Comparison of Payload vs Range for VC10 and 707

Any VC10 related discussions.....
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Jelle Hieminga
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Comparison of Payload vs Range for VC10 and 707

Post by Jelle Hieminga »

I got an E-mail from George Evans asking me about the specifics behind the max payload figures for the 707 and the VC10.

"Could you please expand on how the max payload of this a/c is derived or how it is defined. I want to compare the MPL of the VC-10 with that of the B-707 as both have similar total engine power available yet the B-707 seems to be able to lift 10T more. I presume this is the case for comparable fuel loads and thus range."

The first thing I did was look up some figures:
Image
* The max payload range figure for the 707-320C is quoted with reserves and not at the max payload

I did a bit of figuring (see image above) and indeed the 707 is
able to lift about 10T more than the VC10, but there are quite a few more
details to the story.

Max payload versus range for any aircraft has to be defined using a payload-range diagram. An example (not neccessarily accurate!) can be found in the image below. Basically the maximum payload is defined by the max zero-fuel weight which is a structural issue. Max range is then defined by the size of the fuel tanks of the aircraft, and in between these two there is a slanted section of the graph that is caused by the MTOW of the aircraft. The 707-320C had a higher MTOW than other (civil!) versions because of changes to the structure and undercarriage.

Image

One of the things that had to be sacrificed to get the 707 to carry that
much is take-off and landing distances. The 707-320C needed an extra 800m
that was not always available in the early days. Remember that the VC10
was specifically designed to cope with the shorter runways, and hot and
high conditions, then existing in Africa. It wasn't until the 707 became
commonplace that runways were lengthened to accommodate the aircraft. The
VC10 was designed from a different standpoint: the aircraft accommodated
the then existing runways. This accounts for the difference in thrust
ratings too, even with the biggest P&W fitted to a 707-320C, a Standard
VC10 still had 8000lbs more thrust available. The difference could be seen
when a not even fully laden 707 was slowly gaining altitude climbing away
from a 'hot-and-high' african field while a VC10 would easily clear the
airfield fences at MTOW on a similar day.

One more detail to keep in mind with this comparison is that the 707
version we're talking of here was first delivered 6 years after the first
civil 707 was delivered, and thus had that many years of experience behind
it's design. The VC10 never got the chance to be developed to that point.
I'm quite sure that further developments of the VC10 might have come
pretty close (or even more than that) to the payload figures of the 707,
but unfortunately that was not to be.

As you will be able to see from the figures in the table above, for the
most part the 707s show similar or worse range and payload figures than
the VC10, it's only the 707-320C which manages to surpass the VC10. And
even there I wouldn't be surprised to see that it's airfield performance
(take-off and landing distances) are very much worse than a VC10's.

Anybody else with a view on this? Post your reply!
Last edited by Jelle Hieminga on Sat Dec 31, 2005 3:24 pm, edited 2 times in total.
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GBTYZ

Re: Comparison of Payload vs Range for VC10 and 707

Post by GBTYZ »

Jelle Hieminga wrote:I got an E-mail from George Evans asking me about the specifics behind the max payload figures for the 707 and the VC10.

"Could you please expand on how the max payload of this a/c is derived or how it is defined. I want to compare the MPL of the VC-10 with that of the B-707 as both have similar total engine power available yet the B-707 seems to be able to lift 10T more. I presume this is the case for comparable fuel loads and thus range."

The first thing I did..........
Never mind the payload VC10 are now offically known as prescotts because they can refuel 2 jags at once

motilon
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Joined: Wed Jul 15, 2015 11:20 am

Re: Comparison of Payload vs Range for VC10 and 707

Post by motilon »

Hello Jelle

I've only just seen your reply to my query many thanks. The 320c with a 40 Ton PL is quite impressive I thought it was a typo when I first read it.
An interesting point is that it achieved this PL with lower thrust engines than the S VC10 and presumably with better fuel efficiency than the Conway.

regards
George

motilon
Posts: 2
Joined: Wed Jul 15, 2015 11:20 am

Re: Comparison of Payload vs Range for VC10 and 707

Post by motilon »

I tried to edit the above but its was not obvious to me how ... no edit button.

Anyway it was to say that the key is to carry out comparisons on an equal footing something not so straight forward because the original design requirements, driven by the airlines in those days, are not always known. Nevertheless it would be interesting to know what was modified on the 320c e.g. wing lift devices , wing profile etc to obtain such a large increase in PL with the same or similar engines as the standard 707s.

I never flew on a VC10 but I did on a Conway 707 ( '64) as a kid on the Atlantic route (previously on a Stratocruiser and Britannia on a similar route) a today the experience on a 747 is very similar ( flight time , food) but probably with much worse knee room.

Jelle Hieminga
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Re: Comparison of Payload vs Range for VC10 and 707

Post by Jelle Hieminga »

Hello George,

At a guess I would say that the wing profile wasn't changed as something like that would incur huge costs in changed jigs, tools, etcetera. They could have made some changes in the slats and flaps, that is possible. Generally when a gross weight increase is available as an option the only changes are structural and not visible from the outside. By fitting more powerful engines and beefing up the structure around the center wing box and main gear you can accomplish this but it will most likely also increase your take-off and landing distances.

I never did much research into the 707 family. It is another interesting subject for a rainy day! :wink:

Btw, when you're logged in you should see some buttons at the top right of your post. One has a pencil in it, that's the edit button.
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