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CF6-6 Engine On DC-10... Why The Weird Cone?  
User currently offlineBR715-A1-30 From , joined Dec 1969, posts, RR:
Posted (6 years 8 months 3 weeks 6 days 9 hours ago) and read 12544 times:

If you look at the early DC-10s engines from the 70s, It looks like there is a flat piece where the exhaust cone is today.

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Photo © Frank C. Duarte Jr.



But then if you look at the DC-10s of today, even the -10 models, that "flat piece" is no longer there, and has been replaced with the conventional cone. Can anybody tell me why this is? What was the purpose of this design?

Thanks

[Edited 2008-03-04 08:20:29]

28 replies: All unread, showing first 25:
 
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 1, posted (6 years 8 months 3 weeks 6 days 8 hours ago) and read 12535 times:



Quoting BR715-A1-30 (Thread starter):

From the looks of the photo, it seems that this particular engine has thrust reversing on the core flow as well as the bypass flow. I assume that the flat piece allows the entire cone part to translate backward, which also actives the core reverser buckets. Most if not all newer turbo fans have done away with core reversing, so this may explain why the flat piece is not apparent through the exhaust cone on newer DC-10's.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineBR715-A1-30 From , joined Dec 1969, posts, RR:
Reply 2, posted (6 years 8 months 3 weeks 6 days 8 hours ago) and read 12506 times:

Wow... Thanks JetMech... It would be interesting to see a core reverser in action on a CF6/JT9D. Are there any pictures out there?

User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 3, posted (6 years 8 months 3 weeks 6 days 8 hours ago) and read 12487 times:



Quoting BR715-A1-30 (Reply 2):

I must confess that I am only taking an educated guess with respect to your question. I do know that some early turbofans had core reversing, such as the JT3 on the 707. I'm really not sure for the CF6-6. I could not find any pictures of the CF6-6 with this particular exhaust cone in reverse.


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Photo © Miguel A. Espinar




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Photo © Radek Oneksiak




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Photo © Gary Chambers



Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineDC-10Tech From United States of America, joined Jun 2001, 298 posts, RR: 2
Reply 4, posted (6 years 8 months 3 weeks 6 days 6 hours ago) and read 12421 times:

That's right, Jet Mech. The DC-10's originally had a turbine reversing system on its engines. The system was deactivated at some time and then eventually removed altogether. There's still references and info on this system on some companies' microfilm maintenance manuals.


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User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 5, posted (6 years 8 months 3 weeks 6 days 4 hours ago) and read 12377 times:



Quoting DC-10Tech (Reply 4):
The system was deactivated at some time and then eventually removed altogether.

Any reason for that.Was it ineffective or problematic?
regds
MEL.



Think of the brighter side!
User currently offline113312 From United States of America, joined Apr 2005, 574 posts, RR: 1
Reply 6, posted (6 years 8 months 3 weeks 6 days 4 hours ago) and read 12367 times:

Hot stream reverse was abandoned on high bypass turbofans, such as the CF-6 series, at a relatively early point in their use. Since the percentage of thrust from the cold stream (bypass) increased, it was considered that the mechanics of deflecting the hot stream were not worth it.

User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 7, posted (6 years 8 months 3 weeks 6 days 4 hours ago) and read 12355 times:



Quoting HAWK21M (Reply 5):
Any reason for that.Was it ineffective or problematic?

Pretty much what 113312 says. The JT3D-3 was very low bypass, with a ratio of only about 1.4:1, thus; core reversing would provide a significant amount of the total reverse thrust. The CF6-50 has a bypass ratio of 4.26:1, the CF6-80C2 5.15:1, with the GE90-115B having a bypass ratio of 9:1. Thus, the core reversing on newer turbofans would only provide a very small amount of reverse thrust.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineDC-10Tech From United States of America, joined Jun 2001, 298 posts, RR: 2
Reply 8, posted (6 years 8 months 3 weeks 6 days 2 hours ago) and read 12308 times:



Quoting HAWK21M (Reply 5):
Any reason for that.Was it ineffective or problematic?

