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#41 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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No worries. This aircraft is quite different for sure. The schematic that show the dual ECS systems each driven by two electric motors is quite a shock to me. The amount of horsepower/electric current needed to maintain pressure and condition the air properly must be staggering. In the schematic it also shows each engine with dual starter/gens and the APU with dual starter/gens. That is one electrically HUNGRY aircraft. Basically a flying power station..lol. The electric system is very elaborate...including 270 VDC systems...yes that's DC. See page 9 on this link: http://www.boeing.com/commercial/aer...7_article2.pdf
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Amazing feat of engineering. |
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#42 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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Here's an article on the maker of batteries. They were unprofitable even before this incident (or at least the lithium-ion battery part of their business was). This may kill them I'm afraid. Unless they find out that it wasn't the batteries' fault after all.
Boeing 787 Deal Puts Battery Maker GS Yuasa in Spotlight
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A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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#43 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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new report now claiming there is evidence at least one of the batteries was not overcharged.
http://www.cnn.com/2013/01/21/travel...html?hpt=hp_t3
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So it may be possible that the battery is used to start the APU as well as act as a buffer during momentary high demand functions in flight. However until I see better sources it will be difficult to get an accurate grasp of the exact nature that particular battery is used on this new fangled aireoplane. |
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#44 |
Penultimate Amazing
Join Date: Apr 2003
Location: 16 miles from 7 lakes
Posts: 11,032
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My understanding is that the battery IS the APU--there is no turbine running systems when the engines are not running.
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"Political correctness is a doctrine,...,which holds forth the proposition that it is entirely possible to pick up a turd by the clean end." "I pointed out that his argument was wrong in every particular, but he rightfully took me to task for attacking only the weak points." Myriad http://forums.randi.org/showthread.php?postid=6853275#post6853275 |
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#45 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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See thats where definitions get mixed up in the media. The term APU is mainly used for the small turbine that drives generators and/or provide limited bleed air and hydraulics. The APU battery would typically be the battery that starts that small turbine.
A particular batteries use is usually indicated by the word accompanying it. Main batteries Back up batteries Emergency batteries standby gyro battery emergency lighting batteries An APU could be a battery its self since a battery is a source of auxiliary power and any manufacturer could label it how they want to. The term APU is used almost exclusively to describe the small turbine engine. That terminology is so typical that wiki makes no mention of alternate uses. http://en.wikipedia.org/wiki/Auxiliary_power_unit Also..the rudimentary schematic in my previous links show a battery primarily connected to the APU and it also shows it connected to main bus. However this schematic is almost certainly wrong or extremely limited. It seems to me it is very likely there are more batteries installed on this aircraft. IMO that battery is way too small to be effective in much beyond the normal duties of supplying power during large momentary loads such as APU or engine start or supplementing power momentarily when one or more of the 787s very large electric motors has a large demand. Not saying it couldn't have a drastically different role and terminology than traditional aircraft. It certainly could. I just haven't seen anything yet to indicate or verify that. ETA: also...APU's are typically shutdown after take off. So on a typical aircraft....the battery provides the massive load to start the APU. Once the APU is online it has generators that power systems. Then when its time to start main engines (that have starter/gens as the 787 does) the APU gen provides power along with a battery to start the main engines. When the main engines are up and running...the dual stater/gens provide all power for all ships operation. The APU on some aircraft is typically left on until after take off as an emergency back up. The APU will typically be secured at some time shortly after take-off. The APU will be restarted in the air prior to landing again to provide emergency back up. So yes...during cruise the APU is typically shut down and only turbines running are the main engines which should be providing 100% of electrical power to systems.....including recharging batteries. |
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#46 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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From the article posted earlier regarding the "no bleed architecture"
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The interaction of particular airports GPU's should be looked at as well. Sometimes a common link between failing components is a GPU that is AFU at a particular location. We have had GPUs take out many electronic components in the past prior to discovering a problem with it. |
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#47 |
Penultimate Amazing
Join Date: Nov 2002
Location: Directly under a deadly chemtrail
Posts: 19,794
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There are two main batteries. The APU start battery, and a main battery. Both batteries are primarily used for backup power. They can be used to start the APU and start the main engines, but that would be unusual. Ground power would normally be used. They can also power other things in an emergency, such as some flight instruments. They are not big enough to supply power for very long. No battery would be.
