The RFC was a part of the British Army and did not become an independent arm of the Services until the creation of the Royal Air Force 1st April 1918.
There may be records kept elsewhere but my understanding is that RAF records are available here. It may be that NoK should apply, but contact and find out:-
All service records of the officers and men of the Royal Air Force are maintained and stored by the Ministry of Defence. Copies of records are available only to relatives. Contact:
PMA (CS)2a(2) (RAF) - (validated: as of Feb 2010)
RAF Disclosures
Room 221V
Trenchard Hall
RAF Cranwell
Sleaford, Lincolnshire
NG34 8HB
England
Phone: 01400-268161
Note: while I have not used this service myself, it is my understanding that may be a fee charged for this service.
Also try
Great War Forum (Powered by Invision Power Board) for any information about his WW1 service, with as much detail as is known.
There may be at least one other Service Number, as he would have received an Officers Service Number (believe that's the 5 figure one) so ask if there are other records for before he was commissioned. He might even have some Army service before the RFC.
Good luck and look forward to seeing what can be found!!