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JetMech's Technical Tour Of The Trent 700.  
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Posted (7 years 12 months 2 days 15 hours ago) and read 19014 times:

G'day people   ,

Along the lines of Wing's tributes to various aircraft on the Civil Aviation thread, I have decided to start a similar thread in Tech/Ops. The emphasis will be on the technical aspects of various components and sub-systems, and I would love for other A.netters of a technical bent to produce their own tour of their favorite piece of aircraft related machinery.

Adding ramblings of your experiences with these devices is encouraged. Think of it as a technical trip report from a personal perspective. Most of all, entertain and educate your fellow A.netters.

Anyhow, JetMech has a thing for the Rolls-Royce (RR) Trent 700. So here goes. The Trent 700 (T-700) series of turbofan engines are designed to produce a nominal thrust in the range of 68-72,000lbs. The engine is a triple spool design of the following layout;

N1 spool, 1 stage of Low Pressure Compressor (LPC) driven by a four stage Low Pressure Turbine (LPT).

N2 spool, 8 stages of Intermediate Pressure Compressor (IPC) driven by 1 stage of Intermediate Pressure Turbine (IPT).

N3 spool, 6 stages of High Pressure Compressor (HPC) driven by 1 stage of High Pressure Turbine (HPT).


Moving the "C" duct / thrust reverser. Careful boys; it's VERY heavy!


Here the 'C" duct / thrust reverser (TR) half is being opened for maintenance access. The "C" duct / TR half is forced open by a hydraulic ram, nonetheless, a fair bit of manual handling is still required to fully secure this cumbersome piece of equipment in an open position. This hydraulic ram uses pressurised oil fed to it by the green and orange cart.

The holes in the "C" duct / TR half inner wall are to allow for the compressor bleed valves. The "C" duct / TR halves remain on the strut when the engine is changed. The TR operates by pivoting doors into the cold-steam duct and vectoring air forwards.

The 524G2's and D4's were slightly different. With these RR engines, the thrust reverser was an integral part of the engine, and came away and stayed with the engine when the engine was changed. The TR mechanism was also slightly different in that the entire assembly slid backwards to operate. This backwards sliding simultaneously raised blocker doors in the cold-stream duct, and uncovered cascade vanes which vectored the bypass air forwards.


JetMech in the midst of a RR Trent 772. JetMech's roughly hewn mug has been replaced with something far more pleasant.


Here you can see JetMech standing in the space that is left behind when the "C" duct / TR half is opened. You are literally opening up half of the side of the engine when you open the "C" ducts / TR halves.

Behind my back you can see the exit of the fan case and various components below it. In the fore-ground is the back part of the engine cowling, which is called the Integrated Nozzle Assembly (INA)  . This comes away with the engine during engine changes.

You can also see the last stage of the LPT and the exhaust cone. This exhaust cone is often an exotically beautiful blue colour on new engines. It feels weird to be both "inside" and "outside" of the engine at the same time.


Right hand "C" duct / thrust reverser opened to reveal the innards of the beast.


This photo is the view you get from behind the open "C" duct / TR half. You can clearly see how much of the air bypasses the core of the engine from the size of the bypass region of the fan case.

When the "C" duct / TR half is closed, it's inner wall forms a cowl around the core of the engine whilst simultaneously being part of the inner wall of the bypass duct. The outer wall of the "C" duct / TR half forms part of the outer wall of the bypass duct as well as forming part of the outer aerodynamic shape of the engine pod. This helps to give the T-700 cowling a beautiful, full skirted look.

You can also clearly see the myriad of pipes and tubing that conduct various vital fluids to and from the core and the accessories on the external gearbox and fan case. The fluids include fuel, oil, air, and various electrical and electronic signals carried by the wire bundles.

You can also see how well this area is sealed up. I think the main reason for this is to divide the engine up into fire zones, and also to insulate and protect the pipes, tubes and wire bundles.


Turbine & compressor casings, fuel distribution manifold and injector nozzles, bleed valves and the housing for the external gearbox drive shafts.


Here we get a nice view of what normally is covered by the inner wall of the "C" duct / TR half. I don't have much experience on the T-700, so my following description of the components is based on familiarity with other engines.