Both.



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User currently offlineAloges From Germany, joined Jan 2006, 8735 posts, RR: 42
Reply 9, posted (6 years 8 months 3 weeks 6 days ago) and read 12263 times:

Are the RR Tays on the Fokker 70/100 the last engines to reverse both core and bypass (on commercial airliners)?


Walk together, talk together all ye peoples of the earth. Then, and only then, shall ye have peace.
User currently offlineBoeing767mech From United States of America, joined Dec 2000, 1030 posts, RR: 3
Reply 10, posted (6 years 8 months 3 weeks 5 days 23 hours ago) and read 12247 times:



Quoting Aloges (Reply 9):
Are the RR Tays on the Fokker 70/100 the last engines to reverse both core and bypass (on commercial airliners)?

I think the MD90/95 B717 also has fan/core thrust reversors. Which the MD95/717 finished production long after Fokker went out of business, I also think the ARJ-21 has core/fan reversors like the MD90/95.

David



Never under-estimate the predictably of stupidty
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 8 months 3 weeks 5 days 23 hours ago) and read 12240 times:

As some have already stated, that is/was the core thrust reverser mechanism. Like those found on the early JT9Ds, they were deleted in later models, deactivated and/or removed in the early models. I have some drawings of the CF6-6 reverser on the DC-10-10 if you'd like (me to post).

User currently offlineAvioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11
Reply 12, posted (6 years 8 months 3 weeks 5 days 21 hours ago) and read 12208 times:

The BR715 as well as the JT8 engine have clamshell reversers which simply deflect all air out of the engine forward or, more accurately, not aft.
 Smile



One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
User currently offlineAloges From Germany, joined Jan 2006, 8735 posts, RR: 42
Reply 13, posted (6 years 8 months 3 weeks 5 days 15 hours ago) and read 12161 times:

Thanks! I hadn't thought of the later MDs and the 717.


Walk together, talk together all ye peoples of the earth. Then, and only then, shall ye have peace.
User currently offlineF14D4ever From United States of America, joined May 2005, 319 posts, RR: 4
Reply 14, posted (6 years 8 months 3 weeks 4 days 12 hours ago) and read 11978 times:



Quoting Boeing767mech (Reply 10):
I also think the ARJ-21 has core/fan reversors[sic]

Negative. The ARJ-21 is powered by the GE CF34-10A, which is a 70% scale of the CFM56. Neither the CF34-10, nor the CFM, have core reversing.



"He is risen, as He said."
User currently offlineEx52tech From United States of America, joined Dec 2006, 559 posts, RR: 1
Reply 15, posted (6 years 8 months 3 weeks 2 days 20 hours ago) and read 11787 times:



Quoting HAWK21M (Reply 5):
Was it ineffective or problematic?

A lot of delays, and a mechanics nightmare, I was more than happy to deactivate those........ah........fine pieces of equipment..
Even the deactivated tailpipes caused some problems until the dedicated tail pipes came out, then the trouble finally went away.



"Saddest thing I ever witnessed....an airplane being scrapped"
User currently offlineBuzz From United States of America, joined Nov 1999, 697 posts, RR: 21
Reply 16, posted (6 years 8 months 3 weeks 2 days 12 hours ago) and read 11753 times:

Hi MEL, Buzz here. The Turbine Reversers on the CF6 engines would cause a lot of problems...hard to keep the mechanism running well. So as the engines cycled through the shop the turbine reverser mechanism was removed.

And... the reference was still in the Maint. Manual and A check paper package.

g'day


User currently offlineEx52tech From United States of America, joined Dec 2006, 559 posts, RR: 1
Reply 17, posted (6 years 8 months 3 weeks 2 days 10 hours ago) and read 11721 times:



Quoting Ex52tech (Reply 15):
And... the reference was still in the Maint. Manual and A check paper package

