News French plane lost over Atlantic

[garyw]

The third interim report was released over a month ago and can be found here. The one part I found most interesting the aircrafts attitude at the moment of impact:

The recordings stopped at 2 h 14 min 28. The last recorded values were a vertical speed of -10,912 ft/min, a ground speed of 107 kt, pitch attitude of 16.2 degrees nose-up, roll angle of 5.3 degrees left and a magnetic heading of 270 degrees.

 

[Urwumpe]

10,000 ft/min? That is extremely fast. About 300 km/h, if I convert correctly.

 

[garyw]

Exactly. Seems to prove that the aircraft was in a flat spin when it impacted the water

 

[Cras]

10,000 ft/min? That is extremely fast.

That is a shockingly high number.

What a horrible crash this was. And still so many questions that need answering.

 

[ky]

10,000 ft/min? That is extremely fast. About 300 km/h, if I convert correctly.

That means they died from the force of the impact.

 

[Urwumpe]

That means they probably died from the force of the impact.

:facepalm:

 

[garyw]

That means they probably died from the force of the impact.

that's quite an understatement. The G-Forces at impact would have been hundreds upon hundreds of Gees. You are talking liquification and extreme blunt force trauma. Not a pretty sight.

 

[APDAF]

In Lyman's terms red goo kind of death.

 

[garyw]

A quick back of the envelope calculation shows an impact g-force of 339g.

 

[Evil_Onyx]

Mercifully quick. At least that explains why so little of the aircraft was recovered.

 

[Linguofreak]

A quick back of the envelope calculation shows an impact g-force of 339g.

I'd be interested in seeing that envelope, given that impact physics is not my strong point.

 

[GigaG]

Space Shuttle Challenger's cabin impacted the ocean at 207mph, creating over 200g, which killed any surviving crew members instantly.

300 kph=186.411358 mph, which is pretty close to the Challenger impact. However, the plane was falling at 10,912 f/m, which converts on this calculator to about 124mph. That also would likely kill everybody instantly.

However, consider that the plane is moving forward at 107 knots - 123.133401 mph - at the time the recordings stopped (the slow speed being because of the stalling of the jet). Depending on if you convert from 300kph or 10912 feet/m, this equals that the A330 could have been descending at or faster than the amount it was moving forward.

 

[garyw]

I'd be interested in seeing that envelope, given that impact physics is not my strong point.

Sure:

10,912ft feet per minute to metres per minute = 3 325.9776

Assuming a deceleration time of 1 second you have 3,325/1=3,325

Finally 3,325/9.8 (1g) = 339.28

My math skills are generally pretty awful so corrections are welcome. The formula was nabbed from a website and the assumption of a 1 second decelaration period was utterly arbitary!

 

[Urwumpe]

....

Gary: 3,325 m/s is Mach 6

What you mean is 10,912 feet/Minute => 3 325.9776 meters / minute => 55.43296 m/s

 

[Zeehond]

....

Gary: 3,325 m/s is Mach 6

What you mean is 10,912 feet/Minute => 3 325.9776 meters / minute => 55.43296 m/s

If we assume that the plane has a vertical speed of 55 m/s and that the plane will stop in 2 meters of water (just a wild guess) and that the deceleration is constant (assumption), it will stop in 2/(55/2) = 73 ms.

The deceleration will then be 55/0.073 = 753 m/s^2 and the vertical impact would be 753/9.8 = 77 G. Still pretty deadly for most and we didn't even take the horizontal deceleration into account.

 

[Keatah]

that's quite an understatement. The G-Forces at impact would have been hundreds upon hundreds of Gees. You are talking liquification and extreme blunt force trauma. Not a pretty sight.

Sounds like your brain could escape the skull down through your neck and explode out your pelvic area along with all the other squishy stuff. Skin getting stretched and sloughing off your skeleton like it was being melted and decayed. Just happening in hundredths of a second.

 

[Urwumpe]

Sounds like your brain could escape the skull down through your neck and explode out your pelvic area along with all the other squishy stuff. Skin getting stretched and sloughing off your skeleton like it was being melted and decayed. Just happening in hundredths of a second.

well, the bad thing is: This isn't one human body and this isn't only humans. While such extreme damages will likely only affect parts of the human body (absorbing the energy), the whole chaos that will break out in microseconds will mean that all turns into a wild mix of human remains, debris parts and identifiable body parts.

You sure as hell don't want to be at such a crash site directly after the accident.

I had a scientific paper about water impacts somewhere, but I can already tell you without resorting to the experimental data, that the plane won't dive 2 meters into the water. At such speeds, the inertia of the practically incompressible water means, that it is more like hitting rough concrete. Most deceleration will happen in the first microseconds of impact, and the remaining debris will reach terminal velocity in water a few fractions of a second later.

Instead of just 77g, you will more likely experience something around 200g for a fraction of a second at the body parts in contact with floor and seat, including that the bottom of the plane in such an impact already absorbed a lot of energy. What comes next is pure inertia.

When Princess Diana died, she was not having her seat belts on and impacted at about 1/3 the speed of the aircraft. Was strong enough to kill her alone by dislodging her heart to the opposite side of the chest. Pure inertia. Humans are not really that fragile as it might sound here, but they are really easily damaged by brute force.

 

[Linguofreak]

Sure:

10,912ft feet per minute to metres per minute = 3 325.9776

Assuming a deceleration time of 1 second you have 3,325/1=3,325

Finally 3,325/9.8 (1g) = 339.28

My math skills are generally pretty awful so corrections are welcome. The formula was nabbed from a website and the assumption of a 1 second decelaration period was utterly arbitary!

A full second for deceleration sounds horribly long. (Plus, there's the error Urwumpe pointed out where you used meters per minute for your speed but meters per second squared for your acceleration). 10,912 feet per minute in one second comes out to about 5 g's.

I do think that your 300 g figure is probably closer to what you'd get in such an impact, because I expect the stopping time would probably be in the single or double digit milliseconds.

 

[Suzy]

Popular Mechanics article, 6/12: What Really Happened Aboard Air France 447

 

[mojoey]

I remember reading that cover story, and thinking it was horrible. I had completely forgot about it until now..