c5load
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Are Entire Engines Ever Changed?

Fri May 21, 2010 5:49 pm

I know whole engines are typically changed for mx troubles that damage or destroy the engine, but are they ever wholly changed simply based on a maintenance schedule? Let's say after 3 yrs (just a figure, I might be way off) does the entire engine get swapped out for a rebuilt or new one? Or are components of the engine changed according to a schedule, so in the course of 4 or 5 yrs, the engine is pretty much new?
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fr8mech
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RE: Are Entire Engines Ever Changed?

Fri May 21, 2010 6:02 pm

Yes, the engine is changed. Say you have performance degradation and that degradation is due to a turbine disk or the whole turbine section being worn, the most cost effective way to restore that performance is to replace the engine and send the engine in for a shop visit. Same for the compressor or the combustor. Realistically, just about any internal component that is worn and causes a performance degradation beyond what is tolerated, drives an engine change.
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tdscanuck
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RE: Are Entire Engines Ever Changed?

Fri May 21, 2010 6:49 pm

Quoting c5load (Thread starter):
I know whole engines are typically changed for mx troubles that damage or destroy the engine, but are they ever wholly changed simply based on a maintenance schedule?

Yes. Engines contain life-limited parts (LLP's) that cannot be replaced on-wing (turbine disks, combustors, shafts, etc.). The engine is completely changed and sent back to an overhaul shop.

Tom.
 
viv
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RE: Are Entire Engines Ever Changed?

Sat May 22, 2010 3:58 pm

Yes, engines are changed periodically, for overhaul.
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Tristarsteve
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RE: Are Entire Engines Ever Changed?

Sat May 22, 2010 5:46 pm

Quoting c5load (Thread starter):
but are they ever wholly changed simply based on a maintenance schedule?

OK, a modern engine on a large airliner has life limiting parts inside it. The engine must be changed at this limit. But this limit nowadays is around 20000 cycles, and very few engines will ever reach 20000 cycles without being removed for some other reason. A long haul airliner will fly 30 years before it accumulates 20000 cycles!

When I started on the Tristar, the RB211 was limited to 1200 cycles, and rarely acheived that. How times have changed.

Quoting c5load (Thread starter):
Or are components of the engine changed according to a schedule, so in the course of 4 or 5 yrs, the engine is pretty much new?

Yes components are changed, but rarely the bits inside the engine that count. On a GE90 you can change the engine and leave the fan behind, and on most engines you can change the fan on the wing, but because of time constraints, if a new HP section is required, the engine will be changed and repaired in the shop. We change gearboxes and fan blades and fuel pumps on the wing, but not turbine blades. It just is not worth it, it takes too long.
 
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HAWK21M
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RE: Are Entire Engines Ever Changed?

Sun May 23, 2010 5:50 pm

Certain components of an Engine have a overhaul duration & cannot be replaced on line & need to visit an Engine shop.
regds
MEL.
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AA737-823
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RE: Are Entire Engines Ever Changed?

Wed May 26, 2010 8:24 pm

Well, I think I understand your question.
And the answer is sometimes.
For example, I know a carrier that will drop a JT-8D-17A every 4000 hours. It's usually for the same exact wear region...
I also know a carrier that has over 30,000 hours ON WING with a RB-211 on a Boeing 757.
So, there's a huge range in there, and a lot of it depends on the engine technology, and the power rating of the engine.
For example, a CFM56-7B20 will (all else being equal, which I admit it never is) last longer than a CFM56-7B24. Why? Because it's the same engine, just with different fuel software to crank the power up, raising EGT, reducing turbine wheel life.

Hope that's been helpful.
 
Viscount724
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RE: Are Entire Engines Ever Changed?

Thu May 27, 2010 12:16 am

Quoting AA737-823 (Reply 6):
I also know a carrier that has over 30,000 hours ON WING with a RB-211 on a Boeing 757.
So, there's a huge range in there, and a lot of it depends on the engine technology, and the power rating of the engine.

Press release last year referring to a CFM56 on a 737NG with 40,000 hrs on the wing, and expected to reach about 48,500 hrs. before the first life-limited part would require engine removal.
http://www.cfm56.com/press/news/tuif...+hours+on+wing+without+removal/512
 
N243NW
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RE: Are Entire Engines Ever Changed?

