Ulster

The crew was engaged in an anti-submarine attack simulation of the HMS Sentinal. While cruising at low height, the seaplane hit the water surface, exploded and crashed about 32 km north of the Inishtrahull Island, off Donegal County. Five crew members were rescued while seven others were killed. For unknown reason, the pilot was flying at a too low altitude to complete the exercise. Crew from the 201st Squadron.

The crew left RAF Castle Archdale at 0203LT to localize German submarine cruising off the Irish coast. Weather conditions were marginal and the visibility was limited due to a cloud layer at 1,000 feet. The night was very dark. The aircraft passed over the village of Kellybegs and continued to the north when it hit the slope of Mt Cró na Roda (Mt Crownarad) at a height of 471 meters. All 12 occupants were killed.
Crew (201st Squadron):
F/Sgt R. D. A. Becker,
F/Sgt S. B. Frith,
F/O V. Howkins,
Sgt J. R. Mansfield,
F/Sgt J. G. Robinson,
F/S G. R. Kennedy,
Sgt F. N. G. Ford,
F/Sgt D. J. T. Twist,
F/Sgt C. J. Ryder,
F/O R. Delby,
Sgt R. F. Woodward.
Source: http://www.csn.ul.ie/~dan/war/ml743.htm

The crew was involved in a maritime patrol flight when an engine failed en route. The seaplane crashed into the sea off Bloody Foreland, Donegal County. Nine crew members were killed and one crewman survived.
Crew (423rd Squadron):
F/O Frederick William Greenwood, pilot, †
F/Sgt Laurence Patrick Quinn, †
F/O Edwin Earl McCann, †
F/Lt George Francis Cornwell, navigator, †
F/O Herbert Stanley Seibold, †
F/O Kenneth Mons Liddle, †
W/O Joseph Alphonse Raymond Dore, †
Sgt Nigel McColl Anderson, †
Sgt John Edwin Caton, †
W/O R. H. VOYCE.

The crew was performing a ferry flight from Goose Bay to Belfast-Nutts Corner Airport. While approaching Ireland, the navigator informed the captain that the fuel reserve seems to be insufficient to reach the destination while the radio operator was unable to contact ground. The captain was approaching St Angelo but the airfield was closed due to fog and clouds so he decided to fly back to find a clear zone near Ballyshannon for an emergency landing. After touchdown, the bomber hit a concrete wall and was wrecked. Eight crew members were injured while two others were killed.
Crew:
2/Lt Arthur H. Dittmer,
2/Lt Marvin J. Reddick,
2/Lt Arnold A. H. Grueber,
2/Lt Wayne R. Davis,
S/Sgt Lester M. Clark,
Sgt Edward J. Friedl,
Sgt Carlos F. Maestas, †
Sgt George H. Smith,
Cpl James O. E. Harvey,
Cpl Riley W. Cannon. †
Source: http://www.csn.ul.ie/~dan/war/42-50721.htm

Crew was engaged in a maritime patrol flight and left RAF Pembroke Dock in the afternoon for a 13 hours mission. Aircraft was scheduled to overfly the Lake Lough Erne but for unknown reason, was off the initial track and was flying over a mountainous area in the Donegal County. By night, the four engine aircraft hit the slope of Mt Blue Stak at a height of 2,219 feet. Rescuers arrived on site, some 200 feet from the top, and were able to evacuate six injured crew members while all seven other occupants were killed.
Crew:
Lieutenant Howard Charles Sheffield Armstrong, pilot, †
Lieutenant Maurice Leonard Gillingham, pilot, †
Maurice Vincent Wareing, copilot, †
Joseph George Trull, navigator,
John Bruce Richardson, flight engineer,
Sergeant C. S. Hobbs, air gunner,
Sergeant Cyril Robinson Greenwood, †
Sergeant Frederick George Green, gunner, †
Sergeant John Ernest Parsons, †
Sergeant Frederick Tom Copp, flight engineer, †
Sergeant James Kenneth Gilchrist, rear gunner,
Sergeant A. Gowens.

The crew was performing a meteorological mission (called MERCER) over the Atlantic Ocean and left the RAF Tiree in Scotland during the day. After completing two circuits, the crew was returning to his base and while passing over Ireland, the aircraft was too low by night and hit a cliff near Bundoran, Donegal County. All eight occupants were killed.
Crew:
Lloyd Joyce Upshall, pilot,
Clarence Loree Scott, pilot,
Norman Glyn Gzowski, navigator,
Vladimir Adamic, wireless operator,
Frederick Edward Dawson, wireless operator,
Frank Ash, wireless operator,
Frederick Lewarne Eric Hussey, flight engineer,
Donald Parr Hewitson, meteorological observer.

While cruising in poor weather conditions, the aircraft hit a mountain slope located near Inishowen Head, Donegal County. Four crew members were killed while the fifth occupant was seriously injured. Visibility was low at the time of the accident.
Crew (271st Squadron):
P/O Carol Herbert Brown, †
P/O James William Swaby,
F/Sgt Arthur Bain Shaw, †
LAC Albert Edward James, †
LAC John Thurston Taberner. †

The crew was engaged in a convoy escort mission when he encountered engine problems. The captain informed ground he was attempting to return to RAF Enniskillen when the seaplane crashed into the sea off Donegal. Due to rough sea, SAR operations were abandoned few days later and no trace of the aircraft nor the crew was found.
Crew (423rd Squadron):
F/Lt A. F. Brazenor,
F/Sgt S. G. Brockway,
F/Sgt R. J. Money,
Sgt H. W. Fell,
Sgt H. E. E. Attwood,
Sgt M. F. Flynn,
Sgt D. Bigmore,
Sgt L. Morgan,
F/Sgt R. W. Stiff,
P/O R. H. Wilson
F/O H. B. Pharis.

The crew was performing a training mission off Donegal, Ireland. In flight, the float plane exploded and crashed into the sea. All nine occupants were killed.
Crew:
Sgt Peter Phillip Bacon,
Sgt Cyril Barraclough,
F/O Douglas Haig Disney,
F/O Kenneth Hipwell,
Sgt James Male,
F/Lt Edward Earle Muffitt,
Sgt Charles Edward Poots,
Sgt Harold Edwin Scarman,
Sgt Albert Upton.

The crew left RAF Ballykelly at 0533LT on a maritime patrol flight over the Atlantic Ocean. After the German U-boat U-256 was attacked and sank to a depth of 110 metres, the crew was requested to take part to a SAR operation for a troopship reported to have been torpedoed. At 1220LT, the crew informed ground that he was returning to his base with an ETA at 1627LT. At 1515LT, all four engine lost power, the aircraft lost height and was ditched off the Irish coast. While the aircraft sank and was lost, four crew members were rescued while four others were killed.
Crew:
P/O Victor Dennis James, pilot, †
Sgt Hector Vivian Frances Archer, copilot,
F/Sgt Alfred Burton Craig, navigator, †
Sgt Seymour Clare, flight engineer, †
F/Sgt Kenneth Henry Watson, wireless operator and air gunner, †
Sgt Peter Francis George, wireless operator and air gunner,
Sgt William Charles Gordon, wireless operator and air gunner,
Sgt Fredrick Norman Hollies, wireless operator and air gunner.

Sincere thanks to Peter Clare, son of Sgt Seymour Clare, for his testimony and contribution. All texts below by Peter Clare:
http://www.ww2irishaviation.com/lv341.htm
http://www.bbc.co.uk/history/ww2peopleswar/stories/98/a2600498.shtml