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B707-420 And Conway Powered DC-8  
User currently offlineSAA-SAL From Belgium, joined Nov 2000, 356 posts, RR: 3
Posted (13 years 1 week 1 day 23 hours ago) and read 2005 times:

I read that 69 conway powered B707s and DC-8s were sold in total. Could anyone give me the airlines concerned and how many of these 69 were BOAC ordered B707-420s.

P.S. Did these conway powered 707s and DC-8s have any other modifications and why were so few sold?


SAA B747 SP, Luxavia B747 SP
19 replies: All unread, jump to last
 
User currently offlineIFlyADesk From United States of America, joined Mar 2001, 309 posts, RR: 0
Reply 1, posted (13 years 1 week 1 day 23 hours ago) and read 1923 times:

69? I only count 66 (37 707-400s + 29 DC-8-40s) I wonder what I missed.

User currently offlineBluemeatball From United States of America, joined Oct 1999, 175 posts, RR: 0
Reply 2, posted (13 years 1 week 1 day 22 hours ago) and read 1916 times:

I have a book titled "World's Air Fleets" from 1966 which gives the following information: BOAC had 19 707-400s, Air India had 5707-437s, Varig had 2 707-441s, Lufthansa had 5 707-430s. Air Canada had 10 DC-8-40s, Alitalia had 14 DC-8-40s. That is what I know.

User currently offlineNorthStarDC4M From Canada, joined Apr 2000, 2951 posts, RR: 37
Reply 3, posted (13 years 1 week 1 day 21 hours ago) and read 1912 times:
AIRLINERS.NET CREW
CHAT OPERATOR

Bluemeatball missed the Canadian Pacific DC-8-40s (5) otherwise his list looks complete


Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety.
User currently offlineCedarjet From United Kingdom, joined May 1999, 7934 posts, RR: 54
Reply 4, posted (13 years 1 week 1 day 21 hours ago) and read 1911 times:

The last Conway-powered 707-420 stopped flying a few years ago in Zaire (now Congo). Either it needed a massive overhaul due to running out of cycles and the cost was prohibitive, or there was an engine explosion which came back to cost. Can't remember which, but the aircraft was flying as a passenger liner in Africa, mostly domestic flights in Congo I think.


fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
User currently offlineKarl From , joined Dec 1969, posts, RR:
Reply 5, posted (13 years 1 week 1 day 17 hours ago) and read 1896 times:

Deliveries for the 707-400 were: Air India 6, BOAC 19,
Cunard Eagle 1, El Al 3, Lufthansa 5 and Varig 3. For the
DC-8-40 it was Trans Canada 11, Alitalia 15 and Canadian Pacific 6. The reason that not more were sold was the developement of the Pratt & Whitney JT3D
turbofan which was more economically and operationally
attractive to the airlines. It would be soon availavle to the airlines in the DC-8-50 and 707-320B. Apart from powerplants and related equipment the 707-420 was identical to the 707-320. It was however the first variant to use the taller fin, rear fuselage ventral fin and powered rudder.A DC-8-43 of Canadian Pacific was the first transport to break the sound barrier.


User currently offlineSAA-SAL From Belgium, joined Nov 2000, 356 posts, RR: 3
Reply 6, posted (13 years 1 week 1 day 10 hours ago) and read 1877 times:

Thanks to all for the information!

Cheers SAA-SAL



SAA B747 SP, Luxavia B747 SP
User currently offlineCedarjet From United Kingdom, joined May 1999, 7934 posts, RR: 54
Reply 7, posted (13 years 1 week 1 day 4 hours ago) and read 1863 times:

The reason the -420 was the first 707 to have the taller tail and ventral fin was because it was the British CAA that insisted that the 707 had a problem with stability and dutch roll, and for the aircraft to have a British CofA, it had to prove a certain level of stability that wasn't possible with the original fin. Boeing later introduced it on the -320. The British CAA have always had the highest standards in the world, much to the annoyance of aircraft manufacturers everywhere. We do have very safe airlines as a result, though. I think they were right in this instance, there were at least two accidents caused by dutch roll, one such accident killed some of Braniff's top test pilots when a divergent dutch roll caused the aircraft to shed three of it's four engines and the 707 crash landed in a river.


fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 8, posted (13 years 1 week 1 day 4 hours ago) and read 1862 times:

Just to add to Cedarjet's post, Boeing retro fitted early 707s and 720s with the new tail, though not all had the ventral fin.

User currently offlineCV990 From , joined Dec 1969, posts, RR:
Reply 9, posted (13 years 1 week 1 day 3 hours ago) and read 1858 times:


Hi!

The interesting thing regarding those fins too was the fact that even some of th early B. 707-300B's still had the large ventral fin, I don't know why they still had them and after they stopped adding that, here are the ones that still had that:

TWA - B. 707-331B ( N773TW, N774TW, N775TW, N776TW and N778TW ).

Air France - B. 707-328B ( F-BHSV, F-BHSX, F-BHSY, F-BHSZ ).

USAF - B. 707-353B (62-6000)

Lufthansa - B. 707-330B ( D-ABOS and D-ABOT )

After this ( C/N 18463 ) all the 707-300B and C's came without that fin.
Regards


User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 10, posted (13 years 1 week 1 day 2 hours ago) and read 1848 times:

You are quite right CV990 and I've never found out why.

There seems to be no logic to why these aircraft alone of the 300srs had the ventral fin as they are not all consecutive, either in c/n or line numbers.