The two, big, round and protruding objects are bleed valves. They operate in various combinations according to the operating point of the engine. They bleed air off the compressor to stabilise the airflow through this region of the engine under various operating conditions. This air gets dumped into the bypass duct.

The fuel distribution manifold and fuel injector nozzles are the twisted mass of black tubing the runs behind and under the left hand bleed valve. This manifold surrounds the circumference of the combustion casing with numerous equally spaced fuel injector nozzles that pierce into the casing to deliver fuel to the combustion chamber. The basic idea is to have a homogeneous "ring of fire" around the entire circumference of the combustion chamber.


A close up of the Trent 772's most intimate regions! All that tubing reminds me of a CF6.


Another view of the area reveals some more components. Underneath the left hand bleed valve is a pipe. This pipe seems to be bleeding air off the compressor and ducting it off to the fan case somewhere. Does anyone know what this air is being bled off for? Nacelle anti-ice etc?

You can also see the casing that houses the drive shafts to and from the core and the external gearbox. IIRC on the G2 / D4, the external gearbox is driven from the N3 spool. Does anyone know what happens on the T-700?

You can also see just a small part of the extensive sealing that is used on a modern turbo-fan. One of the most beautiful and amazing sights on an engine is to close the "C" duct / TR half. It is just amazing how all the components move past one another without interfering. It is just amazing to see how all the various seals are made by the simple action of closing the duct. It's like a thousand closely inter-meshing fingers that never actually touch.


The only component I am familiar with in this photo is the oil tank.


Here we see some of the fan case mounted components. The component located in the "middle" is the oil tank. The T-700 has a stand alone oil tank. On the G2 and D4, the oil tank was an integral part of the external gearbox. I am not 100% sure what the other components are, but I will have a guess.

The large component above the oil tank is a Fuel Cooled Oil Cooler (FCOC). The FCOC acts as a heat exchanger between the oil and fuel. The cold fuel is heated up by the hot oil, and vice versa, the hot oil is cooled by the cold fuel.
Cooling the oil is self explanatory, but why would you heat the fuel?

Jet A1 often contains entrained water. At cruising altitudes, the fuel temperature will eventually go below freezing point and may possibly cause ice crystals to form in the fuel. This was a potential problem back in the day of hydro-mechanical engine control units.

These devices where computers; fantastically complex mechanical ones that used the condition of various fluids as inputs to make "decisions" about how to control a multitude of parameters such as the rate of fuelling and the scheduling of bleed valves and stator vanes.

The fear was that ice crystals in the fuel would have the potential to block any number of the fine passages in these hydro-mechanical units and cause malfunction. The solution was to heat the fuel above freezing point and melt these ice crystals back into liquid water before the fuel got to the hydro-mechanical unit.

I am not sure if this needs to be done with the modern crop of Full Authority Fuel Control (FAFC) and Full Authority Digital Engine Control (FADEC) engine types  

I hazard to guess that the component below the oil tank is a supplementary oil cooler, and I suspect it uses fan discharge air as the cooling medium.


Close-up of the stand-alone T-772 oil tank. RB211-524G2's and D4's had the oil tank as an intergral part of the external gearbox.


Here is a closer view of the fan case components. You can see three, medium brown coloured lines going down to a component on the front of the external gearbox. One line is "large", one "medium" and the other "small" in diameter.

I suspect that these are hydraulic lines and and that the component they lead to is an engine driven hydraulic pump. The large line supplies the pump with hydraulic fluid from the hydraulic reservoir. The medium line delivers a certain flow rate of hydraulic fluid to the aircraft's hydraulic systems, whereas the small line is known as the case drain line.

The hydraulic pumps used in aircraft are of the tilting swash-plate design. Basically what happens is that the swash-plate can tilt. This tilt alters the stroke of several piston type pumps within the pump casing. These pistons are designed with a small amount of leakage for lubrication purposes.

The case drain line removes this leakage fluid from behind the pump pistons to prevent a hydraulic lock forming behind the pistons. The hydraulic pump produces a certain flow rate of hydraulic fluid. When this fluid meets an obstruction, hydraulic pressure is generated.

