Closing the 'air gap'

The role of Northern Ireland's air bases in the second world war


Northern Ireland’s primary role in relation to the air-war was to come through its port and airfield bases, mainly as Coastal Command due to Ireland’s geographical position to the North Atlantic, with a later role being extended to facilitate United States Army Air Force Combat Crew Replacement Centres (USAAF CCRCs).

By late 1940, the Allies were in a dangerously critical position in the Battle of the Atlantic. The German U-boats were going through the ‘happy time’ with Britain’s merchant fleet suffering a casualty rate of frightening proportions. In these early days there were little signs of the forthcoming tactics of joint Naval/Coastal Command co-operation, but signs began to appear to close the gap where no air-cover from east to west existed, and that meant building airfields as far west as possible to Britain.

Airfield Building

For this reason an airfield building programme was commenced in Northern Ireland. Convoy protection and anti-U-boat patrols were already underway with No.502 Squadron from Aldergrove, an established pre-war airfield, whilst airfields built early in the war were Limavady, for aircraft engaged in convoy escort and reconnaissance patrols, and Ballyhalbert, for fighter protection of the Belfast area deemed urgent after the German raids of April/May 1941.

There was also a need for flying boat bases which had the advantage of no runway construction. Earmarked for one such base was Lough Erne in Co Fermanagh and despite an unfavourable report of the area in December 1940, the war situation dictated otherwise and work began around the Castle Archdale estate in January 1941. Lough Erne would provide an extra 100 miles of air-cover over the squadrons currently sited at Loch Ryan in SW Scotland.

However, there was one major problem that needed to be overcome for the base to fulfill its intended use – the aircraft needing to fly straight out into the Atlantic over Donegal Bay and hence over Free State territory. Sir John Maffey, the British representative to Eire, began a series of delicate negotiations with the Taoiseach, Eamon de Valera, to ask that aircraft be allowed to fly that route. On January 21, 1941, he received permission with limited conditions. Flights were to be at good height and were not to fly over the Irish Army camp at Finner, near Ballyshannon. Later, many more concessions were granted to the Allies as de Valera’s government engaged in a policy of benevolent neutrality.


The scope of arrangements were later widened. By February 5, 1941, No 240 Squadron RAF began to use Lough Erne. No 240 Squadron had converted to Catalinas and in those early days these aircraft would leave Lough Erne at dawn, patrol the Atlantic as far as Newfoundland and return to Wig Bay at Stranraer in Scotland usually around 04:30 hours, as it was a 21-hour patrol.

Upon arrival at Wig Bay, they would rest until later that morning, then fly over to Lough Erne and fuel up for another patrol the following morning. The reason for this diversion was that landings on Lough Erne at night were, in those early days, considered unsafe owing to the mountainous nature of the district.

Castle Archdale

May of 1941 was to prove eventful for No 240 Squadron when firstly on the 16th, a Catalina depth-charged an Italian submarine. The escorting naval corvettes confirmed the kill. However it was the sighting of the battleship Bismark on the morning of May 26 by Catalina ‘Z’ flown by Flying Officer Briggs and carrying an American co-pilot, Ensign Leonard Smith, that brought Castle Archdale into the history books within months of its opening. Ensign Smith was one of a group of US Naval personnel familiarising RAF pilots with the Catalina, whilst at the same time gaining operational experience. Their presence, as the United States was still neutral, was kept a secret, as was their intention to establish a flying boat base at nearby Killideas to accommodate four Catalina squadrons. A pressing need for US Catalinas in the Pacific put that plan on ice and Killideas became an RAF Operational Training base with No.131 OTU flying Catalinas.

In February 1942, the slipway at Lough Erne was used for the first time to beach a Sunderland.

U-Boat Losses

Also significant for February was that the ‘happy time’ for the U-boats was ending. With the establishment of a Western Approaches command centre in Liverpool, new convoy escorts and an intensification of coastal command patrols, a significant turning point emerged.

March 1941 saw the German U-boat command lose four boats, commanded by ‘aces’.

No 221 Squadron RAF moved to Limavady in May 1941 from Bircham Newton in Norfolk England with their ASV equipped Wellingtons, whilst No.254 Squadron whose Beaufighters had come from Sumbridge at the end of May, took over patrols from Aldergrove until December when it left for Dyce in Scotland.


No 245 Squadron, who had been at Aldergrove with Hurricanes, left on July 15 as Fighter Sector HQ was transferred to Ballyhalbert on June 28, 1941. Aldergrove was then allocated to Coastal Command and No 233 Squadron, who were also stationed there with Hudsons, shot down a long range Condor which was attacking a convoy on July 23.

