operate the piece of equipment, in this case an elt. e.g., if the battery has a capacity of 3 amp/hours and the elt draws 300 ma, then the useful life of that battery would be 10 hours of use (simplification should be adequate for purposes of the logic.)

2. if the expiration date determined the useful life, the manufacture date would have to also be known, in order to figure out what 50% of that span is. arbitrarily saying "2 years before the expiration date" is just that -- arbitrary. someone just posted that they just replaced batteries with an expiration date of 2014. if they were manufactured this year (and they couldn't have been manufactured later than this year, obviously), then 50% of that life span would be 3-1/2 years, which would mandate replacement sometime in 2010. so the 2 years wouldn't work for that.

3. follow up to point #1 -- once you have used the elt for 10 hours (given the example), the batteries are depleted, and the "expiration date" is of little use to you -- it doesn't magically extend the "useful life".

did you notice how the article on the avionics west website mis-quoted 91.207? the article claims "dated life", where the regulation clearly states "useful life". seems to me a disingenuous tactic designed to promote their point.

all that being said, i have no objection if someone wishes to replace their elt batteries "early", what i object to is someone using a "skewed" interpretation to try to brow-beat me into doing the same.
 
Shelf life

johnp said:
......
1. it seems self-evident to me that the "useful life" of a battery is the length of time that that battery can be used to operate the piece of equipment, in this case an elt. e.g., if the battery has a capacity of 3 amp/hours and the elt draws 300 ma, then the useful life of that battery would be 10 hours of use (simplification should be adequate for purposes of the logic.)
........
The other definition of "useful life", often used in the electronics world is "shelf life".
All batteries self discharge (decay?) to a certain extent and loose capacity just sitting on the shelf.
This is essentially what happens to your ELT battery when it sits there in the back of your plane doing nothing.... You need to replace the battery before it looses 50% of it's capacity...
I bet the life spans are set conservatively (as they should be) and are probably set to a worse case (again, a guess, but I bet self discharge is higher when the battery is hot).

gil A
 
Add to that fact

That a 121.5 MHZ is next to useless in actually getting you rescued then spending the money on replacing batteries is a waste of money.

I plane to keep the duracells in there as long as possible and take my PLB with me on trips that take me away from civilisation.

if the engine quits, PLB gets activated...step one. Everything else is secondary apart from keeping the sunny side up.

When 406 units get more reasonably priced I will upgrade and then pay more attention to battery life.

Frank
 
az_gila said:
The other definition of "useful life", often used in the electronics world is "shelf life".
All batteries self discharge (decay?) to a certain extent and loose capacity just sitting on the shelf.
This is essentially what happens to your ELT battery when it sits there in the back of your plane doing nothing.... You need to replace the battery before it looses 50% of it's capacity...
I bet the life spans are set conservatively (as they should be) and are probably set to a worse case (again, a guess, but I bet self discharge is higher when the battery is hot).

gil A


i've spent the last 1/2 hour searching the web for definitions of "useful life" and "shelf life". have yet to find a definition for "useful life", however the term is frequently used in the definition for "service life" ;) go figure.

shelf life, however is defined as
The amount of time a cell or battery will retain a specified percent of its rated capacity, typically under ambient storage conditions.

the percent of rated capacity used in shelf life varies from manufacturer to manufacturer and within the manufacturer among the various technologies (li-ion,nimh,alkaline,nicad,etc.) however, the most common number seems to be 90%. i did find 80% for one panasonic product (li-ion). i found no lower numbers. it would therefore seem reasonable to assume that the date printed on the battery is the "shelf-life" date, and that by that date (assuming zero use), the battery would still have well in excess of 50 percent of its rated capacity remaining. exactly how the usage curve relates to the remaining capacity over time would be an interesting, but complicated study.

my conclusion is that the shelf-life is a non-issue, and is handled by the fact the by the expiration date, vastly more than 50 percent of the rated capacity remains (inductively reasoned by the samples i saw -- it's not easy to find shelf-life specs on the web. they tell you the number of years, but not the percentage of rated capacity remaining in many cases.) i think my conclusion is reasonable and supportable. ymmv

regards
 
So I installed new batteries with a date of 2014. I also logged the voltage reading. Each year during my inspection I will take a reading and log that on the card that I left in the case.

