The pinched wires, I would suppose, are on the wiring between the battery and the connector to the PCB, which could be subject to being moved and not fixed in location and routing. More like the design of a portable phone battery than a cell phone. Only fuses right at the place where the wiring enters the battery, or inside the battery casing, would be total protection.

However, they add another layer of risk in the failure flowchart, and engineers could have decided the cost outweighed the benefit.

Of course, this is all guessing, that could be halted by one decent picture of an open unit.

I don't know if it is any help, but here is the company product brochure for the Honeywell RESCU406AFN2

http://www51.honeywell.com/aero/comm...U_406_AFN2.pdf

The Roadie
 

Very true and the FIT number for thermal fuses is horrid but given the aviation world's dislike of battery powered equipment and their potential failure modes, I would have hoped the fuse would have won out. Especially as there was, by the look of it, scope for a good margin between fault and operating current?

Electic
Meanwhile everybody should be aware, as it was already posted in post 581,

post 581

Karel_x posted it in post 769,
Post 769

What has not been discussed is, how they could save over 50% of weight by maintaining the same power output. Could this weight saving be on behalf of less built in safety, insulation and more risk when using 2 cells instead of 6 cells?

checks for Honeywell ELTs on other model aircraft
 

Bloomberg is posting a story stating that Boeing "asked specific operators of 717, next-generation 737, 747-400, 767 and 777 airplanes to also inspect aircraft with fixed emergency locator transmitters, or ELTs, from Honeywell". This is described as pursuant to an AAIB recommendation.

The Bloomberg story is directly sourced to Randy Tinseth's (Boeing marketing VP) blog, which you can find easily enough, but which when updated will no longer carry this entry at the top.

Except it, that new battery could have greater capacity, I can imagine one more way. I suppose that in standby mode the consumption of ELT is very low, lower then 1 mW and battery life is limiting by its self discharging process. In case of emergency, I suppose that the transmission of data is not continuous, that between data blocks could be time breaks, eg. 5s "telegrams" in 30s interval. If you have not energy enough, you can make intervals longer. My speculation.

And of all the airplanes it decides to catch on fire on:uhoh:

I did, only 13 posts ago! :ok:

http://www.pprune.org/rumours-news/5...ml#post7964412

@ SoS

Following from Honeywell -Note the 12 year battery life.

I believe there are 2 packs comprising 4 cells in each and most likely of the Li-MnO2 type.

Can anybody tell me the cost per life saved by fixed ELTs in heavy transport aircraft? My strong suspicion is that not a SINGLE life has been saved and the cumulative cost over the last thirty years probably in the hundreds of millions of dollars. As well as the cost, the PROVEN increase in risk must be taken into account.

Just because a thing CAN be done doesn't mean that it is sensible that it should be done*.

In my view fixed ELTs MIGHT be justifiable in aircraft up to light twins but that is all.

*In the mid seventies the head of training, on F27, of a national carrier, carried out a GA from 1500 ft on final on glide path below all cloud, with gear down and locked**, after there was an explosion in one wheel well. He could do it, but should he have? Nah.

** There were still three greens after the explosion. That's all one needs to land an F27 on 10000'.

mm43
 

Thanks for that.

There seems to be a number of data sheets around giving different information.

I'm still struggling to understand how a greatly reduced number of cells can provide the same amount of power or even more, using the same Li-MnO2 chemistry. :confused::confused:

Bigger capacity cells, combined with more modern electronics that run at a lower voltage = lower cell count?

As others have said too, we don't know how long the transmissions have to last when used in anger perhaps the MKI battery was over specified in that respect?

mm43
 

The 12 year life for the battery is the same for the portable RESCU 406 ELT that Honeywell makes, which is also fitted to some B787 aircraft.
My guess would be the same type of battery, but l am not in a position to check at this time.
The batteries are replaced however at 10 years as per the MPD for the fixed ELT.
It is the same interval also for the portable ELT, which aligns with the second 5 year off wing inspections.

Mangere1957,
As you suppose, the answer is NIL!
See my posts a few pages back, the in-service failure rate in accidents for fixed ELT is better (or worse)than 95%, or 100% in water.
They are simply not justified on any aircraft. The Australian research and results on the subject is very clear.
Fixed ELT are an utter waste of money, without regard to any additional risks they may introduce.
What other piece of equipment with a 95%+ failure rate is tolerated on an aircraft??
Tootle pip!!

787 Chief Project Engineer at Boeing, Mike Sinnett, sidelined :

Boeing changes chief 787 engineer in management shuffle | Reuters

fenland787
 

That 's what I am getting at.

