LH707330
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707 Stretches And W/B Issues?

Sat Jun 16, 2012 12:19 am

Hi All,

I've read a number of articles about the various lengths of the 707, and was somewhat puzzled by how they are stretched fore and aft relative to the -120 model. Per this website, the tubes are stretched and shrunk in 20-inch increments, yielding the following four lengths, from shortest to longest:
Model: frames fore/aft vs -120, fuselage length
707-138B: -3/-3, 128' 10"
720: -1/-4, 130' 10"
707-120: 0/0, 138' 10" (baseline)
707-300: +4/0, 145' 6" (per Boeing ACAP)

I'm curious to know:

a. Why do the -138 and the 720 have a dissimilar shortening fore and aft despite sharing the same wing. Wouldn't this create W/B issues, or was this remedied by some of the different systems in the 720?
b. Is the ACAP incorrect, or was the 707-300 only stretched ahead of the wing? I looked at the difference in the wheelbase and compared it to the length to get the a/c to get the +4/0 frames relative to the -120. Did the new wing have a longer chord length at the root that moved the gear back, or was there something else that prevented to design from being nose-heavy?

Regards,
M
 
Viscount724
Posts: 18850
Joined: Thu Oct 12, 2006 7:32 pm

RE: 707 Stretches And W/B Issues?

Sat Jun 16, 2012 1:04 am

The 720 has a lighter-weight structure than the 707-120. It even has slightly smaller wheels and tires.

I've never heard of any weight and balance issues due to the minor differences between the 720 and the 707-138 built for QF which are almost the same length but not quite.
 
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n901wa
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RE: 707 Stretches And W/B Issues?

Sun Jun 17, 2012 11:10 am

From a Old WAL plate chart book. The 707-320 shows a plug fwd of the wing center at section 43 and a plug aft of the wing in section 46. The Fwd plug section 43 starts at 600 around 20 inches fwd of the aft end of the Main Deck Cargo Door (on a 320C ) and shows 600D/E/F/G/H/J/K/L and continues 620 thru 960. The aft section 46 plug starts at the aft end of the main wheel well at 960 and shows 960M and 960N and then continues 980 1000 at the aft emg doors aft of the wing. I have compaired it to the 720B and the aft section 46 shows no plug and goes 960 then 1020 so a shrink of 40 inches, and the fwd section 43 shows a 60 inch plug at 600, from a baseline 707. I do have a 707-120 plate chart book somewhere from when WAL flew the 120 early on, and if I can find it I will post the fuse stations for you. Sorry my scanner is inop, other wise I would scan the drawings for you. HTH.
 
LH707330
Topic Author
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RE: 707 Stretches And W/B Issues?

Mon Jun 18, 2012 5:32 pm

Quoting n901wa (Reply 2):

Do you know how much of the stretch was added to each section?
 
707fan
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RE: 707 Stretches And W/B Issues?

Wed Jul 11, 2012 8:49 am

I am refering to the first post frrom LH707330 who refers to a link to the Ultimate Boeing 707 Guide.

This is a very detailed guide and is really the ‘ultimate 707 guide’. Much more detailed than even Boeing have made.

I have two corrections:
707-120: Neither Air France nor Pan Am ordered the -120. Pan Am operated some -120’s which was bought from American Airlines and Lufthansa.
And 120B it is also stated that this model was ordered by Pan Am. Not. But again, operated by Pan Am.

I have also two questions:
Most of the 320B and C’s didn’t have t/c’s on engine no. 1. I believe the absence of that bump did cause some yaw to the right. Right? I have never seen that this has been mentioned anywhere. Any comments?

The other thing is that I have never seen a description or any pictures regarding the extension of the vertical stabilizer. As I have understood it was BOAC which initiated this modification due to their demand of using RR engines on their 707’s. Any comments?
 
iRISH251
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RE: 707 Stretches And W/B Issues?

Wed Jul 11, 2012 11:02 pm

Quoting 707fan (Reply 4):
I have two corrections:
707-120: Neither Air France nor Pan Am ordered the -120. Pan Am operated some -120’s which was bought from American Airlines and Lufthansa.
And 120B it is also stated that this model was ordered by Pan Am. Not. But again, operated by Pan Am.


The other thing is that I have never seen a description or any pictures regarding the extension of the vertical stabilizer. As I have understood it was BOAC which initiated this modification due to their demand of using RR engines on their 707’s. Any comments?

Pan Am did order the 707-120 - twenty of them, in fact. The first commercial 707 service ever was operated by one of these aircraft, on 26 October 1958, from New York to Paris via Gander.