We ran about 50% of the fleet on deactivated turbine reversers, and the deactivated reversers got neglected. They would occasionally remind you that they were there when the bolts that held them shut would wear down spinnning in the holes, then break off and the translating tail pipe would deploy.........and then depart the aircraft.
This all started to happen when the heavy checks got farmed out. We kept an eye on them in heavy check.........they didn't.  Wow!
An airplane would show up at the gate with no tailpipe, and no conical nozzle, or center body. Management would blame us, when they farmed it out.  banghead 



"Saddest thing I ever witnessed....an airplane being scrapped"
User currently offlineNorthwest727 From United States of America, joined Jul 2005, 491 posts, RR: 0
Reply 18, posted (4 years 1 week 2 hours ago) and read 8931 times:

Sorry about bringing this post up from the dead, I saw it at the bottom of the screen, and thought I'd add to it

Quoting JetMech (Reply 1):
I assume that the flat piece allows the entire cone part to translate backward, which also actives the core reverser buckets.

JetMech, the cone part stayed fixed, it was the flat "blade" that slid backwards, which exposed a set of cascades that would "pop-out" into the core flow:

CF-6 Core Thrust Reverser


User currently onlinekiwiandrew From New Zealand, joined Jun 2005, 8602 posts, RR: 13
Reply 19, posted (4 years 5 days 17 hours ago) and read 8621 times:
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Quoting BR715-A1-30 (Thread starter):
If you look at the early DC-10s engines from the 70s, It looks like there is a flat piece where the exhaust cone is today.

Thanks for starting this thread , I have wondered about that for a long time , but never actually thought to ask on here . Glad to have my question answered after 30 years   



Moderation in all things ... including moderation ;-)
User currently offlinejetmech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 20, posted (4 years 5 days 1 hour ago) and read 8337 times:

Quoting Northwest727 (Reply 18):

Thanks for the info! What an interesting design. You would never think anything so delicate as those vanes could withstand the heat and force of the core exhaust stream!

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineNorthwest727 From United States of America, joined Jul 2005, 491 posts, RR: 0
Reply 21, posted (4 years 4 days 21 hours ago) and read 8262 times:

Quoting jetmech (Reply 20):

Glad to see you liked the info. By the way, I always enjoy reading your posts, good info you put on here yourself!

As for the delicate vanes, I'm not sure they even could withstand the heat and force of the core exhaust stream, that's why they were later removed  


User currently offlineFly2HMO From , joined Dec 1969, posts, RR:
Reply 22, posted (4 years 4 days 20 hours ago) and read 8242 times:

Quoting Northwest727 (Reply 21):

As for the delicate vanes, I'm not sure they even could withstand the heat and force of the core exhaust stream, that's why they were later removed

Probably just not worth the extra MX, weight and cost, as it always is with these type of things.


User currently onlinekiwiandrew From New Zealand, joined Jun 2005, 8602 posts, RR: 13
Reply 23, posted (4 years 4 days 19 hours ago) and read 8225 times:
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Was this only on the number 2 engine ? I don't recall ever noticing it on other engines.


Moderation in all things ... including moderation ;-)
User currently offlineAccess-Air From United States of America, joined Sep 2000, 1939 posts, RR: 13
Reply 24, posted (3 years 11 months 3 weeks 2 days 9 hours ago) and read 7414 times:

Quoting kiwiandrew (Reply 23):
Was this only on the number 2 engine ? I don't recall ever noticing it on other engines.

It was on all three engines....

Actually the L1011 also was first produced with a bucket type system on the core stream section of the ole RB211s...

Access-Air



Remember, Wherever you go, there you are!!!!
25 Post contains links and images Northwest727 : You can see the "tracts" for the core stream thrust reversers on the L1011 in the photo View Large View MediumPhoto © Ralph M. Pettersen
26 Post contains images kiwiandrew : Thanks for that , when I look at photos in the database I can see it on numbers 1 and 3 in some photos ... it is just a lot more obvious on the numbe
27 faro : So what has changed since the early 1970's to make MD/Boeing go back to turbine thrust reversers on the C-17's PW engines, or can we assume that thes
28 tdscanuck : I'd hope they learned something and they're not as much of a maintenance nightmare, but I fully expect them to be a pain in the a$$. The C-17 has an
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