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CFM56 on DC8 Super 70s versus early A340
A340 and DC-8 are two aircrafts of considerably difference in size and yet they are euipped by same amount and same type of engine. Does that mean the super 70 is overpowered and does that mean they would have comparable fuel consumption? What else does "using same amount/type" of engine mean for the two aircraft types?
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- WIederling
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Re: CFM56 on DC8 Super 70s versus early A340
c933103 wrote:A340 and DC-8 are two aircrafts of considerably difference in size and yet they are euipped by same amount and same type of engine.
You can count? ( 4 versus 2 engines )
and rather different per engine thrust ( 22klb versus 33klb ):
https://en.wikipedia.org/wiki/CFM_Inter ... 6#Variants
Re: CFM56 on DC8 Super 70s versus early A340
WIederling wrote:c933103 wrote:A340 and DC-8 are two aircrafts of considerably difference in size and yet they are euipped by same amount and same type of engine.
You can count? ( 4 versus 2 engines )
and rather different per engine thrust ( 22klb versus 33klb ):
https://en.wikipedia.org/wiki/CFM_Inter ... 6#Variants
Which of the two planes have two engines...?
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- WIederling
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Re: CFM56 on DC8 Super 70s versus early A340
c933103 wrote:WIederling wrote:c933103 wrote:A340 and DC-8 are two aircrafts of considerably difference in size and yet they are euipped by same amount and same type of engine.
You can count? ( 4 versus 2 engines )
and rather different per engine thrust ( 22klb versus 33klb ):
https://en.wikipedia.org/wiki/CFM_Inter ... 6#Variants
Which of the two planes have two engines...?
Ouch. I was thinking of the twin shortranger.
But anyway. It still is a 50% markup in thrust.
DC8s with CFM56 engines were a conversion !?
The A340 was a rather modern frame with a supercritical wing, efficient aerodynamcis.
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- Francoflier
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Re: CFM56 on DC8 Super 70s versus early A340
The A340 never really got the engines it wanted, and instead had to make do with CFM56's pumped up to an inch of their thermal capacity (and a couple extra discs).
It ended up being slightly short on thrust.
The DC-8, on the other hand, got all the thrust it ever needed from off-the-shelf low-mid thrust 56's...
The thrust/weight ratio favors the Douglas, but performance really all lies on the wing design, as mentioned.
It ended up being slightly short on thrust.
The DC-8, on the other hand, got all the thrust it ever needed from off-the-shelf low-mid thrust 56's...
The thrust/weight ratio favors the Douglas, but performance really all lies on the wing design, as mentioned.
Re: CFM56 on DC8 Super 70s versus early A340
Here's a pretty exhaustive article on the CFM56, which details the differences: https://www.flightglobal.com/pdfarchive ... 01456.html
edit: oops, wrong one, try this: https://www.flightglobal.com/pdfarchive ... 01385.html
edit: oops, wrong one, try this: https://www.flightglobal.com/pdfarchive ... 01385.html
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- WIederling
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Re: CFM56 on DC8 Super 70s versus early A340
try this: Super. Thanks.
Re: CFM56 on DC8 Super 70s versus early A340
LH707330 wrote:Here's a pretty exhaustive article on the CFM56, which details the differences: https://www.flightglobal.com/pdfarchive ... 01456.html
edit: oops, wrong one, try this: https://www.flightglobal.com/pdfarchive ... 01385.html
Thanks for the link.
Re: CFM56 on DC8 Super 70s versus early A340
WIederling wrote:c933103 wrote:A340 and DC-8 are two aircrafts of considerably difference in size and yet they are euipped by same amount and same type of engine.
You can count? ( 4 versus 2 engines )
and rather different per engine thrust ( 22klb versus 33klb ):
https://en.wikipedia.org/wiki/CFM_Inter ... 6#Variants
the A340 had 4 engines just like the DC8-71/3 had, the A340 was just so much bigger an airframe than the DC8,
The DC8-71/73 was a "Hot Rod" with the CFM56-2's on it.
Re: CFM56 on DC8 Super 70s versus early A340
My understanding is that the 72s were the biggest hot rods, given that they were the biggest of smallest and lightest of the frames to be re-engined.
The CFM56s fitted to the A340s are bespoke to the A340 application specifically, and share no compatibility with any other installation that I'm aware of. As mentioned above, I belive they are run closer to the thermal limits, and I have heard there are a number of extra stages in compression, etc.
The CFM56s fitted to the A340s are bespoke to the A340 application specifically, and share no compatibility with any other installation that I'm aware of. As mentioned above, I belive they are run closer to the thermal limits, and I have heard there are a number of extra stages in compression, etc.
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- 747classic
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Re: CFM56 on DC8 Super 70s versus early A340
The A340 was orginally designed to be powered by the IAI Superfan, a high-bypass engine with a single-rotation, geared fan configuration with variable blade pitch. The fan diameter was expected to range from 108 to 118 in while having a bypass ratio of 18:1 to 20:1.
In 1987 the Superfan project was cancelled (indef delayed) and the A340 was adapted ( +larger fuel quantity) to accept the less efficient CFM56-5C engine.
See : http://en.wikipedia.org/wiki/IAE_SuperFan
In 1987 the Superfan project was cancelled (indef delayed) and the A340 was adapted ( +larger fuel quantity) to accept the less efficient CFM56-5C engine.
See : http://en.wikipedia.org/wiki/IAE_SuperFan
Re: CFM56 on DC8 Super 70s versus early A340
Interesting topic. This leads me to ask: were the CFMs that replaced the old JT3s on the DC-8 much heavier than the original engines? Or were they the same weight, despite their larger size, because they were built with lighter materials? How was the wing able to cope with the additional weight? Did it change the aerodynamics? I know that it affected crosswind landings because there was a greater chance of scraping the outboard engine. I flew on quite a few -63s, but never on the upgraded -71/-73.
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- longhauler
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Re: CFM56 on DC8 Super 70s versus early A340
DaveFly wrote:This leads me to ask: were the CFMs that replaced the old JT3s on the DC-8 much heavier than the original engines? Or were they the same weight, despite their larger size, because they were built with lighter materials? How was the wing able to cope with the additional weight? Did it change the aerodynamics? I know that it affected crosswind landings because there was a greater chance of scraping the outboard engine. I flew on quite a few -63s, but never on the upgraded -71/-73.
The 22,000 lb/thr CFM56 was about 150 lbs lighter than the JT-3D, but the nacelle was about 500 lbs heaver, with a net increase of about 350 lbs per engine. However, the increased thrust over the 17,000 (JT-3D-3B on the -61) and 18,000 on the (JT-3D-7 on the -63) produced take off, altitude and cruise performance increases ... along with fuel burn and noise reductions.
The -61 had further aerodynamic improvements as the new nacelle attached under the wing instead of "through" the wing, improving wing perfomance.
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