When the voltage drops to 90% or I reach the date printed on the battery, I will change them. Or they WILL be changed after one hour of use.

I had a 1% drop in voltage in two years.....
 
gasman said:
...When the voltage drops to 90% or I reach the date printed on the battery, I will change them. Or they WILL be changed after one hour of use.

I had a 1% drop in voltage in two years.....
Voltage drop under a no-load condition is not a good indicator of capacity.
 
Correct batteries

johnp said:
my conclusion is that the shelf-life is a non-issue, and is handled by the fact the by the expiration date, vastly more than 50 percent of the rated capacity remains (inductively reasoned by the samples i saw -- it's not easy to find shelf-life specs on the web. they tell you the number of years, but not the percentage of rated capacity remaining in many cases.) i think my conclusion is reasonable and supportable. ymmv

regards
John ... that makes sense.

Ameri-King, while they recommend a yearly change (lawyers?) say the batteries are good to the date stamped on them.

However, they do specify a particular make and model of battery. I guess this gets around the differing end-life specifications used by different battery makers.

So, if you do replace your batteries frequently, ensure you follow the STC and use only the correct make and model cells....

gil A

PS .. I'm with Frank H on the ELT usefulness. We recently had a Bonanza with an ELT activation that sat most of the day in a shade port "bleeping". It was only discovered by our airport manager's monitor radio when he returned in the evening. When I notified FSS, they had no reports... :(
I'm going to spring for a 406/GPS EPB.... :)
 
Last edited:
Ok, here is a different perspective. In older ELT's that used the same type of batteries, except packaged in to battery PACKs that were infinitely more expensive, they had to be replaced every two years. I therefore replace the cheep ones every two years too, and use them for other things afterwards. And ELT, while not a promise of rescue, isn't something I pinch penny's on.
 
elt battery replacement.

osxuser said:
Ok, here is a different perspective. In older ELT's that used the same type of batteries, except packaged in to battery PACKs that were infinitely more expensive, they had to be replaced every two years. I therefore replace the cheep ones every two years too, and use them for other things afterwards. And ELT, while not a promise of rescue, isn't something I pinch penny's on.

and that is an entirely reasonable thing to do. i'm just saying that it is not a requirement of the far's that you do so.

elt tales --

in the mid '90's i had a c-150 with an ebc-102 elt. i knew that the elt battery was coming up for replacement, so i ordered one from chief, along with some other stuff -- landing light bulbs, etc. the package came, i opened it and took out some part or another. coupla days later i was going to go out and change the elt battery, so i looked for it, and couldn't find it. so i ordered another one (iirc, it was about $35). it came, and in the meantime, i found the battery from the original order hiding in the packing peanuts in the box. so i took one out to the aircraft -- only to find when i got there that someone had stolen my elt. (the ebc-102 was one of those yellow ones that just slid in a yellow bracket, antenna mounted on the unit itself, not remote.) so now i had 2 elt batteries that i couldn't use. decided to 'disect' one to see what was inside, and it was nothing more than 6 AA's wired in series and glued in a plastic box, with a red and black pigtail coming out. boy, did i feel cheated.

i also agree with the relative uselessness of elt's. prior to 1970 they were not required (2 u.s. congressmen crash in alaska, never found, so a new law is born.) i've read somewhere that over 95% of elt activations are false-alarms, and in real crashes, elt's fail to activate some huge percentage of the time. so i look at the elt deal as a bureaucratic hurdle i have to cross, and use the cheapest elt that will fulfill the legal requirement. no question the 406 MHz ones are an improvement. but i'm still ambivalent towards the "necessity" to have one. if i were to crash and am conscious, i can manually operate the elt or other comm that might be still functional (2 panel mounts and a handheld). if i'm not conscious, then just maybe an elt might help. but the current track record is not too good. and if i'm already dead, who cares?
 
n5lp said:
Voltage drop under a no-load condition is not a good indicator of capacity.

An AGM battery like we use to power our RV's is fully charged at 12.8 volts. And at 12.2 volts, it is only 50% charged. The only way to check capacaty is to discharge at a given amount over a period of time. Of course if the battery is not rechargable, this would render it useless. So we take a voltage reading. :D
 
Temp and batteries....

az_gila said:
I bet the life spans are set conservatively (as they should be) and are probably set to a worse case (again, a guess, but I bet self discharge is higher when the battery is hot).

gil A
When I was in the service, we kept spare batteries in the frig whenever possible. I was told that the battery shelf life was greatly extended. I continue to do this myself now.