If the same, or greater power can be derived from a 60% smaller volume of cells, then the energy density of those cells must be more than double.

Energy efficiency savings gained by better circuit design would be somewhere around 5-10%, and only then if the mark one electronics were very inefficient to start with.

A further thought on battery size and life...
The monthly system self-test described in the data sheet is declared as having a total duration of 5 seconds (unchanged between unit types), elsewhere the data sheet states "Enhanced ... and self test".
There is a merit in keeping the outside observable maintenance procedures unchanged, to eliminate possible adverse risks of forward and backwards compatibility.
A reduced battery size can be speculated, based upon a system self-test using less power per usage (month), by enhancement to the test sequences and better test result data integration.

Agreed, do we know the cell volume is decreased by 60% or just the housing/battery pack? Not disputing, just asking! :)

On the BBC Business news:

BBC News - Boeing requests worldwide inspection of aircraft

In the Bloomberg report Boeing changes chief 787 engineer in management shuffle | Reuters


is the following throwaway line...

Obviously, a fire in another aircraft type would be of zero interest to the baying peanut gallery - but when it happened in a 787 it is suddenly worldwide news. So the various regulatory bodies only took action after the media interest?

fenland787
 

I am basing this on a low-res pic of a section through both a AFN and an AFN2 which showed 5 batteries in the former and 2 batteries in the latter. They looked identical in shape and size and only the amount installed differed.

I wish I could find the damn jpeg as a few people have asked what the inside of the beacon looks like! :ugh:

Eclectic
 

Don't believe all that you read from the unreliable press. :=
Not all EASA supervised airlines operating the B787 have removed the fixed ELT, l know of one that is inspecting the wiring around the ELT and the outer case for signs of overheating, on a daily basis. :ok:

Well that's reassuring - has anyone told them just how quick these things can go up if they decide they are going to? :eek:

Remove all fixed ELTs at once.
 

LeadSled @ #796

Thanks for that(to others; confirming my conjecture that ELTs are useless).

Because ELTs have never saved, and will never save, a single life in heavy transport operations, but cost a lot and introduce risk they should be removed at once.

Prognosis: This will not happen. Regulatory authorities(and manufacturers) will never admit that they stuffed up mightily(just imagine AI admitting that having un-moving thrust levers was a bad idea).

All discussion of battery size, capacity, etc is irrelevant. ELTs must be removed.

Only irrelevant if your prognosis is incorrect surely? If your prognosis is correct these things need to be made safe. So the failure mode needs to be first understood, then fixed.

Well the ELT didn't help with finding the Kenyan Airways 737-800 at Douala a few years ago. They were looking miles away when all the time it was in a swamp at the end of the runway.:rolleyes:

Fixed ELT's have a one hundred percent failure rate.:hmm:

ELT's are nor required, according to some folks.
 

Tell that to all the crew and aircraft found and saved (in some cases) in Canada's North, and elsewhere in NA ! If it had not been for the ELT signal being received for direction to its location, we'd still be looking for an appreciable amount of crashes with the loss of more life.
Signals now include GPS co-ordinates and that speeds up a search.
Unfortunately there are too many misuses of the ELT's causing false alarms and, possibly, delayed reactions. :=

It seems that some readers and writers on this forum never had their asses over unlandable terrain for a long time !!!

I don't think anybody doubts the value of ELT in General Aviation (specially for VFR flights) but I think they are much less useful for larger air transport aircraft whence for example FAA in the US doesn't mandate them for airliners.

Do you remember how difficult it was to track AF447?

Possibly for the same reason that submarines come to the surface to use their radios, rather than transmitting from 12,000 feet down? :ugh:

This is why I would prefer to maybe add even more buoy ELTs/PLBs/EPIRPs and whatnot instead of completely removing them.

It's the old news axiom dog bites man is not news, man bites dog is news. Frequently hear of various airliners making unscheduled/emergency landing due to cockpit smoke, but they are back page slow news day fillers. Smoke in a 787 overwhelms even the birth of Prince George (naw, even here in a colony fighting to rid themselves of control by another George it overrode everything). But now I read, "Oh, yeah, there have been other ELT fires." To be honest the current alert to travelers resulting from intelligence sources that a terrorist attack planned very soon overrides thoughts of there maybe being an in flight 787 fire or an uncontained A-380 engine explosion that damages much of a wing structure. Scarier yet is seeing the evac photos of people carrying their luggage away from the emergency escape slides. Those are all people who could have blocked my exit and killed me as sure as if they shot me.

The tlot phlickens re ELT
 

or in other terms- the fail safe may not have been a fail safe ??

