Air carrier first officer reported oxygen system failure associated with the captain's mask during c...

Attributes
ACN	1706193
Time
Date	201911
Place
Locale Reference	ZHN.ARTCC
State Reference	HI
Environment
Light	Night
Aircraft 1
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Component
Aircraft Component	Oxygen System/Crew
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance

Narrative:

I was the pilot monitoring when we originally departed hawaii on time for the flight back to the mainland. After leveling at cruise and checking in with sfo radio (and making our first position report) I asked the captain if we could set up a bathroom break. During that process the captain's mask became detached from the oxygen system and he was forced to turn off the crew oxygen system supply due to uncontrolled flow. In accordance with ETOPS requirements we initiated a turn around back to hawaii. During that process; we had very difficult communication with sfo (1x1) and very little communication with honolulu on VHF. We were unable to clearly ascertain our altitude clearance; so after discussing it we elected to vertically offset. When we confirmed the clearance; we returned to our original altitude and returned to hawaii uneventfully.

Original NASA ASRS Text

Title: Air carrier First Officer reported oxygen system failure associated with the Captain's mask during cruise. Flight crew elected to return to the departure airport.

Narrative: I was the pilot monitoring when we originally departed Hawaii on time for the flight back to the mainland. After leveling at cruise and checking in with SFO radio (and making our first position report) I asked the captain if we could set up a bathroom break. During that process the Captain's mask became detached from the oxygen system and he was forced to turn off the crew oxygen system supply due to uncontrolled flow. In accordance with ETOPS requirements we initiated a turn around back to Hawaii. During that process; we had very difficult communication with SFO (1x1) and very little communication with Honolulu on VHF. We were unable to clearly ascertain our altitude clearance; so after discussing it we elected to vertically offset. When we confirmed the clearance; we returned to our original altitude and returned to Hawaii uneventfully.

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.

Air carrier first officer reported oxygen system failure associated with the captain's mask during cruise. Flight crew elected to return to the departure airport.