The Honeywell LF 507 engines fitted to the Avro RJ seies are flat rated at 7000lb to 23.5degreesC. The cancelled RJX with its Honeywell AS977 engines were flat rated at 7000lb to 35degreesC.
The AS977 engines were 15% more efficient resulting in a 17% increase in range. The RJX would have been a better performer in the hot&high scenarios discussed here.
Best bit about the RJX ...... dual FADEC!
