B767 flight crew reports deviating around a thunderstorm on a north atlantic track using captain's e...

Narrative:

Approaching soory on nat track; we were given two sigmets by commercial radio concerning thunderstorms. The areas were plotted on our chart showing our cleared track in the center of the area. Between soory and 44n50w we detected severe weather on our track. We requested deviation from track 90 miles from the storm. At 30 miles from the thunderstorm we started a deviation to stay clear of weather. Approximately 10 miles left of track we received a SELCAL relaying ATC message 'unable deviation'. I informed ATC that I was exercising captain's emergency authority and we would descend 300 ft. All part 1 and north atlantic orientation chart procedures were followed and we twice relayed new estimates for the next fix. In spite of having pegasus aircraft with data link we never received sigmets from dispatch. We copied entire sigmets via HF. It would be useful to have a printed copy of sigmets instead of writing them in turbulence at night from a fast talking radio operator. It would also reduce frequency congestion if we could answer affirmative when asked if we have sigmet XXX. Nowhere could I find that it is required to declare an emergency in this circumstance. It would be helpful if are manual could address this issue.

Original NASA ASRS Text

Title: B767 flight crew reports deviating around a thunderstorm on a North Atlantic Track using Captain's emergency authority when ATC cannot provide a clearance to do so.

Narrative: Approaching SOORY on NAT track; we were given two SIGMETS by Commercial Radio concerning thunderstorms. The areas were plotted on our chart showing our cleared track in the center of the area. Between SOORY and 44N50W we detected severe weather on our track. We requested deviation from track 90 miles from the storm. At 30 miles from the thunderstorm we started a deviation to stay clear of weather. Approximately 10 miles left of track we received a SELCAL relaying ATC message 'unable deviation'. I informed ATC that I was exercising Captain's emergency authority and we would descend 300 FT. All part 1 and North Atlantic orientation chart procedures were followed and we twice relayed new estimates for the next fix. In spite of having Pegasus aircraft with data link we never received Sigmets from Dispatch. We copied entire Sigmets via HF. It would be useful to have a printed copy of Sigmets instead of writing them in turbulence at night from a fast talking radio operator. It would also reduce frequency congestion if we could answer affirmative when asked if we have Sigmet XXX. Nowhere could I find that it is required to declare an emergency in this circumstance. It would be helpful if are manual could address this issue.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1008299
Time
Date	201204
Local Time Of Day	1801-2400
Place
Locale Reference	ZNY.ARTCC
State Reference	NY
Aircraft 1
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Person 1
Function	Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying Relief Pilot
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

B767 flight crew reports deviating around a thunderstorm on a north atlantic track using captain's emergency authority when ATC cannot provide a clearance to do so.