The tilt of the swash-plate responds to the pressure in the aircrafts hydraulic system. In low demand situations, the swash plate tilts in a manner to cause the stroke of the pump pistons to be short or zero. This results in the hydraulic pump delivering a small amount of hydraulic fluid flow to the hydraulic systems.

In high demand situations, the swash-plate tilts in a manner to maximise the stroke of the pump pistons and hence maximise the flow of hydraulic fluid delivered by the pump to the aircraft's hydraulic systems.


The external gearbox is sandwiched between the starter motor and the IDG. Above the starter motor is the kevlar fan blade containment band.


This picture is taken from the other side of the fan case. You can see the starter motor on the left hand side, the Integrated Drive Generator (IDG) on the right hand side (the black object), the external gearbox sandwiched in between, and a pipe the runs above all of them.

In the 5th, photo, I alluded to the purposes of a pipe coming off the compressor casing. I presume that this is the continuation of that pipe, and the purpose of bleeding off the air is to provide Nacelle Anti Ice (NAI).

The starter motor is a pneumatically driven turbine. Under normal operations, the APU will supply a large volume flow rate of air at a medium pressure to the starter. This will spin the turbine in the starter. This is geared down to the output shaft of the starter.

This output shaft enters into the external gearbox. It then spins a gear train inside the gearbox which eventually turns drive shafts. These are the drive shafts between the engine core and external gearbox, and were mentioned in the 5th photo.

These drive shafts transmit torque to one of the spools in the engine which causes it to spin. This spinning spool will induce airflow through the core of the engine which will impinge on the compressor and turbine blades of the spools not driven by the starter. This airflow will eventually cause all the spools to spin.

Once a high enough "motoring" RPM is reached by each of the spools, fuel and ignition can be provided to fire up the engine.

The IDG is so named because on modern jetliners, the drive section is integrated with the generator section; with this arrangement constituting a single device. Earlier jetliners often had these items as separate devices, with the generator piggy-backed on to the drive section.

Modern aircraft electrical systems require the generator to deliver electric current with a certain, constant frequency. This is a difficult chore as the engines that drive the generators operate at many different speeds.

This is where the drive section comes in, the drive section delivers a constant output RPM to the generator no matter what the RPM of the input from the engine is. ( In reality of course, the output will vary within a narrow band, and the range of engine RPM inputs are from ground idle to maximum power   ).

The drive section is basically two hydraulic pumps back to back. One is a tilting swash-plate design similar to the hydraulic pump discussed in photo 7. The other pump is also a swash-plate design, but the tilt of the swash-plate is fixed at some intermediate angle.

IIRC, the tilt-able pump is connected to the engine, whilst the fixed pump is connected to the generator, with a fluid circuit between the two pumps. The tilt-able pump adjusts itself via the tilt of the swash-plate, such that the flow rate of fluid it delivers to the fixed pump is just enough to spin the generator at the correct constant RPM.

Imagine an airliner on the runway waiting to take off. Its engines are at ground idle. The tilt-able pump would be at maximum tilt so as to deliver maximum fluid flow to the fixed pump. This would act as a gearing up mechanism to make up for the slow RPM of the engine.

When the pilot slams the throttle to maximum RPM, the swash plate of the tilt-able pump will reduce it's tilt to reduce the fluid flow to the fixed pump driving the generator.

At maximum engine RPM, the tilt of the swash plate of the tilt-able pump will be quite small, and thus, the engine driven pump will be delivering a relatively small flow rate of fluid to the fixed pump driving the generator. This would act as a gearing down mechanism to make up for the fast RPM of the engine.

If the system is designed and developed correctly, the engine driven pump will adjust itself in such a manner that the generator RPM will remain relatively constant even during the quick transition period from ground idle to take off power.


Well A.netters, that's it, I'm spent. Don't take what I just posted as gospel for the Trent 700, as I have very limited experience with this engine type. Most of my post is with respect to generic descriptions and my much greater experience with other engine types. I have also taken many liberties in my explanations. Nonetheless, most of it should apply in a broad sense to the T-700.

Regards, JetMech.

P.S. I'm having a hard time reconciling the beautifully graceful exterior of the T-700 with the warts and all innards. Surely a case of beauty being skin deep?