Wed Jun 02, 2010 2:05 am

Here's one of my all-time favorites, depicting exactly what you were asking about:

http://www.youtube.com/watch?v=zUR-lutN_vk
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Rj111
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RE: Are Entire Engines Ever Changed?

Wed Jun 02, 2010 6:16 pm

One strategy is to remove say 1 engine of a twin halfway through its life, so the plane isn't flying around with 2 older engines as time goes by.

Also at BA i believe new RB211-524s usually go on the 767, as these have ETOPS standards to comply with. Then as they get older they'll go to the 744.
 
IFIXCF6
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RE: Are Entire Engines Ever Changed?

Thu Jun 03, 2010 2:35 am

Another tactic was the use of "rotable" modules and components. A fleet operator might match an engine shop visit overhaul for a shorter time life limited module with assembly to a longer life limited module with approx. the same time left, so as to try to get that engine off wing because the "entire" engine or the "entire" hot section needed maintenance. Hard to really schedule, without a huge fleet.

Mike
 
ex52tech
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 2:25 pm

Quoting Tristarsteve (Reply 4):

OK, a modern engine on a large airliner has life limiting parts inside it. The engine must be changed at this limit. But this limit nowadays is around 20000 cycles, and very few engines will ever reach 20000 cycles without being removed for some other reason. A long haul airliner will fly 30 years before it accumulates 20000 cycles!

When I started on the Tristar, the RB211 was limited to 1200 cycles, and rarely acheived that. How times have changed.

Now I could be totally wrong here but at the two airlines I worked at, and in the engine overhaul shops that I worked in we measured engine life in hours not cycles. I m thinking you meant hours.

Hopefully this will help the thread starter. In a perfect world. If you started with a 0 build or an engine that has 0 hours on it, that engine will be in the shop about half way through its life hour limit for a new hot section, which is usually replacement of everything from the burner can (combustion chamber) all the way to the back of the engine. Then theoretically it would run until it needed a new hot section again, and would be at its cold section or compressor hourly limits, or overall hourly time limit.

That generally does not happen, due to engine damage or some type of premature deterioration of an internal component. Some airlines will install components inside engines at a shop visit that may not have enough time left on them to make the max time limit of the engine because they see some deterioration of performance and are betting that the engine performance will fall off below limits before the engine reaches its maximum hourly limit.

On many occasions I have personally installed turbine modules on an engine that have much less time on them than the engines max hourly limit, because we knew that the compressor had deteriorated enough ( usually due to blade tip clearance issues) that the engine was going to fall below performance limits within say 1,000 to 2,000 hours, but the engine still had 4,000 to 5,000 hours left on it.

Hope that helps.
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boeing767mech
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 2:46 pm

Quoting c5load (Thread starter):
Let's say after 3 yrs (just a figure, I might be way off) does the entire engine get swapped out for a rebuilt or new one?

The little airline I work, which was shown in the video in this thread had a 767-323ER that had an engine on wing for over 62K hours of total time on the engine. If I remember right the airframe was about 10 years old.

In this time the engine and various valve pumps and fuel controls changed. It also had a couple fan blades changed. Any damage found during a boroscope was checked and recorded to keep a eye on it to check to back sure it was with in limits per the AMM. We also boroblended any damage like rough edges on compressor blades.

It also had coke washes, and water washes to help clean the compressor blades in the gas path. And of course it had ignitors and filters changed and chip detectors inspected during b check.

We also did a couple blade balances during the life of this engine to help with vibrations.

But after 62K hours on wing we did change this engine.

David
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maddog888
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 5:48 pm

Quoting N243NW (Reply 8):
Here's one of my all-time favorites, depicting exactly what you were asking about:

http://www.youtube.com/watch?v=zUR-lutN_vk

I have a couple of questions regarding stuff I saw in the video. Please excuse the lack of technical terminology, I am not an engineer. Nice video btw.

When they removed the engine , I saw that the side fairing panels & intake cowling remained with the plane not the engine. Is this usual? I always just assumed that the whole thing was dropped off the pylon and a new one attached but then I suppose I shoudn't have as everyone knows about ass-u-me.

Secondly I know it was time lapse photography but it looked like the engineers had the fan rotating whilst they fitted the cowling. I assume (there I go again) that they have to check for clearance but I would have thought there was less risk of damage to do it after the cowling was fitted.

