Qantas latest engine out
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Rushing to bearfoil defense, it depends on POV.
From an aero standpoint, bear's post #4 is exactly right.
From a mechanical standpoint, it's of course sdrawkcab.
From an aero standpoint, bear's post #4 is exactly right.
From a mechanical standpoint, it's of course sdrawkcab.
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So, What Drives What???
Perhaps this Pratt & Whitney video will answer the question of what drives what. Listen to the audio as the turbines and their roles are discussed.
I believe the failure of this engine, if it the same as the Qantas SFO engine failure, would be turbine blade failure related, not compressor blade related. The SFO engine failure was uncontained as well.
I believe the failure of this engine, if it the same as the Qantas SFO engine failure, would be turbine blade failure related, not compressor blade related. The SFO engine failure was uncontained as well.
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The earliest HPgas (jet) engines had piston engines driving the compressor, so the concept of drive/driven was established straightaway, imo. The thrust came from the exhaust. Long since retired, turbojets were noisy, wasteful, and high maintenance. So FANjets derive propulsion from the mechanical capture of the "exhaust", expressed in the Low Pressure Compressor (The Fan), which is driven by the Low Pressure Turbines at the back end. IMHO, and grateful to TD and barit1 to keep us all honest.
When a large wheel stops being driven, and starts to drive, bad things can happen. Worse things happen when drivers start to get driven (Turbine).
Or, a massive propellor in high Pitch in cruise that loses hydraulics and cycles to Low, (Flat) Pitch. Runaway Prop. Runaway Turbine. (Overspeed, nasty).
When a large wheel stops being driven, and starts to drive, bad things can happen. Worse things happen when drivers start to get driven (Turbine).
Or, a massive propellor in high Pitch in cruise that loses hydraulics and cycles to Low, (Flat) Pitch. Runaway Prop. Runaway Turbine. (Overspeed, nasty).
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Hi Bear,
In a purist sense, be it a fan-less jet engine or a turbo fan engine, the turbine or turbines drive the compressor or compressor/fan combination. The only time the compressor or compressor/fan combination "drives" is during the start operation. Here, the compressor or compressor/fan combination through an auxiliary energy source initiates rotation, driving the turbine/turbines while compressing the air delivered to the combustor. When the combustor delivered air pressure is sufficient, fuel flowing into the combustor is ignited. From that point onward, the turbine/turbines drive the compressor or compressor/fan combination.
Hope this clarifies this discussion.
In a purist sense, be it a fan-less jet engine or a turbo fan engine, the turbine or turbines drive the compressor or compressor/fan combination. The only time the compressor or compressor/fan combination "drives" is during the start operation. Here, the compressor or compressor/fan combination through an auxiliary energy source initiates rotation, driving the turbine/turbines while compressing the air delivered to the combustor. When the combustor delivered air pressure is sufficient, fuel flowing into the combustor is ignited. From that point onward, the turbine/turbines drive the compressor or compressor/fan combination.
Hope this clarifies this discussion.
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In fact, one will regularly see a negative EPR (measured from inlet to outlet N1} when an RB-211 is at flight idle during descent, meaning the fan is being driven by inlet airflow, as opposed to gaseous outflow from the combustor....never heard it to be an issue, as the intermediate, and hi pressure compressor were absorbing the load and keeping the gas path flowing in the "right direction"..
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next time Qantas roll out that old chest nut of WORLDS BEST PRACTICE i think some one needs to ask for the definition,it may high light a few of the problems Qantas are going through at the moment.
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My take is that the process being reported on in the papers is normal to the operation of a fleet and unlikely to play any significance to the greater majority of passengers
Too many headlines, too often ???
The general public are not safety experts. Perception for them is often reality. And if there is a growing perception among the general flying public that Qantas has a problem, it has a problem.
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So the secret is to manage risk, shower the mushrooms with BS, and act as if it is not a thang..........Say, what about that duff stub pipe, Hans?
If the non-public, the Pros, engineers, and safety guys think there is a problem, that is a Horse of a different Hue. And kudos to PPRuNe.
I kind of hope no one reads this, but I will say this. A loss of airspeed reads is nothing to manage as/if...... Neither is teaching the wrong things to do at STALLWARN. Allowing suspicions to fester on the Hull while the industry changes out (got a "round tuit"?) seemingly "redundant" probes is another thing. "Marginal" service life of TurboFans onwing is another. Maybe the Public isn't so dumb after all?
Fortunately, there are no orphanages or hospitals any where near TASIL.
TD. Well, you are exactly right. I need the works in a word, however, and I know turbine can no drive unless it is also driven. No free lunch?
If the non-public, the Pros, engineers, and safety guys think there is a problem, that is a Horse of a different Hue. And kudos to PPRuNe.
I kind of hope no one reads this, but I will say this. A loss of airspeed reads is nothing to manage as/if...... Neither is teaching the wrong things to do at STALLWARN. Allowing suspicions to fester on the Hull while the industry changes out (got a "round tuit"?) seemingly "redundant" probes is another thing. "Marginal" service life of TurboFans onwing is another. Maybe the Public isn't so dumb after all?