TWA - B. 707-331B ( N773TW, 18405,305; N774TW, 18406, 320; N775TW, 18407, 323; N776TW, 18408, 326; N778TW, 18409, 331.

Air France - B. 707-328B F-BHSV, 18456, 325;
F-BHSX, 18457,327; F-BHSY, 18458, 329; F-BHSZ, 18459,335.

USAF - B. 707-353B 62-6000, 18461, 303

Lufthansa - B. 707-330B D-ABOS, 18462, 333; D-ABOT,
18463, 363.

To summarise we have line numbers:

303,305,320,323,325,326,327,329,331,333,335,363

c/ns

18456/7/8/9
18461/2/3
18485/6/7/8/9

So no real clue there. I've never seen any printed detail on the reason why these airframes are "odd balls".

Anyone out there KNOW why?


User currently offlineTimz From United States of America, joined Sep 1999, 6708 posts, RR: 7
Reply 11, posted (13 years 1 week 22 hours ago) and read 1833 times:

PhilB, in your first post you seem to be saying some early 707/720s were retrofitted with the taller fin but no ventral fin. Can you think of an example (hopefully with a pic)?

The Putnam says that Advanced 707-320Bs and all -320Cs had wing/flap/slat modifications that made the ventral fin unnecessary. So maybe Boeing continued to produce a few unAdvanced -320Bs after the Advanced model first appeared?


User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 12, posted (13 years 1 week 19 hours ago) and read 1831 times:

Started to research this and found we may be in a minefield!

C/n 17663, as HS-VGC is pictured in JP Airline Fleets 1975 with a tall tail and no ventral fin. This is a 131 built as N736TW line no 24. C/n 17666, HS-VGA is pictured in the 1974 edition WITH a ventral fin, yet this is line no 32, again a 707-131, ex TWA. These would both have had tall tails fitted retrospectively.

In JP 1981 there is a pic of B707-120 N930NA of NASA which is a KC-135 conversion with a tall tail and no ventral fin.

Also, looking at a range of photos of 707-100 srs, 300srs and B720s, there seem to be at least three sizes of ventral fin.

I'd be delighted if someone could explain the logic behind the different/lack of ventral fins and the logic of the fitting of ventral fins to the aircraft CV990 listed.


User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 13, posted (13 years 1 week 10 hours ago) and read 1816 times:

Bump - because I'd really like the answer, though I suspect there is no work of reference that gives it!!

User currently offlineTrident From United Kingdom, joined Feb 2000, 484 posts, RR: 0
Reply 14, posted (13 years 1 week 10 hours ago) and read 1814 times:

N930NA IS a KC-135, not a conversion to a 707-120. The 707 and KC-135 are quite different aircraft. No KC-135's feature ventral fins, probably because the location of the ventral fin is precisely where the refueling gear is positioned.

User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 15, posted (13 years 1 week 10 hours ago) and read 1816 times:

Agreed the KC135 is a different airframe - narrower fuselage etc. etc. but N930NA has had a great deal of 707 retrobuilt into it and many listings show it as a B707-120 (when, of course, a civilianised KC135 should be shown as a B717). Do you know how it is/was listed in USCAR?

Back to the tail, the tall tail is obviously a retrofit, as with other 135s. Agree that the refuelling boom would be in the way of a ventral fin but it only adds to the "mystery" of the reasons for/effects of the fin and the need for different sizes and why some aircraft were fitted whilst contemporaneous airframes were not.


User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 17, posted (13 years 6 days ago) and read 1793 times:

No he didn't, he's still got two eyes which work, even with specs  Smile/happy/getting dizzy.

The photo is a black and white taken by Frank Bucher at Bangkok with the reg very clear, date not given and there is no ventral fin - and certainly not the big one in the photo you highlight.

I haven't got a flat bed scanner so I can't get the shot to you.

As I said before, the whole area of the ventral fin seems (apart from the UK involvement with the 707-436) to be shrouded in a little bit of mystery.

HS-VGA may have been able to operate under Thai jurisdiction without the fin but either Israeli Aircraft Industries or the US authorities had it replaced before the aircraft wound up in Mojave


User currently offlineTimz From United States of America, joined Sep 1999, 6708 posts, RR: 7
Reply 18, posted (13 years 5 days 21 hours ago) and read 1781 times:

Cearley's TWA book has a broadside shot of N736TW clearly showing the reg and ventral fin.

User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 19, posted (13 years 5 days 21 hours ago) and read 1772 times:

Trying to think logically about this, the Brits forced Boeing to make the tail taller and add the ventral fin on the Conway powered 707-436. The Conway was the first by-pass or turbo fan engine in service, albeit with a small by-pass ratio.

Given the already recognised dutch roll problems associated with the type, The Brits probably thought the problem would be worse with more powerful engines.

Eventually, every 707/720 still flying was retro-fitted with the taller tail but there seem to be three types of ventral fin.

A small, long one, generally on the 707-138 and 720/720B though some 120Bs have it, a medium sized, long one which appears on the 120 and some early 320Bs and the full size long one on the 320 and 420.

Then, of course the bulk of the JT3D engined 320Bs and the 320Cs had no ventral fin. I seem to remember that 62-6000, the VC-137 had a ventral fin when built and this was removed at some stage.

The KC-135 re-tailing saga seems to have managed without the ventral fin due to the boom.

But why the variations? It must be to do with the engines fitted. BUT the JT3D was more powerful than the Conway - so why no fin?

I've now found a pic of HS-VGA with a full size ventral fin taken in 1973.....aaaaaagh!


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