Narrative:

I was performing some approved aircraft inspection program (aaip) inspections on a spare as-350 aircraft on the roof top pad. I was doing the maintenance on a maintenance delay. Since I was on a delay I wanted to take advantage and top off the liquid O2 (lox). The lox is contained in the aircraft right/H baggage hold. I removed the lox container and took it into the hospital to service it with lox. After the converter was full I let it sit in the hospital for awhile to thaw the frost that builds up during the fill process. I continued with the inspections. At some point I took the container back out to the ship and re-installed it. The lox has two electrical wires for quantity indication; and two flexible hoses; one for vent; and one for pressure. After I installed the full converter I checked the installation for O2 flow by turning on the O2 shutoff valve and the flow control on the O2 panel. I had O2 flow and the quantity indicated 8 liters +. I learned this morning when I returned to work that I had left the pressure hose disconnected. Because of this no O2 was available from the aircraft O2 cabinet. I was informed the flight was ok because there was back up gaseous O2 available. This was very confusing because I had O2 flow during the post installation flow check. Today I was at another base working on my normal ship. It also has lox system. I attempted to duplicate this situation. I found that even after the lox pressure hose is disconnected from the lox container there is still enough residual O2 in the system that it is possible to get a flow from the O2 panel. If the flow control is not set to high flow rates it is possible to get flow for longer than one would expect. [Recommend:]1.while performing multiple tasks better planning can be done to avoid starting and stopping midway thru a task. 2.when checking flow from the O2 panel one must turn the flow control full on and run the O2 until such a time as the quantity indicator shows a decrease in quantity. The quantity display is very sensitive and will indicate even a small amount of O2 use.3.the medical crew needs to be alerted when the lox is serviced so as to implement an additional layer of checks.

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Original NASA ASRS Text

Title: An Aircraft Maintenance Technician (AMT) was informed he had left a pressure hose disconnected from an LOX sphere after reinstalling the serviced oxygen sphere on an AS-350 Medical helicopter. Residual pressure in the oxygen system line was enough to show oxygen flow at the O2 panel during his O2 check. Technician recommends the Medical STC require a low pressure O2 light be added to the center panel to alert Medical Staff of sudden O2 loss.

Narrative: I was performing some Approved Aircraft Inspection Program (AAIP) inspections on a spare AS-350 aircraft on the roof top pad. I was doing the maintenance on a maintenance delay. Since I was on a delay I wanted to take advantage and top off the Liquid O2 (LOX). The LOX is contained in the aircraft R/H baggage hold. I removed the LOX container and took it into the hospital to service it with LOX. After the converter was full I let it sit in the hospital for awhile to thaw the frost that builds up during the fill process. I continued with the inspections. At some point I took the container back out to the ship and re-installed it. The LOX has two electrical wires for quantity indication; and two flexible hoses; one for vent; and one for pressure. After I installed the full converter I checked the installation for O2 flow by turning on the O2 shutoff valve and the flow control on the O2 panel. I had O2 flow and the quantity indicated 8 liters +. I learned this morning when I returned to work that I had left the pressure hose disconnected. Because of this no O2 was available from the aircraft O2 cabinet. I was informed the flight was ok because there was back up gaseous O2 available. This was very confusing because I had O2 flow during the post installation flow check. Today I was at another base working on my normal ship. It also has LOX system. I attempted to duplicate this situation. I found that even after the LOX pressure hose is disconnected from the LOX container there is still enough residual O2 in the system that it is possible to get a flow from the O2 panel. If the flow control is not set to high flow rates it is possible to get flow for longer than one would expect. [Recommend:]1.While performing multiple tasks better planning can be done to avoid starting and stopping midway thru a task. 2.When checking flow from the O2 panel one must turn the flow control full on and run the O2 until such a time as the quantity indicator shows a decrease in quantity. The quantity display is very sensitive and will indicate even a small amount of O2 use.3.The medical crew needs to be alerted when the LOX is serviced so as to implement an additional layer of checks.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.