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Boeing 707B  
User currently offlineCancidas From Poland, joined Jul 2003, 4112 posts, RR: 10
Posted (11 years 12 months 4 days 19 hours ago) and read 3254 times:

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look at that picture. the #1 engine does not have the same vents above the leading edge of the cowling as the other three engines. why is this? is this the case only on this one a/c, or one model of the 707?

"...cannot the kingdom of salvation take me home."
4 replies: All unread, jump to last
User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 4
Reply 1, posted (11 years 12 months 4 days 19 hours ago) and read 3241 times:

You win kudos from me for being observant, but I can't tell you why it is that way.

User currently offlineOkie From United States of America, joined Jul 2003, 3807 posts, RR: 3
Reply 2, posted (11 years 12 months 4 days 18 hours ago) and read 3207 times:

The first 707's did not use bleed air for presurization but used turbo compressors. The number 1 engine was not fitted with a turbo compressor as it was determined that 3 were more than enough. The inlets and ducting for the air for pressurization was fed through the pylon. It was thought at the time by the powers that be, that the bleed air had too much chance for oil contamination.
Hence your first example of a bleedless engine at least for pressurization, but oh wait that is something new for the 7E7.


[Edited 2004-05-28 20:37:45]

User currently offlineTimz From United States of America, joined Sep 1999, 7224 posts, RR: 7
Reply 3, posted (11 years 12 months 4 days 14 hours ago) and read 3145 times:

Most 707-320B/C looked like that, but as I recall they didn't all have three turbocompressors-- one pylon might be empty. A few -320Cs had a #4 pylon like the #1-- AA's freighters, if no others.

User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 4, posted (11 years 12 months 4 days 13 hours ago) and read 3148 times:

ALL models of Boeing 707 and 720 aircraft had turbocompressors for cabin pressurization, and in addition SOME also had provisions for engine bleed air for cabin pressurization as well.
If engine bleeds were used, cabin ventilation was rather severely compromised, and descent had to be started much furhter out due to the low volume of bleed air available.
Having said this, if ultimate range was a consideration, using engine bleeds improved SFC by approximately 2.5% with fan engines, 2% for non-fan engines. In this case, turbos needed to be started every hour or so. If this was not done, they might not start at ALL due to cold soak, and be unavailable for use during descent.

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