fdr This is more germane

so far, a new "case", firmer mount, and separation cell to cell......

Lyman... the prior advice to TBC/FAA if corroborated, should have some people reflecting on the efficacy of their SMS programs. Without that advice, the situation is just poor project risk management, with the advice it looks more like expediency with a tinge of hubris.

Germaine?:)

Gill from Aircraft Spruce


:E

The standard set by the FAA for this safety critical event is one occurrence in one Billion flight hours. IOW not even once in the life of the fleet.

Boeing negotiated a lower threshold, one in ten million flgiht hours. A reduction in standard of 100:1.

There have been two occurrences in less than one hundred thousand Flight Hours. A further reduction in threshold of 100:1.

Twice.

From Boeing:

Quote:
“We are working collaboratively to address questions about our testing and compliance with certification standards,” the statement said. “We will not hesitate to make changes that lead to improved testing processes and products.”

This translates to a continuation of Boeing making the rules. Boeing still wants to drive.

See, the regulator is FAA. FAA is the problem. In allowing the process to deteriorate, in the first place, and in staying mum while Boeing explains "the way it's going to be..." J

Self certification and writing the rules for the FAA to endorse? Maybe the FAA could be "redesigned" ?

And so far, it's just the back up batteries.

Precisely.

Quote:
Originally Posted by fdr
the prior advice to TBC/FAA if corroborated, should have some people reflecting on the efficacy of their SMS programs.


And a closer look at the RTCA criteria, I should think. With an eye toward incorporating them in toto.

Batteries cell voltages in JA829J and JA804A were recorded?
 

Hi,

Why NTSB, JTSB didn´t mention cell voltages?

The comments on "no overcharging" because 32 V limit was observed is almost irrelevant. Battery destruction could start due a cell failure. It´s voltage shows it.

Question:

Considering FDR are designed to allow investigators fully understand WHAT and WHY, should FDR access inside black boxes like batteries (looking to ea. cell)?

FDR, specially in teething phase of a new airliner would "benefit" to record some information coming from important sensors? (raw data from AoA vanes, Pitot´s etc.)

New technologies are constantly being introduced in airliners. Current FDR approach to look "outside" of boxes is enough for allow a conclusive investigation?

RR_NDB:

Two problems: First, think about the volume of raw data that could be collected from the internals of each subsystem. The FDR architecture would have to be revised significantly. And since that is a certified part of a production aircraft, backing down to the 'standard capability' FDR would require recertification.

Second: The internal charger/battery data is taken from the same sensors that drive the charge controllers. So if these are faulty, so too is the recorded data. Faulty data might tell investigators something. An anomalous zero cell voltage reading may indicate a broken sense lead for example. But at what point do we stop incorporating redundant sensors into systems just to satisfy these enhanced FDR requirements?

This is what certification test instrumentation is for. Redundant and separate from the systems under test. There just isn't much room left on an aircraft instrumented to this degree for SLF.

RR

You don't get it. BOEING "demonstrated" that a single cell failure would not "propagate" to adjacent cells, and cause a fire.

The FAA was satisfied that that was the case.

Why should they bother to install a system to protect from something they showed could not happen?

Having failed to predict the problem, they should be relieved of the duty to rejig the tests and certs, and the RTCA requirements should obtain.

Once "burned", twice shy.....

OK?

Data from specific points to FDR
 

Hi,

EEngr:

Quote:

---

First, think about the volume of raw data that could be collected from the internals of each subsystem. The FDR architecture would have to be revised significantly. And since that is a certified part of a production aircraft, backing down to the 'standard capability' FDR would require recertification.

---

Carefully selected TEST POINTS. E.g. Pitot´s, AoA vanes, cell voltages, etc. Limited data. Optimized by "caching" more data inside important boxes. Actually this is being done (QAR). (for other purposes)

It´s VERY EASY to have a NEAR PERFECTION probing for all cells inside a Li ion batt case. LOW COST!

If this info were recorded NTSB and JTSB VERY PROBABLY long ago reported WHY both batteries (JAL and ANA) failed.

How many bits/bytes for this? Easy to have ALL REQUIRED info on cell voltage in less than 1MB. Yes! ~ 8 M bits. I could reduce, if necessary further.

PS

Cache inside batt case operating like a CVR. If crash, stops recording and make available it to aircraft FDR. Redundantly stored in cache AND FDR.

I think what you describe may well eventuate post grounding.

The point is, you ask why no such system of monitoring was installed.

It was considered unnecessary, not required. Why install "Test Equipment" on a certificated airframe?

I wonder how much weight they saved by going for Lithium

what they got:
75 ah
60 lbs
32 v

what specs would a "conventional" battery of a similar capacity have?

A bit of Googling would suggest that a beast of the sealed lead-acid variety could be made but would weigh a little over double.

That sounds like a trivial cost, but I'm not sure any other technology could produce the peak current required of the 787 battery when starting the APU. Any experts care to comment?

vovachan,

I read somewhere that the weight saving by going for a Lithium-ion battery system instead of a NiCd system on the A350 project is 180 lbs/82kg.

Furthermore, the NiCd system would occupy twice as much space.

I guess that the figures for the B787 are more or less the same.

A Ni-Cad battery of similar size and weight is capable of starting a heavier APU for the 777.

I was watching a TV program the other day that mentioned Li-Ion batteries and it suggested that Ni-Cads of similar performance would be six times larger/heavier. I took it with a pinch of salt but you never know.

Bearing in mind that Boeing removed the original access door from the forward hold to the forward electrical bay and replaced it with a fixed panel just to save weight gives you an idea of how weight critical they are.

If the Li-Ion Battery is half the equivelant weight or more of a Ni-Cad......:hmm:

Ni Cd retrofit
 

Hi,

Pub User and TURIN:

No problem!

