Sir - I have recently flown on "Friendly Skies'" new "Mega Twin" (United Airlines' Boeing 777) and there is no doubt that the aircraft is most impressive in terms of space and cabin layout.
One thing surprised me, however, and that was the high level of noise and vibration in certain parts of the cabin.
In a window seat adjacent to the engine, about 2m (6ft) back from the fan plane, the noise at take-off seemed to be much higher than that, say, of a Boeing 747, and, furthermore, it was accompanied by an incessant droning from the out-of-sync engines, together with unpleasant vibration, which appeared to be magnified by the wall panels.
Seated further forward, however, (about 1m ahead of the fan) the noise was less apparent, although still accompanied by droning and vibration. The effect is obviously localised, since colleagues sitting towards the rear of the aircraft commented on how quiet it is.
Is this an inherent feature of the new, large-fan, engines to which we are going to have to become accustomed, or something which designers will be able to improve with time?
NIGEL SPOONER
Hampton, Middlesex, UK
Source: Flight International
