If you know where he was brought up you could send a letter to the local paper asking for information about your Granddad .
If you could find which squadron your Granddad flew with you may be able to get info from the Public Records Office at Kew.
My uncle flew Blenheim bombers and was shot down over France early in the war but we were able to get his log book and we got in touch with a relative of his gunner .