I'm glad we're having this debate. A hundred years ago the average life span in the US was only 47 years...
|Quoting JoeCanuck (Reply 54):|
Quoting Stitch (Reply 5):
And we are fortunate that we have members who understand these exact technicalities in this specific field and have tried very hard to provide specific definitions so that these incidents can be correctly and accurately discussed.
I further add that. I am an expert in flight test, fluid analysis, and a few other things; but not batteries, so I appreciate the education and patience of our members who do know more.
|Quoting prebennorholm (Reply 11):|
About heat: Those batteries went to full destruction on their known thermal runaway failure mode. We have no evidence telling that any other equipment suffered any heat damage. Therefore the heat can be assumed to be contained in these incidents.
They will engineer in labs. If it was the worst case scenario (probably not, that would be the peak day temperature), then it has proven itself.
|Quoting Stitch (Reply 12):|
I have heard an unconfirmed report that some 787s recently received a software update that changed the power system battery charging algorithm(s) and controls
I wouldn't be surprised. The question is how much did it reduce the chance of a runaway battery?
|Quoting WingedMigrator (Reply 37):|
Sorry, I read that somewhere and must have mis-remembered it. It obviously can't be that high... probably closer to 130,000.
I speculate the 787s are being used at a low daily utilization rate, probably down at 13 hours/day.
50 planes * 13 hours/(day per plane)*365 days/year=237,250 hours/year. Considering how recent many of the deliveries have been, I would think 130,000 hours would be a reasonable number.
|Quoting AlfaBlue (Reply 58):|
Some of the posts on this topic seem to try to downplay this as a no-event
It isn't a non-event, but it is an event that can be engineered to a far lower level of probability. For example, gasoline is an extremely dangerous substance. Many cars in the past would just catch fire due to defects. But we haven't gotten rid of gasoline in our cars, we instead made them more leak proof and put a pad in the gas tank so that there is far less risk of detonation in a crash. These batteries have containment that has done its job not only in the lab but in the real world. Now to re-engineer so there is less chance of a run away battery.
But it wasn't just the batteries on the 787. The two aircraft had fuel system issues that created spills. That must be corrected to.
I personally think the idea of individual cell monitoring must be considered (voltage per cell?). But I am not a battery expert and I will let them make the suggestions.
|Quoting AlfaBlue (Reply 58):|
This aircraft has a deeply flawed electrical system and the recent incidents just made that very clear to very many people. Only very naive people will think that there is an easy fix and that the 787 will do long ocean crossings again in a few days.
Were hydraulic systems deeply flawed after the DC-10?
This isn't a simple solution, but all military aircraft are heading to electrical aircraft as they are *safer* in the long run. Skydrol is a nasty chemical. The joke is there will always be a career for safety engineers as long as there is Skydrol (hydraulic fluid) in aircraft. It is taking some debugging. All high energy subsystems need to be treated with respect. The issue for electrical systems is for an aircraft of this size, there was no predecessor. But most of the electrical system is working as intended.
Here is the neat thing. A hydraulic aircraft that has a stability issue is stuck with it (e.g., the challenge of the 727). All fly by wire aircraft are 'retuned' about every 3 to 5 years and the 787 will be far more tunable than the 777 or A320/A330. That means constant safety and efficiency improvements throughout the first 20 years of the aircraft service (after then, there are few, if any, changes).
A decade from now a 787 will be a safer aircraft than the 767 or A330 to fly on. Those will still be fine aircraft, but they simply do not have the computers no electrical systems to be refined to the degree the 787 will be.
The batteries will have to be addressed. With Lithium batteries, a simple change in the charging voltage profile can reduce the risk of a battery fire by a ten thousand (or more).
Think of this like composite fan blades. They were pulled out of the 757 due to safety issues but are now standard with millions of flight hours upon them. Some technology needs to be refined. Luckily, batteries are an easy technology to fix as why they fail are known. e.g., one cell over-charges and 'runs away' which can be diagnosed by voltage across that one cell. While that might not be the end answer, there is more than one way to dramatically reduce the risk without a battery change.
Now I'm of the opinion the batteries will have to be changed as a PR
move... I would rather they aren't as the Lithium batteries are an excellent technical solution.
As to living with fire... Ummm... LROPS contains a cargo fire. As long as the probability of the fire decreases to a value low enough, that is ok. You do realize the requirement is so strict that the most dangerous part of your flight is as a pedestrian getting to and from the flight?
|Quoting Cubsrule (Reply 61):|
The issue today is the frequency of battery failures, not that they happen. Battery failures were anticipated and designed for.
And that sums it up... Get the frequency down and then the plane will fly again.
I cannot wait to get vaccinated to live again! Warning: I simulated that it takes 50%+ vaccinated to protect the vaccinated and 75%+ vaccinated to protect the vac-hesitant.