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Not many Oxygen fires in flight or on the ground

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Not many Oxygen fires in flight or on the ground

Old 11th Nov 2023, 21:10
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RMC
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Not many Oxygen fires in flight or on the ground

It seems very few aviation accidents involve the crew oxygen system. The only ones I am aware of are Egypt Air 804 (where an O2 mask left in emergency mode caused an O2 rich atmosphere that was ignited by either a window heat short circuit or a pilot smoking). The Swissair 111 had an IFE fire which breached the high pressure system resulting in a cockpit blow torch.

Are there still many ground fires resulting from repressurising oxygen with dirty equipment etc or is this also a thing of the past.

Thanks
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Old 13th Nov 2023, 10:57
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Not a lot it would appear.

I remember two, one in 1975 - a new SOAF (Oman) BAC 1-11 (1003) was being charged with oxygen at Muscat for the first time since delivery about 10 days previously. The Oxy cart regulator was sticky and suddenly opened with full, 3600psi, pressure. The charging adaptor had the wrong type of seal fitted and it caught fire. The cockpit was gutted by the fire and the aircraft was dismantled and returned by sea to the factory at Hurn for repair. Total aircraft hours was 78 hrs 45 mins at the time. I know this as I had to fill out the avionic component record cards when the aircraft returned to Muscat in 1976 after repair.

The other I know of was a Saudi DC-8-63 at Luxemburg about 1981. A friend of mine worked there. They had just completed a major check on the aircraft and when he came to work the day it was due to depart he found fire engines everywhere and the aircraft cabin was burnt out to the floor line.
In each case nobody was hurt.
Hopefully these events are very rare.
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Old 13th Nov 2023, 11:10
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Thanks for the actual examples. I spoke to the engineers in JFK today and they said the FAA no longer allowed oxygen bottles to be charged so if the O2 level is low they have to replace the bottle! Apparently it is still allowed in the UK but my company chooses to replace bottles rather than take the risk of an O2 fire.
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Old 13th Nov 2023, 17:45
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The old adage about loaded weapons comes to mind here: Perfectly safe until you forget they're dangerous.
Charging gaseous O2 bottles should be a simple process if common sense and the relevant precautions are followed. Added to authorisations once the correct procedure has been overseen by Inspection and Quality Departments.
I've never worked with LOX but imagine systems are best replenished outside due to the increased amount of contamination in hangars and the limitation of fire tender access. Somebody more knowledgeable will no doubt be along shortly.
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Old 24th Nov 2023, 22:57
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Originally Posted by RMC
Thanks for the actual examples. I spoke to the engineers in JFK today and they said the FAA no longer allowed oxygen bottles to be charged so if the O2 level is low they have to replace the bottle! Apparently it is still allowed in the UK but my company chooses to replace bottles rather than take the risk of an O2 fire.
As long as I've worked on large passenger aircraft oxygen systems [40+ years] I only remember there being two minor incidents and they were both down to [charging] equipment failure. Now whether that was down to the equipment just failing or not being checked properly prior to use I cannot say. On both occasions though the fire was contained on the oxygen charging rigs and didn't spread to the actual aircraft.
At the end of the day I think the main reason for the good safety record in the particular large UK airline in question is down to the fact that the charging of oxygen systems was left to staff who were basically instrument/avionic types, who all had training on oxygen charging, were more likely to have only clean tools [and overalls ] and the oxygen charging cylinders and steps were kept in [and returned to after use] a separate oxygen charging area on the engineering base and were only used for that purpose. It is a sad fact in the industry that there has long been the opinion that separate Engine/Airframe and Avionic trades are not required any more and that all engineers in the future should be B1 and B2 combined. While you may get away with that at line stations there is still the need for separate specialists at main bases/hubs but like everything it all boils down to costs.
In all the years I've worked on aircraft, FAA aircraft have never allowed on board charging as I worked on a number of US/FAA registered airliners back in the 1980s on major checks and they had no charging points.

