Scuba bottles are filled to 3000psi (200 bar) IIRC (I have a couple here).

Aviation o2 bottles are rebadged diving bottles and all those I have had are redlined about 150 bar (about 2200psi). That is what enables a number of them to be filled from a rented BOC bottle which comes in at 3000psi, before the source bottle gets down too far.

As regards damage, I have seen some movies of them being fired at with a high velocity rifle to make sure they stay in one piece, with the gas escaping through the hole (or 2 holes) with a huge bang. This apparently works but assumes there is no internal corrosion. If the bottle is corroded then it could rupture and then you have a big problem...

If the two seats and occupants were ejected sideways with just compressed air, that would be an astonishing vertical speed (not 2000fpm i.e. 20kt).

I suspect you guys are making more of a mystery of the seats/cabin configuration then is necessary. I have looked more closely at the pictures. The team on the mountain have clearly already done a reasonable amount of recovery. As such, the state of the cabin and the location of the seats is probably a result of the recovery team cutting open the aircraft and removing seats to access the interior so as to remove the crew and passengers rather than a direct result of the crash dynamics.

It is still quite a mystery has to why it looks like it hit vertically.

The first pic (horrible as it is), is taken from the chopper, apparently shows the seats in their final position before any rescue team arrive at the site, so I suspect they were ejected on impact.

Surely an exploding gas cylinder would simply blast through the side/top/ bottom/skin of the aircraft? I know of one medical one which decided to malfunction in a hospital corridor. It blasted its way down the corridor riccocheting off the walls until it finally came to a stop - empty. The walls in question were thick, brick ones, an aircraft is far less substantial.

That's if the valve comes off. Valves do get broken off through mishandling.

If a whole end comes off, as happened on that 747 recently, the whole cylinder shoots out and makes a hole which in that case was an amazingly close match for the cylinder diameter.

The worst one is if the whole cylinder splits and all the gas comes out in one go. That's a proper explosion. Those are very rare.

I know the damage an exploding O2 bottle would do. I have been handling 02 and 02 filling systems as well as teaching the physiology of it for 25 years. I have seen diving cylinders and O2 cylinders fail. I have caused many of them to fail during testing over the years. For an O2 cylinder to fail in an explosive manner would require a combustion incident. For it to split on impact would require it to be attached to a point on the aircraft where the loads were transferred directly to it. A loose O2 cylinder is more likely to have bounced out intact rather than rupturing. I had one fall of the back of the RIB once and bounce down the dual carriageway without harm!

I think the O2 bottle in this instance is a red herring. I posted some photographs a few years ago on here of what an O2 explosion does look like.

Fuel starvation may account for the lack of combustion? from the looks of those wings the cells had to have been puntured?

FlyingKiwi

Running out of fuel would be a possibility. I remember being asked by what was then known as Anglo American the piper dealership at bournemouth to fly a PPL from Luton to Nice.
The Guy had just bought a shiny new Seneca Five from them but had no instrument ratings.
We left luton with the demands from this PPL that we made Nice in one. That was why he bought the aircraft to make Nice in one.
I told him that he was wishful thinking unless we got a blinding tailwind.
The Seneca has a DDMP which is very accurate on endurance and fuel at destination.
Passing Grenoble it was obvious that no way were we going to make it.
"The DDMP says we will have 4 gals a side when we get there". He said with delight! We had a blazing row mid flight and dropped into Grenoble to refuel.

It would not be the first time that a pilot has stretched the fuel too far.
That still would not account for panning into a mountain side rather than crash landing into the valley

Pace

4 Gals a side! not caring about legal reserves then? whats the unsuable on a Seneca, can't be far off?

Maybe the crash pilot was trying to glide into the valley and the ridge got in the way? raised nose to 'hop' over and bam, stall, flop.

Still very sad when family trips end like this, happen in Queenstown here in NZ ti think it was a very low hours ME pilot tried to take a nice fast 402 (i think) out with the family, over loaded and i think came to grief not far from the end of the runway.

Anybody know how many hours the pilot had on type?

Actually that (trying to fly down into the valley for whatever reason) seems quite plausible. Being at a flying speed would explain the high speed of the impact.

A Seneca can surely do Luton to Nice nonstop? About 600nm. A TB20 could do that and back to Luton without landing, down to nearly zero fuel.
For one in a good condition, sure. I don't recall blowing one up myself recently; I restricted my pranks to stacking up some 7.62mm machine gun ammo on top of a firelighter brick, setting fire to it, then running off and hiding behind a tree (age ~ 9).

Wow thats a bit naughty, how did a 9 yr old get 7.62 rounds?

A much older me (teenager) with friend whose father was a black powder nut, filled a toilet roll with black powder (wrapped in roll of duct tape) improvised a fuse and got the shock of our lives.

still have all 11 fingers....

