I was a bit shocked to see a newspaper article announcing "a sunset" for the famous Boeing 747. In my book I describe the 747 Environmental Control System (air conditioning) that I helped design for Hamilton Standard Div. of United Technology Corp in Windsor Locks Conn. I was excited to be a part of the jumbo jet industry trend fresh out of college. The 747 was the first twin aisle airplane with double the capacity of any commercial aircraft during its maiden voyage in 1970.
This ECS package utilized bleed air from the engines or ground cart directed
into a primary heat exchanger. Outside ambient air is used as the coolant in
this air-to-air heat exchanger. Once the hot bleed air had been cooled, it is
then compressed through the compressor impeller. This compression heats the air
and it is directed to the secondary heat exchanger, which also uses outside air
to reduce the temperature. The temperature of the compressed cooled air is
somewhat greater than the ambient temperature of the outside air. The
compressed air then passes through the turbine wheel that extracts work from
the air as it expands, cooling it to below ambient temperature. The work
extracted by the expansion turbine wheel is transmitted by a shaft to rotate both
the compressor and fan impellers which draws in the external air for the heat
exchangers during ground running; ram air is used in flight. Finally, the
fan impeller draws the cooled air through the aircraft cabin to the individual
air vents.That approach resulted in the combination turbine,
compressor and fan impellers on one shaft thus reducing both weight and
manufacturing cost of the system per plane.
As with any product, sales started to diminish with time due to competition from smaller and more efficient aircraft that could utilize shorter runways. Currently United Parcel Service holds all but three unfilled orders for the 747. Boeing's corporate historian Michael Lombardi claimed "It was the plane that shrank the world, that's the legacy of the 747.
