A321 NEO PW1100 case crack on DEP from Brussels.

[underfire]

Turkish Airlines A321 NEO PW1100 gearbox case crack and oil leakage on DEP from Brussels. Ac returned to Brussels for engine change.

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/768x1024/dtftgbrxoaayxtz_13f7e71d7373de74b51c9b517c639a76a1b4e1be.jpg

[RufusXS]

Was an accessory gearbox according to this:

https://aviation-safety.net/wikibase/wiki.php?id=218702

[Buster15]

Was an accessory gearbox according to this:

https://aviation-safety.net/wikibase/wiki.php?id=218702

Gearbox/Accessory Gearbox is the same thing. The engine gearbox is there to provide drive for the accessories - oil pump, fuel systems, electrical systems etc.

Another PW1100 problem. In my experience cracked gearboxes like this are very rare especially so early on.

[underfire]

Gearbox case is the operative term here. jeez

All the same, a very unusual looking crack in a new engine accessory gearbox case.

Doesnt look like a crack, but more like tear failure?

[FE Hoppy]

Great! Another round of inspections.
That's a hell of a failure. Wonder how long it takes to produce a full suite of new gearbox casings for all the PW1000s out there?

[WHBM]

What did John Glenn say about "sitting on top of 2 million parts all bought from the low bidder" ?

[Buster15]

Great! Another round of inspections.
That's a hell of a failure. Wonder how long it takes to produce a full suite of new gearbox casings for all the PW1000s out there?

Very good point...

[Loose rivets]

The casting in that region looks very strange - the surface faceted as though the metal was applied with a trowel.

[underfire]

Closeup of break...(and limits of break)

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/662x492/fwzz9sp_6d5479e92aabbc6f54510369ac277d78bb64b361.jpg

Avio Aero gearbox:
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/556x253/img_left_70754e9d950fdda83b77e40a7f477af5e68cfb75.png

[WHBM]

The casting in that region looks very strange - the surface faceted as though the metal was applied with a trowel.
I was thinking the same myself, maybe the lighting but it doesn't give the impression of a beautifully finished component.

Casting or forging ?

[underfire]

Aluminum casting.

One part shows a manufactured date of 10.05.2017

[tdracer]

Gearbox/Accessory Gearbox is the same thing. The engine gearbox is there to provide drive for the accessories - oil pump, fuel systems, electrical systems etc.

I don't disagree that it appears to be the Accessory Gearbox, but on the PW1100 don't they have a separate 'gearbox' for the geared fan?
I'm not very familiar with the PW1100 architecture but I'd assumed they they had two gearboxes - the accessory gearbox, driven off the high spool, and a fan gearbox driven from the low spool?

[DaveReidUK]

I don't disagree that it appears to be the Accessory Gearbox, but on the PW1100 don't they have a separate 'gearbox' for the geared fan?
I'm not very familiar with the PW1100 architecture but I'd assumed they they had two gearboxes - the accessory gearbox, driven off the high spool, and a fan gearbox driven from the low spool?

PW1100G fan gearbox (3:1 gearing):
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/784x832/pw1100g_gear_system_f5cb6419ea85f8972db606fc1ce0041240e50306 .jpg

[FlightlessParrot]

I was thinking the same myself, maybe the lighting but it doesn't give the impression of a beautifully finished component.

Casting or forging ?
It looks like the lighting and a degree of tonal separation (posterization) in the heavily compressed image are exaggerating the appearance of surface unevenness.

[Turbine D]

The gearbox is an aluminum sand casting, not an investment casting where surfaces as cast are much smoother. Almost all accessory gear boxes are sand cast either made out of aluminum or magnesium and are not polished to make them look good. Nothing new about the way the surface looks except for the crack.

[Sqwak7700]

PW1100G fan gearbox (3:1 gearing):
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/784x832/pw1100g_gear_system_f5cb6419ea85f8972db606fc1ce0041240e50306 .jpg
Shiver me timbers. With such a simple mechanical part, what could go wrong? Looks like a Rube Goldberg device.