Julian
 
boeing767mech
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 6:20 pm

Quoting maddog888 (Reply 13):
I saw that the side fairing panels & intake cowling remained with the plane not the engine. Is this usual? I always just assumed that the whole thing was dropped off the pylon and a new one attached but then I suppose I shoudn't have as everyone knows about ass-u-me.

The cowling and thrust reversors are connected to the pylon via hinge points. The inlet cowl remains with the airplane most of the time. Some engines have the inlet already fitted and is part of a QEC (Quick Engine Change).

Quoting maddog888 (Reply 13):
Secondly I know it was time lapse photography but it looked like the engineers had the fan rotating whilst they fitted the cowling. I assume (there I go again) that they have to check for clearance but I would have thought there was less risk of damage to do it after the cowling was fitted.

The fan is spinning because of the wind blowing thru the hanger. There is a freight door in front part of that hanger that was open during the time of the shoot. There was also a thunderstorm going thru AFW when they where shotting this video so there was some strong winds

David
Never under-estimate the predictably of stupidty
 
Tristarsteve
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 7:14 pm

Quoting ex52tech (Reply 11):
Now I could be totally wrong here but at the two airlines I worked at, and in the engine overhaul shops that I worked in we measured engine life in hours not cycles. I m thinking you meant hours.

No I did mean cycles. The life limit on a HPTB, of a Turbine disc is how many high power take offs it has performed, not how many hours it has droned along at 38000ft. Modern jet engines are basically on-condition. There is no hours limit, you keep inspecting it until a decision is made to remove it. This decision comes from the engineer in the office. But some cyclic parts are life limited. This is a hard life, and the engine comes out. But a B744 operator may never reach this limit because the aircraft spends all its time in the cruise.

Quoting maddog888 (Reply 13):
When they removed the engine , I saw that the side fairing panels & intake cowling remained with the plane not the engine. Is this usual?

Not on the RB211!!! The whole engine is removed complete with thrust reverser.

Quoting ex52tech (Reply 11):
On many occasions I have personally installed turbine modules on an engine that have much less time on them than the engines max hourly limit

  

When an engine is removed a conference takes place in engine planning to decide what work to do. The engine is removed for a hot section failure, but do we only change the hot section, or shall we change the LP turbine as well? Lots of financial decisions here.

Another factor keeping engines on the wing is that many engine SBs are rated next shop visit. So if the engine stays on the wing, the work (and expenditure) is deferred.


p.s., by inspection I also mean MCDs, filter analysis. SOAP oil checks, routine boroscopes, and print outs from the QAR.

When the Tristar RB211 had a 1200cycle life, we were boroscoping it twice a week at the end of its life to try and keep it flying. We kept a book of drawings of the cracks in the engine (no video boroscopes in those days) and checked the crack propogation. We didn't miss many failures.
 
FlyingColours
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 7:31 pm

Quoting boeing767mech (Reply 14):
The fan is spinning because of the wind blowing thru the hanger. There is a freight door in front part of that hanger that was open during the time of the shoot. There was also a thunderstorm going thru AFW when they where shotting this video so there was some strong winds

Plus it does not take much of a breeze to get engines windmilling...

Quoting N243NW (Reply 8):
Here's one of my all-time favorites, depicting exactly what you were asking about:

Good Video

I've seen an engine change on the 757-200 a long time ago, I unfortunately couldn't hang around long (no pun intended) but it looked like it was going to take some time, 5-6 hours seems about right for the RB211 I'd guess.

Quoting AA737-823 (Reply 6):
I also know a carrier that has over 30,000 hours ON WING with a RB-211 on a Boeing 757.

Would that be Monarch by any chance? Their engineers are incredible, they have kept their 757s going (and going well) since well, forever. They also did work on our 757s but sadly even they couldn't keep ours going  
Incidentally the engine change I saw was the Monarch guys working on one of our 757s, there is a funny and yet awful story which I won't go into (for a change).

Phil
FlyingColours
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boeing767mech
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 7:34 pm

Quoting Tristarsteve (Reply 15):
Not on the RB211!!! The whole engine is removed complete with thrust reverser.

Not on the 757's. The C ducts and cowlings stay on the pylon in the RB211-535E on our airplanes. Only the inlet and common nozzle stay with the engine.

David
Never under-estimate the predictably of stupidty
 
FlyingColours
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 7:48 pm

Quoting boeing767mech (Reply 17):
Quoting Tristarsteve (Reply 15):
Not on the RB211!!! The whole engine is removed complete with thrust reverser.