Also another point from even deeper in the past, I remember my Grandpa putting D cells from his flashlight that had become to weak on the back of the wood cook stove to bring back some life back into them. I seem to remember that they work for awhile after he did this.... Strange...

Kent
 
Maybe true, but....

frankh said:
That a 121.5 MHZ is next to useless in actually getting you rescued then spending the money on replacing batteries is a waste of money.

I plane to keep the duracells in there as long as possible and take my PLB with me on trips that take me away from civilisation.

if the engine quits, PLB gets activated...step one. Everything else is secondary apart from keeping the sunny side up.

When 406 units get more reasonably priced I will upgrade and then pay more attention to battery life.

Frank
I would be more concerned about how my insurance company might respond to a claim if they thought that I had not maintained my airplane correctly.

Kent
 
Good point but

You have self certified the annuals on time and the ELT was not the cause of the accident..I think the Insurance company would have a hard justifying not paying out. But then again insurance companies can be a law unto themselves..

Just ask any State Farm Homeowner in Louisianna!

Frank
 
A simpler view of it all

I view the ELT as a temporary "flashlight battery holder". Each year I pull them out for the flashlight but of course, I have to replace them with new ones. So the new ELT batteries don't cost me anything! :) :)

Keeps me legal, I see if they are corroded or whatever and I know that I have NEW ones back there.

On another point, while at SnF a year or two ago, I accidentally hit the button to activate the ELT. I get a phone call from "Colonel ???" (or was it someone from the FAA???) informing me that I had an ELT situation and that I needed to meet him and the team at my plane. OOOOPPPS!!!!:eek: Amongst the x,000 planes there in Lakeland, after a couple of passes of the satellites and some work with a cheap Radio Shack scanner, they had me pinned.

They were really nice about it and had three things to say ...

1) They wondered where the antenna was (under the fairing at the vertical stab)
2) They had me show him the serial number of the ELT and
3) "You gotta replace those batteries NOW, as it has been activated over an hour."

Yes Sir! :D

And I was REALLY glad that I had batteries in there that were without question.

James
 
kentb said:
I would be more concerned about how my insurance company might respond to a claim if they thought that I had not maintained my airplane correctly.

Kent
IMHO the issue would be if you had a friend with you and he/she died as a result of not getting help in time AND "they" found the batteries were not replaced at the appropriate time. I'm not an attorney but that might constitute negligent homicide. (?)
 
All of You All are right

Annual Duracell "D" bat changes = good idea

The FAR's are clear (as mud) but the folks who say change the Duracell D's at 50% of their shelf-life are correct. I use to think it was annual and that's not corrects. All this assumes you know the mfg and exp date to calculate 50%.

I think there is a little wrinkle in the 50% shelf life rule, especially if shelf life is only 2 years. What if Exp date (use/install by) is only 16 months out? Does that mean you only get 8 months out of it? So the 50% shelf-life is NOT an advantage[/B], thus going on 1 hour or expiration date, what ever is shorter is what ELT manual backs-up. I guess the confusion is, does a Duracell have an EXP date or USE/INSTALL BY date? Don't know.


To muddy the waters the ACK ELT manual says replace by:

THE ACK MODEL E-01 ELT IS DESIGNED TO USE ONLY DURACELL., MNI300, MXI300 OR PCI300 ALKALINE BATTERIES WHICH ARE DATED BY THE MANUFACTURER. (no mention of math calcs to figure exp.)

THE USE OF ANY OTHER BATTERY WILL VOID ANY WARRANTIES OF THE ELT BY ACKTECHNOLOGIES, INC. THE ELT DOES NOT MEET THE REQUIREMENTS OF TSO-91 a OR FAR 91.207 IF USED WITH ANY OTHER TYPE OF BATTERY.

BATTERY REPLACEMENT IS REQUIRED UPON REACHING THE DATE MARKED UPON EACH CELL. ALL CELLS MUST BE REPLACED AT THE SAME TIME AND ALL CELLS MUST HAVE THE SAME EXPIRATION DATE.

