| Unit Name: | No. 521 Squadron RAF |
| Dates: | 1 August 1942 – 31 March 1943 1 September 1943 – 1 April 1946 |
| Country: | United Kingdom |
| Branch: | Royal Air Force |
| Role: | meteorological |
| Command Structure: | No. 16 Group RAF, Coastal Command |
| Identification Symbol Label: | Squadron Badge heraldry |
| Identification Symbol 2: | 5O (Jun 1944 – Apr 1946) |
| Identification Symbol 2 Label: | Squadron Codes |
No. 521 Squadron of the Royal Air Force was a Second World War meteorological observation unit operating from Norfolk.
See also: RAF Coastal Command during World War II.
The Squadron began on 4 February 1941 as No. 401 (Met) Flight of RAF Bomber Command. When all the meteorological flights were put under RAF Coastal Command it became No. 1401 (Met) Flight. On 1 August 1942 at RAF Bircham Newton the flight combined with 1403 flight to form No. 521 (Met) Squadron. It took part in Coastal Command's Meteorological operationsThe squadron had inherited from its 1401 flight aircraft such as Gloster Gladiator biplanes and some Hawker Hurricanes. From 1403 flight came its Bristol Blenheims and Lockheed Hudsons. Later the squadron received some Supermarine Spitfires and de Havilland Mosquitos. The operations of the original Flights and later the Squadron was taking meteorological information for weather forecasting – previously provided by merchant shipping to the Met Office. The aircraft would take measurements of temperature and humidity in set areas over the North Sea from an altitude of 40,000 ft downwards. The squadron's Mosquitoes would operate on "PAMPA" flights that took them deep into occupied Europe to assess the weather over target areas for the bombers. On 31 March 1943 at Bircham Newton the squadron was split into nos. Nos. 1401 and 1409 (Met) Flights.
The squadron reformed on 1 September 1943 at RAF Docking, a satellite of the Bircham Newton station, adding to its original equipment Handley Page Hampdens, but doing without the earlier Mosquitos and Blenheims. In December 1943 the squadron received Lockheed Venturas to replace its Hudsons. Additional Hurricanes arrived in August 1944, to supplement the aging Gladiators, which were still on strength. Hudsons arrived again in September 1944, because the Venturas were needed elsewhere. In October 1944 the squadron moved a few miles to the other satellite of Bircham Newton, RAF Langham. For long-range missions the squadron received some Boeing Fortresses in December 1944, which were supplemented after the end of the war with Handley Page Halifaxes, by which time the squadron operated from RAF Chivenor, where the unit disbanded on 1 April 1946.
| August 1942 | March 1943 | Mk.IV | ||
| August 1942 | March 1943 | Mk.IV | ||
| August 1942 | March 1943 | Mks.I, II | ||
| August 1942 | March 1943 | Mk.III | ||
| August 1942 | March 1943 | P.R Mk.IV[1] | ||
| After re-formation | ||||
|---|---|---|---|---|
| September 1943 | December 1943 | Mk.I | ||
| September 1943 | January 1944 | Lockheed Hudson | Mks.III | |
| September 1943 | April 1945 | Gloster Gladiator | Mks.I, II | |
| September 1943 | November 1945 | Supermarine Spitfire | Mk.IX | |
| December 1943 | October 1944 | Mk.V | ||
| August 1944 | February 1946 | Mk.IIc | ||
| September 1944 | March 1945 | Lockheed Hudson | Mk.VI | |
| December 1944 | February 1946 | Mk.II | ||
| May 1945 | February 1946 | Mk.III | ||
| December 1945 | April 1946 | Mk.VI |
| 1 August 1942 | 31 March 1943 | Det. at RAF Oakington, Cambridgeshire | ||
| 1 September 1943 | 30 October 1944 | RAF Docking, Norfolk | Det. at RAF Skitten, Caithness, Scotland | |
| 30 October 1944 | 3 November 1945 | RAF Langham, Norfolk | Det. at RAF Brawdy, Pembrokeshire, Wales | |
| 3 November 1945 | 1 April 1946 |