I am researching the origins of the use of Bleed Air for Pressurization in Commercial Jet Aircraft and any input would be much appreciated.
With the introduction of commercial jet powered aircraft there was extensive use of turbo compressors as a means of providing air for pressurization and heating. Aircraft like the Comet, Convair 880, VC
-10, Boeing 707, DC-8 etc.. appear to have extensively used turbo compressors, a technology introduced on aircraft like the Lockheed L-647/749 Constellation in 1943.
It appears that the French Caravelle was the first commercial jet aircraft to use bleed air directly for pressurization (without turbo compressors) when in flew in 1955. Yet it seems US aircraft continued to use turbo compressors until the Boeing 727 arrived in 1963.
It has been suggested in 2001 and 2005 on this forum that the reason for this was:
"Back in the old JT3D / Conway days the bleed air provided from the engines was too oily to be used directly for cabin pressurization, therefore they used the turbo compressor inbetween."
"In the early jet airplane days, the FAA did not allow engine bleed air to be used for cabin pressurization, they had to use outside air. The turbo compressors used engine bleed air to drive a pump the compressed the outside air and pumped it into the cabin."
I have found at least six reports from the early 50s from Boeing, Douglas, North American etc.. that show their awareness of contaminated bleed air (oil contamination) dates back to the introduction of the J-57 engine and the first use of synthetic jet engine oils. The 1955 North American paper also states:
"“The Separate Compressor As A Solution' – This method of eliminating contamination is considered to be the most positive… also the heaviest, most complicated and most expensive.”
I have also read a 2008 IFALPA Safety Bulletin - 09SAB02 (21 May 2008) - which states:
"The FAA had mandated the use of turbo compressors because of the risk of cabin air becoming polluted due to leaks in the compressor bearings."
However, I cant find any official FAA documentation to confirm this. If anyone has a reference in this regard please let me know.