SAA-SAL
Topic Author
Posts: 345
Joined: Sun Nov 05, 2000 11:41 pm

B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 5:59 am

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
 
IFlyADesk
Posts: 307
Joined: Mon Mar 19, 2001 6:36 am

RE: B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 6:16 am

69? I only count 66 (37 707-400s + 29 DC-8-40s) I wonder what I missed.
 
bluemeatball
Posts: 174
Joined: Mon Oct 18, 1999 10:44 am

RE: B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 7:21 am

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.
 
northstardc4m
Posts: 2724
Joined: Fri Apr 28, 2000 11:23 am

RE: B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 7:43 am

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.
 
cedarjet
Posts: 8101
Joined: Mon May 24, 1999 1:12 am

RE: B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 7:58 am

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
 
karl
Posts: 43
Joined: Sun Feb 19, 2012 7:16 pm

RE: B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 11:51 am

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.
 
SAA-SAL
Topic Author
Posts: 345
Joined: Sun Nov 05, 2000 11:41 pm

RE: B707-420 And Conway Powered DC-8

Sun Apr 15, 2001 7:11 pm

Thanks to all for the information!

Cheers SAA-SAL
SAA B747 SP, Luxavia B747 SP
 
cedarjet
Posts: 8101
Joined: Mon May 24, 1999 1:12 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 1:06 am

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
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 1:09 am

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.
 
CV990
Posts: 4224
Joined: Sat May 22, 1999 3:49 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 2:12 am


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
CV990, the Maserati of the skies!
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 2:55 am

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?
 
timz
Posts: 6121
Joined: Fri Sep 17, 1999 7:43 am

Ventral Fins Etc

Mon Apr 16, 2001 6:54 am

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?
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 10:27 am

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.
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 6:39 pm

Bump - because I'd really like the answer, though I suspect there is no work of reference that gives it!!
 
Trident
Posts: 477
Joined: Sun Feb 27, 2000 4:49 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 6:42 pm

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.
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: B707-420 And Conway Powered DC-8

Mon Apr 16, 2001 7:03 pm

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.
 
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: Don't Have JP 1975, But...

Wed Apr 18, 2001 5:06 am

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
 
timz
Posts: 6121
Joined: Fri Sep 17, 1999 7:43 am

The Minefield Thickens

Wed Apr 18, 2001 7:43 am

Cearley's TWA book has a broadside shot of N736TW clearly showing the reg and ventral fin.
 
philb
Posts: 2645
Joined: Mon May 24, 1999 5:53 am

RE: The Minefield Thickens

Wed Apr 18, 2001 8:06 am

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!