[underfire]

As Dave noted, the planetary gear assembly is directly on the shaft...the fan is connected to the outer ring, and the shaft through the center...I believe the planetary gear assembly is made by Kawasaki...


https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1600x978/pytj3gx_f1250df94398a0211cd078f485012094a5e20d5c.jpg

[WHBM]

Shiver me timbers. With such a simple mechanical part, what could go wrong? Looks like a Rube Goldberg device.
C'mon guys, it's a straightforward Epicyclic sun & planet gear train, been used for all sorts of uses for about 100 years or more. For Pratt & Whitney, the good old PT6 turboprop, like most turboprops, had its reduction gearing using the same concept, though that had three intermediate carrier gears instead of five.

[lomapaseo]

Also, where is the subject gearbox in this thread title?

Can someone tell me which way the Fan turns, the LPC turns, the HPC turns, the HPT turns and the LPT turns ? I'm getting mixed up with two rotor system and a fan as a separate rotor?

[Sallyann1234]

Would there normally be sufficient stress on the casing to cause such a fracture, unless it had a manufacturing fault?

Surely the casing is a container, rather than a load-bearing component.

[DaveReidUK]

Also, where is the subject gearbox in this thread title?

Can someone tell me which way the Fan turns, the LPC turns, the HPC turns, the HPT turns and the LPT turns ? I'm getting mixed up with two rotor system and a fan as a separate rotor?

5Bg8Nk_isDc

[FE Hoppy]

C'mon guys, it's a straightforward Epicyclic sun & planet gear train, been used for all sorts of uses for about 100 years or more. For Pratt & Whitney, the good old PT6 turboprop, like most turboprops, had its reduction gearing using the same concept, though that had three intermediate carrier gears instead of five.
except it's sun and stars. They are fixed.

[FE Hoppy]

Also, where is the subject gearbox in this thread title?

Can someone tell me which way the Fan turns, the LPC turns, the HPC turns, the HPT turns and the LPT turns ? I'm getting mixed up with two rotor system and a fan as a separate rotor?

HPT, HPC and FAN all turn anticlockwise viewed from the front. LPT and LPC turn the opposite way.

[underfire]

Also, where is the subject gearbox in this thread title?

Located at 8 oclock positionhttps://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1920x1403/rolls_royce_trent_xwb_engine_cut_out_873776c44848acfe01efe95 dc087a5d191f0f45e.jpg

[underfire]

An example:
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/780x405/aeroengine_accessory_drive_train_780x405_fc27b75e892745ce6ac af4c9e44d6282a86fc18f.jpg

[The Ancient Geek]

This has nothing to do with the main gearbox driving the fan, the crack is in the auxiliary gearbox.
A simple case crack is unlikely, something inside probably cut loose and gave it a whack.

[DaveReidUK]

except it's sun and stars. They are fixed.

It's still referred to as a sun-and-planet gear, regardless of whether it's the ring gear that's fixed or (as in the case of the PW GTF) the planet carrier.

[glad rag]

I was thinking the same myself, maybe the lighting but it doesn't give the impression of a beautifully finished component.

Casting or forging ?

It's the place where "Made in China" was ground out and surface finish re-applied.

[FE Hoppy]

It's still referred to as a sun-and-planet gear, regardless of whether it's the ring gear that's fixed or (as in the case of the PW GTF) the planet carrier.
not according to the PW operating instructions, the AMP, the MTM and the FCOM all of which I have open in front of me

[tdracer]

This has nothing to do with the main gearbox driving the fan, the crack is in the auxiliary gearbox.
A simple case crack is unlikely, something inside probably cut loose and gave it a whack.

Agreed - likely an internal failure caused the case crack. There were a couple events early on with the GEnx-1B (787) where an internal gear failure actually punched a hole in the gearbox (yes, the design was changed to address it).
Planetary gearboxes are commonly used for very high torque applications since it distributes the loads through multiple gears and hence lessens the loads on the individual gears. Planetary gear boxes were common on the early automobiles for that reason - the metallurgy at the time had difficulty making the gears strong enough for a conventional gearbox to last (IIRC the Ford Model T used a planetary gear box). As the metallurgy improved, planetary gearboxes fell out of favor due to their greater complexity and manufacturing costs.
Hoppy - "planetary gear-set" is a rather generic term - commonly used regardless of whether the 'planet' gears are fixed or rotating.
Just curious - is the fan gearbox (regardless of what it's called) readily visible/accessible on the PW1100 series engines? Or is it pretty much covered up and hidden?

[DaveReidUK]

Just curious - is the fan gearbox (regardless of what it's called) readily visible/accessible on the PW1100 series engines? Or is it pretty much covered up and hidden?