[Edited 2006-10-27 19:53:23]


JetMech split the back of his pants. He can feel the wind in his hair.
32 replies: All unread, showing first 25:
 
User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 1, posted (7 years 12 months 2 days 14 hours ago) and read 19009 times:

Great work...I briefly toyed with the idea of having your handle on vanity license plates back in the late seventies but couldn't scrounge up the thirty five bucks it cost at the time...so we may be related LOL.

I do not have too many pics from my A&P working career,
as my Pentax Spotmatic II of blessed memory was far too costly to leave in my rollaway. I do have one though, it is a picture of a much younger me and a very badly holed Garrett TPE331

Big version: Width: 708 Height: 504 File size: 68kb
Dead motor boogie


User currently offlineFlyMatt2Bermud From United States of America, joined Jan 2006, 563 posts, RR: 7
Reply 2, posted (7 years 12 months 2 days 14 hours ago) and read 19002 times:

Professor, are there going to be any pop quizes in this class?


"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 3, posted (7 years 12 months 2 days 14 hours ago) and read 18999 times:

Beautiful, and well done. I like that you went into great detail on this engine; any possibility of other engine types and manufacturers (although QF is a big fan of RR)?

Quoting JetMech (Thread starter):
I am not sure if this needs to be done with the modern crop of Full Authority Fuel Control (FAFC) and Full Authority Digital Engine Control (FADEC) engine types  

I'm not sure on the Trent, but I have a book somewhere that identifies a CPU "black box" on the side of a P&W 300 series turbofan as a FADEC unit.

Also, doesn't that female mechanic have an overly-musculine body?

BTW: There is a Canadian member on this site with an unknown explanation for hating RR engines, so I just hope he doesn't hijack this thread.


User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 4, posted (7 years 12 months 2 days 14 hours ago) and read 18987 times:

Quoting N231YE (Reply 3):
Also, doesn't that female mechanic have an overly-musculine body?

I thought it was a male mechanic with an overly feminine face  biggrin !

Quoting N231YE (Reply 3):
BTW: There is a Canadian member on this site with an unknown explanation for hating RR engines, so I just hope he doesn't hijack this thread.

Yes I did consider that. Perhaps he could write us a technical article on the GE90-115B?. I would really like to see that  Smile ! Anyway, if he hijacks so be it.



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineAirfoilsguy From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 12 months 2 days 14 hours ago) and read 18966 times:

Great thread

Quoting N231YE (Reply 3):
There is a Canadian member on this site with an unknown explanation for hating RR engines, so I just hope he doesn't hijack this thread.

Lets just hope he has more class then to do that.


User currently offlineTristarsteve From Sweden, joined Nov 2005, 4024 posts, RR: 33
Reply 6, posted (7 years 12 months 2 days 13 hours ago) and read 18945 times:

Brilliant. I just wish I had your energy for taking good pictures.
Must make an effort one day.
Well done


User currently offlineFuturecaptain From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 12 months 2 days 13 hours ago) and read 18934 times:

Basically the long way of saying suck, squeeze, bang, blow.  Wink
Good report, dont get to see the inside of jet engines here very often.


User currently offlineEjazz From United Arab Emirates, joined May 2002, 723 posts, RR: 34
Reply 8, posted (7 years 12 months 2 days 12 hours ago) and read 18905 times:

Quoting N231YE (Reply 3):
BTW: There is a Canadian member on this site with an unknown explanation for hating RR engines, so I just hope he doesn't hijack this thread.

I'm sure he has already suggested the deletion of this thread.

It's not just a hatred toward RR, in the civil aviation forum it seems BA is the target of his hate.

Great thread Jetmech and thank you for the great post and pics.



Etihad Girl, You're a great way to fly.
User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 42
Reply 9, posted (7 years 12 months 2 days 10 hours ago) and read 18854 times:

Quoting JetMech (Thread starter):

Superb. I've rarely seen so many good photos and descriptions in one place before. If this starts a trend I certainly won't be complaining.

Quoting JetMech (Thread starter):
JetMech's roughly hewn mug has been replaced with something far more pleasant.

