FAA Grounds 787s
Boeing always liked to present a unified face to regulators, the press, customers, etc. This might be one reason why we are not seeing the breadth of investigation that I'd expect on this topic. They can't have multiple teams of engineers pursuing various hypothesis. That would look like uncertainty. And that could undermine their image as the ultimate technical authority for all things flying.
Nobody here wants Boeing to go down an inappropriate path, it is so disappointing that the general feeling is that they are doing so. I really can't see any professional in the business going ya-ha-ha if they drop back to a previous generation of battery. OK, it didn't work out, right fix applied, on we go. Big boys stuff.
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Like the bench test idea, providing it accurately reflects the actual operating conditions. I also hope the FAA is invited so that all relevant parties can have input, although I suspect that the NTSB and FAA won't be buying each other lunch.
There's probably scope for rerunning some of the previous tests to see if the results are the same, be a tad interesting if the test rig throws up different results for tests carried out by the individual suppliers.
In fairness, all suppliers should have tested to known criteria and the results will be on record.
Just glad that there's some progress.
There's probably scope for rerunning some of the previous tests to see if the results are the same, be a tad interesting if the test rig throws up different results for tests carried out by the individual suppliers.
In fairness, all suppliers should have tested to known criteria and the results will be on record.
Just glad that there's some progress.
Last edited by Momoe; 12th Mar 2013 at 19:18.
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Mr Battery meet Mr Circuit Breaker
Barrieh,# 1232
Quite understandable..
Yes, and some some of them might even fail even if they are operated within specification.
I don't completely agree.
A mechanical circuit breaker is a reliable component, and would be the first choose for sort circuit and thermal overload protection.
But circuit breakers can fail, and nobody would detect it, and I have hard about several fires in my industry due to malfunctioning circuit breakers. (From a leading European manufacture)
If you really know what you are doing, a better protection can be achieved by contactors, and electronics. It would be possible to design a system that is fault tolerant, and have selftest to prevent dormant faults.
I'm a professional electrical engineer. I don't work in aviation. I have just read the NTSB Interim and I am horrified.
We (the overall engineering sector) have know for a long time that Li Ion batteries don't play well with others. They are have an *inherent* tendency to get hot and catch on fire if they are at all mis-treated (over-charge, over-discharge, sudden changes in rates of charge).
The standard solution is always to provide an old-style circuit breaker (or fuse) and an old-style over-temp breaker. By old style I mean "mechanical".
Boeing chose to use a "contactor" do both jobs, based on software calculations performed by the BCU. This is just plane (no pun intended) poor engineering. I have written thousands of lines of controller code in my career, I would never support a decision to protect a Li Ion battery with a breaker which makes decisions based on software (Even if I had written it).
Boeing chose to use a "contactor" do both jobs, based on software calculations performed by the BCU. This is just plane (no pun intended) poor engineering. I have written thousands of lines of controller code in my career, I would never support a decision to protect a Li Ion battery with a breaker which makes decisions based on software (Even if I had written it).
A mechanical circuit breaker is a reliable component, and would be the first choose for sort circuit and thermal overload protection.
But circuit breakers can fail, and nobody would detect it, and I have hard about several fires in my industry due to malfunctioning circuit breakers. (From a leading European manufacture)
If you really know what you are doing, a better protection can be achieved by contactors, and electronics. It would be possible to design a system that is fault tolerant, and have selftest to prevent dormant faults.
Seattle Times article here:
FAA gives OK to 787 test flights for battery fix | Business & Technology | The Seattle Times
FAA gives OK to 787 test flights for battery fix | Business & Technology | The Seattle Times
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.As long as the language can be broken down into predictable blocks of assembler, it's not a problem. Most of the issues one runs into with compiled languages has to do with the libraries used, not the language itself.
Real-time coding is a very specific discipline that is at best only obliquely comparable to the processes used by the rest of us mere mortals!
Speaking as an ancient 6502 bod from 1977 vintage
Last edited by DozyWannabe; 13th Mar 2013 at 02:36.
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Quoting the FAA
Press Release – FAA Approves Boeing 787 Certification Plan
> The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit
Seems good news to me. Wish we had details on that one. I'm ready to swallow the whole plan if it solves both a probable cause of the incidents, and the most damaging consequences of a fire, that will remain conceivable with Lithium-Oxyde chemistry.
