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?
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.
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.
DC-10Tech From United States of America, joined Jun 2001, 298 posts, RR: 3 Reply 4, posted (5 years 2 months 3 weeks 1 day 1 hour ago) and read 10015 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.
113312 From United States of America, joined Apr 2005, 537 posts, RR: 1 Reply 6, posted (5 years 2 months 3 weeks 22 hours ago) and read 9961 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.
JetMech From Australia, joined Mar 2006, 2588 posts, RR: 53 Reply 7, posted (5 years 2 months 3 weeks 22 hours ago) and read 9949 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.
DC-10Tech From United States of America, joined Jun 2001, 298 posts, RR: 3 Reply 8, posted (5 years 2 months 3 weeks 21 hours ago) and read 9902 times:
Quoting HAWK21M (Reply 5): Any reason for that.Was it ineffective or problematic?
Boeing767mech From United States of America, joined Dec 2000, 992 posts, RR: 3 Reply 10, posted (5 years 2 months 3 weeks 18 hours ago) and read 9841 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.
N231YE From , joined Dec 1969, posts, RR: Reply 11, posted (5 years 2 months 3 weeks 18 hours ago) and read 9834 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).
Avioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11 Reply 12, posted (5 years 2 months 3 weeks 16 hours ago) and read 9802 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.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
F14D4ever From United States of America, joined May 2005, 319 posts, RR: 4 Reply 14, posted (5 years 2 months 2 weeks 6 days 7 hours ago) and read 9572 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.
Ex52tech From United States of America, joined Dec 2006, 559 posts, RR: 1 Reply 15, posted (5 years 2 months 2 weeks 4 days 15 hours ago) and read 9381 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"
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 24 Reply 16, posted (5 years 2 months 2 weeks 4 days 7 hours ago) and read 9347 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.
Ex52tech From United States of America, joined Dec 2006, 559 posts, RR: 1 Reply 17, posted (5 years 2 months 2 weeks 4 days 4 hours ago) and read 9315 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.
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.
"Saddest thing I ever witnessed....an airplane being scrapped"
Northwest727 From United States of America, joined Jul 2005, 491 posts, RR: 1 Reply 18, posted (2 years 6 months 6 days 21 hours ago) and read 6525 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:
kiwiandrew From New Zealand, joined Jun 2005, 8435 posts, RR: 14 Reply 19, posted (2 years 6 months 5 days 12 hours ago) and read 6215 times:
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 ;-)
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.
Northwest727 From United States of America, joined Jul 2005, 491 posts, RR: 1 Reply 21, posted (2 years 6 months 4 days 16 hours ago) and read 5856 times:
Fly2HMO From , joined Dec 1969, posts, RR: Reply 22, posted (2 years 6 months 4 days 15 hours ago) and read 5836 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.
Access-Air From United States of America, joined Sep 2000, 1939 posts, RR: 15 Reply 24, posted (2 years 5 months 2 weeks 4 days 4 hours ago) and read 5008 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...
26 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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