The 787 has a massive turbine powered APU for ground and backup power. The 787 can be dispatched with the APU inoperative, if necessary. It doesn't really need it to fly, even on ETOPS flights. Each 787 engine has 2 generators, and the APU has 2 generators, making a total of 6. There is a lot of redundant power generating capability. Including a backup RAT.
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What a fool believes, no wise man has the power to reason away. What seems to be, is always better than nothing. 2 prints, same midtarsal crock..., I mean break? |
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#48 |
Penultimate Amazing
Join Date: Nov 2002
Location: Directly under a deadly chemtrail
Posts: 19,794
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The 777 also has 2 generators per engine, and it can also be dispatched with it's APU inoperative.
The 747-400 series has an APU, but it's not expected that it would ever be used in flight. I have read that there is no normal in-flight start procedure for the 744's APU. The 744 has 4 engines, of course. So, it has 4 generators. In addition, the 744's engines are capable of windmilling and continuing to supply electrical and hydraulic power even if they quit running. |
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What a fool believes, no wise man has the power to reason away. What seems to be, is always better than nothing. 2 prints, same midtarsal crock..., I mean break? |
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#49 |
Penultimate Amazing
Join Date: Apr 2003
Location: 16 miles from 7 lakes
Posts: 11,032
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I stand corrected.
Must have been confused in that the APU is not used in flight... |
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"Political correctness is a doctrine,...,which holds forth the proposition that it is entirely possible to pick up a turd by the clean end." "I pointed out that his argument was wrong in every particular, but he rightfully took me to task for attacking only the weak points." Myriad http://forums.randi.org/showthread.php?postid=6853275#post6853275 |
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#50 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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Now that makes everything quite clear. So this is the APU battery. And when we say APU battery we mean the battery that primarily there to start the APU when needed and then is recharged after APU start. This is a fairly standard configuration for aircraft with starter/gens on APU and engines.
But we also now know that according to FDR info the APU battery did not see an over voltage scenario. This again puts the onus back on the battery manufacturer. I would not want to be them right now....lol. ETA: it does state in the aviationweel article that the other "main" battery was the one that overheated. It seems likley these batteries are probably the same architecture if not the same part number. It also states in the article that the manufacturer of the batteries also makes the charging system. |
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#51 |
Illuminator
Join Date: Aug 2006
Posts: 4,080
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#52 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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#53 |
Philosopher
Join Date: Jul 2006
Posts: 6,387
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I just want to thank the experts here, especially 383LQ4SS, for these detailed explanations. "Putting the E in jrEf" as they say.
Here's a question---probably unrelated. Do you have a sense of how much power and weight (including cabling) goes into the seatback-entertainment screens? It must be huge. |
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#54 |
Illuminator
Join Date: Aug 2006
Posts: 4,080
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#55 |
post-pre-born
Join Date: Dec 2003
Location: Santa Barbara, CA
Posts: 22,522
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Fitter, I don't understand that reply. Can you say more.
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#56 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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Understood. I do not know enough about the specifics of usuable air across the N2/N3 sections on 747's in flight. But at 250-350 kts I would not doubt it could still spin a decent enough to provide some system power. Especially hydraulics. I am sure someone has read a 747 manual and can confirm or deny.
For those that dont know...the main fan (N1) does not directly drive hydraulic pumps or generators. Those are driven by the inner core or the high pressure turbine (N2 and/or N3). When looking from the front the cross section of the high pressure turbine is significantly smaller than the large low pressure fan section. It really hugs the center of the engine. As a matter of fact it can be difficult to even see.This high pressure section is directly connected to the gearbox typically...and in no way connected to the low pressure fan (the big one in front, N1). N1, N2 N3 are speeds of the various turbine sections. Typically displayed in the cockpit as % of RPM...such as 99.1% N1. This would mean the main fan is turning 99.1% of rated design rpm. |
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#57 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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Hmmm..I really dont. I have never worked on one of the ultra modern large jets with all the interior gizmos. I too would guess it to be quite significant. A portion of that may be offset on modern aircraft that incorporate LED lighting. LED lighting is ideal for use in passenger jets for many reasons.
