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Boeing 707-320C

Old 16th Mar 2023, 20:42
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Boeing 707-320C

Hi everyone, I have a question.
On the Boeing 707-320C (with JTD3 motors) the outer port wing nacelle pylon has a straight top compared to the inners. This appears to be only on the port side and not the starb. Anyone know the reason why it's just the port side?

Thanks.



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Old 16th Mar 2023, 21:03
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Three turbocompressors for pressurisation. Explained by the late 411A here:

707 Engine pylons
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Old 16th Mar 2023, 21:05
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Hi Bazzarius.Engine pylons 2,3 and 4 contain a 'turbo compressor '-this is an engine bleed air powered air pump supplying air to the air-conditioning packs-when the first generation jet airliners came into service bleed air from the engines wasn't allowed to go straight into the cabin as there were concerns about contamination.
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Old 16th Mar 2023, 21:11
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Thankyou. My apologies I hadn't realised that the subject had already been raised. Anyway, mystery cleared up.
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Old 16th Mar 2023, 23:00
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Originally Posted by exwessex
Hi Bazzarius.Engine pylons 2,3 and 4 contain a 'turbo compressor '-this is an engine bleed air powered air pump supplying air to the air-conditioning packs-when the first generation jet airliners came into service bleed air from the engines wasn't allowed to go straight into the cabin as there were concerns about contamination.
And 30 years later, the person who'd decided that said 'told you so'
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Old 17th Mar 2023, 10:32
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Just for completeness, it was not just the -320C, but the -320B as well. While we are on the subject the 720B generally only had turbo compressors on the inners.
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Old 17th Mar 2023, 10:41
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Originally Posted by Bazzarius
Thankyou. My apologies I hadn't realised that the subject had already been raised. Anyway, mystery cleared up.
No apologies needed, not something I knew (or perhaps had forgotten) and every day is indeed a school day.
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Old 17th Mar 2023, 15:44
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However there are some 707-320C's that were built as all-cargo (such as those for Pan Am 707-321C)
and those built for AA (707-323C's both Pax and all-cargo) had TC's only on engines #2 and #3.

Also AA's 707-323B's also only had 2 TC's.

the 707-138B had 3 TC's
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Old 17th Mar 2023, 16:18
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Originally Posted by exwessex
...an engine bleed air powered air pump supplying air to the air-conditioning packs-when the first generation jet airliners came into service bleed air from the engines wasn't allowed to go straight into the cabin as there were concerns about contamination.
Same for the CV880, IIRC.
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Old 17th Mar 2023, 19:11
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I seem to remember a VIP 707 with 4 TCs, Maybe Saudi royal flight.
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Old 17th Mar 2023, 22:01
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The photo's of the BOAC B707-436 with RR Conway engines seem to show 4 TCs.
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Old 18th Mar 2023, 00:20
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I've flown in a Boeing 707-338C back in the early-1970s on two separate occasions.

I also twice flew in a Douglas DC-8-52.

Somehow, flying on international routes was much more fun back then.

Today it is like a journey in a bus which flies, and crammed-in too. You just want it to end.
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Old 18th Mar 2023, 06:44
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I had never noticed the difference in the Number 1 pylon before!






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Old 18th Mar 2023, 08:46
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Originally Posted by Kiwithrottlejockey
I've flown in a Boeing 707-338C back in the early-1970s on two separate occasions.

I also twice flew in a Douglas DC-8-52.

Somehow, flying on international routes was much more fun back then.

Today it is like a journey in a bus which flies, and crammed-in too. You just want it to end.
I did a fair bit of lfying in the back of 707-300's. they were pretty good but they were cramped, especially width wise, the storage was poor and who can forget the pull down movie screen at the front ......

Every aircraft I've flown since on long haul has been a very significant improvement
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Old 18th Mar 2023, 08:54
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Originally Posted by Asturias56
I did a fair bit of lfying in the back of 707-300's. they were pretty good but they were cramped, especially width wise, the storage was poor and who can forget the pull down movie screen at the front ......

Every aircraft I've flown since on long haul has been a very significant improvement
Interesting. Flew in many 707s, mainly to and from Africa and cannot ever recall movie screens.I disagree with you about them being cramped, there was much more room than today's awful experience at the back end..
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Old 18th Mar 2023, 15:31
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They were pretty cramped width wise (737 is the same fuselage isnt it) but they definately had far more leg room pitch 32-34 being very common. And they were so so noisy especially the 400 series coneway powered and the non fan P&W 300s .

I prefered the DC 8 so long as you got a window seat by a window and of course neither came close to the VC10, which prompts me to anwer the question why did the 707s have turbo compressors and not the VC10. As I recall the DC 8 had them under the cockpit giving the airfcraft a sort of odd toothy look

Maybe they were right about the cabin contamination though
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Old 18th Mar 2023, 16:46
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OK can we now play a game of spot the difference with other aircraft? Spent time making noise recordings of competitors engines (as you do) and never ever noticed the odd man out!
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Old 18th Mar 2023, 20:07
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[QUOTE=why did the 707s have turbo compressors and not the VC10. [/QUOTE]


VC10's had Godfrey screw compressors in the wing root fed by air from a small intake in the wing leading edge, what I cannot remember is how the compressor was powered.
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Old 18th Mar 2023, 23:40
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Evening Sandringham,

I believe the Godfrey compressors were fitted above the engines and not in the wing root. I only worked on the VC10 as a BOAC apprentice so stand to be corrected. I recall that the compressors were mechanically driven by a shaft from the main engine gearbox.. I believe the air conditioning units were fitted in the wing root. I used to test the Godfrey blowers when working in the BOAC 'component test house' - on one occasion a blower actually blew up on test after the two parts of the compressor touched (there was only a few thou clearance between what we called the mangles) - it was a mess. Only we Brits could design such a thing and actually fit it to a passenger airliner. We also used to test the turbo compressors as fitted to the B707 - a much simpler and more effective design in my opinion. Anyway a bit of thread drift for which I apologise.

Back on thread. As far as turbo compressors fitted to B707 variants - when I worked in the BOAC hangers all B707-436's and 336's had 3 turbo compressors fitted to engines 2,3 and 4 whereas all B707-320's (they were foreign operators) had 2 turbo compressors fitted to engines 2 and 3 only.


Kind regards
Exeng

Last edited by exeng; 18th Mar 2023 at 23:45. Reason: Added detail on where the air conditioning units were fitted
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Old 19th Mar 2023, 07:20
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I wonder why the 707-436 had the same TC fairing on all 4 engines but only had 3 TCs fitted. Was it a style thing to make it look symetrical?
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