Further runway construction at Aldergrove began in September 1941, but the airfield remained operational with No 206 Squadron also flying Hudsons based there. Aldergrove was one of three airfields being upgraded in terms of runway length and layout, the others being Ballykelly and Ballyhalbert.


The creation of Ballykelly was clear from the start – to base long range reconnaissance aircraft to operate out into the Atlantic to cover ‘the Mid Atlantic Gap’ - ‘The Black Gap’ – where no air-cover could be provided allowing the U-boats to track the convoys with impunity.

The Liberator

The answer was the American built B24 Liberator bomber!  No 120 Squadron, RAF was already forming up at Nutts Corner, ten miles North of Belfast with the Mk 1, but the specialised maritime equipment needed for the conversion of this ‘bomber’ to a maritime role was still in short supply, so for the next year, until August 1942, the squadron would remain the only Liberator squadron. Two further squadrons, Nos 59 and 86 would also later operate from Aldergrove and Ballykelly flying Mk V Liberators. Ballykelly’s first operational Coastal squadron was No.220 Squadron, flying B17 flying fortresses.

16-Hour Patrols

The following year, in July 1942, No 120 Squadron joined No 220 at Ballykelly, as No 120 Squadron had occasionally used Ballykelly as a landing ground during their time at Nutts Corner after sweeps out into the Atlantic. (Ballykelly aircraft used Bishopscourt in Co Down in a similar way.) During the summer of 1942, later versions of the Liberator, the Mk II and Mk III were joining No 120 Squadron and they were now able to patrol out to 30 degrees west and beyond with an endurance of over 16 hours. This now ensured that the squadron would be able to encounter U-boats in the notorious ‘air gap’.

ASV Radar

All Liberators up to the Mk III standard were equipped with ASV Mk II radar, with a range of some ten miles. Transmitter aerials were located obliquely at the front on the outer wing and looking out sideways on the rear fuselage. When a contact was picked up, the aircraft would turn on to the relevant bearing and home in with an aerial on the nose.

The Mk III aircraft retained the two .50 calibre machine guns in the rear ‘Glen Martin Turret,’ instead of the four .303 machine guns and the ‘Bolton Paul’ turret of the more extensively modified aircraft. A more important feature was the American H2X centimetric radar whose scanner was housed in the ventral ball turret position, the first Coastal Command aircraft to use the new radar operationally.

Construction standards at airfields were modified as the war developed. The largest and best equipped airfields were Cluntoe, Toome, Greencastle (all three later passing to the USAAF as CCRCs) and Bishopscourt, which were all built to 1942 Class A Bomber Standard which stipulated optimum runway length and gradients enabling operation of the heaviest aircraft then in service.

Fighter Squadrons

After a spell at the Dumlambert Hotel in Belfast, No 82 Group Fighter Command set up HQ in the Senate Chamber in Northern Ireland’s one-time seat of Government, Stormont Castle, with an ‘emergency’ underground HQ bunker sited at Kircubbin in Co Down. Three fighter stations were set up at Ballyhalbert, Eglinton and Kirkistown, with a fourth station Maydown earmarked for USAAF use.

Many famous Battle of Britain squadrons were to find themselves at these bases over the years, such as No 152, who whilst based at Eglinton in 1941 lost two DFC (Distinguished Flying Cross) holders in crashes, Flying Officer Williams, DFC, and Squadron Leader Bodie, DFC. They were buried in St Canin’s Church, Eglinton.

Several Polish squadrons of the RAF such as No 303 and No 315 saw service at Ballyhalbert, as did No 504 squadron, who shot down a Ju88D which was on a return leg from a photographic reconnaissance patrol on August 23, 1942. They shared the ‘downing’ with No 315 Squadron (RAF Valley) and No 152 Squadron (RAF Angle) both in Wales. At this stage of the war, German aircraft were running the gauntlet through British airspace and such flights were becoming very hazardous. The Ju88D crash-landed near Tramore, Co Waterford, and the crew survived.

Defeat of the U-boats

By March 1943, despite the U-boats still marking up the successful sinking of British and Allied merchant shipping, there were signs of the Allies taking the upper hand in the North Atlantic. Long range aircraft had closed the gap across the Atlantic.

In May 1943, U-boat command suffered its worst setbacks of the war and would lead them to contemplate defeat. They lost 41 boats, sank in that ‘one month’. Their total loss for 1943 had totalled 237, of which 148 were credited to joint Royal Navy/RAF Coastal Command operations. The tide had turned and the hunters had now become the hunted.

By John Quinn

Further reading:
Down in a Free State – Wartime Air Crashes and Forced Landings in Eire 1939 – 1945 (1999) by John Quinn