Comment by aphextim | Hacker News Reader

Comment by aphextim | Hacker News Reader

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Pretty sure that dumping fuel can be quite common when there is a critical malfunction before they return to land. As someone pointed out they would prefer to keep the fuel because it is expensive and they really don't want to dump over populated areas. I would rather have some kids have to take a shower, than have 140+ passengers killed in a possible explosion. Also the Jet Fuel would have been pretty dispersed by the time it reached them vs someone who is fueling an aircraft with it.

The MSDS sheet on Jet Fuel

http://www.usor.com/files/pdf/4/Jet%20Fuel%20-%20SDS%20941%2...

From the article:

>A total of 60 patients were treated, at least 20 of them children. The Los Angeles County Fire Department said more than 70 firefighters and paramedics headed to Park School Elementary, where 20 children and 11 adults were treated for minor injuries. No one was taken to the hospital.

So 20 children and 11 adults treated for minor injuries and not one was hospitalized vs not ejecting the fuel and possibly causing an explosion upon landing for 140+ passengers.

I'm a huge aviation enthusiast and while I understand your point, I disagree.

I think the captain of this flight should be in major trouble. If you listen to the ATC recordings, they ask the captain multiple times if he needs to dump fuel and offer him vectors to do so.

Instead of taking those vectors, the captain says they won't need to dump fuel and then turns over downtown SF and dumps fuel all over a bunch of people, necessitating medical help.

Calling this a "media frenzy" is probably the most disingenuous thing I've heard this week.

downtown SF? The linked story happened near LAX in LA.

typo.

Describing this as a "media frenzy" doesn't seem valid. It's quite notable, and certainly not something we'd want to see repeated.

If this was dire enough that they didn't have time enough to empty over the ocean or desert, it may well have been justified. That should be investigated, though, and not just assumed. IIRC, LAX has had a significant history of pilots deviating from required flight paths, etc.

Noted and updated to remove.

Diluted how? As in, dispersed in air, so they got misted rather than drenched?

(If so, "doused" is a poor choice of words for the headline, though par for the course in modern journalism.)

Dispersed was the word I was looking for. Nothing was added to the fuel to dilute.

I incorrectly use Diluted probably because I had an old roommate was in water tech always use the phrase jokingly, "The solution to pollution is dilution".

I will edit my post to be correct.

Ah, sorry. Hadn't meant to be pedantic. I was just wondering if perhaps there was some sort of dilution process applied to jet fuel, maybe for safety reasons.

From my understanding fuel is supposed to be dumbed above a certain height. High enough that it should evaporate fully before reaching the ground.

Yeah, you don't dump fuel unless you have to. It's expensive, especially in an industry with such tight margins as the airlines.

It'll typically be done in an unpopulated area, if they can, but if they were dumping over LA it means they really wanted to get it back on the ground fast.

edit: Something very odd about this case. Given the ATC recordings linked elsewhere, there was no reason for them to be dumping over populated areas - they were offered an over-water hold to do so and said they wouldn't need it. Baffling.

Very true, I shouldn't have said standard practice and should have phrased it differently as I'm sure they would rather keep the fuel than waste it as you describe.

Fuel is dumped to get the weight of the plane at or below the defined max landing weight.

While a plane is unlikely to explode during an overweight landing, it might receive expensive structural damages from an overweight landing. Anyway expensive investigations will be needed to check for such damages after an overweight landing.

It's not just a structural limitation, there's also a limitation to how much energy the brakes and tires can absorb. Landing at a higher weight requires a higher landing speed, so more energy to dissipate. At very high weights, the tires/brakes will catch on fire during/after landing.

Yeah but at LAX they have a 12000 foot runway. Hard to imagine that would be an issue there.

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