Ethiopean 787 fire at Heathrow

[fenland787]

The Roadie

However, they add another layer of risk in the failure flowchart,

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?

[RetiredF4]

Electic

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

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?

[archae86]

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.

[Karel_x]

how they could save over 50% of weight by maintaining the same power output

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.

[ironbutt57]

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

[Speed of Sound]

What has not been discussed is, how they could save over 50% of weight by maintaining the same power output.

I did, only 13 posts ago!

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

[mm43]

@ SoS

Following from Honeywell -

Specifications (RESCU 406 AFN2)
MTBF 100,000 hours (estimated)
Certifications Approved by Boeing, Airbus, Dassault, FAA
RF Power 100 mW 121.5 MHz, 5 watts (406 MHz)
Battery Service Life 12 Years
Compatibility Backwards compatible with RESCU 406 AFN

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.

[mangere1957]

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'.

[Speed of Sound]

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.

[fenland787]

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

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?

[Mr @ Spotty M]

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.

[LeadSled]

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.

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!!

[WHBM]

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

Boeing changes chief 787 engineer in management shuffle | Reuters

[Speed of Sound]

fenland787

Bigger capacity cells,

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.

[noughtsnones]

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.

[fenland787]

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.

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

[joy ride]

On the BBC Business news:

BBC News - Boeing requests worldwide inspection of aircraft

[Ian W]

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


is the following throwaway line...

Investigators traced that incident to pinched wires in an emergency beacon and regulators instructed airlines to inspect or replace the units. Since then, other reports of fires have surfaced.

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?

[Speed of Sound]

fenland787

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

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!

[Mr @ Spotty M]

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.