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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 30th Nov 2010, 01:52
  #1461 (permalink)  
 
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The LP TB is an intershaft bearing; so, we see the IP TB (29) is beefier as it has to accommodate the LP + IP thrust loadings. The HP TB (33) is the smallest of the three; also, fewer stages than the IP.

I suspect the hot gas efflux thrust is distributed among the TBs and the turbine stators. There's also a rotational component in the gas flow that absorbs and produces rotational forces in the compressors, turbines, and stators.
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Old 30th Nov 2010, 02:53
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Whilst the media have made much of the 'heavy' crew, I very much doubt that the presence of the two extra guys made any difference whatsoever to the outcome. The captain flew it whilst the FO did the ECAMS. Apart from being able to work out the landing data and do some comms/PAs, there is very little that extra people can do...
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Old 30th Nov 2010, 03:05
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mrdeux.
I suspect from that comment that you have never been in a situation where there are cascading major problems well outside of any practised senario.

Give me a heavy EXPERIENCED crew in this A380 situation any time. I reckon 2 crew would have been feeling more than a little bit lonely.

Wunwing
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Old 30th Nov 2010, 08:00
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Wunwing, in M'deaux's glider, there is only one pilot perch, room for only one aviator, in a very simple flying device, thus he cannot fathom the complexities of very large commercial jets and multiple cascading malfunctions.
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Old 30th Nov 2010, 08:04
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If you guys knew who mrdeux was you'd be eating your words. You actually both owe him an apology.

And I agree with him.
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Old 30th Nov 2010, 08:14
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extra crew members

How come we've not heard anything about "wrestling with the controls".

They could have helped pull harder on the joystick, or looked outside for any schools, orphanages, to avoid.
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Old 30th Nov 2010, 09:26
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Multiple role FE on very long-haul flights

For 380 and other long-haul flights, why shouldn't crews be overtrained and rotated through multiple roles, including FE?

FE and captain are not the same stress level, nor the same boredom level ...

Edmund
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Old 30th Nov 2010, 10:07
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Wunwing & S...Flyer,
I've just read through a few of mrdeux's previous posts and worked out who he is. Take Kremins advice and pull your heads in. If 'mrdeux' says it, you can bank on it.
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Old 30th Nov 2010, 12:10
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If you look at mrdeux's profile, it clearly states that he is a current A380 captain. If that's not relevant experience, then I don't know what is!
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Old 30th Nov 2010, 12:56
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JFX90:
24 tonnes of this thrust comes from the fan, hence there is a force of this amount acting on the LP bearing.
I greatly doubt it.

My reasons for stating this:
1) The fan aero system includes both the rotor AND stator vanes. The rotor creates some thrust, but the stator also creates thrust by converting dynamic pressure to static (by capturing and converting swirl energy). This stator portion of fan thrust has no connection to the thrust bearing.

2) The forward face of the LPT disc assembly is a large piston area with several atmospheres' worth of static pressure applied. (This is completely separate from forces acting on the airfoils.)

Thus it's the elephants' tug-of-war I referred to earlier. The NET LOAD on the LP thrust bearing -- believe it or not -- is a small fraction of the total engine thrust. In fact -- believe it or not -- the LPT could win this tug-of-war, creating a net AFT load on the bearing, at least at some conditions.
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Old 30th Nov 2010, 14:50
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barit1

Isn't the Fan in the 72 more like 30 tonnes at Maximum? I kind of think we are saying the same things relative to the Fan's Pull. The LPT (including the intense pressure on all the parts, as you describe) is forced "Aft" by this Pressure, itself a product of the LP area spinning up the Fan? Someone had stated before (incorrectly, I believe) that the system would have no net energy if the LP pulled back while the Fan pulled forward. Yet this is exactly the process that propels the a/c forward, to include gas efflux that has escaped the LP out the back. I take your point relative to the very light loads on the LP TB. It is the vanes of the LP Turbine that convert the gas Pressure to (Fan) motive Power. This motive Power begins at the intake of the LP, is enhanced by the IP compressors, and ignites in the HP cavity.