Fortunately, there are no orphanages or hospitals any where near TASIL.
TD. Well, you are exactly right. I need the works in a word, however, and I know turbine can no drive unless it is also driven. No free lunch?
Last edited by bearfoil; 17th Jul 2011 at 23:10.
Not 767 mate. The short 767 transits mean the compressor case doesn't cool down between flights. It is about the blade tip clearance.
Before you get upset with this question, I realize EDTO for B747 does not come into effect until 2015, however engine failures at an airline where that same engine is used on B767 twins, supposedly maintained to EDTO standards, it appears to me no-one is counting these failures in their IFSD rate calculations.
I would have thought they would have figured somewhere in their statistical analysis for EDTO. Are QANTAS still swapping engines between B767 and B747 like they used to many years ago?
Nunc est bibendum
I would have thought they would have figured somewhere in their statistical analysis for EDTO. Are QANTAS still swapping engines between B767 and B747 like they used to many years ago?
As far as I recall, the Rollers on the current 767s are not the same as those on the 744 and we got the first Roller 767 in 2001/02. Therefore they've never been swapped. The CF6s on the 300s are not the same as the CF6s on the 744s and they've never been swapped. That only leaves the Pratts that were on the 767-200s and I'm not sure what 'overlap' there was from when we got the first 767-200 in about the mid 80s and Pratt engined jumbos.
It is worthwhile reading the ATSB report released in May 2011 reached at the link below.
The latest fix for this ongoing HPC stage 1 blade problem is SB RB211-72-GO36 which was issued in Feb 2009. This covers revised geometry blades.
At the time of issuance of the report, only 18% of QF's engines had this SB incorporated. At that time there was no apparent urgency to implement the SB, but the SB would be incorporated when other work was required on the HPC:
"The operator is continuing to embody SB RB211-72- G036, issued in 2009, at engine shop visits where the HPC module is removed. However, should the rate of failures increase significantly, a review of current modification policy will be undertaken."
I don't know if the failure rate has increased significantly. But the perception is that it has, certainly more than the 0.8 events per year predicted by RR and quoted in the ATSB report.
The question remains as to whether QF has increased the pace of SB implementation since then.
If QF has not voluntarily sped up the SB implementation, then CASA needs to urgently review this case.
http://www.atsb.gov.au/media/3422442...040.pdf#page=9
The latest fix for this ongoing HPC stage 1 blade problem is SB RB211-72-GO36 which was issued in Feb 2009. This covers revised geometry blades.
At the time of issuance of the report, only 18% of QF's engines had this SB incorporated. At that time there was no apparent urgency to implement the SB, but the SB would be incorporated when other work was required on the HPC:
"The operator is continuing to embody SB RB211-72- G036, issued in 2009, at engine shop visits where the HPC module is removed. However, should the rate of failures increase significantly, a review of current modification policy will be undertaken."
I don't know if the failure rate has increased significantly. But the perception is that it has, certainly more than the 0.8 events per year predicted by RR and quoted in the ATSB report.
The question remains as to whether QF has increased the pace of SB implementation since then.
If QF has not voluntarily sped up the SB implementation, then CASA needs to urgently review this case.
http://www.atsb.gov.au/media/3422442...040.pdf#page=9
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How many incidents?
March 2010: QF5 SYD-SIN VH-OJ?
April 2010: QF1 BKK-LHR VH-OJF
September 2010: QF74 SFO-SYD VH-OJP
November 2010: QF6 SIN-SYD VH-OJD
I haven't even bothered to keep track this year. I was cabin crew on board one of these flights and let me tell you, it can be quite a scary event. These failures can be pretty spectacular. When you're only 800 feet off the deck and the entire cabin is lit up bright orange from an engine that has just "exploded", the last place you want to be in in the air.
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B747 and B767 P&W Engine Swap
The P&W engines on the B747 and B767 were not interchangeable. They were like chalk and cheese. 747 has cable driven air operated fan reversers, 767 was hydraulic with screwjacks. Cowlings different on both types, 767 was of the FADEC thrust era wheras the 747 was manual. Instructor told us that the engine overhaul shop found only seven parts that were interchangeable between the engine models.
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RB211's are interchangeable between the 747 & 767. Three mechanical items, data plate and rating plug. Has to be tested to 'H' standard at the build stage which they mostly are.
CF6's can be interchanged too, but only with the one and only FADEC 767.
CF6's can be interchanged too, but only with the one and only FADEC 767.
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From what I hear an Avalon Manager stated that there were high vibes during an engine run on 3 x 'ER' engines and that his facility was too blame...
Someone also apparently denied this and suggested that it was more to do with many, many layers of lube still covering the blade roots and spinner on arrival...
Is the Manager hiding something by blaming those that are not guilty?
Someone also apparently denied this and suggested that it was more to do with many, many layers of lube still covering the blade roots and spinner on arrival...
Is the Manager hiding something by blaming those that are not guilty?