Contra rotating propeller model, used originally on the 1/9th scale dynamic model of the Blackburn N2/42 flying boat fighter. Later used on the 1/7th scale model of the Supermarine Walrus. Tested in sea plane tank for spray formation.

These contra-rotating propellers were made originally for use in tests on a 1/9 scale dynamic model of the blackburn N2/42 flying-boat fighter. The tests were conducted in the seaplane tank to observe the spray formation and for longitudinal stability (porpoising) tests. The proposed aircraft design was a single engined mid-wing monoplane fitted with a napier sabre IV engine. The full-scale tractor propeller was to be 13 ft in diameter.

Later, as a suitable model turbine was not available, these propellers were modified to represent 1/7 scale dynamic model of the pusher propeller of the supermarine walrus seaplane. This model was tested in the RAE seaplane tank as part of a larger test-programme to compare the dynamic behaviour of models with that of the full-scale aircraft.