For me, I see the Power as a dynamic system, that in its most simple description involves seeing the forward motion as a reaction against the gases moving aft. I may be missing some details, but is this concept suitable? The Fan is resisted by the force on the LP, "nothing" more, which force "begins" at the intake, and gains power as it moves through and out the back. Everything that propels this a/c exits out the "back", whether it be hot gas, or cold "bypass". Is this correct? I have explained the Fan system to my young son as me holding a rope whilst sat in a chair, the Fan is the "opponent" pulling on me/chair, but has purchase on the floor, I do not.

Thx for your patience and knowledge here

bearfoil

To add: As the aft portion of the LP system is connected to the Forward through a rigid coupling, (Splines, etc.) and there is that hot gas signature on the aft section forward on the Shaft, my imagination places the sooty bit under the TB that may have failed. Other rings on the aft LP Shaft may coincide with positioning under Hot parts of the IP Shaft? I see the IPT as a dynamic Flow check valve, containing the massive Pressure in the IPT/LPT cavity. The failure of the Intermediate Wheel is an open topic. If fire happened at the TB area, and the TB's were damaged, the aft migration of the IPT may have caused the damage to the LPT, and the disintegration of the IT. The Carbon deposit has a well defined border at its aft limit, that is a stumper. Just musing, don't mind me.

bearfoil

Last edited by bearfoil; 30th Nov 2010 at 15:18.
 
Old 30th Nov 2010, 17:45
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Wow! MrDeaux may be a current A380 pilot. If so, with his statement that apparently 3 more experienced pilots in the CP just have nothing to offer.....I would offer that (Top Gun semi-quote) his ego is writing checks his body can't cash. I flew 2 and 3 engine commercial jets around the world for 30 years as a line pilot and line CKA. I never felt more assured of a better resolution of a potential major inflight incident than when I flew DC-10's and was fortunate to have experienced and grizzled professional flight engineers with me on the flight deck. When the FE's went away, it was a sad day. I never flew with ANY fellow airline pilot in the days since FE's who (when asked) expressed that it was a good thing to do away with FE's. I encountered many inflight incidents and emergencies with 2 pilot jets. The easiest to deal with were those when augmented crews were aboard for long haul. Yes, there was but ONE command authority....but other experienced pilot human brains...present in the fight were ALWAYS preferred in an effort to better cover all bases, particularly when all bases were loaded, the count was full; and I as pitcher (command Captain) faced a deadly batter who could easily end my game in a fatal way with an error on my part.
I flew single and dual seat fighters in the military with more than 100 carrier arrested landings day and night and blue water ops. Did I have a huge ego; you bet. Could I escape the planes if my decision was wrong? Yes, within the confines of the envelope of the ejection seat.
Did I learn to appreciate the aviating/systems experience and knowledge of additional hands on deck in later years in aircraft with many folks behind the flight deck door as well as my own butt on aircraft I could not escape from in the event of perhaps really bad judgement? YES.
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Old 30th Nov 2010, 18:27
  #1473 (permalink)  
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OK I'll stop lurking and head goes above parapet.

If we really, really want to get fundamental over this, bear is of course right, it's to do with the hot gas signature and the energy being released by the combustion process.

The super scripts and subscripts are getting a trifle mangled here - the square should be a triangle and they should carry the standard state symbol that looks like a flying saucer but here goes anyway:

The theoretical maximum energy available from the engine is directly proportionate to the relationship:

 G =  H (c) - T S (system)

- which is one way of writing the second law of thermodynamics. (Yes, yes standard conditions.)

G is measuring the energy ‘available’ from/to a reaction relative to equilibrium - hence the name (Gibbs) free energy and which gives us a handle on the maximum thrust theoretically available.
 H (c) is the enthalpy of combustion of the fuel
T is the temperature in Kelvin
 S (system) is the entropy change of the chemicals in the system

• we have the mother of an exothermic reaction going on here as the fuel burns making H negative which in turn makes G negative
• we have a large positive value for T but the - sign in front of TS makes this contribution negative too, making G negative, making the reaction more likely statistically.
• we also have a large, positive, S (sys) as we are forming lots of gas molecules on the right hand side of the combustion reaction, the - sign in front of TS makes this contribution negative too, making G negative, making the reaction more likely statistically.