FAR 91.207 (c)(1) REQUIRES THAT BATTERIES BE REPLACED WHEN THE TRANSMITTER HAS BEEN IN USE FOR MORE THAN ONE CUMULATIVE HOUR. (no mention of the 50% rule) THE EXPIRATION DATE OF THE BATTERIES MUST BE INDICATED ON THE OUTSIDE OF THE ELT BATTERY CASE AND RECORDED IN THE AIRCRAFT LOGS.



The "TSO'ed manual" for the TSO'ed ELT units (ACK or AmeriKing) dictates what you need to do. Of all the goodies in homebuilt planes the ELT and transponder are two items that need to be "TSO'ed" (from my reading). It's clear they don't get into the 50% rule in the manual, just expiration date. So if the expiration (best if installed BY) date is out 18 or 24 months you are good to go for that long, not half. It kind of makes sense to have a printed battery date controlling and not some math to calculate 1/2 of mfg-exp or installed-exp. Just food for thought...

I'm buying the expensive bat-paks so I forgot all this stuff. The factory bat paks are a different deal, the 1 hour or printed expiration date are in effect for sure. Some new (factory) ELT bat paks are good for 5 years!

I agree, just replace the D's annually (at/less than $1 a cell). They won't go to waste; I'm sure your wife or girlfriend can put them to good use.
 
Last edited:
RTFM for legality

gmcjetpilot said:
Annual Duracell "D" bat changes = good idea

The FAR's are clear (as mud) but the folks who say change the Duracell D's at 50% of their shelf-life are correct. I use to think it was annual and that's not corrects. All this assumes you know the mfg and exp date to calculate 50%.

What if the the exp date is only 16 months out? Does that mean you only get 8 months out of it? I recall :confused: Duracell D's have a typ shelf life of 2 years, so the 50% shelf life is NOT an advantage, thus go on 1 year or expiration date, what ever is shorter. I think the Duracell "Ultra" is approved as well, so may be that's 6 year shelf? Than in theory I guess you could get 3 years out of it. Check the package.
George.. the 50% life is built into the "expiration date" on the cells, and is a lot longer than 2 years. ACK quotes 95% remaining after two years...

But all that matters legally is that you follow the specific battery instructions in the FAA approved Manual for this TSO'd product.

This is one case where RTFM is the correct legal thing..... :) Sooner replacement, even annually is OK, but not really needed.

How many owners of an Ameri-King ELT checked that they bought Duracell MN 1300 Alkaline batteries? Nothing else is legal.

The ACK owners need PC 1300 or MX 1300 Duracells to be legal. Did you check the part numbers of those batteries you bought?

The TSO requirements trump all other thoughts/ideas for legality....

gil in Tucson

UPDATE....
This response to George's previous message still stands, but is very confusing due to major edits by George to the version I responded to... :rolleyes:
 
Last edited:
WHAT COULD BE BETTER?

ACK says..... replace by date on battery. I purchased duracells three days ago. The date on the battery is MARCH 2014. If we start the clock from the day that I purchased the batteries, I would get 6 years and 6 months before the next change and be ok with 91.207. And I am sure if I change them any time in between I would still be in compliance. :D

Looking at SPRUCE PRICES for elt batteries, the prices go from $22.25 to $56.50 for a 24 month battery. So when you consider that you can stop off at the store on the way home from the airport and spend about $5.00 for your elt batteries and pay no shipping, what could be better! :)

How about when they make the next gen elt's, they make the unit flatter and use "C" cells and make it about 1 1/2 pounds or less with TX & RX.. and you could RESET the unit from outside a locked plane by just keying a handheld radio "X" amount of times near the aircraft. This would save the 3am phone call. :eek:
 
A coupla things

Batteries are like women, no two are alike, they are unpredictable and are likely to not function when you need them to. So, I replace them at the annual, (condition inspection for you technical types) The batteries that is, not the women!!!!

In the AZ the heat is a killer of batteries. That is why I use only Optima batteries in my vehicles. One is going on 9 years now.

Since I'm back there behind the bulkhead doing an inspection I might as well spend the $6 and replace them. I then use the old batteries as needed in flashlights.

