AC320tech
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747 JT9D Cascades

Sun Aug 13, 2006 11:25 am

In this picture you can see (what looks to be) reverser cascades at the top of the engine, just forward of the the reverser cowling.


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Photo © Julio Ribeiro



Why are they up there?
 
n8076u
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RE: 747 JT9D Cascades

Sun Aug 13, 2006 11:33 am

The reverse thrust fan exhaust does exit from where that upper vane section is located, so it is normal for the cascade vanes do go up that high.

Neat photo, brings back memories...

Chris
Don't blame me, I don't work here...
 
MarkC
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RE: 747 JT9D Cascades

Sun Aug 13, 2006 11:41 am

That is what they are. That is where they are. I see these on a daily basis. The other ones are removed in your picture. They go around the circumference of the Fan Exit Rear Case just like the one shown.
 
twal1011727
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RE: 747 JT9D Cascades

Mon Aug 14, 2006 12:57 am

That looks like a/an oil cooler or some type of heat exchanger.

KD
 
fr8mech
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RE: 747 JT9D Cascades

Mon Aug 14, 2006 12:19 pm

Quoting TWAL1011727 (Reply 3):
That looks like a/an oil cooler or some type of heat exchanger.

Nope, it's a cascade segment.
When seconds count...the police are minutes away.
 
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HAWK21M
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RE: 747 JT9D Cascades

Mon Aug 14, 2006 4:32 pm

Are the Remaining Cascades Removed.
& Why so much Forward.Any reason.
Any pic of a Running JT9D in Reverse.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
AC320tech
Topic Author
Posts: 193
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RE: 747 JT9D Cascades

Tue Aug 15, 2006 12:08 am

Quoting MarkC (Reply 2):
The other ones are removed in your picture. They go around the circumference of the Fan Exit Rear Case just like the one shown.

But if that is true, wouldent we be able to see the guide stop outlines on the cowling?
 
fr8mech
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RE: 747 JT9D Cascades

Tue Aug 15, 2006 1:45 am

Quoting AC320tech (Reply 6):
But if that is true, wouldent we be able to see the guide stop outlines on the cowling?

Guide stops? Not sure what you're asking here.

Here's a brief anatomy of what we're seeing:
-At the very top, fwd of the pylon is the thrust reverser air motor (just visible).
-Below that, as discussed is a cascade segment.
-The green ring the segment is attached to (fwd) is the translating ring. This ring moves fore and aft and is continuous from the top of the engine to the other side. If I had to guess, about 320 degrees.
-The cascade segment is attached, at its aft mount, to the translating sleeve. Housed in the sleeve, inner, out of our view, are the blocker doors and the operating links.
-Forward of the ring, are 2 of the TR gearboxes and their jackscrews. These are linked together, in series, with 2 more on the other side, by shafts (heavy cables) to the TR air motor.

I don't see any other TR component from this view. Incidently, the fixtue on the engine fan case about half way up, is the attach point for the engine change equipment.
When seconds count...the police are minutes away.
 
n8076u
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RE: 747 JT9D Cascades

Tue Aug 15, 2006 11:37 am

Don't blame me, I don't work here...
 
fr8mech
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RE: 747 JT9D Cascades

Tue Aug 15, 2006 11:55 am

Quoting N8076U (Reply 8):

Oh my, the memories (and the pain) come flooding back!
When seconds count...the police are minutes away.
 
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HAWK21M
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RE: 747 JT9D Cascades

Tue Aug 15, 2006 5:08 pm


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Photo © Simon Ng


Fantastic view.

Quoting Fr8Mech (Reply 9):
Oh my, the memories (and the pain) come flooding back

What was the pain for.Was it a tough Engine Mx point of view to Maintan.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
fr8mech
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RE: 747 JT9D Cascades

Tue Aug 15, 2006 7:56 pm

Quoting HAWK21M (Reply 10):

Yes, the engine was (is) maintenance intensive. Chapter 75 is a bear on the -7A/AH's and only marginally better on the -7Q. The reverser is always locking up. The early engines leaked oil and the fuel leaks on the -7Q would clean off the oil. The core cowl could kill you if you're not careful.
When seconds count...the police are minutes away.
 
