Operation Overlord: RDF/Radar & LCTs

1943 marked a major turning point in WWII as the tide began to flow in the allies’ favour. In January Japanese forces conceded the island of Guadalcanal to US Forces and in February German forces were defeated by the Russians at Stalingrad. In March the British continued to push the German Afrika Korps back through Tunisia and after failing to halt the allies, Field Marshal Rommel retired from Africa entirely (Farrington, K., 2011 p.255). On Hoy the situation was far less confrontational but still continued to serve a critical role in support of the war at sea. Luftwaffe reconnaissance sorties continued to monitor the disposition of capital ships in Scapa Flow as a means of estimating the departure of the next Arctic Convoy (Hinsley, F., 1981 p.200), however, more advanced radar directed gun laying and a balloon barrage of over 80 balloons meant that few hostile aircraft lingered over the Fleet anchorage for long.

Being such a new and complicated technological development, RDF had its fair share of teething problems. In the majority of Navy cases, malfunctions were found to originate from poor operative training and so in 1941 a small radar repair and maintenance unit was despatched to Hoy to address issues encountered with ship installed gunnery direction and IFF sets (Identification Friend or Foe) (TNA: ADM116/5790 p.186 & 187). The Radar Centre also maintained shore based early warning Admiralty Experimental Stations and radar navigation beacons which were often positioned in remote locations where repairs had to wait weeks before the weather conditions were good enough to transport personnel and parts to the sites. As a direct result, in 1945 Rinnigill became one of the first places in the UK to operate the Sikorsky R-4B helicopter which meant repair trips could be undertaken in a matter of hours as opposed to weeks (TNA: ADM116/5790 p.190).

WWII Hoy Then & Now - Rinnigill Helicopter Pad

WWII Hoy Then & Now – Rinnigill Helicopter Pad

In January 1943 the radar unit moved from their two small huts at Lyness to a custom built Radar Repair & Servicing Centre at Rinnigill (HY60) where they began to take on fitting work as well as maintenance (ibid.). Radar development advanced at quite a pace during WWII and as a result Home Fleet capital ships were continually requiring upgrades to the latest gun directing, navigational & target tracking radar sets. In the opening months of 1944, the radar staff at Rinnigill played an important role in the preparations for the allied invasion of Europe codenamed Operation Overlord, installing top secret CXFR radar sets in many of the capital ships destined for the invasion force (ibid.).  CXFR was an experimental high-powered radar jamming system which could identify the enemy radar frequency and then transmit modulated noise on that channel. The value of this fitting work cannot be understated as it was largely due to the jamming of German radar on the night of the 5th June that enabled the allied invasion fleet to approach the beaches of Normandy undetected.

Hoy based personnel also played an active role in the allied invasion of Europe. In August 1942 the 10th and 23rd Landing Craft Tank (LCT) flotillas had arrived in Scapa Flow to be fitted out specifically as Close Protection Anti-Torpedo vessels (TNA: ADM116/5790 p.9). The LCT was the largest landing craft in the British Navy and could carry 5 tanks or 350 tons of cargo. It was the shallow draft, long length and narrow beam that inspired the trial of LCTs as boom defence vessels and 30 of them were converted by the Boom Defence Office at Lyness to carry 9m deep anti-torpedo nets underneath their hulls (TNA: ADM116/5790 p.70). In this configuration, the LCTs could be allocated to up to 10 capital ships and 15 cruisers in the Fleet anchorage area sitting alongside the larger vessels to protect them from attack.

In September the pier at North Ness (NMRS: ND39SW 100) was constructed to service the LCTs which were moored in Longhope and provide access to a camp at Crockness (HY75) which was completed in 1943 to accommodate the crews (TNA: ADM116/5790 p.71). The LCT Close Protection scheme wasn’t entirely successful with many LCTs found to drag in the strong winds causing damage to the warships they were meant to be protecting. It was therefore with some relief that the LCTs were withdrawn from the Close Protection role in April 1944 to take part in Operation ‘Neptune’, the air and seaborne transportation of allied forces to the beaches of Normandy as part of Operation Overlord (ibid.). In less than two months, the LCT crews who had been living at Crockness found themselves landing Canadian troops and amphibious Duplex Drive Sherman Tanks on the sands of Juno beach in Normandy.

© Source: Lindsay, G.J. & Dobney, K. (2014). Legacies of Conflict: Hoy & Walls Wartime Heritage Project, Wartime Development Document. Island of Hoy Development Trust.


FARRINGTON, K., (2011). Handbook of World War II: An Illustrated Chronicle of The Struggle For Victory. London: Anness Publishing Ltd.

HINSLEY, F.H., (1981). British Intelligence in the Second World War. Volume 2: Its Influence on Strategy and Operations. London: HM Stationary Office.

THE NATIONAL ARCHIVES OF THE UK (TNA), (1937-1946). ADM116/5790 Main Fleet Base – Scapa Flow: Inception, Development and History. Unpublished Archive Document.

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5 thoughts on “Operation Overlord: RDF/Radar & LCTs

  1. I have found a picture of HMS Malaya with the said LCTs alongside with what I take to be boom defence nets deployed over the side

  2. I have an original copy of the photo Sikorsky R-4B Hoverfly at Rinnigill in 1945 © The National Archives, ref. ADM116/5790 that I believe has my Grandfather Gordon Fowler at the controls. How do I confirm this? Tips much appreciated

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