Full disclosure: I'm an engineer, there's electrical engineering written on my diploma, but I made most of my professional life in electronics applied to systems where "security" means resistance to hacking.
Press Release – FAA Approves Boeing 787 Certification Plan
> The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit
Seems good news to me. Wish we had details on that one. I'm ready to swallow the whole plan if it solves both a probable cause of the incidents, and the most damaging consequences of a fire, that will remain conceivable with Lithium-Oxyde chemistry.
Full disclosure: I'm an engineer, there's electrical engineering written on my diploma, but I made most of my professional life in electronics applied to systems where "security" means resistance to hacking.
Last edited by fgrieu; 13th Mar 2013 at 07:25.
FAA gives OK to 787 test flights for battery fix | Business & Technology | The Seattle Times
The redesign has been approved for testing, a design that should been used from the start.
Doesn't mean the 787 is much closer to flying with paying passengers, for that they have to identify the problem.
From Press Release – FAA Approves Boeing 787 Certification Plan the good news is:
1. “The plan establishes specific pass/fail criteria, defines the parameters that should be measured, prescribes the test methodology and specifies the test setup and design. FAA engineers will be present for the testing and will be closely involved in all aspects of the process.” AND
2. “The certification plan is the first step in the process to evaluate the 787’s return to flight and requires Boeing to conduct extensive testing and analysis to demonstrate compliance with the applicable safety regulations and special conditions.” All Special Certification Conditions must be met. Put simply that mean batteries must not burn, except possibly once or twice during the lifetime of the entire 787 fleet. If batteries do overheat or burn, any fire must be safely contained within the battery enclosure and any harmful fumes must be vented overboard.
All of this should have been proven much more cautiously first time around. In fact NTSB Airworthiness Report at http://www.ntsb.gov/investigations/2...cket_doc13.pdf shows that certification assumptions and testing were woefully inadequate. Battery system components were tested in isolation, not even connected together! This time the job will be done better because there will be independent scrutiny.
My bigger concern is that NTSB gives us an insight into the inadequacies of Boeing self-certification but we have no idea what other tests were fudged elsewhere on the plane.
1. “The plan establishes specific pass/fail criteria, defines the parameters that should be measured, prescribes the test methodology and specifies the test setup and design. FAA engineers will be present for the testing and will be closely involved in all aspects of the process.” AND
2. “The certification plan is the first step in the process to evaluate the 787’s return to flight and requires Boeing to conduct extensive testing and analysis to demonstrate compliance with the applicable safety regulations and special conditions.” All Special Certification Conditions must be met. Put simply that mean batteries must not burn, except possibly once or twice during the lifetime of the entire 787 fleet. If batteries do overheat or burn, any fire must be safely contained within the battery enclosure and any harmful fumes must be vented overboard.
All of this should have been proven much more cautiously first time around. In fact NTSB Airworthiness Report at http://www.ntsb.gov/investigations/2...cket_doc13.pdf shows that certification assumptions and testing were woefully inadequate. Battery system components were tested in isolation, not even connected together! This time the job will be done better because there will be independent scrutiny.
My bigger concern is that NTSB gives us an insight into the inadequacies of Boeing self-certification but we have no idea what other tests were fudged elsewhere on the plane.
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I would expect any certification of this solution will at least involve taking the plane up to some high altitude airport, start one engine, pressurize the cabin to get the air flowing, short circuit the battery and wait 180 minutes or whatever ETOPS time is required and see what happens.
I would also advocate placing some kind of animals in the cabin to see if the exposure to fumes within that time frame will not prove hazardous - though I do hope there is some more humane way of assessing this particular risk.
The whole experiment could of course be filmed and then published on the web - actually seeing it work will convince people it can be trusted.
I would also advocate placing some kind of animals in the cabin to see if the exposure to fumes within that time frame will not prove hazardous - though I do hope there is some more humane way of assessing this particular risk.
The whole experiment could of course be filmed and then published on the web - actually seeing it work will convince people it can be trusted.
HighWind, #1239
Circuit breakers can fail, but imho, an electronic solution driving a contactor
is not enough on it's own, since the contactor coil drive transistor itself can
fail short circuit, not to mention the possibility of other hardware or software
failures.
For such a safety critical design, belt and braces, using a normally open
contactor and a mechanical circuit breaker or hrc fuse, would provide
disimilar solution redundancy that covers either circuit failure.