Regarding the usefulness of the ELT, I flew law enforcement helicopters for a few years including SAR. I can recall responding to roughly 20 aircraft crashes over the years. Only one of those was an ELT "find." And, it didn't matter. The only positive thing we found the ELT useful for was finding the plane on the ramp that had a hard landing :eek:
 
That a 121.5 MHZ is next to useless in actually getting you rescued then spending the money on replacing batteries is a waste of money.

I plane to keep the duracells in there as long as possible and take my PLB with me on trips that take me away from civilisation.

if the engine quits, PLB gets activated...step one. Everything else is secondary apart from keeping the sunny side up.

When 406 units get more reasonably priced I will upgrade and then pay more attention to battery life.

Frank

Replacement of the battery pack is nearly $300. Has anyone just replaced the battery cells? They are just D Cell size Lithium batteries with solder tabs.
 
Replacement of the battery pack is nearly $300. Has anyone just replaced the battery cells? They are just D Cell size Lithium batteries with solder tabs.

I believe some have. In most cases this is not legal, as the approved elt manual usually calls for a specific battery - one which is only available from the elt manufacturer!
 
My ACK E-04 sports a sticker as shown on the picture. Also, the battery expiration date is etched into the battery case, so it can't be updated if you were to cut the case open and add a new set of batteries.
If true, the battery being unairworthy could be cited by the insurance company as grounds to deny coverage in the even of a claim? I'm not a lawyer. Does that make sense?
34C1FFB6-E046-4C31-9D6F-98237F5749CD_1_201_a_heic.webp
 
I'm sure someone will debate me on this but before you do please cite regulatory references backing up any claims. Since the airplane is experimental one can experiment with ELT batteries. There are no TSO requirements for any parts in an aircraft certified in the experimental amateur built category.
 
I Will!

I'm sure someone will debate me on this but before you do please cite regulatory references backing up any claims. Since the airplane is experimental one can experiment with ELT batteries. There are no TSO requirements for any parts in an aircraft certified in the experimental amateur built category.

Please read §91.207.

"(a) Except as provided in paragraphs (e) and (f) of this section, no person may operate a U.S. registered civil airplane unless------" It goes on to list the requirements of ELT. There are no exceptions for Experimental Certificated Aircraft.

ELTs and Transponders must meet TSO for Experimental Amateur-Built Aircraft.
 
Concerning Duracell Batteries.....

I have discovered in the last few years that Duracell batteries seem to leak at a much higher rate than other brands. This timing seems to relate to the shift to China manufacturing.

I no longer use Duracells. (Personal choice)
 
Me Too

I have discovered in the last few years that Duracell batteries seem to leak at a much higher rate than other brands. This timing seems to relate to the shift to China manufacturing.

I no longer use Duracells. (Personal choice)

I have had the same experience. I also have claimed damage and Duracell covered it to some extent. I now use Energizer and have had no issues...
 
Condition Inspection

As I was doing the inspection on an RV-4 on Wednesday, I opened up the ACK E-01 ELT battery case to find discoloration of two of the battery contact springs. No visible leak on any battery, and they all have a Dec 2024 exp date.
The two year replacement suggestion in the ACK manual is a good idea.
 
If true, the battery being unairworthy could be cited by the insurance company as grounds to deny coverage in the even of a claim? I'm not a lawyer. Does that make sense?
]
I’m not a lawyer, but I know that in legal jargon your question revolves around ‘strict liability’. e.g., you have a contract with the insurance company. Usually that contract requires you to maintain and inspect your airplane in accordance with the FARs. You have an accident that has nothing to do with the ELT battery, but after the accident it’s noted that the battery is beyond its expiration date. Can the insurance company deny coverage because you violated the contract? In some states, yes. This is called strict liability. But in other states, no. They require the expired battery to be relevant to the accident.
Like so many legal things, clear as mud.
 
Please read §91.207.
ELTs and Transponders must meet TSO for Experimental Amateur-Built Aircraft.

Its not a matter if a TSO is required for an ELT but rather can an owner modify the ELT to use a regular battery. I argue yes, they can, because there is no provision requiring the ELT be maintained to certification standards because there simply aren't any for an experimental. The TSO applies to manufacture, not installation in an experimental. If one wants to get technical the ELT batteries can be replaced as an owner produced part under 21.303.
 