Don't DO that! I went through a very worrying moment there.  biggrin 


User currently offlineKELPkid From United States of America, joined Nov 2005, 6408 posts, RR: 3
Reply 10, posted (7 years 12 months 2 days 9 hours ago) and read 18826 times:

Thanks, JetMech.

A true first-class post, reminiscent of the "classic" airliners.net.

Now, if MEL would do the same for the RB211 on the 757... Big grin



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 11, posted (7 years 12 months 2 days 4 hours ago) and read 18779 times:

G'day everyone  Smile ,

Thank you very much for reading and commenting on the thread!

Taking pictures can be a bit of a hassle in these situations, as you are usually taking time off helping others, and the dirty, greasy environment of an open engine is no place for a delicate camera. Also, at the end of a long and busy shift, you are very tired, sweaty, dirty and hot; the last thing you can be bothered doing is getting your camera out for some happy snaps. It was pretty laid back in this case, the boss was the one that took the photo of myself (isn't JetMech pretty  innocent !) standing in the engine.

Anyway, this was a very rare occurrence. It was just about the first time anyone could remember where we had the cowlings open on a T - 700. It actually took much head scratching and work to figure out how to latch the "C" duct / TR halves together.

The latching system is pure medieval crudity compared to the rest of the engine, with all those massive hooks and forcefully driven shear pins and shoot bolts. The usual scope of our engine "work" is limited to pouring in MJII and making sure the filler cap is on.

I would love to do similar reports on engines from GE, P&W and CFM, but unfortunately, my access to opened examples of such would be even more restricted (funnily enough, on this same day, there was a completely open CF6-80C2 on a B763 just outside the office).

Firstly, I don't think another airline would take kindly to me taking photos of their engines and secondly, due to recent changes, the Major Maintenance operations of this airline are no longer at my location  Sad .

Anyway, the intention was to put the technical into Tech / Ops, and this can be done with most of the discussion threads by adding a nice initial technical element to discuss; which is something I will endeavour to do, and my camera will now accompany me to work at all times!

I should be getting a fair bit of work over Summer, so I may have many more photo sequences to write stories about.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 12, posted (7 years 12 months 2 days 4 hours ago) and read 18768 times:

I was just thinking about this Tribute thread in Tech ops too & a Good start this is.
Great reading. bigthumbsup 
regds
MEL



Think of the brighter side!
User currently offlineChksix From Sweden, joined Sep 2005, 345 posts, RR: 4
Reply 13, posted (7 years 12 months 1 day 10 hours ago) and read 18656 times:

Very nice! And that girl alias of yours is real sweet LOL Big grin

It's so clean and shining compared to the diesels I work on. White shirts would last seconds in my engine room. In fact, going down the stairs is enough to get dirty.

More threads like these are indeed needed  Smile



The conveyor belt plane will fly
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 14, posted (7 years 12 months 1 day 3 hours ago) and read 18613 times:

G'day people  Smile,

I was actually thinking about the IDG description I gave the other day. I can't find the reference, but it seems I may have got it a bit wrong.

The basic principle is correct, but I have this nagging memory that tells me that the fixed pump is driven by the engine, with the tilt-able pump driving the generator. The fixed pump is set such that it delivers an intermediate fluid flow at all times.

I would suspect that the tilt-able pump is set at a relatively short stroke at low engine RPM. Thus the tilt-able pump driving the generator will have to spin faster than the fixed pump to "make use" of all of the intermediate flow from the fixed pump. This acts as a gearing up mechanism when engine RPM is low.

The opposite occurs when engine RPM is high. The tilt-able pump goes to a long stroke, and thus it will spin slower than the fixed pump due to the flow from the fixed pump still being set an intermediate flow. This will act as a gearing down mechanism when engine RPM is high.

I suspect that this setup would give more responsive and immediate RPM control of the generator. It would probably maintain the constant, required generator RPM within a narrower band, and respond much quicker to changes in engine RPM.

Does anyone have any references that would clear this matter up?

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Reply 15, posted (7 years 12 months 17 hours ago) and read 18555 times:

I'm quite suprised how different the Trent 700 is to the Trent 500...
There seem to be way more pipes than the trent 500.

