Have been travelling, very late to the party. Picking up some stuff from the prior threads:
"Am still hoping Tdscanuck or CM
will comment in whether or not atmospheric pressure changes might have a role.. (See post 1)"
Possible, but heavily tested so unlikely.
|Quoting art (Reply 7):|
Could any of the cognoscenti hazard how long the grounding will be if it is determined that the problem is "simply" manufacturing defects in the batteries concerned?
Best case is they discover a manufacturing defect that's detectable...then they just have to inspect the fleet batteries for the defect and clear those that don't have the defect. An approximately similar thing happened with 737NG fuel pumps several years ago (they had to be X-rayed to make sure some internal wires were in the right place). That could be done on the order of days/a few weeks.
|Quoting Aesma (Reply 15):|
The basis for certification is that many kinds of failures can happen, without downing the aircraft. If we now discover failures that were not predicted, all bets are off.
cornutt summed this up far better than I could. Failures that weren't predicted are very bad, but this isn't a failure that wasn't predicted. It's just that the failure probability might be way off...this is also bad, but considerably more tractable than unanticipated failure modes.
|Quoting PW100 (Reply 16):|
Can't we all just agree that in the view of the regulators (FAA, EASA etc), anything supposed to be airborne that has not been demonstrated to be safe, is by definition unsafe?
No. That's not how the regulations work. Under that system, nothing would ever get certified.
|Quoting francoflier (Reply 27):|
in flight fire is never, ever something where you can say there is no risk of losing the aircraft. Especially when it happens in an inaccessible area with little fire protection/fighting capability.
Although it's true that you can never say there is *no* risk of losing the aircraft, you can estimate how likely it is for a fire to result in loss of the aircraft. In this case, since a battery fire was a design condition, the probability of a catastrophic event is still very very low. That doesn't make fires acceptable, in any way, but it does moderate the gap between likelyhood of a battery fire and likelyhood of a hull loss.
|Quoting RickNRoll (Reply 55):|
Not wanting to be a pain, but it only fixes the problem of the batteries failing as they have recently. They still need to address the issue of containing a battery adequately when it does fail.
So far, the existing events have demonstrated that the containment *does* work.
|Quoting JoeCanuck (Reply 60):|
My opinion is that these Li-ion batteries, (and batteries of similar chemistry), are unsuitable for high power applications on aircraft. The probability of failure and the difficulty in predicting failures, as well as the violent way they fail, raise them above the level of acceptable risk.
That's not necessarily true; you could assume the probability of a battery fire is 1, then modify the containment to still keep the probability of a catastrophic event to be extremely remote. This is, obviously, not what will actually happen but risk gets assessed at the aircraft level, not the component level, so component reliability doesn't directly inform what acceptable risk is.
|Quoting bonusonus (Reply 69):|
How and when does each type of battery get charged? And how much recharging is typically required in each?
Both batteries are charged anytime the airplane system is energized by another source (ground power, engine generators, or APU) until they're full, then they're just periodically checked. Since Li-ion doesn't discharge quickly when not used, they'll basically just sit there until they experience a current draw again. Since 787's like to stay powered up, any carrier that keeps them on ground power may never be charging the battery in any significant way.
|Quoting KC135Hydraulics (Reply 82):|
If a pickup-sized Diesel engine requires upwards of 700 cranking amps to turn over, imagine the instanteous draw from the electric starter on the 787's APU. It has to be quite high.
Not so bad...700Ax12V = 8400W. The 787 APU doesn't have a load compressor so it's only operating at very low power when starting and the battery is at higher voltage...I suspect it's actually pulling a lot less than 700A.
|Quoting sweair (Reply 90):|
So to repeat my question, would or could a fuel cell fueled by Jet-A be safer than a battery?
Could? Yes. Would? Unlikely.
|Quoting sweair (Reply 90):|
They create heat, but has there been any serious incidents with fuel cells?
I think fuel cells have melted down, but the problem is usually around the fuel or reformer rather than the cell itself.
|Quoting packsonflight (Reply 92):|
The 787 did not contain the battery failure properly. As far as I can see this is a fact, and Boeing definitely have to make some hardware changes here and get them certified.
How is this a fact? In both cases, the battery fire was contained and no other equipment was taken down in the process. Isn't that the containment requirement?
|Quoting teme82 (Reply 113):|
Quoting WingedMigrator (Reply 111):
That much is easy. 32V x 65Ah = 7.5 megajoules
I think that is more than enough to cause serious issues with the aircraft. If all the batteries would fail at the same time it would be really bad day for that plane and it's occupants.
The batteries aren't co-located and both battery areas are designed to contain the full energy of a battery fire indefinitely. It would be very very bad from a reliability standpoint but, at least based on the current facts, wouldn't present a danger of loss of the aircraft.
No. The plane is grounded because the regulators don't feel that Boeing has adequately proven that it meets the requirements. It is absolutely true that the regulators will ground a plane that is unsafe but that's not the only reason.
|Quoting F9animal (Reply 116):|
A fire from a battery is dangerous. Stop downplaying it, because it is what it is.
I agree it shouldn't be downplayed, but it also shouldn't be up-played. Fire is dangerous. Fire in an area designed to contain a fire, however, is a heck of a lot less dangerous than fire in an area not designed for it. This is *the* major difference between these events and Swissair111.
You can always put them up to 1 and see how that impacts the rest of the fault tree; this is conservative and gives you an idea of what the allowable range of numbers is.
|Quoting WingedMigrator (Reply 146):|
Since the time for the battery to combust itself totally is far less than the certified ETOPS time, is it not a condition for certification that the battery be allowed to combust itself totally, in flight, without endangering life?
|Quoting prebennorholm (Reply 150):|
The batteries will be removed from the EE-bays. Their failure mode has proved incompatible with other equipment in there.
How so? What other equipment stopped functioning?
|Quoting Skydrol (Reply 156):|
With all the negative publicity, will anyone ever really trust the outcome of the investigation, even if they announce they have found the fault?
Well, at least one person will. I suspect I know others.