However, it took Rolls-Royce nearly 25 years to bring its three-shaft RB211 bypass engine
to fruition from the first patented designs.
Thus was invented the propfan, an "ultra-high" bypass engine
that is a throwback in two ways.
(1) is largely determined by bypass flow in a high bypass engine
the fan pressure ratio (which could be 1.6 for a bypass ratio of 8:1) is the key parameter.
Simpson recalled that in the early 1960s all engine contractors in this country and abroad said the highest bypass engine
they knew how to build was 3.5.
The main driver for sea level testing is that larger fan high bypass engines
require orders of magnitude more bypass airflow than PSL can deliver under high altitude ice crystal icing test conditions.
Sukhoi said its SU-34 Fullback bomber, which is replacing SU-24s now in service, is a twin-seat day/night all-weather platform with large capacity internal fuel tanks and fuel-efficient bypass engines