Last edited by MAC 40612; 24th Nov 2023 at 23:23.
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Old 24th Nov 2023, 23:38
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I think there was an oxygen fire with one of the ex BA 747s when it was being dismantled.

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Old 25th Nov 2023, 00:59
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Originally Posted by TURIN
I think there was an oxygen fire with one of the ex BA 747s when it was being dismantled.

https://twitter.com/BombersDipcas/st...MkAGr3Onw&s=19
Yes, but we're talking a fire while scrappies were dismantling an aircraft here, so not really in the realms of an oxygen fire in the normal operation of an aircraft. They obviously didn't have a clue about what they were doing otherwise the system would not have been still pressurised. I doubt if they had even bothered to turn off the bottles and purge the system.

Last edited by MAC 40612; 26th Nov 2023 at 23:21.
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Old 28th Nov 2023, 21:09
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I recall 2 oxy fed fires on RAAF aircraft.

One on an Orion https://aviation-safety.net/database...?id=19840127-0 and another on one of their Caribous, A4-275. ADF Serials - Caribou
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Old 9th Dec 2023, 16:55
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Pretty sure I can recall in either Pakistan or India they did not have charging facilities on the airport, our slightly depleted bottle was to be taken off field and at that point the Captain put on a pair of specs and declared it was just acceptably in the green band; after that we carried a spare bottle when going East.
Whilst at Andrews we lost nearly all our B747 O2 due to overnight temperatures and cold seals; the USAF had no problem topping us up on stand; guess this would be the case for military operations; future cold operations we shut the bottles off at their necks and left a flag in the flight deck. The charging point was just inside the cargo door.
Of course the UK build standard was LH charging thread.
If I recall USA built commercial aircraft for USA Operators did not have external O2 charging points.
We kept dedicated tools with our O2 charging rig as a precaution; if we were working under the radome on O2 bottles (extended range business jet) we would have an airline blowing to dilute any O2 leak concentration.
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Old 9th Dec 2023, 20:17
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Originally Posted by aeromech3
Pretty sure I can recall in either Pakistan or India they did not have charging facilities on the airport, our slightly depleted bottle was to be taken off field and at that point the Captain put on a pair of specs and declared it was just acceptably in the green band; after that we carried a spare bottle when going East.
Whilst at Andrews we lost nearly all our B747 O2 due to overnight temperatures and cold seals; the USAF had no problem topping us up on stand; guess this would be the case for military operations; future cold operations we shut the bottles off at their necks and left a flag in the flight deck. The charging point was just inside the cargo door.
Of course the UK build standard was LH charging thread.
If I recall USA built commercial aircraft for USA Operators did not have external O2 charging points.
We kept dedicated tools with our O2 charging rig as a precaution; if we were working under the radome on O2 bottles (extended range business jet) we would have an airline blowing to dilute any O2 leak concentration.
Oxygen charging points are all left hand thread, to avoid the nasty mistake of nitrogen bottles which also tend to be around a ramp area [for inflating tyres] being used. Even so, it's been done in the past!!

Not a lot has changed on the B747 from what you remember probably. Taken on an Oxygen top up in 2020, as the aircraft was about to depart on it's final flight. Note the dent/worn away paint at the bottom left of the oxygen gauge, where numerous engineers over the years have given the panel a 'light tap' to overcome 'stiction' on the oxygen level gauge.



Last edited by MAC 40612; 9th Dec 2023 at 21:15.
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Old 9th Dec 2023, 20:43
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AFAIK, there are three hazard levels.
1) LOX, liquefied oxygen is mainly a cold-burn hazard without some ignition source, though as it vaporizes it moves to condition 3.
2)Pressurized oxygen is a big hazard as it can cause hydrocarbons to spontaneously combust - mainly seen when someone uses petroleum grease on o-rings or leaves fingerprint oils on screw threads.The burning o-ring can be a high enough temperature to allow ignition of the metal. Metal fires are especially not fun.
3) Oxygen rich atmospheres are a particular hazard as those exposed to them don't have the feedback of the other two cases. For example - oxygen tents in hospitals. A small spark from electrostatic discharge that would not ordinarily be of concern can cause a rapid combustion of the materials the spark terminates in. This was the cause of the Apollo conflagration - no one gave much thought to a 15 psia oxygen atmosphere.

