DC-8 Super Seventies Conversion - effect on performance
 

As a kid (and adult) I used to see quite a few DC-8s but unfortunately I never got to fly one and suspect that I never will.

Could anyone who has flown both the non CFM powered and CFM powered versions explain what sort of effect the upgrade had on aircraft performance and operating costs?

I flew on a good number of diesel DC-8's and they seemed to be somewhat underpowered, especially the -63 versions which took ages to get off the ground and climb sluggishly. Otherwise a nice aircraft all in all. I stand to be corrected, but apart from a VIP version, I'm not sure if any of the uprated -73's were passenger versions, only UPS led cargo ships. No doubt the economics improved markedly when they had 4 CFM56's compared with the JT3D's as did the climb and cruise and uplift capabilities. Are there many freighters still flying ? All the African one's seem to have been retired, but maybe in the USA there are examples still going.


SHJ

Many passenger -70's, the improvements in all parameters was excellent. That's why airlines paid for the changes.

Quieter, less runway, better fuel economy, cheaper to upgrade than buy new a/c, built like the proverbial ......

Didn't the 'stretch 8' need more runway for t/o because it could only rotate to a shallow angle due the length of fuselage behind the main gear?

That may well be true, though of course it would apply equally to the -60 Series (P&W), not just to the -70 Series (CFM).

I rode the jumpseat with UPS a number of times, the 2 stage rotation was very noticeable, watching them depart from Cologne with a full load and fuel for Philadelphia was interesting; they used an incredible amount of runway prior to leaving the ground.

Rated take off?

The old engines produced 18,000 lbs of thrust, the CFMs 22,000. Net gain of 16,000 lbs, almost a fifth engine.
Fuel flow went from 18,000 lbs per hr to 12,000, same tanks.
More power and more range on less fuel, clever conversion for sure..
Yes, 2-stage rotation: Rotate at 3 degrees per second up to 9 degrees, lift off, then continue rotation to target pitch.
The -73 was my first jet, quite a handful for a young guy coming from DC-3s but great planes, flew 'em on a cargo contract for Air India some 26 years ago.:cool:

Douglas Tulsa did the prototype conversion, and Delta received their first ship from Douglas (same ship maybe?).

And Delta decided they would buy parts from Tulsa to convert the rest of their fleet themselves in Atlanta; they had no plan to do any third party work. But other airlines started lining up - Delta offered faster/cheaper work; eventually Delta converted more ships than Douglas!

4Screwaircrew

Ever seen an A340-300 take off at 270 tons? The run goes on forever even at full chat.

The most exciting take-off I ever experienced in a jump seat was a DC8 flying direct from Exeter (2000m) to Toronto; it was the inaugural flight for a charter series. It only happened once; all subsequent flights went via a fuel stop.

As the roll just went on and on and on and on, I was whimpering with fear.

I was told afterwards that the main wheels left the ground 150m short of the end. The aircrew had completed the loadsheet, no copy could be found. The aircraft was operated by a fairly short-lived company based in Scotland, whose name I forget.

I've been in the jump seat of a BAC 1-11 taking off from Bail al Falaj with one engine deliberately failed at VR plus a second or two (CAA test flight), and of a Concorde departing from Exeter (twice).

But nothing came close to the terror of that DC8 take-off.

Empty the DC-8-63 could have almost STOL performance like many aircraft :-)
https://www.youtube.com/watch?v=6bvK6enoQDg
One of the strange things about the transformational CFM56 is how long it took to find a market ...even Boeing thought its use in the 737-300 was just a stop-gap until UDFs took over apparently

The big marketing hurdle was the fact CFMI was a joint venture, two companies in two countries, two languages, two legal systems, separated by a pond. Few thought the deal could reach Vr, let alone survive. The venture was within weeks of collapse when the first order came through.

Yet it turned out to be incredibly successful.

I believe the US Govt was fining GE at one point in a dispute over technology rights....but eventually it got settled
1999 | 1357 | Flight Archive

I found the -60 series DC-8 a little scary.
As teenager, back in the early 1970's, I was flying back from London to Bangor on a DC-8-60 ONA charter. A high school concert band tour - 250 passengers, crew, plus luggage, band instruments, a months worth of souvenirs, and gas to go across the pond.
I had a window seat for takeoff from London - we trundled down the runway - and trundled, and trundled, and trundled. A bunch of mainly teens, we were chanting "get it up, get it up". Finally the nose came up and we gave a cheer "come on". The main gear finally left the ground, and an instant later the runway ended :eek: :eek:. The part I found really amazing was the instant silence through the cabin - somehow even those without window seats knew how close it had been .:uhoh:
We landed in Bangor, Maine to refuel and go through customs. On takeoff from Bangor, they banged the tail :ugh:

Every time I flew on a 60's series the take-off followed the same pattern as described above and no matter how many times it happened my palms started to sweat and fear surfaced..Perhaps the cockpit crew were the only ones without this feeling ;) The two stage rotation was no doubt very trying, especially when the crew was fatigued and the odd tail scrape not uncommon.

Within the last decade a cargo DC-8-60, perhaps with an optimistic load sheet, took off at night in the UK for the dark continent. It made it skywards due to the curvature of the earth, but the next day tyre tracks on the grass extending from the runway were observed…..:ooh:


SHJ

If I have already told this story on prune before then I apologise. In the 1980s I was flying DC-10s based at JFK. Our company had a lot of DC-8s of just about every variety (-54, -61, -62, -63 and -73). I was in the bar one night with one of my friends who was on the DC-8 and asked him which one was his favourite. "Without a doubt it would be the -62" said he. I asked him what he thought of the -63. "Hell" he said "it's like flying a dog with worms." Very descriptive!

That would be from EMA carrying, if my memory serves me correctly, a cargo of freshly printed bank notes?

A30 #14: aero-engine IPR. Tks for the Flight item on F101 technology transfer (to an Ally!) UK twice went through the same exercise..but with prospective targets (as in, military) for engine IPR: 1946, centrifugals/USSR and 1975 (reheated turbofan/PRC). The IPR owner may receive near-term benefit - cash, perhaps - but the recipient may (expects to) capture long-term benefit.

The Flight article was wrong to dismiss objectors as "ossified" civil servants. These are not easy issues. Everyday, right now, China comes along offering deals of near-term benefit: the London taxi, MG Cars. But will long-term jobs flow down the Yangtze? The logic of Protection says: exactly that; the theory of Free Trade says: overall market expansion to mutual benefit...which is the outcome of transfer F101 core into CFM56 (in late-1980s its largest Customer was USAF - KC-135 upgrades).

tornadoken...I do sometimes speculate on what might have happened if Rolls has built a CFM56 class engine in the early Seventies instead of the RB-211...an engine that size could have extended the lives of the BAC-111 and VC-10 programs, kept the DC-8 in production.....might have made a better Mercure :-)...instead Rolls bankrupted themselves and the big 3 American companies went head-on at each other until only Boeing was left doing civil airliners.

I read a curious thing about the KC-135...the CFM-56 version though radically improved didn't have a higher MTOW but it had a higher empty weight (heavier engines) so, if there was unlimited runway length, the original KC-135A could carry more transfer fuel to a nearby refuelling point (though it might need an extra mile of runway to get off) EDIT...think I got it somewhat wrong....may have been the KC-135E version and it only applied to a hypothetical refuelling transfer closeby the base