I'll try to snatch some photos when i get back online (I'm currently 4 weeks through my Module 15 B1 Course...)



Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineCCA From Hong Kong, joined Oct 2002, 838 posts, RR: 14
Reply 16, posted (7 years 12 months 8 hours ago) and read 18504 times:

Great post, can you put those pics into http://www.myaviation.net/ so they will be available for further tech discussions?

Cheers CCA



C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 17, posted (7 years 11 months 4 weeks 1 day 20 hours ago) and read 18418 times:

Quoting CCA (Reply 16):
Cheers CCA

G'day CCA  Smile,

Have a read of the instant message I sent you, and we'll see what we can do  Wink.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineTepidHalibut From Iceland, joined Dec 2004, 210 posts, RR: 6
Reply 18, posted (7 years 11 months 4 weeks 1 day 19 hours ago) and read 18411 times:

Good stuff JetMech !

Quoting JetMech (Thread starter):
This pipe seems to be bleeding air off the compressor and ducting it off to the fan case somewhere. Does anyone know what this air is being bled off for? Nacelle anti-ice etc?

You'll see that the pipe in question is attached to the Combustion Outer CAsing, and on the inside of that casing is HP3 (Stage 3 of HP Compressor) air. That air is used in cooling / sealing in the Turbines, and is also used as Nacelle Anti-Ice (NAI) air, so your guess is correct.

Quoting JetMech (Thread starter):
You can also see the casing that houses the drive shafts to and from the core and the external gearbox. IIRC on the G2 / D4, the external gearbox is driven from the N3 spool. Does anyone know what happens on the T-700?

Yes, all of the current RB211s (including Trents) have an external gearbox which is powered by / drives the HP System. The Trent 1000 will be different, with a gearbox having both HP and IP connections.

Quoting JetMech (Thread starter):
I'm having a hard time reconciling the beautifully graceful exterior of the T-700 with the warts and all innards. Surely a case of beauty being skin deep?

Ah, but what you've pictures aren't the real innards. You've photographed the "externals", and the delights of Turbine Blades, preswirlers, discs and shafts will have to await a module strip (or borescope.) You'll have to wait quite a while for one of those on the 700.


User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 19, posted (7 years 11 months 4 weeks 1 day 19 hours ago) and read 18402 times:

G'day TepidHalibut  ,

Thanks for having a look at this thread!

Quoting TepidHalibut (Reply 18):
That air is used in cooling / sealing in the Turbines, and is also used as Nacelle Anti-Ice (NAI) air, so your guess is correct.

Is the HP3 air used for sealing taken off this pipe, or is this sealing air routed to the required locations internally? The last 3 stages of HPC must be real compact given the limited lateral distance between that duct and what I suspect is the fuel injectors  . This is unless of course that where the duct enters the casing is not the exact location of HP3.

Quoting TepidHalibut (Reply 18):
The Trent 1000 will be different, with a gearbox having both HP and IP connections.

I suspected that there was a Trent model who's external gearbox was not going to be driven off N3. I had no idea that it was going to be N2 as well as N3. I only though it was going to be N2. Interesting   .

Quoting TepidHalibut (Reply 18):
Ah, but what you've pictures aren't the real innards.

I agree there! Unfortunately, I trained as a hangar AME, so I never had much chance to see the real innards (entrails?) of a jet engine   . To see the raw turbo-machinery would make a very interesting report   .

[Edited 2006-10-30 14:12:08]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineTepidHalibut From Iceland, joined Dec 2004, 210 posts, RR: 6
Reply 20, posted (7 years 11 months 4 weeks 1 day 17 hours ago) and read 18387 times:

Quoting JetMech (Reply 19):
Is the HP3 air used for sealing taken off this pipe, or is this sealing air routed to the required locations internally? The last 3 stages of HPC must be real compact given the limited lateral distance between that duct and what I suspect is the fuel injectors . This is unless of course that where the duct enters the casing is not the exact location of HP3.

