Try any of the following in Google:
Queens' Commendation for Valuable Service
Queens' Commendation for Valuable Service in the Air
Queens' Commendation for Bravery
Queens' Commendation for Bravery in the Air
Each subtly different from the other...
If you want to rank them relative to better-known awards then QCVS / QCVSA are below a MBE but above any of the military commendations. They can be awarded for non-combat achievements - theoretically, at least, one could be awarded a QCVS for revolutionising procedures for accounting for paper clips at a deployed base (OK a joke example but just for illustration!). They can also be awarded for merit in combat, but where there was no direct requirement for bravery in the face of the enemy.
QCB / QCBA are the entry-level gallantry awards. They can be awarded for bravery in combat which falls short of Mention in Dispatches / DFC / MC etc. They can also be awarded for bravery in non-combat activity which falls short of Air Force Cross levels. AFCs themselves are sometimes awarded for great skill in the face of a serious aircraft emergency (former CAS, ACM Stirrup, got one for bringing a Jaguar back to base after it suffered a massive birdstrike) - the QCBA could be seen as one step down this ladder.
Given the date of 1952-53, it's possible that the award could relate to operations in Korea. However, given the high accident rate across the RAF in general in that era, I would say the most likely scenario is that your uncle encountered some kind of dire airborne emergency and showed bravery / skill in its resolution. Pure speculation - if you found his flying logbook there might be some clues in there? You might also be able to find a copy of his citation with some help from the Air Historical Branch.
Last edited by Easy Street; 24th Mar 2012 at 21:20.