Some assembly sequences near the start of this video:

vgQgEftEd8c

It looks like it's pretty well impossible to see the fan gearbox in situ in an assembled engine.

[FE Hoppy]

Some assembly sequences near the start of this video:

vgQgEftEd8c

It looks like it's pretty well impossible to see the fan gearbox in situ in an assembled engine.

Yep can't see it unless you take the fan off.

[Buster15]

Would there normally be sufficient stress on the casing to cause such a fracture, unless it had a manufacturing fault?

Surely the casing is a container, rather than a load-bearing component.

In practice it has both functions.
There will be an amount of oil in the gearbox but the front and rear faces of the alloy casing have mounts for the various systems driven by the gears.

These would include Fuel Systems, Oil Pump, Hydraulic Systems and ElectricalPower Generator.
Some of these can be reasonably heavy hence load bearing.

However, compared to the extremely highly stressed engine components the alloy gearbox casings would have low stresses.

It is possible that at the end of the manufacturing process the casing would be heat treated to normalise the stresses.

[FE Hoppy]

Agreed - likely an internal failure caused the case crack. There were a couple events early on with the GEnx-1B (787) where an internal gear failure actually punched a hole in the gearbox (yes, the design was changed to address it).
Planetary gearboxes are commonly used for very high torque applications since it distributes the loads through multiple gears and hence lessens the loads on the individual gears. Planetary gear boxes were common on the early automobiles for that reason - the metallurgy at the time had difficulty making the gears strong enough for a conventional gearbox to last (IIRC the Ford Model T used a planetary gear box). As the metallurgy improved, planetary gearboxes fell out of favor due to their greater complexity and manufacturing costs.
Hoppy - "planetary gear-set" is a rather generic term - commonly used regardless of whether the 'planet' gears are fixed or rotating.
Just curious - is the fan gearbox (regardless of what it's called) readily visible/accessible on the PW1100 series engines? Or is it pretty much covered up and hidden?

There is a difference between calling it a "planetary gear-set" and referring to the star gears as planets.
By doing so the poster is incorrectly describing the way the gearing works as planets orbit the sun gear whereas stars do not.
I only corrected the poster as he incorrectly described the gear system while glibly saying "C'mon guys, it's a straightforward Epicyclic sun & planet gear train".
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1762x890/screenshot_2018_11_30_at_21_36_23_3cfa3bb4e92abd29cc56f17f0c 0a2b10feb588af.png

[DaveReidUK]

There is a difference between calling it a "planetary gear-set" and referring to the star gears as planets.
By doing so the poster is incorrectly describing the way the gearing works as planets orbit the sun gear whereas stars do not.
I only corrected the poster as he incorrectly described the gear system while glibly saying "C'mon guys, it's a straightforward Epicyclic sun & planet gear train".

I think we've just got to the stage where we're arguing about definitions, which is rarely productive.

I'd favour this one (my emphases):

"An epicylic gear is a planetary gear arrangement consisting of one or more planet (epicyclic) gears meshed and rotating round a central sun gear. The planet gears are also meshed and rotate within an internal ring gear. The planet gears are fixed to a planet carrier-crank arm designed to rotate on the same centre as the sun gear. Only one planet-carrier/crank arm is used in a single epicyclic gear train. This complicated arrangement has a number of modes of operation depending on which members are locked."

The three possible modes of operation are then described as:

Planetary arrangement: The ring gear is fixed
Star arrangement: The planetary arm is fixed
Sun arrangement: The sun gear is fixed

Epicyclic Gears (http://www.roymech.co.uk/Useful_Tables/Drive/Epi_cyclic_gears.html)

So it looks like we're all correct. :O

[Ancient-Mariner]

In underfire's picture, please what is the difference between an EDG - Electric Drive Generator and a PMA - Permanent Magnetic Alternator?

[tdracer]

In underfire's picture, please what is the difference between an EDG - Electric Drive Generator and a PMA - Permanent Magnetic Alternator?

Again, not particularly familiar with the PW1100, but Pratt routinely uses a PMA to power the FADEC. FADEC power is separate from the aircraft Generator so that the FADEC will remain powered (and able to control the engine) regardless of whatever failures might affect the aircraft electrical power system.

[Ancient-Mariner]

Thanks for that.
Clive