This is a transcript for my Great Uncle from the British Royal Air Force, Airmen's service records 1912-1939:
No 165384 Charles William Smith; b. 29 Nov 1887 in Sheffield, Yorkshire, CoE; RAF Engaged 9 May 1918 Age: 30yr 5mo for Duration of War. Occ: hairdresser; NoK: Martha (sic Matthew) Grayson Smith of 129 Frank Street, Benwell, Newcastle-on-Tyne, mother. Ht: 5ft 8 1/4ins, Hair: dark brown; Eyes: Grey, Complexion: Sallow. Transferred to RAF Reserve; 11 May 1919; Discharged: 30 April 1920.
Enlisted Private 2: to RD 9 May 1918; RD to BEF 18 July 1918; Appointed A/Corporal 7 Sep 1918; BEF to RD 17 Dec 1918; RD to 1 Ball Sqdn 22 Dec 1918; 1 Bln Sqdn to Des Cen Ripon 11 April 1919. Trade Classification: Batman. France: 18 July 1918 to 17 Dec 1918; BW & V Medal

First I would like to know what RD is. Is it possible to determine where in France he would have been with the RAF? I'm assuming 1 Ball (or Bln) Sqdn is 1 Balloon Squadron, was this a home based squadron? His RAF trade classification was Batman; is this in support of a commander or pilot?
Thanks in advance
Cockatoo, Victoria, Australia