Not on the 757's. The C ducts and cowlings stay on the pylon in the RB211-535E on our airplanes. Only the inlet and common nozzle stay with the engine.

Not sure if it helps clear things up either way but here is a photo of an RB211-535E4 being changed.


View Large View Medium
Click here for bigger photo!

Photo © Canarian666



Phil
FlyingColours
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Tristarsteve
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RE: Are Entire Engines Ever Changed?

Mon Jun 14, 2010 7:52 pm

Quoting boeing767mech (Reply 17):
Not on the 757's

Yes writing too fast.
The RB211-535 was always a strange engine. Its nothing like any other RB211, except for the inside bits that you never see on the ramp. It so different, you might think that Rolls gave the core engine to an outside co, and told them to design their own engine around it.
It s got C ducts
A hyd thrust reverser
a little BVCU computor that controls the bleed system
The gearbox is back to front, mainly the oil tank is on the other side.
Its got an EEC, which is in the aircraft electronic bay, and steel cables to the FFR.
But in its -E version, it is a brilliant engine that works well. (we used to have -Cs as well.)
 
tdscanuck
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RE: Are Entire Engines Ever Changed?

Wed Jun 16, 2010 5:31 am

Quoting ex52tech (Reply 11):
Now I could be totally wrong here but at the two airlines I worked at, and in the engine overhaul shops that I worked in we measured engine life in hours not cycles. I m thinking you meant hours.

It depends on which component you're talking about. Safe-life components are usually critical in fatigue and don't care about hours, but do care about cycles. Components that suffer erosion/ablation as their primary failure mode (combustors, IGV's) are more likely to be hours than cycles.

Quoting maddog888 (Reply 13):
I saw that the side fairing panels & intake cowling remained with the plane not the engine. Is this usual?

Yes. Besides being mounted to the pylon (not counting oddball RB211's), the reversers are absurdely expensive and hard to source pieces of equipment in their own right, and nobody wants to stock more than they have to.

Quoting maddog888 (Reply 13):
I assume (there I go again) that they have to check for clearance but I would have thought there was less risk of damage to do it after the cowling was fitted.

There's no need for a fan clearance check during an engine change...that was done long before, when the engine was being built-up and test run. The clearance is usually zero anyway, for the critical case, because most engines use an abradable fan case liner that's intentionally a bit too small initially; the fan wears the proper clearance in during the intial engine runs.

Tom.
 
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HAWK21M
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RE: Are Entire Engines Ever Changed?

Wed Jun 16, 2010 3:32 pm

Quoting Tristarsteve (Reply 19):

But in its -E version, it is a brilliant engine that works well. (we used to have -Cs as well.)

The -Cs used to have issues of Oil fumes in Flt deck on T/O power in case serviced with oil to 18-19.
Heard there is a 18% improvement in Fuel consumption on the -E4s in comparism.Can Anyone confirm.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
ex52tech
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RE: Are Entire Engines Ever Changed?

Fri Jun 18, 2010 8:41 pm

Quoting Tristarsteve (Reply 15):

When the Tristar RB211 had a 1200cycle life, we were boroscoping it twice a week at the end of its life to try and keep it flying. We kept a book of drawings of the cracks in the engine (no video boroscopes in those days) and checked the crack propogation. We didn't miss many failures.

I remember those days before video borescopes.

Twice a week, we would have pulled the sucker before it ended up in Denver on a hot day and took itself out. I can see the cycles point, but we did everything on hours, condition, and engine data.
"Saddest thing I ever witnessed....an airplane being scrapped"
 
Tristarsteve
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RE: Are Entire Engines Ever Changed?

Sat Jun 19, 2010 4:24 am

Quoting HAWK21M (Reply 21):
Heard there is a 18% improvement in Fuel consumption on the -E4s in comparism.Can Anyone confirm

Yes, definitely a big improvement.
I used to depart C and E engined B757s, The fuel load out of here to LHR was 12 tons on a E aircraft, and 13 on a C. So around 14pc better fuel consumption.
 
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HAWK21M
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RE: Are Entire Engines Ever Changed?

Sun Jun 20, 2010 3:07 pm

Quoting Tristarsteve (Reply 23):
So around 14pc better fuel consumption.

Amazing.
Any news on the Proposed RB211-535E4-C which never entered service.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
tepidhalibut
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RE: Are Entire Engines Ever Changed?

