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HAWK21M
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Differences On B707 Types.

Wed Feb 28, 2007 6:49 pm

Is it correct to state that the only difference between the B707-120 & B707-220 was the Powerplant ie JT3 & JT4 so cruise speed would be different.
And B707-320 & B707-420 ie JT4 & RR Conway but no difference in Cruise speed.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
DH106
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RE: Differences On B707 Types.

Wed Feb 28, 2007 8:07 pm

The -300 & -400 series have many minor differences,

To name a few:

-400's always have the large size ventral fin under the rear fuz.
-300's seem to have none, small or large - depending on exact version (but even then there doesn't always seem to be a corrolation)

-400's have the early single trailing secondary nose gear door
-300's have the 2-doors, one on each side arrangement.

-400's have pylons arranged for 4 turbo compressors
-300's only have 3 (no comp. on #1 engine)
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
411A
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RE: Differences On B707 Types.

Thu Mar 01, 2007 1:35 am

Other differences as well, if you look on the FD, between the JT4 and RR Conway powered models.
The Conway powered airplanes had no EPR gauges, as the Conway power was set by N1 and EGT only.

Ventral fin.
Two varieties, the 13 inch and the 39 inch.
On the 707's with parallel type yaw dampers, the larger 39 inch ventral fin was fitted.
The smaller ventral fin was fitted to the airplanes with the series type yaw damper....which did not apply to the Conway powered airplanes, as they all had the parallel type.

On later long body models, the ventral fin was eliminated, as the vertical stabilizer was higher.

Cruise speed.
No difference in the JT4 or Conway powered airplanes.
Most were cruised at M.82, however if very long range flights were undertaken, long range cruise was used...M.81.
 
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HAWK21M
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RE: Differences On B707 Types.

Thu Mar 01, 2007 2:08 am

Quoting 411A (Reply 2):
The Conway powered airplanes had no EPR gauges, as the Conway power was set by N1 and EGT only.

Any Numbers Stats on How much percentagewise of the Engines on the B707.

Also why were the Dash numbers reffered to as -120/220 etc & not the normal -100/20 etc.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
timz
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RE: Differences On B707 Types.

Thu Mar 01, 2007 8:35 am

Quoting DH106 (Reply 1):
-400's always have the large size ventral fin under the rear fuz.
-300's seem to have none, small or large - depending on exact version

The first -300s didn't have a ventral fin, but after a few years didn't they all get the larger one? Anyone find a pic of a JT4A-powered 707 with no ventral fin after, say, 1963?

Quoting DH106 (Reply 1):
-400's have pylons arranged for 4 turbo compressors
-300's only have 3 (no comp. on #1 engine)

JT4A-powered -300s?
 
411A
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RE: Differences On B707 Types.

Thu Mar 01, 2007 9:50 am

Some long body (-300's) were delivered with no ventral fins.
This all changed when the Conway powered airplanes were brought onto the UK register, for BOAC.
The UK Air Registration Board (headed by DP Davies) insisted that the rudder power and spiral stability of these airplanes was not up to ARB standards, and Boeing fitted a 39 inch ventral fin to accomodate the UK requirements.
Then, if I recall correctly, ventral fins were retrofitted to existing models and the rudder power system was changed as well.
DP Davies passed away several years ago, and an article about him appeared the the London Sunday Times.
In the article, Davies mentioned that the hardest experience that he had was getting Boeing to change the 707 rudder power system.
Now, having flown these old airplanes, I suspect he was right.
 
Viscount724
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RE: Differences On B707 Types.

Thu Mar 01, 2007 1:38 pm

Quoting HAWK21M (Reply 3):
Also why were the Dash numbers reffered to as -120/220 etc & not the normal -100/200 etc.

The correct generic terminology for 707 models is -120/-220/-320/-420, not -100/-200/-300/-400. Boeing's own 2-digit customer number is "20". For some reason -100/-200 etc. became the generic model terminology for Boeing types after the 707. The customer numbering system was the same for all Boeing models, i.e. the first number assigned to a customer was -21 (Pan Am) and when they reached -99 they continued with -01 through -19, and then used alpha-numeric designations (-A0, -A1, -A2 etc.) for subsequent customers.

Quoting Timz (Reply 4):
The first -300s didn't have a ventral fin, but after a few years didn't they all get the larger one?



Quoting 411A (Reply 5):
Some long body (-300's) were delivered with no ventral fins.



