[Graham Boak]

I refer you to Francis Mason's book on the Typhoon/Tempest, where at least one photograph is printed showing the armour fitted to late production Typhoons around the cockpit (not just pilot back armour) and, IIRC, the engine. Liquid cooled engines are vulnerable to "the golden BB" as our US friends put it, but the Sabre installation was less vulnerable than most because the close mounting of the radiator to the engine resulted in shorter piping.

The vulnerability to small arms is of course one reason for the use of the rocket, permitting operation at greater stand-off distances. You may like to study the recently published history of 351 (Yugoslav) Squadron, with its interesting comments on the much higher loss rates of its Spitfires than its sister squadron with rocket-firing Hurricanes.

The Il 2 was indeed in a different category of armour, but given the number of Il 2s shot down by Bf 109s and Fw 190s, it clearly was rather less invulnerable to 20mm cannon than General Pickert believed. Perhaps his flak was also less accurate? The similar IL.10 proved vulnerable to the 0.5in machine gun fire of US fighters in the Korean War, and was driven from the skies by mainly a mix of P-51s and F-82s. Not a great advertisement for the concept, and closer to the loss rates of the Battle in 1940.