Quote:

---

A Ni-Cad battery of similar size and weight is capable of starting a heavier APU for the 777.

---

For MAIN the issue is a little bit more "complex". The diode module (certainly) would be removed and there will be new algorithms in the retrofit.

Better to compensate airliners (PAX number) than prolonged grounding. :mad:

I will post ASAP a detailed comparison to Ni Cd. I estimate the same figure.

Certainly Boeing is working considering ALTN solution(s). ABSOLUTELY FEASIBLE

From Pub User: A bit of Googling would suggest that a beast of the sealed lead-acid variety could be made but would weigh a little over double.

That sounds like a trivial cost, but I'm not sure any other technology could produce the peak current required of the 787 battery when starting the APU. Any experts care to comment?

Wouldn't describe myself an expert, but I do have experience with Lead acid batteries in the renewable energy field. A little over double is fanciful due to the way apparent battery capacity varies with the rate of discharge.

If you are judging the weight based on a 75Ah lead acid battery, then that battery 'capacity' is obtained by finding that the battery can withstand a 3.75A load for a 20 hour period before the battery voltage drops to a point where the battery is considered fully discharged. If you upped the discharge rate to say 7.5 amps the battery would probably not give a 10 hours of discharge as a linear regression would suggest (75ah/ 7.5A = 10 hours), instead it would probably give 9.5 hours for a capacity of 71.25Ah. If you increase the discharge to say 20 amps, instead of the battery lasting the linearly theoretical 3.75 hours it would probably last 3 hours giving a battery capacity of 60Ah. And it gets worse from there - a 150a discharge current would probably give only 15 minutes before being flat - so 37.5Ah. This is known as the Peukert Effect.

Someone on here mentioned peak loads of 700a when starting the APU - to cope with that load you'd probably need a battery in the 400-500ah range - that much lead will end up weighing well over 140kgs (battery alone - not counting interconnects, racking etc. The end effect of having to redesign the racking etc and the additional space required would mean the impact with lead acid would be several hundreds of Kg's more. Lead acid because of this quirk in its chemistry (Peukert Effect) is not well suited to high current short duration/low weight applications.

Ni Cd retrofit. Some general information (2001)
 

Hi,

Some initial information:

http://www.buchmann.ca/shim.gif Advantages
Fast and simple charge — even after prolonged storage.
High number of charge/discharge cycles — if properly maintained, the NiCd provides over 1000 charge/discharge cycles.
Good load performance — the NiCd allows recharging at low temperatures.
Long shelf life – in any state-of-charge.
Simple storage and transportation — most airfreight companies accept the NiCd without special conditions.
Good low temperature performance.
Forgiving if abused — the NiCd is one of the most rugged rechargeable batteries.
Economically priced — the NiCd is the lowest cost battery in terms of cost per cycle.
Available in a wide range of sizes and performance options — most NiCd cells are cylindrical.
Limitations
Relatively low energy density — compared with newer systems.
Memory effect — the NiCd must periodically be exercised to prevent memory.
Environmentally unfriendly — the NiCd contains toxic metals. Some countries are limiting the use of the NiCd battery.
Has relatively high self-discharge — needs recharging after storage.

http://www.buchmann.ca/shim.gif Advantages
High energy density — potential for yet higher capacities.
Relatively low self-discharge — self-discharge is less than half that of NiCd and NiMH.
Low Maintenance — no periodic discharge is needed; no memory.
Limitations
Requires protection circuit — protection circuit limits voltage and current. Battery is safe if not provoked.
Subject to aging, even if not in use — storing the battery in a cool place and at 40 percent state-of-charge reduces the aging effect.
Moderate discharge current.
Subject to transportation regulations — shipment of larger quantities of Li-ion batteries may be subject to regulatory control. This restriction does not apply to personal carry-on batteries.
Expensive to manufacture — about 40 percent higher in cost than NiCd. Better manufacturing techniques and replacement of rare metals with lower cost alternatives will likely reduce the price.
Not fully mature — changes in metal and chemical combinations affect battery test results, especially with some quick test methods.

The following table is for small batteries.

http://i49.tinypic.com/20asxur.jpg

Source:

About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Richmond (Vancouver) British Columbia, Canada.

lomapaseo

"financial contracts not included"

Really? Do you think that its possible to divorce economics from engineering? I don't. There has to be someone that can report to that VP, "Yes, the technology is mature. But No, Boeing isn't prepared to make the necessary investment into the skill sets needed to exploit it. So in the final analysis, the answer is 'No'".

Someone else pointed out that Boeing moved their HQ to Chicago to keep the engineers out of the boardroom. They appear to be reaping the rewards (or consequences) of that decision.

EEngr et al.

Many thanks for post 715 and following discussing the effect of AC on "DC oriented" power plants. I fully agree with what has been written, having seen these effects as well on large-ish power plants requiring paralleled cells. Having had a slightly different internal resistance was enough to have them sent across Jordan.
This applies more and more to low ESR battery packs - the more current they can deliver, the more dramatic are the (very small) differences within the internal resistances of the batteries.
We've always considered the AC behaviour of our DC installations and I would be very surprised if the engineers at the LiIon battery developer hadn't considered this.

Anyway, thanks for the update, and I'll keep on reading...

not to be too simplistic, but as the calendar pages go by, there will come a point in time when going down to the local apple store and buying a bucket full of iphones and plugging them into the system will be cheaper than the cost of grounding a multi billion dollar program over the concern of a battery mass. The NiCd battery has been running for a fair old time, the guys in the hanger will be pretty familiar with them, and there are enough ex douglas guys there to string some more cabling as they were fond of doing.

Right now, the simple solution is a least risk solution.