Note that the oxygen itself doesn't combust - it is the materials around it that do. A spark in mid-oxygen does nothing. A cigarette in an oxygen rich environment should burn vigorously, but not explosively and if it doesn't make contact with any other combustible, will rapidly extinguish. However, if the smoker is startled by the flare of the cigarette and drops it onto something else combustible, then look out for the runaway fire.

High pressure oxygen is used in medical and industrial settings all the time and I don't recall seeing it make the news. I think the hazard is so firmly presented that doing stupid things is largely avoided. (Then sees videos of oxy-acytelene gas mixtures put into party balloons and ignited. Sigh.)

The greatest hazard is a large number of oxygen generators loaded as unprotected cargo. Not only do they build sufficient heat to ignite other materials when triggered, they produce oxygen to ensure a robust fire, which cascades to operating all the other oxygen generators. Individually they contain no liquid or high-pressure oxygen and one could probably kick them around - unless the safety provisions weren't installed.
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Old 10th Dec 2023, 05:49
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Had one near miss long time ago on a weary DC08-21 at JFK. Radio Mech went out to check something and turned on the Master radio switch. Blue flash in cockpit, his eyebrows were singed and, being a radio techie, had no trace of oil on him..
I checked log book, found rather frequent refiling of crew oxy.
I ordered a complete bubble juice check of every crew oxy line. Having torn out three quarters of cockpit line they finally found it. It appears leaking oxy accumulated behind liner and radio switch caused it to eat up all the accumulated dust. No progression though, no damage except trying to put all the petrified liners back on.
Remember lots of aircraft types had external oxy fillers. Fitting was a sweated on small fitting. There was a section of tubing with a mesh inside to dissipate heat. Was rarely used in my experience. Never could find fitting.
Eastern Air had an oxy fire when charging a removed bottle. The equipped a clean room at each station complete with water tubs to keep bottles cool as they were filed.
Did get a bottle filled by an approved vendor that almost knocked out F/E when pulled an oxy check with his mask. Had it empty sent to me and smell from it was noxious. Apparently the shut iff valve on the bottle had a base seal and it combusted during a too rapid filling. Would have been fatal if crew had needed it in flight. Added a "sniff check" to our procedure whenever fitting a refilled bottle. Crack open just a slight bit and wave the gas to you. No problem to detect a bad one.
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Old 11th Dec 2023, 05:34
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Just remembered a really odd oxy story. My company had a contract for Convair T-29 (militarized CV-340)) IRANS.T-29 was a navigational trainer so there was a line of work stations down interior with bubble type astrodomes above. Each station had a crew type oxy setup.
I was assigned to tale down some interior wall liners below the window line. I observed a meta tube running fore and aft that supplied oxy to each station. It looked very odd. The line was supported by clamps. Between each clamp the line bulged outward. It resembled a row of sausage links tied off in sections.
Very neat looking, each section evenly sized. It rather resembled a line of link sausages. In fact so neat it looked right, like it was designed so.
Only being a techie, I called the Lead, he called supervision and then Engineering and the Air Force Inspector too. Couple of days later I was told it appeared there had been a low order explosion inside the tubing, almost certainly caused by a contaminated line. It had caused the metal to expand except where it was held by clamps.Hence the resemblance to sausage links. Great problems ensued as the line ran though the fuselage ring formers and had to be cut out in sections. Much more tearing out of wall panels to chase down further damage. Never heard if it was ever determined when it occurred. Must have been long time ago as there were no reports of odors from oxy system.
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