Fog Investigation and Dispersal Operation

Fog Investigation and Dispersal Operation (FIDO) (which was sometimes referred to as "Fog Intense Dispersal Operation" or "Fog, Intense Dispersal Of") was a system used for dispersing fog and pea soup fog (dense smog) from an airfield so that aircraft could land safely. The device was developed by Arthur Hartley for British RAF bomber stations, allowing the landing of aircraft returning from raids over Germany in poor visibility by burning fuel in rows on either side of the runway.

The FIDO system was developed at the department of chemical engineering of the University of Birmingham, United Kingdom, during the Second World War. The invention of FIDO is formally attributed to Dr John David Main-Smith, an ex-Birmingham resident and principal scientific officer of the Chemistry Department of the Royal Aircraft Establishment at Farnborough, Hampshire, and as a courtesy the joint-patent (595,907) held by the Ministry of Supply was shared by the department head Dr Ramsbottom as was normal practice at the time. This formal government recognition is enshrined in an Air Ministry postwar letter to the late inventor's late widow and held by his son, Bruce Main-Smith (February 2008). It also deals with the lesser role of those developing support equipment, notably the FIDO burner.

"It is my memory", writes Bruce Main-Smith, "that much of the airfield installation was pioneered at Hartford Bridge Flats airfield (aka Blackbushe near Yateley, Surrey [sic]) a convenient few miles from the RAE's Farnborough aerodrome." Though J. D. Main-Smith co-owned the FIDO patent, no royalties accrued from any UK civilian usage after World War II, its being too petrol-hungry. At an attempt to quantify the saving of aircrew life, Bruce Main-Smith suggests possibly 11,000 airmen but not all would be fit to fly again.

It is difficult for the modern (2008) UK resident to comprehend what World War II fogs were like. It was not uncommon for a person to be unable to see the hand at the end of an outstretched arm. The post-war Clean Air Act hugely ameliorated UK fogs.

— B. Main-Smith