I'm a bit disappointed about the lack of real meat in the proposed solution as
well, in that it's only discussed in general terms. The really sad thing is
that Boeing had to be kicked so very hard to get their act together and do the
job properly. The bean counters will still think they were right though. They
will probably see the whole exercise in terms of damage limitation and will
learn nothing from it at all
...
If you really know what you are doing, a better protection can be achieved by contactors, and electronics. It would be possible to design a system that is fault tolerant, and have selftest to prevent dormant faults.
is not enough on it's own, since the contactor coil drive transistor itself can
fail short circuit, not to mention the possibility of other hardware or software
failures.
For such a safety critical design, belt and braces, using a normally open
contactor and a mechanical circuit breaker or hrc fuse, would provide
disimilar solution redundancy that covers either circuit failure.
I'm a bit disappointed about the lack of real meat in the proposed solution as
well, in that it's only discussed in general terms. The really sad thing is
that Boeing had to be kicked so very hard to get their act together and do the
job properly. The bean counters will still think they were right though. They
will probably see the whole exercise in terms of damage limitation and will
learn nothing from it at all
...
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Syseng68k,
Good post, especially last paragraph.
Boeing stock being at a 5 year high on the back of this is ironic!
There will be a bottom line to this, it's just not been written yet, let's see if the stock market is as enthusiastic then.
Good post, especially last paragraph.
Boeing stock being at a 5 year high on the back of this is ironic!
There will be a bottom line to this, it's just not been written yet, let's see if the stock market is as enthusiastic then.
The surprising thing to me is the battery, made by a Japanese company, the charging system electronics, made in Arizona USA under the direction of the French company Thales, who is in turn in charge of power electronics for the 787, have all never been fully tested as an integrated package.
Standard practice!
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Looks like it worked (for Boeing stock that is)
"Some analysts said the high-tech plane, which was grounded worldwide in January, might be flying passengers again as early as May, after the Federal Aviation Administration on Tuesday approved Boeing's plan to certify the battery system."
Boeing tests prompt analysts' upgrades, but risks still lurk - Yahoo! Finance
"Some analysts said the high-tech plane, which was grounded worldwide in January, might be flying passengers again as early as May, after the Federal Aviation Administration on Tuesday approved Boeing's plan to certify the battery system."
Boeing tests prompt analysts' upgrades, but risks still lurk - Yahoo! Finance
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Not exactly sure what the fix is here... but assuming that the batteries are enclosed in some kind of fireproof "safe", what kind of added weight do we foresee here? Is any extra weight simply going to cancel out the weight savings of these batteries in the first place?
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The following are the markups to the “revised” FAA Special Conditions:
In lieu of the requirements of 14 CFR 25.1353(c)(1) through (c)(4), the following special conditions apply. Lithium ion batteries must be designed and installed as follows:
(1) Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the charging or battery monitoring system not shown to be extremely remoteimprobable. The lithium ion battery installation must preclude explosion in the event of those failures. (working group to refine).
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure. (this may be met with requirement (1) - working group to refine).
(3) No explosive or toxic gases emitted by any lithium ion battery in normal operation, or as the result of any failure of the battery charging system, monitoring system, or battery installation not shown to be extremely remoteimprobable, may accumulate in hazardous quantities within the airplane. (this may be redundant with (1)).
(4) Installations of lithium ion batteries must meet the requirements of 14 CFR 25.863(a) through (d). (may also need to include parts 23, 27, & 29).
(5) No corrosive fluids or gases that may escape from any lithium ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition, in accordance with 14 CFR 25.1309(b) (also 23, 27, & 29) and applicable regulatory guidance. We may want to give other means of compliance such as venting gases off-board, containment enclosure, etc.
(6) Each lithium ion battery installation must have provisions to prevent any hazardous effect on structure or essential systems caused by the maximum amount of heat the battery can generate during a short circuit of the battery or of its individual cells. NOTE: Need to add a requirement to report maximum temperature reached during the RTCA/DO-311 Short circuit test. The equivalent UN 38.3 short circuit test states that testing occur at 55 deg C. DO-311 2.3.12 – External Short Circuit With Protection Disabled: states to report maximum temperature.