Sun Jun 20, 2010 9:43 pm

Quoting HAWK21M (Reply 24):
Any news on the Proposed RB211-535E4-C which never entered service.

Minor correction. It did enter service. 2001, IIRC. It was tailored to ATA's operation out of Chicago Midway airport, with just a little more thrust at certain ambient conditions. Throttle-push on their 753's, as opposed to any component redesign.

ATA, however, went under in 2008. Someone will have bought their 753's, and unless they're also flying out of Midway, they won't be needing the E4-C rating, and will be flying them as E4Bs.
 
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readytotaxi
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RE: Are Entire Engines Ever Changed?

Tue Jun 22, 2010 7:38 pm

So is this a bit like Grand Prix where airlines have "ready to go" engines waiting to be bolted on and then out of the pit lane?
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Tristarsteve
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RE: Are Entire Engines Ever Changed?

Tue Jun 22, 2010 8:08 pm

Quoting readytotaxi (Reply 26):
So is this a bit like Grand Prix where airlines have "ready to go" engines waiting to be bolted on and then out of the pit lane?

Well yes. 25 years ago definitely. Engines failed so often then, that engines were assembled onto airfreight stands ready to go. Nowadays, engine failures are not that common so most airlines do not keep packaged engines ready to go. The serviceable engines are stored in an engine bay where they can be fitted with the correct pieces and packaged for transport when required.
 
PresRDC
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RE: Are Entire Engines Ever Changed?

Fri Jun 25, 2010 8:14 pm

I've done two deals in the past couple of years where we sold new engines to an airline with minimal discounting in lieu of having the engines overhauled (the shop visits would have involved replacing the LLP stack). While more expensive in absolute terms, the airline ended up with new product and we were able to break down the old engines for parts to use for our power-by-the-hour customers or to sell through our used serviceable material sales entity.
 
c5load
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RE: Are Entire Engines Ever Changed?

Fri Jun 25, 2010 11:13 pm

Quoting FlyingColours (Reply 18):
Not sure if it helps clear things up either way but here is a photo of an RB211-535E4 being changed.

Looking at the photo of the 757 engine change, I noticed two hose hookups on the top of the engine core. Anyone know what those are?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
tdscanuck
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RE: Are Entire Engines Ever Changed?

Fri Jun 25, 2010 11:33 pm

Quoting c5load (Reply 29):
Looking at the photo of the 757 engine change, I noticed two hose hookups on the top of the engine core. Anyone know what those are?

Bleed air. One is probably the starter supply and the other is the engine output, but one might be a surge vent. But bleed air is the only thing on the engine that needs a duct that large.

Tom.
 
c5load
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RE: Are Entire Engines Ever Changed?

Fri Jun 25, 2010 11:37 pm

Quoting tdscanuck (Reply 30):
Bleed air. One is probably the starter supply and the other is the engine output, but one might be a surge vent. But bleed air is the only thing on the engine that needs a duct that large.

Thanks for the info Tom. What is the difference in putting bleed air directly into the engine vs putting an air cart up to the normal bleed air port?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
tdscanuck
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RE: Are Entire Engines Ever Changed?

Sat Jun 26, 2010 12:51 am

Quoting c5load (Reply 31):
What is the difference in putting bleed air directly into the engine vs putting an air cart up to the normal bleed air port?

Nothing from a systems point of view; the ducts are all interconnected. The only difference is where the air is coming in to the system.

The duct you can see there (if it is the supply duct) is feeding air from the airplane pneumatic system to the engine starter...the source of air in that duct could be the other side engine, the APU, or an air cart on the normal pneumatic port.

Tom.
 
boeing767mech
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RE: Are Entire Engines Ever Changed?

Sat Jun 26, 2010 12:53 am

Quoting c5load (Reply 29):
, I noticed two hose hookups on the top of the engine core. Anyone know what those are?

The aft pipe is the High Stage Bleed Air.
The Fwd pipe is the Intermediate Stage Bleed Air.

At lower power setting the High Stage Bleed is being used to supply pneumatic air. When the power of the engine goes above a certain EPR setting the High Stage Valve which mounts to the top of the aft duct closes and the Intermediate Stage takes over and supplies pneumatic air. If I remember right I think the bleed shift is around 1.6 EPR but this all depended on altitude and power settings.

The starter duct is up on the forward part of the plyon on the Left hand side. The duct comes down over the Fan section of the engine.

David
Never under-estimate the predictably of stupidty

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