If G is negative this implies that the reaction will be spontaneous (on energetic grounds) and will make energy available to do work on shoving the 380 hard.

How this energy gets transferred around the engine is for the engineers and not mere chemists.....

Last edited by chris weston; 30th Nov 2010 at 21:24.
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Old 30th Nov 2010, 19:25
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I rather like the squares, Delta makes it somehow, Egyptian.

bear
 
Old 30th Nov 2010, 19:57
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If we really, really want to get fundamental over this
It would be a relief if that was possible, however I fear that the current attempt to set a new standard of obtuseness will continue.
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Old 30th Nov 2010, 20:29
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SKS

Take the hint before you dig the hole deeper.

After Capt K and Trent posted, I went and had a look myself - yes, I'm pretty sure I know who Mr Deaux is as well and in that context yours and WW's posts attacking him are hilarious.

And yes, I agree with him and Capt K about the 2 pilot crew, despite you mis-representing what Mr D said.


n
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Old 30th Nov 2010, 21:49
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"fan produces 24 tonnes of thrust"....I greatly doubt it.

My reasons for stating this:
1) The fan aero system includes both the rotor AND stator vanes. The rotor creates some thrust, but the stator also creates thrust by converting dynamic pressure to static (by capturing and converting swirl energy). This stator portion of fan thrust has no connection to the thrust bearing.

2) The forward face of the LPT disc assembly is a large piston area with several atmospheres' worth of static pressure applied. (This is completely separate from forces acting on the airfoils.)
To what extent to you "greatly doubt it"?

For a high by-pass turbofan engine producing 30 tonnes of thrust overall at full power, what percentage of that thrust do you estimate is produced by the fan, the fan stators and jet efflux?
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Old 30th Nov 2010, 22:19
  #1478 (permalink)  
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JFZ90

You forgot the part of barit1's post that makes your comment look sly, at the very least. He is telling you that there is not 24 tonnes of thrust on the Thrust Bearing. Your out of context post is low, unless you don't get that the Thrust Bearing has little to do with "Thrust".

The Fan is a PROXY for gas that would otherwise exhaust out the exit. Without the Fan, 36 tonnes of thrust would still propel the a/c, but at extremes of noise, and waste. Much quieter to push larger volumes of slower, quieter and colder air with a slower, much larger wheel.

Perhaps a reread, eh?

bear
 
Old 30th Nov 2010, 22:35
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JFZ90

You forgot the part of barit1's post that makes your comment look sly, at the very least. He is telling you that there is not 24 tonnes of thrust on the Thrust Bearing. Your out of context post is low, unless you don't get that the Thrust Bearing has little to do with "Thrust".

The Fan is a PROXY for gas that would otherwise exhaust out the exit. Without the Fan, 36 tonnes of thrust would still propel the a/c, but at extremes of noise, and waste. Much quieter to push larger volumes of slower, quieter and colder air with a slower, much larger wheel.

Perhaps a reread, eh?

bear
Not at all, just lazy quoting.

He "greatly doubted" my approximated explanation of the thrust due to the fan.

I maybe mistaken, but I would expect any fan stator thrust to be minor, I thought their purpose was principally to smooth the mass flow post the fan, increasing efficiency, not to mention support the cowling!

What do you think he will say for the proportion of thrust from the fan stator transmitted as forward thrust into the casing - 50%? 20%? 5%? 2%?
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Old 30th Nov 2010, 22:45
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I read his post quite differently than you. As a matter of fact, the Thrust Bearing is indeed virtually "Neutral" at most Power Settings. My guess is a too rapid decel would subject the Fan to Windmill, and an uncomfortable disparity in Fan LP might ensue? The thrust that flows through the LP turns into cold air in bypass, eh? Same power, different exit?

KBPsen,
Who is it that is being obtuse here? Shun the scoundrel, attack his posts without anything to offer of value, there's the ticket!!

bear
 

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