Sidney was the son of Charles and Sarah Smith who predeceased him. Sidney was bought up as an orphan with his sister. Research is ongoing for further information about his life.

Sidney was the navigator on Lancaster NN775 which departed RAF Waterbeach on a daylight operation to bomb Gelsenkirchen. The aircraft crashed at Bunsbeek in Belgium.

All seven aircrew were killed.
Pilot, F/O Holman Kerr, age 23
A/B, F/O Frank Clarke
Nav, F/Sgt Sidney Smith
W/Op, F/Sgt Allan Olsen RAAF, age 20
MUG, Sgt Christopher Hogg, age 20
R/G, Sgt Herbert Thomas, age 23
F/E, Sgt William Marsden, age 20

Remains of the airmen at the time were buried in a single grave at
Heverlee War Cemetery. The large hole created by the crash, which quickly filled with water,
and was then filled in by a farmer.

On 11 Nov 2016 work began by the Planehunters Group and the Belgium Aviation History
Association Archaeology team (BAHAAT) to excavate the wreckage of NN775, with the permission of the Flemish official archaeological board. They found the Lancaster was still buried but in a badly damaged state. Amongst the articles found relating to the crew was a wristwatch, oxygen mask, a uniform cap and British coins. Once the aircraft and any remains were fully exhumed a reburial commemoration service was held on 28 April 2017 at the Heverlee War Cemetery. Information from by FS Matt Bowen, SHAPE RAFALO