Happy-flier
Topic Author
Posts: 287
Joined: Sat Dec 25, 1999 4:41 pm

Bypass Ratio Of The CJ-805-23 Engine?

Wed Jun 18, 2008 3:03 pm

Anyone know what the bypass ratio was in the rear-fan-stage CJ-805-23 that powered the Convair 990? I have been looking around but could not find this info online.

Interestingly, there are some rare videos on Youtube of a Spantax CV990 in operation in its twilight years. Like most, I had never heard or seen one flying, so it was nice to finally get a chance. Here are some interesting ones:

CV990 landing: http://www.youtube.com/watch?v=ZXl9AgWTb0w
CV990 taxiing in: http://www.youtube.com/watch?v=sPF-bNgpYHk
CV990 taxiing out: http://www.youtube.com/watch?v=ZHN8AfDSCbo
CV990 takeoff: http://www.youtube.com/watch?v=HTlT2-i4gjw

Interesting sound; different than the JT3Ds that were so much more common in those days. Note the wild howl on power-down, just on the landing flare ...
May the wind be always at your back . . . except during takeoff & landing.
 
Viscount724
Posts: 19304
Joined: Thu Oct 12, 2006 7:32 pm

RE: Bypass Ratio Of The CJ-805-23 Engine?

Thu Jun 19, 2008 2:07 am

Page 29 of the following document shows the bypass ratio of the CJ-805-23B as 1.46.
http://ntrs.nasa.gov/archive/nasa/ca...asa.gov/19770012125_1977012125.pdf

[Edited 2008-06-18 19:07:54]
 
Blackbird
Posts: 3384
Joined: Wed Oct 06, 1999 10:48 am

RE: Bypass Ratio Of The CJ-805-23 Engine?

Thu Jun 19, 2008 3:38 am

Viscount724,

Fascinating, I always thought it was 2.2 : 1 as lots of sources listed it as such including a book I own.


Andrea Kent
 
Happy-flier
Topic Author
Posts: 287
Joined: Sat Dec 25, 1999 4:41 pm

RE: Bypass Ratio Of The CJ-805-23 Engine?

Thu Jun 19, 2008 1:57 pm

Thanks for the info. It seems that it was an engine ahead of its time in some ways, although the smoky exhaust was terrible.

They must have done something to modify the core because as you can see in the videos above, the Spantax 990 was actually a pretty clean burning jet - not much smoke at all.
May the wind be always at your back . . . except during takeoff & landing.
 
Blackbird
Posts: 3384
Joined: Wed Oct 06, 1999 10:48 am

RE: Bypass Ratio Of The CJ-805-23 Engine?

Fri Jun 20, 2008 3:20 am

Happy-flier,

That's correct they did go to great lengths to reduce the smokiness of the exhaust and apparently succeeded. Not only did this curb the smoke, it increased thrust slightly


Andrea Kent
 
boeing767mech
Posts: 805
Joined: Fri Dec 15, 2000 5:03 pm

RE: Bypass Ratio Of The CJ-805-23 Engine?

Fri Jun 20, 2008 8:57 pm



Quoting Happy-flier (Reply 3):
They must have done something to modify the core because as you can see in the videos above, the Spantax 990 was actually a pretty clean burning jet - not much smoke at all.

The reduced smoke was a result of the miltary wanting to reduce the smoke from the J-79's. GE found by welding some of the cooling holes in the burner can you increase the temp of the flame which reduces the soot. The added bonus was the increase in thrust. My friend was a crew chief on a f-4 that had one engine with a ashless can and a regular engine, he said it was interesting to see on finally appoarch.

David
Never under-estimate the predictably of stupidty

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