Higher density charge air by reducing the length of intake ducts and increasing the size of the compressor wheel.
Near floor level, something had tampered with an eighteen-inch-square intake duct to the building's ventilation system.
One of the intake ducts was arcing.
The intake ducts were visible instead of being hidden inside the ceiling.
A more permanent and much more efficient solution is to install a fresh-air intake duct leading directly from outside to the base of the fireplace.
The roar of air through the eight intake ducts stilled, but a high-pitched whine indicated various parts continued to spin in readiness for any need.
Icing conditions should be avoided, though, because the first components to suffer a build-up are the throttle-rods in the intake ducts ahead of the engines.
Placing the intake duct so as to use the ram-air effect to give positive pressure at speed.
This position minimized thrust losses due to the length of the intake duct and allowed the engine to be changed much more easily than its predecessor.