Back to thread: what Aircraft, beside the 747 old and new have more than two Packs? I cant think of any, except older aircraft like the 707 and similar.
Don't confuse potential engine bleed sources versus number of packs.
B707, two packs only, one pack dispatch OK (not long overwater) however altitude restrictions apply.
L1011, three packs installed and normally used, two pack dispatch OK, no restrictions.
why not shutting down an engine to save fuel now?
This was once proposed by DanAir while they were operating Comets, but the ARB nixed the idea, pronto.