How small could an aviation cruiser be?

At what size did cruiser aviation facilities stop being worthwhile, and did radar displace them?

There was no hard size or radar cutoff; the decision followed the intended mission, and compact aircraft such as the Seafox served on small light cruisers.

Radar did not impose a simple size threshold beyond which cruiser aircraft became obsolete. Even destroyers could be fitted for aircraft if the mission justified the space and weight. The Royal Navy omitted aviation from ships it did not expect to use that way, while fitting small cruisers with the compact Fairey Seafox. The Seafox offered nearly five hours of endurance from a relatively low-powered Napier Rapier engine. Seafoxes aboard Leander-class cruisers contributed to the hunt for Admiral Graf Spee. The efficient, sub-four-hundred-horsepower Rapier helped lead the Navy to ask Napier for a two-thousand-horsepower engine.