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Comment by jerrya | Hacker News Reader

Placing the batteries in a steel cased compartment with a vent to the exterior of the plane to limit future, perhaps inevitable explosions and fires is an example of

    1) __ An inspired engineering fix

    2) __ A kluge

    3) __ A feature, once the proper FAA documentation has been filed

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All of the above?

Mitigating your failure modes is an important and legitimate part of engineering. If anything, designing your product as if it can't possibly fail in horrifying ways is the surest way to kill several hundred people at once.

Yep, it's an inspired kludge that results in a nice feature. If you design a machine never to fail, you only ensure that you can't recover when it does fail.

There's noting inspired about "put the fire hazard in a fireproof box". I'm not sure it amounts to a kludge, either - it's a quick fix, and probably not the most elegant one possible, but there's a good chance it would have been deemed the most cost-effective solution even without the time pressure.

The sarcasm isn't warranted. This is appropriate. The actual engines on these planes have non-zero failure rates. Every year or so (someone will have to look up stats because I'm too lazy) a jet lands with the smoking remains of one under its wings.

Stuff breaks. The goal of safety engineering is as much to reduce the impact of failures as it is to reduce their frequency. Everything is about tradeoffs.

The original design, years in the making, was based on batteries that would never catch fire.

They have moved from never catch fire, in a period of a few months, to batteries they hope will not catch fire, with features to enable survivability should a battery catch fire.

If this new design is appropriate, that earlier design was engineering malpractice.

I doubt this design would be the outcome of the same Boeing design engineering effort without the get it to market time constraint. Just like when a web service goes down mysteriously and the engineers desire is to take it down and debug it and the required response is to patch it, and get her flying again. But I wouldn't term that "design" or "engineered".

"Malpractice" seems like a loaded word chosen more for debate impact than suitability. We can certainly agree that the original design was wrong (or "mistaken" if you want to load it on the other side). Isn't that enough?

I honestly don't know. I am hard put to explain what malpractice might be for a lawyer or doctor that wouldn't be the same for the largest US manufacturer of aircraft and her engineers.

This was a huge mistake, and it seemed as though they should've known.

While the failure rate is certainly not zero (Hudson miracle, Qantas A380 engine explosion) jet engines are so extremely reliable that I doubt such statistics can even be found.

There are additional safeguards when it comes to a jetliners powerplants. For example: The oil is never exchanged at the same time in all engines on a plane.

I fail to see, however, what this has to do with burning batteries on a plane.

A fire on a plane in flight is one of the worst imaginable scenarios, while the chances to land a plane without engine power are actually quite good. Unless you're in the middle of an ocean, that is.

Jet engines fail with decent regularity. It's not exactly common, but nor is it too rare to measure. For example, this claims a failure rate of about once per thirty years:

http://www.airbus.com/fileadmin/media_gallery/files/safety_l...

Which, based on the number flying regularly, means there's an in-flight failure happening somewhere in the world every few days or so.

There is a reason that every airliner of appreciable size has two engines or more.

The 787 is rated to fly up to three hours away from the nearest airport. A gliding airliner will be lucky to make a tenth of that distance.

This Airbus documents suggests a failure rate of of <1 per 100,000 flight hours [1]. (just an FYI, pretty increasing. 40 fold decrease since start of the jet liner era).

I think the point he was trying to make is that while Boeing's actions clearly do not reduce the risk dangerous battery fire to zero, Boeing not only does not have to reduce it to zero, but really there should be no expectation that it be reduced to zero, given that we already fly accepting some sort of failure rate on the engine. This stems from the original posters implication that Boeing just used some sort of cheap hack fix so they could stem the deluge of bad PR and start making money again - with the further implication that the actions taken are a cheap hack fix since they clearly do not reduce risk to zero.

[1] http://www.airbus.com/fileadmin/media_gallery/files/safety_l...

While the statistical failure rate is quite low, with the total hours flown, they still happen regularly. http://avherald.com/h?search_term=engine+shut+down&opt=6...

A contained battery overtemp failure is not a big deal, but an uncontained battery thermal runaway is a huge safety issue. Qantas A380 was a extremely rare uncontained failure, the most serious type of malfunction. The Hudson A320 was a double engine failure, also is extremely rare. There have been incidents of maintenance SNAFU causing oil loss in all 3 engines on a DC-10, but ETOPS rules for twin aircraft prevent such incidents from maintenance causes.

An uncontrolled fire on a plane is a worst case scenario, and ironically in some cases a water ditching might actually be advisable. A contained and extinguished engine fire in one engine is not nearly as critical.

I would imagine that increasing the spacing between the cells actually fixed the problem, while the case and vent are just limiting the PR and financial liability.

pooch, your post is appearing as [dead] to me so your account may be hellbanned, which you may want to get fixed since you've made an informative post that many users won't be able to see.

Can you copy/paste it?

"From an electrical engineering standpoint, that makes no sense. Thermal runaway starts when too much power is being drawn from the batteries and they begin to overheat until exploding or melting, their promixity to each other may limit the damage of an overloaded or malfunctioning cell, however the core problem remains, why are 787 electronic systems overloading the batteries?"

"If one cell explodes or melts, you still essentially have a fire in progress. Protecting the other cells buys you time, but how much time do you have when there is fire on a plane?"

"Obviously its a design issue, probably very complex that Boeing simply doesnt have the time and money to investigate thoroughly."

"So this is a patch. Nothing I have read indicates an engineering approach was taken to prevent the previous result."

https://news.ycombinator.com/item?id=5740563

The spacing between the cells minimizes the chance of a multi-cell cascading fire. I think they also changed the charging controller to better monitor the battery status and charge/discharge current. Changing the controller was part of the "fix".

I'm guessing at some point, they'll make a change to the Lithium cell chemistry for enhanced safety. Changing the chemistry of the battery, and controller software updates is the real fix. The rest is just failure mitigation.

It is a necessary engineering fix. Any new design they introduce will have to go through extensive testing and verification that will take months. The goal here is to be able to assure the authorities and the public of absolute safety as quickly as possible.

You have multiple factories staying still at an enormous cost because of this. You have angry customers that have billions of dollars worth of planes standing still (while they have to pay interest on those billions of dollars). This is not the time to get creative.

If they were starting from scratch they certainly should have done something better and put it through the usual verification channels. But there is no time for this now.

I don't believe they idled their factories. In fact, there was an article about how they had to find parking for all their newly assembled airplanes while they were grounded:

http://www.nytimes.com/2013/02/20/realestate/commercial/to-b...

and, what if they DIDN'T put a fireproof box around the batteries that had caught on fire multiple times in the past, when given the opportunity as the whole fleet was grounded?

is that smart, or stupid?

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