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707 Engine Pylons

Hemispheres From United States of America, joined exactly 9 years ago today! , 85 posts, RR: 0
Posted (8 years 4 months 19 hours ago) and read 1824 times:

I've always wondered this but was too dumb to ask. Why is the engine pylon for the #1 engine different than the rest. It's missing the distinctive hump toward the front of the engine. Anyone know the purpose? (enlarge the first pic, you can see what I mean better)

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6 replies: All unread, jump to last

BR715-A1-30 From , joined Dec 1969, posts, RR:
Reply 1, posted (8 years 4 months 19 hours ago) and read 1799 times:

Didn't it have something to do with RAM-AIR or BLEED-AIR or some AIR thing in order to start the engines. 4-3-2-1... In either way, 1 was the last to be started at any given time.

Send an email to John Travolta Big grin

Jetstar From United States of America, joined May 2003, 1523 posts, RR: 10
Reply 2, posted (8 years 4 months 19 hours ago) and read 1792 times:

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The foward part of the engine pylons for #2, 3 & 4 have the turbo compressors needed for the aircraft cabin pressurization system, Engine #1 did not have the compressor.

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.

Nowadays engine bleed air is now used for direct cabin pressurization.

SATL382G From , joined Dec 1969, posts, RR:
Reply 3, posted (8 years 4 months 19 hours ago) and read 1786 times:

Ah yes, the weekly what is that thing on top of the 707 pylon thread.

It's a turbocompressor. Essential for aircraft pressurization.

If you look at the entire Boeing/KC135 series you'll see a variety of diffent configurations. Some have 3 turbocompressors, some 2, others 1, etc.

regards

Bully707 From , joined Dec 1969, posts, RR:
Reply 4, posted (8 years 4 months 16 hours ago) and read 1699 times:

And the TF33 powered AWACS have none.... Big grin

Bully

Andz From South Africa, joined Feb 2004, 8298 posts, RR: 11
Reply 5, posted (8 years 4 months 6 hours ago) and read 1569 times:

Ah yes, the weekly what is that thing on top of the 707 pylon thread.

First time I've seen it, the poster learned something and so did I. That's what the forum is for.

After Monday and Tuesday even the calendar says WTF...

Bucky707 From United States of America, joined Aug 2000, 1028 posts, RR: 4
Reply 6, posted (8 years 4 months 3 hours ago) and read 1478 times:

"And the TF33 powered AWACS have none....

Bully"

Are you an AWACS driver?

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