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HAWK21M
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RE: 747 JT9D Cascades

Wed Aug 16, 2006 5:12 pm

Quoting Fr8Mech (Reply 11):

Was these ever cured by some SBs,or it always stayed that way.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
fr8mech
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RE: 747 JT9D Cascades

Wed Aug 16, 2006 7:27 pm

Minor improvments, but no real change. The engine doesn't really leak much oil, but the breather/cowl interface isn't the best and you always get a film of oil under the cowl. The engine uses a horrendous amount of oil compared to today's standards. I believe our limit is 1.25 qts/hour.
When seconds count...the police are minutes away.
 
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HAWK21M
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RE: 747 JT9D Cascades

Wed Aug 16, 2006 8:53 pm



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Photo © Vatche Mitilian
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Photo © Nikolas Stassinopoulos



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Photo © Lindsay Hockey


Have seen them on the old B742 of AI a lot.Is the Type used on the B742 different from the rest or just the Fairings differ.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
fr8mech
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RE: 747 JT9D Cascades

Thu Aug 17, 2006 11:49 am

The B747-2XX normally has -7Q engines (if PW equipped) though I know of at least one tail that had a set of -7J engines installed.

As for the fairings; I think there are a couple of -1XX that have the high speed fairings installed, I don't believe it's a -2XX installation only. I'll keep on eye on our birds as they cycle through to confirm.
When seconds count...the police are minutes away.
 
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HAWK21M
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RE: 747 JT9D Cascades

Thu Aug 17, 2006 3:01 pm

Quoting Fr8Mech (Reply 15):
The B747-2XX normally has -7Q engines (if PW equipped) though I know of at least one tail that had a set of -7J engines installed

Whats the Difference -Q & -J
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
fr8mech
Posts: 6845
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RE: 747 JT9D Cascades

Fri Aug 18, 2006 4:48 am

Other than max EGT being different, I don't recall anything else.
When seconds count...the police are minutes away.
 
MarkC
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RE: 747 JT9D Cascades

Fri Aug 18, 2006 8:32 am

Quoting HAWK21M (Reply 16):
Whats the Difference -Q & -J
regds
MEL

The Q is very different.

The Q had the 5 stg LPC instead of 4, and also added an extra roller bearing on the LP shaft. The Q's are really a lot like the R4's.
 
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HAWK21M
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RE: 747 JT9D Cascades

Fri Aug 18, 2006 1:35 pm

Quoting MarkC (Reply 18):
The Q had the 5 stg LPC instead of 4, and also added an extra roller bearing on the LP shaft. The Q's are really a lot like the R4's

Interesting.Thanks.
What were the Different variants on the 9Ds.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
MarkC
Posts: 238
Joined: Tue Apr 25, 2006 8:10 am

RE: 747 JT9D Cascades

Sun Aug 20, 2006 3:09 am

Quoting HAWK21M (Reply 19):
What were the Different variants on the 9Ds.

The answer would take a while, and I would not be the one to give it completely, but here's what I do know.

The original was the 4 main brg, 4 stg. LPC -7A, H, AH, F, J and -20's. (-20 was DC-10) That's one family.

The -7Q's and -59A/-70's were the next development. These had 5 main brgs and a 5 stg. LPC. 59/70 had a fan mounted gearbox, and were for DC-10, A300, and a few 747.

The -7R4 was further updated. All the -7R4's differ upon the application, but the core is essentially the same, but not always.

The 4000's are so much more the common engine.
 
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HAWK21M
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RE: 747 JT9D Cascades

Sun Aug 20, 2006 11:03 am

Was checking out the P&W website & found this.
http://www.pratt-whitney.com/prod_comm_jt9d.asp
regds
MEL
I may not win often, but I damn well never lose!!! ;)

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