Quoting 411A (Reply 2):
On later long body models, the ventral fin was eliminated, as the vertical stabilizer was higher.

Only early production -320s had a ventral fin (or were retrofitted with it in the case of a few very early production -320s). I believe only the long ventral fin used on the R-R Conway -420 was used on the early production -320s. I'm not sure how many early -320s were originally built with the short vertical stabilizer and no ventral fin; I don't think it was very many. The ventral fin was eliminated on later production -320Bs and no -320C models ever had a ventral fin to the best of my knowledge.

Early production -120s and the five -220s built for Braniff (only 4 of which went into service as the first one crashed on a pre-delivery acceptance/training flight), built without the ventral fin and with the short vertical stabilizer, were retrofitted with the 3-foot longer stabilizer and short ventral fin. Later production -120s and all 720s were built with the longer stabilizer and short ventral fin. I believe the majority of all 707s built fall into the "late production -320" category and thus never had a ventral fin.

Following the modification of early-build 707s to lengthen the vertical stabilizer, all 707s (and 720s) eventually had the same longer stabilizer.

Good description of the Boeing customer numbering system:
http://www.aerospaceweb.org/question/planes/q0048.shtml

This site, although mainly devoted to a very detailed history of the QF 707 fleet, also has a good general description of 707 development and models here:
http://www.707.adastron.com/history/707-history.htm
 
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HAWK21M
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RE: Differences On B707 Types.

Thu Mar 01, 2007 3:41 pm

Quoting Viscount724 (Reply 6):
For some reason -100/-200 etc. became the generic model terminology for Boeing types after the 707.

Any Particular reason why,or was the -100/200 etc preferred tonewise.
Very Interesting links.Thanks.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
justplanesmart
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RE: Differences On B707 Types.

Thu Mar 01, 2007 3:53 pm

Here's another link with lots of descriptions of the differences between models of the 707:

http://www.diecastaircraftforum.com/...raft/21531-ultimate-707-guide.html
"So many planes; so little time..."
 
timz
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RE: Differences On B707 Types.

Fri Mar 02, 2007 5:29 am

Quoting DH106 (Reply 1):
400's have pylons arranged for 4 turbo compressors
-300's only have 3 (no comp. on #1 engine)

As expected, he seems to be talking about fanjet -300s. Looks like #1 and #4 nacelles are the same on all JT4A-powered -300s.
 
411A
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RE: Differences On B707 Types.

Fri Mar 02, 2007 5:48 am

Ah, not really, Timz.
The -320 JT-4A powered airplanes that I have flown, both the -321's (PanAmerican) and the -331's (TWA) had 3 turbocompressors.
A standard fit, direct from the factory...unless modified elsewhere.
 
Tango-Bravo
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RE: Differences On B707 Types.

Fri Mar 02, 2007 6:10 am

Not to overlook another one of a kind 707 variant ordered by and delivered new to only one airline, the 707-138 (became 707-138B when converted to fan engines). Based on the 707-120 with the fuselage shortened by 6' (?) the variant was designed especially for QANTAS for their very long range routes. Ironically, some of QANTAS's 707-138Bs were picked up secondhand by Braniff who were also the only customer for the other 707 type ordered by and delivered to only one airline (Braniff), the 707-220, or 707-227 as the variant as delivered to Braniff was known.
 
Viscount724
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RE: Differences On B707 Types.

Fri Mar 02, 2007 7:43 am

Quoting HAWK21M (Reply 7):
Quoting Viscount724 (Reply 6):
For some reason -100/-200 etc. became the generic model terminology for Boeing types after the 707.

Any particular reason why,or was the -100/200 etc preferred tonewise.
Very Interesting links.Thanks.

I expect -100/-200 etc. was considered simpler and less cumbersome for marketing and promotional purposes.
 
Viscount724
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RE: Differences On B707 Types.

Fri Mar 02, 2007 7:52 am

Quoting Justplanesmart (Reply 8):
Here's another link with lots of descriptions of the differences between models of the 707:

http://www.diecastaircraftforum.com/....html

Thanks for the link. One of the best I've seen on 707 differences.
 
timz
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RE: Differences On B707 Types.

Sat Mar 03, 2007 2:40 am

Quoting 411A (Reply 10):
both the -321's (PanAmerican) and the -331's (TWA) had 3 turbocompressors.

Oops-- I didn't write carefully. I meant to say the #1 and #4 nacelles on JT4A-powered 707s look the same, from the outside. No idea which ones are empty.

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