C-5 Galaxy loss of pressure - what would happen?

[mbattlem]

Hi all, I am writing a movie and really need to know what would happen on board a C5 if part got smashed open and there was a loss of pressure.

Would anyone know anything about this? (i.e. what happens with oxygen, where are the masks etc, what happens with fire system to stop flames from smashed burning side, what happens with emergency lights and alarms etc)

ANY HELP WOULD BE AMAAAAAZING.

Thank you so so much

[EAP86]

MBM perhaps start here https://en.wikipedia.org/wiki/1975_T%C3%A2n_S%C6%A1n_Nh%E1%BB%A9t_C-5_accident or here https://en.wikipedia.org/wiki/1975_T%C3%A2n_S%C6%A1n_Nh%E1%BB%A9t_C-5_accident? You could always try talking to Lockheed who may be interested in ensuring the script is reasonably realistic.

EAP

[ICM]

I could tell you what happened in a C-141, Lockheed's predecessor to the C-5 - but happily nothing had "smashed open" and there was no fire. Are these excitements - a missile strike or mid-air collision - to be an essential part of your scenario? Any idea of the altitude at which you want all of this to happen - that makes a considerable difference to the number of seconds of useful consciousness if you don't get on to oxygen PDQ? What sort of load do you envisage - purely cargo, at a guess? Crews do get training in decompression chambers to have an idea of what may happen for real and, in the case I recall, the chamber runs proved very accurate indeed. And it can all be much less dramatic than I suspect you want it to be.

[Tankertrashnav]

As ICM said, things are a lot less dramatic than the movies would have you believe. I've done both an explosive decompression test and the one where your oxygen is cut off and you gradually become hypoxic. One thing is common to both scenarios - full consciousness returns very quickly once oxygen supply has been restored, usually within the time it takes to take several breaths. Films would have you believe that occupants will be gasping and clutching at their throats for an age - that is simply not the case. No experience of the C5 but the principle is essentially the same for any aircraft.

[Dan Dare]

I have no expertise, just scientific curiosity. One thing I’ve never seen in films, but feel certain would happen with explosive decompression is fog/cloud formation at least while the air in the aircraft holds more moisture than the ambient pressure can keep in vapour and after a period of cloud formation all surfaces should have condensation on them until the ambient air is dry enough for it to evaporate again. Hero in the hold trying to stop cargo from going would also have to contend with wet, slippery containers.

unless I’m wrong and someone here would be kind enough to point out why it all happens too quickly to make it worth showing on film

[ancientaviator62]

Had two on the RAF C130K and it is much as Dan has suggested.. A large bang followed by whiteout and a gradual clearing of the mist. Ours were both caused by the doppler panel blowing out. Scary on the first understood what was happening on the second. Drill for this sort of thing was oxygen and descend if possible. Note only the crew had oxy masks on our 'K'.

[KenV]

Hi all, I am writing a movie and really need to know what would happen on board a C5 if part got smashed open and there was a loss of pressure.
Would anyone know anything about this? (i.e. what happens with oxygen, where are the masks etc, what happens with fire system to stop flames from smashed burning side, what happens with emergency lights and alarms etc)

Keep in mind that the C-5 is a double deck aircraft. Cargo goes on the main deck and passengers go in the upper deck. The upper deck is similar to an airliner but without windows. In the event of decompression oxygen masks drop down just like in an airliner. Lights and alarms are similar as well. There are two big differences:
1. The passengers and loadmasters all face aft
2. There are two passenger compartments, one forward and one aft of the high mounted wing. There is no pass through between the compartments thru the wing.

The C model is the exception. The aft passenger compartment has been removed on the C model to provide a much taller cargo bay aft of the wing. This was done to accommodate large satellites and other space gear (official designation of C-5C is C-5A(SCM) which stands for Space Cargo Modified.). Both Cs were upgraded to the M configuration and are now C-5M(SCM).

[sandiego89]

The C-5 is equipped with emergency masks at all primary crew stations (like airliner cockpits) and the relief and courier stations aft the main cockpit, portable tanks/masks to allow crew to walk around the cargo bay and drop down masks (airliner like) in the aft troop deck and other places. The normal and emergency oxygen system is described here in section 13-1. http://www.usaf-sig.org/index.php/references/downloads/category/61-c-5-galaxy-lockheed?download=187:c-5-handbook

[ICM]

So, allowing for the essential differences in size between the two Lockheed airlifters,I'd say that the C-141A had a similar fit to the C-5. Despite that, what made the incident I recall just a bit out of the ordinary was that it emerged that not all crew masks at the time (late 1972) had the same webbing support system, and we had a chap who apparently did not understand how the demand regulator system worked. The net result was an "I Learned about flying from that" occasion from which, fortunately, we all walked away.

[sycamore]

mbattlem, read thru `rumours and news`, for the `A319 WINDSCREEN BLOWOUT` to a Chinese airliner ,as well...