From http://en.wikipedia.org/wiki/Boeing_707

"The 707-420 was identical to the -320 but fitted with Rolls Royce Conway 508 turbofans (or by-pass turbojets as they were known at the time). First announced customer was Lufthansa. BOAC's controversial order was announced six months later but the British carrier got the first service-ready aircraft off the production line. The British Air Registration Board refused to give the aircraft a certificate of airworthiness in the form presented, citing insufficient lateral control, excessive rudder forces and the ability to over rotate on take off, stalling the wing on the ground (a fault of the de Havilland Comet 1). Boeing responded by adding 40 inches to the vertical tail, applying full instead of partial rudder boost and fitting an underfin to prevent over rotation. These modifications became standard on all 707 variants and were retrofitted to all previously built aircraft."
 
Viscount724
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RE: 707 Stretches And W/B Issues?

Wed Jul 11, 2012 11:04 pm

Quoting 707fan (Reply 4):
I have two corrections:
707-120: Neither Air France nor Pan Am ordered the -120. Pan Am operated some -120’s which was bought from American Airlines and Lufthansa.

That's not correct for Pan Am which most definitely ordered 6 707-121s although they didn't have the range for Pan Am's transatlantic routes. But since they were the only model available that early Pan Am ordered the 6 -121s in order to be able offer jet service (usually with a fuel stop at Gander) before their transatlantic competitors that waited for the long-range -320/-420. And, had PA not ordered the 6 -121s, BOAC would have had a much longer headstart with jet service using the Comet 4, which also lacked nonstop transatlantic range but even with a fuel stop was still faster than the piston types they replaced.

Pan Am also acqured 2 707-139s built for Cubana which couldn't be delivered due to the trade embargo that was imposed just before the aircraft were due for delivery. The 6 factory-delivered -121s and the 2 -139s were the only -120 series 707s operated by Pan Am. They didn't acquire any of AA's 707-123s and LH didn't operate the -120 series.

Pan Am did acquire 3 used 720Bs from AA and 6 from LH for use on Caribbean and Latin America routes, which is where the 8 707-121s/139s were also primarily used after they were replaced on transatlantic routes by the long range -321s starting in late 1959..

[Edited 2012-07-11 16:04:40]
 
LH707330
Topic Author
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RE: 707 Stretches And W/B Issues?

Thu Jul 12, 2012 4:17 am

Quoting 707fan (Reply 4):
The other thing is that I have never seen a description or any pictures regarding the extension of the vertical stabilizer. As I have understood it was BOAC which initiated this modification due to their demand of using RR engines on their 707’s. Any comments?
This article has plenty of pages and descriptions of the fins. In the pictures you can easily spot the short/tall fin difference.
 
ImperialEagle
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RE: 707 Stretches And W/B Issues?

Thu Jul 12, 2012 1:04 pm

Quoting IRISH251 (Reply 5):
These modifications became standard on all 707 variants and were retrofitted to all previously built aircraft."

With the exception of the ventral fin which was usually not applied to the 320B/C series.
"If everything seems under control, you're just not going fast enough!"
 
707fan
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RE: 707 Stretches And W/B Issues?

Thu Jul 12, 2012 4:04 pm

Irish251 and Viscount724 are of course right with regard to the PanAm order of 707-120z.

It was ment to read 720B and not the -120. Pan Am had a lot of the -120s.
I appologise.
 
Viscount724
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RE: 707 Stretches And W/B Issues?

Thu Jul 12, 2012 11:40 pm

Quoting LH707330 (Reply 7):
Quoting 707fan (Reply 4):
The other thing is that I have never seen a description or any pictures regarding the extension of the vertical stabilizer. As I have understood it was BOAC which initiated this modification due to their demand of using RR engines on their 707’s. Any comments?
This article has plenty of pages and descriptions of the fins. In the pictures you can easily spot the short/tall fin difference.

However that article doesn't mention the the origin of the vertical stabilizer extension. It was the result of a requirement of the British certification authority which wouldn't certify BOAC's 707-420s with the original short tail due to instability issues. As far as I recall, the extended vertical stabilizer and ventral fin proposals originated with the British regulatory authority.

Quoting ImperialEagle (Reply 8):
Quoting IRISH251 (Reply 5):
These modifications became standard on all 707 variants and were retrofitted to all previously built aircraft."

With the exception of the ventral fin which was usually not applied to the 320B/C series.

It was applied to the early model -320B. Due to other changes to wings/flaps etc. the ventral fin was deleted on the Advanced -320B and was never used on the -320C.

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