b707 turbocompressors
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Joined: Sep 2003
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From: temporarily unsure :-)
b707 turbocompressors
hi all,
just was wondering,since i'm not that familiar with the 707's airframe & technical details,if anybody could tell me why the 707 lacks a number one engine turbocompressor?
just was wondering,since i'm not that familiar with the 707's airframe & technical details,if anybody could tell me why the 707 lacks a number one engine turbocompressor?
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
Three sources for pressurization are a plenty for the two packs installed.
In addition, for the times when all turbocompressors fail enroute (an unlikely occurance), 9th stage bleed air is available on most models, expect the freon air conditioning equipped aircraft.
Have personally (when maximum range was required), switched OFF all turbocompressors and used engine bleeds for pressurization (3% improved specific fuel consumptioin). This is OK for freighters, but results in rather low cabin ventilation rate with pax aircraft.
IIRC, the 707 used by the USAF to transport the president, had 4 turbocompressors installed.
Nothing but the finest for the boss, I guess.
In addition, for the times when all turbocompressors fail enroute (an unlikely occurance), 9th stage bleed air is available on most models, expect the freon air conditioning equipped aircraft.
Have personally (when maximum range was required), switched OFF all turbocompressors and used engine bleeds for pressurization (3% improved specific fuel consumptioin). This is OK for freighters, but results in rather low cabin ventilation rate with pax aircraft.
IIRC, the 707 used by the USAF to transport the president, had 4 turbocompressors installed.
Nothing but the finest for the boss, I guess.
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
Yes, normally three.
Turbocompressor and bleed air normally could not be mixed, either one or 'ta other.
If bleeds were used, turbos needed to be started every hour to warm 'em up...otherwise they might not be available for descent.
Descent with bleeds only was rather difficult, to say the least. 
Then, the Flight Engineer earned his salary...big time.
Turbocompressor and bleed air normally could not be mixed, either one or 'ta other.
If bleeds were used, turbos needed to be started every hour to warm 'em up...otherwise they might not be available for descent.
Descent with bleeds only was rather difficult, to say the least.
Then, the Flight Engineer earned his salary...big time.
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
Oddly enough, only one time did I have a turbocompressor fail on the 707, and I operated several of the early models (with JT4A engines) as well as the -320B advanced.
Turbocompressors were needed because insufficient bleed air was available from the engines at lower RPM's to keep the cabin pressurized during descent. Also, using bleeds reduced the climb performance greatly, whereas the TC's were more efficient at delivering cabin air.
In addition, engine bleeds did not supply enough air for sufficient cabin ventilation with a full (189) pax load.
Turbocompressors were needed because insufficient bleed air was available from the engines at lower RPM's to keep the cabin pressurized during descent. Also, using bleeds reduced the climb performance greatly, whereas the TC's were more efficient at delivering cabin air.
In addition, engine bleeds did not supply enough air for sufficient cabin ventilation with a full (189) pax load.
