annular radiator - advantages?

[Graham Boak]

The annular radiator is not necessarily draggier, as the drag of every radiator has to be considered into the total drag of the aircraft. This can indeed differ depending upon the installation position: note how the Typhoon's radiator is mounted further forward than that of the Hurricane.

Aircraft such as the 109 and the Spitfire made use of internal ducting to reduce the drag of the radiator installations: the Mustang being perhaps the finest example of this. In allied nations this was known as the Meredith effect, after the RAE engineer who suggested it in a 1930s report.

This was not possible with "flat fronted" installations such as the Ju 88, which was known as a "ring" installation". Later annular radiators - Ta 152 - used similar ducting with radiators angled away from the flight direction, this was known as a "drum" installation. See Hoerner's Fluid Dynamic Drag (and I hope I haven't got the two names reversed! It has been many years since I was using the reference.)