Sir - I was surprised to read in the article "GE looks at increasing GE90 thrust levels" (Flight International, 26 April-2 May, P6) that the preferred approach to achieving greater power is by removing one or two high-pressure stages from the core.
Such a change would allow a cycle-temperature increase, but would cost the loss of cycle efficiency and fuel consumption. Also, considering the higher rating of 480kN (108,000lb), the power increase from known certificated levels is about 20%.
To achieve this power - retaining the existing fan, low-pressure systems and casings and leaving only speed, temperature and material changes as options - seems a high-risk strategy.
Following the certification saga of the fan elements, to leave it unchanged is understandable. I do not recall, however, having seen confirmation of the logic behind the GE90 blade-off test (Letters, Flight International, 24-30 August, 1994, P66), which was queried by the UK Civil Aviation Authority.
D F NEWLAND
Watford, Hertfordshire, UK
Source: Flight International