Still seeking cause of 787 fire in U.K. | Business & Technology | The Seattle Times

Still seeking cause of 787 fire in U.K.
As Canada’s Transport Ministry examines Honeywell’s emergency beacons, the company confirms the devices should have been able to prevent overheating in case of a short circuit.

By Dominic Gates
Seattle Times aerospace reporter
:confused:
The small off-the-shelf electronic device at the center of the investigation of a fire aboard a Boeing 787 Dreamliner at Heathrow airport last month contains a fail-safe mechanism that should have prevented overheating even in the event of a wiring short-circuit, a Honeywell spokesman confirmed Friday.

The Emergency Locator Transmitter (ELT), supplied to Boeing by Honeywell and used in many other aircraft besides the 787, contains a current limiter — a standard feature, like a fuse, that shuts off the current if it gets above a certain level.

Boeing and government investigators inspecting the damaged ELT from the Ethiopian Airlines jet found that internal wires connected to the device’s lithium battery had been trapped and pinched when the cover was reattached as the batteries were inserted.

That led to a theory that the pinching of the wires compromised the insulation, and that crossed wires short-circuited to start the fire.

Honeywell spokesman Steve Brecken said Friday that the ELT contained a current limiter that should have stopped any surge of current caused by a short.

Did the limiter somehow fail? Or was the fire started some other way?

Brecken said all that’s known is that the fire was “in the area” of the ELT and that the investigation led by the U.K’s Air Accidents Investigation Branch is continuing. “We don’t know that the current limiter failed,” he said.

The Wall Street Journal reported Friday that Transport Canada, the aviation regulator in Canada, is preparing to order the inspection of ELTs in all types of planes carrying the device, including Airbus and Dassault.

Last week, Boeing sent out a service bulletin to operators of all its planes — not only the Dreamliner — recommending inspections of the ELTs.

The ELT is manufactured and assembled by a Honeywell subcontractor, Instrumar, of St. John’s, Newfoundland. Instrumar’s main business is technology connected with the production of carpet fiber, and the ELT appears to be its only aerospace product.

Brecken said Instrumar ships the ELTs for the 787 to Honeywell’s Deer Valley facility, near Phoenix, Ariz., and from there they are sent to Boeing.

He said Instrumar ships ELTs for other aircraft and for other manufacturers to Honeywell’s Mississauga facility, outside Toronto.

The Journal said Transport Canada this week inspected the Mississauga facility and will inspect Instrumar’s plant next week.

I imagine it should not be tough to test this theory, they don't need the whole 787 for that, just a small section of a fuselage with all the relevant tubing/insulation/electrics, etc.

Not even that, all that is needed initially is an ELT, or perhaps even just some of the battery packs.

I'm not sure what the 'Current limiter' is, but that is not a description I would use for a 'conventional' fuse so I suspect it is a self-resetting fuse of some sort. These work by increasing their resistance with temperature and that increase in temperature is caused by resistive losses due to the current flow through the device then, as the resistance increases, the current drops or limits.

If the sizing of that device is wrong for the equipment, or the device was faulty, and it is in thermal contact with the battery I could imagine a scenario where it is possible to get a combination of over-current and temperature where the device is cycling 'on and off' (I know it's not quite on and off but you get the idea) and the combination of a hot day, hot limiting device and self-heating in the battery due to the fault current could be, over time, that the Li battery is heated to the point of thermal runaway.

How's that for speculation from someone who doesn't speculate?

It can’t be coincidental the Honeywell are one of the worst OEMs to deal with in just about every aspect and every division.

Whether it’s APUs, Avionics, spares, repairs, rip off pricing policies, general support issues such as updating EGPWS, there are a myriad of issues. These issues are spread across the complete aviation community too. Absolutely nothing to do with Boeing.

These aren’t new issues and maybe, just maybe they are indicative of cultural issues within a corporation that has lost its way?

Where is the current limiter located? On the ELT circuit board? That would be too far along the current path to be of any use in the case of a pinched battery wire. The current limiter would have to be in the battery pack itself.

Which raises another interesting issue: If the original Honeywell batteries were replaced (and they incorporated said limiter), were they replaced with OEM batteries? Or is there a generic 'equivalent' that may have been substituted?

Only initially perhaps, but at some point they better get more aircraft structure to replicate the overall damage, fire propagation, etc.

EEngr
 

There is no way anything other than a Honeywell part could be used and maintain certification I would hope?

As you point out, the polyfuse (or whatever) must be part of the battery pack to be any use, hence my thought about it being in close thermal contact with the cells - perhaps deliberately in the hope that it would shut things down if the cells got to hot? Wouldn't be any use in a thermal runaway situation though.