I don't think that the aircraft ran out of fuel, the preliminary report here:

http://www.bfu.admin.ch/common/pdf/HB-GDS.pdf

states that it had only been airborne for less than 30 minutes and that fuel leaked from the wreck.

This is a rumour network so I will speculate:

I know that the weather at the time was benign, clear skies and light winds. I would assume that the father was seated forward with his wife and children behind. He twisted round in his seat to speak to his family behind him and in doing so inadvertently pressed full rudder. This set off a chain of events leading to loss of control of the aircraft ending in a flat spin, perhaps even with structural damage before impact. Unlikely? No, it has happened before.

The aircraft first flew in 1962, so would have been later fitted with GPS. I am sure that the investigators will be trying to read the memory, if any, of this and certainly of any mobile phones or cameras that often include a GPS function in order to get an idea of the flight profile.

Without going into a long diatribe about what causes a gas cylinder to fail or what even counts as one in poor condition it is still not my view that the ejection of the seats and occupants was anything to do with a gas explosion.

Cylinders fail rarely and for a relatively limited number of circumstances. Crystallisation of the metal caused by over heating and over pressurisation during many filling cycles is one cause. This generally causes a rupture which will cause the cylinder to move but not create the explosive energy to throw two seats and the occupants out.

A cylinder with heavy internal corrosion will provide a source of ignition and fuel for an explosion but this would occur during filling due to adiabatic heating completing all sides of the fire triangle.

A cylinder will not explode due to impact damage. If it was attached the airframe and received enough damage to split then it could force a stream of directional gas out but not enough to rip a seat and it's occupant out let alone two in different directions. A loose cylinder recieving enough damage to burst would become a projectile. Again probably doing serious damage to anything it hit but not enough to eject 2 seats and occupants.

Why do you think ejector seats use rockets and not compressed gas.........

Its about 660 nm Luton to Nice the Seneca will fly 5 hours to dry tanks at 160 kts or 4 hrs with an hours reserve.
Four hours will take you 640 nm.

Take them up into oxygen land and yes the TAS will increase to around 200 kts

We had a headwind which gave us a GS of around 130-140kts go figure and flew at around 10K?


Pace

I have never been sure about the dynamics of the Flat Spin, are they recoverable? how does one get into a flat spin (yes i have seen Top Gun) in a light A/C

As far as I understand it, a flat spin results from too great a rate of yaw when the gyroscopic effect causes the nose to rise. To get out you must get the nose down somehow -unlike normal spin recovery you may need to try pro spin controls and/or even add engine power. Keeping the COG forward is the best insurance against it.

my 2c

MF

Seems from the report it was not a business charter flight but a private flight by a private owner in a private operation so they must have known each other...

The report states it hit a ridge violently and subsequently came to a stop. This suggests two different actions? The hit and coming to a stop? Perhaps the pictures we were seeing do not tell the entire story and the nose hit another rock which does not appear on the pics, dramatically lost speed and stalled into the ground perhaps some 50 m beyond...

The report says: In an alpine flight, the aircraft struck a ridge violently
mountain on which it stops thereafter.

There would always be a fuel leak anyway - every plane like this will have a few gallons of unusable fuel.

I am no spin specialist but I gather a flat spin results in a relatively low VS. I have read one aero champion saying a flat spin is a reasonable way to descend through cloud if caught above an overcast... In this case the VS was very high.

Twins are not required to be able to recover from a spin, AFAIK. But I don't think this was a spin.

It almost makes sense that the pilot may have been doing some "amateur aeros" and in a descent into the valley he misjudged it and hit that rock. That would account for it - except for the evidently zero forward speed. In flight, there is no way to translate say 150kt into a VS of say 100-150kt and zero forward speed.

I don't think the O2 ejected the passengers, reasonably theory that it is, and they may not have had O2 onboard not being a "P". I reckon it was just the force of the impact which destroyed the aeroplane and threw the seats out.

I *expect* the pilot had a fair few hours, certainly enough to get insurance on a Baron, which would mean he was reasonably experienced.

I don't think weather was a factor in this.

Fuel - surprisingly there doesn't seem to be much evidence of spilled fuel and you'd expect that with full tanks and those hot exhausts laying around that there would have been some fire with full tanks. All the fuel tanks must have ruptured duing that impact spraying avgas everywhere. It might have been luck or the pics may not show properly.

Barcli brought up the point of the Baron wing spar AD - that could be a likely cause if the wings folded up.

Pressing the rudder pedal? Hmm, it has happened before but it is a long shot. Besides you wouldn't enter a flat spin if flying at Baron crusie speed and deflecting the rudder pedal and would probably break something on the back of the aeroplane.

Maybe....he just flew into the ridge while trying to get some nice close video or pictures....?

It is a mystery.

The roof looks to me as if it has been peeled back during the rescue attempt, and then allowed to flop forward again, hence the appearance of having blown upwards.

Really horrid, sobering photo's which will be kept from my wife at all costs.