Test is run at 23 deg C. (7) Lithium ion battery installations systems must have a system means to control the charging
rate of the battery automatically, so as to prevent battery overheating or overcharging, and,
(i) A battery temperature sensing and over-temperature warning system with a means for automatically disconnecting the battery from its charging source in the event of an over- temperature condition, or,
(ii) A battery failure sensing and warning system with a means for automatically disconnecting the battery from its charging source in the event of battery failure.
(8) Any lithium ion battery installationsystem whose function is required for safe operation of the airplane must incorporate a monitoring and warning feature that will provide an indication to the appropriate flight crewmembers whenever the state of charge of the batteries has fallen below levels considered acceptable for dispatch of the airplane. (this is a new requirement that is applicable to Li-ion batteries/systems).
(9) The Instructions for Continued Airworthiness required by 14 CFR 25.1529 must contain maintenance requirements for measurements of battery capacity at appropriate intervals to ensure that batteries whose function is required for safe operation of the airplane will perform their intended function as long as the battery is installed in the airplane. The Instructions for Continued Airworthiness must also contain procedures for the maintenance of lithium ion batteries in spares storage to prevent the replacement of batteries whose function is required for safe operation of the airplane with batteries that have experienced degraded charge retention ability or other damage due to prolonged storage at a low state of charge. (this requirement is already required to meet compliance to 1529).
In lieu of the requirements of 14 CFR 25.1353(c)(1) through (c)(4), the following special conditions apply. Lithium ion batteries must be designed and installed as follows:
(1) Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the charging or battery monitoring system not shown to be extremely remoteimprobable. The lithium ion battery installation must preclude explosion in the event of those failures. (working group to refine).
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure. (this may be met with requirement (1) - working group to refine).
(3) No explosive or toxic gases emitted by any lithium ion battery in normal operation, or as the result of any failure of the battery charging system, monitoring system, or battery installation not shown to be extremely remoteimprobable, may accumulate in hazardous quantities within the airplane. (this may be redundant with (1)).
(4) Installations of lithium ion batteries must meet the requirements of 14 CFR 25.863(a) through (d). (may also need to include parts 23, 27, & 29).
(5) No corrosive fluids or gases that may escape from any lithium ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition, in accordance with 14 CFR 25.1309(b) (also 23, 27, & 29) and applicable regulatory guidance. We may want to give other means of compliance such as venting gases off-board, containment enclosure, etc.
(6) Each lithium ion battery installation must have provisions to prevent any hazardous effect on structure or essential systems caused by the maximum amount of heat the battery can generate during a short circuit of the battery or of its individual cells. NOTE: Need to add a requirement to report maximum temperature reached during the RTCA/DO-311 Short circuit test. The equivalent UN 38.3 short circuit test states that testing occur at 55 deg C. DO-311 2.3.12 – External Short Circuit With Protection Disabled: states to report maximum temperature.
Test is run at 23 deg C. (7) Lithium ion battery installations systems must have a system means to control the charging
rate of the battery automatically, so as to prevent battery overheating or overcharging, and,
(i) A battery temperature sensing and over-temperature warning system with a means for automatically disconnecting the battery from its charging source in the event of an over- temperature condition, or,
(ii) A battery failure sensing and warning system with a means for automatically disconnecting the battery from its charging source in the event of battery failure.
(8) Any lithium ion battery installationsystem whose function is required for safe operation of the airplane must incorporate a monitoring and warning feature that will provide an indication to the appropriate flight crewmembers whenever the state of charge of the batteries has fallen below levels considered acceptable for dispatch of the airplane. (this is a new requirement that is applicable to Li-ion batteries/systems).
(9) The Instructions for Continued Airworthiness required by 14 CFR 25.1529 must contain maintenance requirements for measurements of battery capacity at appropriate intervals to ensure that batteries whose function is required for safe operation of the airplane will perform their intended function as long as the battery is installed in the airplane. The Instructions for Continued Airworthiness must also contain procedures for the maintenance of lithium ion batteries in spares storage to prevent the replacement of batteries whose function is required for safe operation of the airplane with batteries that have experienced degraded charge retention ability or other damage due to prolonged storage at a low state of charge. (this requirement is already required to meet compliance to 1529).
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So correct me if I am wrong please, but they still dont know what the cause is (and probably never will), so the "fix" from Boeing is to "contain" a runaway battery, ie contain and released fluids and thermal damage inside a stronger box, not stop it from happening in the first place, am I correct?