Not surprisingly with a component called "Combustion Outer Casing" there's a component called "Combustion Inner Casing" which sits inside the COC. The annulus between the COC and CIC forms the passage-way that HP3 air travels through to get to the turbine. You can drill into this annulus at any axial position along the COC and get HP3 air. The axial position of the HP3 rotor is located slightly forward of the front flange of the COC front flange. (If you can't make that out in the pics, have a look for the difference in colour between light grey COC and dark grey Intermediate Casing.


User currently offlineLMP737 From , joined Dec 1969, posts, RR:
Reply 21, posted (7 years 11 months 4 weeks 1 day 17 hours ago) and read 18381 times:

Quoting JetMech (Thread starter):
This picture is taken from the other side of the fan case. You can see the starter motor on the left hand side, the Integrated Drive Generator (IDG) on the right hand side (the black object), the external gearbox sandwiched in between, and a pipe the runs above all of them.

Just to add a little something. On the starter motor sight guage there are oil level markers for the 777 and A330. RR equiped 777 and A330's use the same starter.


User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 22, posted (7 years 11 months 4 weeks 1 day 17 hours ago) and read 18381 times:

Quoting TepidHalibut (Reply 20):
You can drill into this annulus at any axial position along the COC and get HP3 air.

Cheers TepidHalibut, I suspected as much  Smile .

I remember with the GE's that you could quite clearly see the bleed-air collection annuli that surrounded the engine at various axial locations. They were very distinctive, raised lumps on the compressor casings.



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineVref5 From , joined Dec 1969, posts, RR:
Reply 23, posted (7 years 11 months 4 weeks 1 day 17 hours ago) and read 18371 times:

Quoting JetMech (Thread starter):
The IDG is so named because on modern jetliners

I'm not lucky enough to be an A&P... but I understand that the older version was the CSD (constant speed drive). Just curious: any significant difference or preference in working on CSDs vs. IDGs from an A&P perspective?

I'm most familiar with the momentary flicker from the IDG resynchronization cycle as it switches from one power source to another. Having seen its requirements for correct functioning, believe me, I have great respect for its abilities.

Quoting JetMech (Thread starter):
The drive section is basically two hydraulic pumps back to back.

Oddly enough, for some reason, that description reminds me of the Airbus PTU (power transfer unit) which is basically something similar, though for the hydraulic system pressure stuff between, uh, the Blue and Green hydraulic systems... is it a common arrangement to have two back-to-back hyd pumps in various aircraft systems?

As a side note: very nice post and photographs; thank you.

[Edited 2006-10-30 16:50:04]

User currently offlineLMP737 From , joined Dec 1969, posts, RR:
Reply 24, posted (7 years 11 months 4 weeks 1 day 17 hours ago) and read 18366 times:

Quoting Vref5 (Reply 23):
I'm not lucky enough to be an A&P... but I understand that the older version was the CSD (constant speed drive). Just curious: any significant difference or preference in working on CSDs vs. IDGs from an A&P perspective?

The signifigant difference is that on a CSD the generator is seperate from the drive unit. IDG's are much more reliable than CSD's. They are also easier to work on since on a CSD you have to seperate the generator form the drive unit when removing the CSD.


25 Kaddyuk : An IDG is oil cooled and a CSD is air cooled. IDG Oil Air Cooler...
26 Post contains images JetMech : With my previous employer I worked on RR's, GE's and P&W's, and I pretty much think it was the same starter motor for all of them. G'day Vref5, you c
27 LMP737 : Yes, the generator on a typical CSD is air cooled. The drive portion is oil cooled with the cooler for a motor like the JT8D being in the six o'clock
28 Post contains images RJ111 : Great thread and very kind of you to spend the time creating it for us. Cheers, Rj111
29 Kaddyuk : The trent -500 doesnt have a supplimentary engine oil cooler (it has the FCOC for that) however it does have an IDG Oil Cooler which looks the same h
30 LMP737 : Thanks for the info. I've never worked on the GE or PW motors that power the 777 and always wondered if they had some "commonality" in some of the ac
31 Post contains images JetMech : Hi Kaddyuk , I was back at work for the first time tonight, and I managed to have a look at some T - 700 training notes. The cooling device below the
32 CcrlR : I like your explaination of the RR Trent 700. Mabye you could do more for us if you have time. Great pictures too!
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