Rolls-Royce Tyne R. Ty. 20 Mk. 21 is an exact historical turboprop variant in the Tyne family. The Musée de l’Espace identifies two of these engines on Breguet Br.1150 Atlantic 61 aircraft and gives 6,150 EHP for each engine. This exact variant remains distinct from the broader Rolls-Royce Tyne family and the existing Tyne Mk.101 node; no broader aircraft application is inferred.