I remember looking into this a couple of years ago. I found a site that had all the information and apparently it (IIRC) was ok for the ACK brand originally, but ACK had to change their language to specifically declare the unit non-airworthy if a user replaced the cells. SAFT LSH 20, 13,000 mAh, and they are much higher price now. [5/23 update - Saft SO 26SX is the exact replacement battery number]

At the time the very specification and manufacturer was located and at the time it was $80 for a new part, and $55 for all the batteries, today it is $197 @ Spruce. This discussion is again relevant for the higher prices, assuming that the cells can be located at a reasonable price, legality not withstanding.

5.31.23 Spruce $321 with tax and shipping (USA) or $94 for 4 SAFT batteries, including $25 for haz shipping and tax.
 
Last edited:
... This discussion is again relevant for the higher prices, assuming that the cells can be located at a reasonable price, legality not withstanding.
Same for the PLBs - I have one where the battery replacement cost is over half way to the price of a new unit.
 
Please read §91.207.

ELTs and Transponders must meet TSO for Experimental Amateur-Built Aircraft.

Actually, after the last FAR re-write, this is not strictly true. It now says that they must be ‘approved’. Same for gps used under ifr, ‘approved’. What does that mean? Well in 14CFR 1.1 (definitions), under ‘RNAV (including gps)’, it says stuff like ‘approved means it conforms to various faa standards published in regulatory and non-regulatory guidance…’ (huh?). It also says, ‘Obtaining a TSO is one way, but not necessarily the only way, of obtaining approval’. Anyone try asking their FISDO for approval of their home-brew gps system? It’s in the regs! When I look around and see ‘hidden’ gps and elt antennas, and TSO’d gps units feeding non-TSO’d CDI’s or HSI’s, all of which are not in the TSO’d installation instructions, but they are so numerous I can only assume the faa knows about them and has, by their inaction, given their tacit ‘approval’. So when it comes to ELT batteries, who knows what the faa is thinking is needed for ‘approved’.
 
OK I will add my 2cents.

If you replace the authorized ELT batteries with Duracell batteries, how do you prove the ELT still operates within the required standards? Same with a transponder, GPS, etc. If you build your own transponder, how do you prove it operates within the required standards?

For some equipment proving it operates within required standards isn't a difficult task. But other equipment (ELT, GPS, Transponders...) proving it operates within required standards require some serious test equipment, testing criteria and obtaining test data far beyond the reach of mere mortals like us.

IMHO, Yes in experimental aviation you legally do not have to have a TSO'd transponder or other pieces of equipment. But you don't have the resources to prove to the FAA your equipment operates within the required standards. That is unless you are an Elon Musk or Jeff Bezos equivalent. Just another case where theory and reality are not the same.

:cool:
 
Last edited:
Mmm hmm.

I've followed this thread and it's interesting. This A&P is really not sure what to tell owners of experimentals about all this. What's legal, what's common practice and somebody finding out are all different things. I always say nuthin' happens until after the accident.
 
... I always say nuthin' happens until after the accident.

Good point - one thing that's confusing to me is it's common knowledge that ELTs often don't work after most crashes. The times that they do save a life seems to be headline news. Has the FAA or NTSB or ATSB or CAA or ICAO or Ralph Nader ever gone to an ELT manufacturer and said, "hey, your device didn't work in this crash, what are you going to do to fix it?"
 
If you replace the authorized ELT batteries with Duracell batteries, how do you prove the ELT still operates within the required standards? Same with a transponder, GPS, etc. If you build your own transponder, how do you prove it operates within the required standards?
This raises a related question... uAvionix' TailBeaconX is a Mode S transponder that fits all in one unit. There is no external antenna connector on it. So how does an avionix shop validate that it meets transmit power requirements? Or anything else that would normally be done by plugging the test equipment into the antenna port?
 
This raises a related question... uAvionix' TailBeaconX is a Mode S transponder that fits all in one unit. There is no external antenna connector on it. So how does an avionix shop validate that it meets transmit power requirements? Or anything else that would normally be done by plugging the test equipment into the antenna port?
There is transponder test equipment available that is calibrated based on placing it's receiver antenna a specified distance from the transponder antenna. All of the parameters required for a 14 cfr 91.413 test
 
Back
Top