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#58 |
Scholar
Join Date: Jun 2010
Posts: 103
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British Airways flight 9 ( Speedbird 9 ) which suffered a four engine flameout due to volcanic ash ingestion over Indonesia, had both Hydraulic and (Intermittant) electrical power from its windmilling engines.
ETA: I have seen full hydraulic pressure from a C-130 Allison T56 engine during airstarts prior to ignition (<16%rpm), when doing multiple air tests. |
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#59 |
post-pre-born
Join Date: Dec 2003
Location: Santa Barbara, CA
Posts: 22,522
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#60 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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The high pressure section (n2) provides the usuable thrust/energy to the LP turbine (n1)...which in turn spins the large LP fan at the front.
here is a decent video. http://flyopia.com/turbine-videos-ho...-engines-work/ Its basically a jet engine in the middle sandwiched by a turbine at the rear to extract thrust energy that turns the front fan. When I say not connected...I mean mechanically connected. |
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#61 |
post-pre-born
Join Date: Dec 2003
Location: Santa Barbara, CA
Posts: 22,522
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#62 |
Illuminator
Join Date: Aug 2006
Posts: 4,080
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Boeing 787s grounded by Japan
Sezme, it provides a visual indication that the fan is turning. On Rolls-Royce maintainers also use it to locate the number one blade for maintenance purposes. Not sure if GE uses it for blade identification or not, I've only worked on fighter engines from them.
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#63 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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__________________
A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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#64 |
Director of Hatcheries and Conditioning
Join Date: Jul 2002
Location: Waiting for the pod bay door to open.
Posts: 38,610
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If anyone was hoping for a quick fix, it's not going to happen. Boeing will have to demonstrate that what it is proposing works to the satisfaction of the NTSB and FAA, then implement that on each plane.
It will also have to fly the batteries around the to the planes on the ground, but transporting them as standard cargo now is also a problem. They aren't safe for that, either. Airlines that have the 787 are reportedly making plans out for up to six months for alternatives. |
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Continually pushing the boundaries of mediocrity. Everything is possible, but not everything is probable. For if a man pretend to me that God hath spoken to him supernaturally, and immediately, and I make doubt of it, I cannot easily perceive what argument he can produce to oblige me to believe it. Hobbes |
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#65 |
Graduate Poster
Join Date: Dec 2009
Location: UK
Posts: 1,696
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#66 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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Setback to Boeing’s Hopes for Longer Range for 787
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A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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#67 |
Scholar
Join Date: Jun 2010
Posts: 103
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Yep thats a procedure in the Flight Manual known as a "Buddy Start" used to start an engine with an inoperative starter motor. I have done one for practice and it is very unpleasant and even though carried out on a concrete pad still resulted in the aircraft being peppered with debris.
Our prefered procedure was to carry out a "windmill taxi start" which involves setting the propellor blades on the inoperative engine to 90 degrees than charging down the runway and carrying out essentially the airstart procedure and reducing the blade angle to cause the propellor to spin, until either 16% rpm, 100 Kts or 3000 feet of runway remained at which point we carried out an abort and all being well the engine accelerated to on speed. These were massive examples of crew coordination with all three on the flight deck kept very busy. Good times. now back to the scheduled programme |
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"It couldn't be that all the pious people are liars, couldn't be an artifact of confirmation bias, a product of groupthink,a mass delusion , an emperors new clothes style fear of exclusion" Tim Minchin "Thank you god" |
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#68 |
No longer the 1
Join Date: Apr 2007
Posts: 19,198
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As human right is always something given, it always in reality reduces to the right which men give, "concede," to each other. If the right to existence is conceded to new-born children, then they have the right; if it is not conceded to them, as was the case among the Spartans and ancient Romans, then they do not have it. For only society can give or concede it to them; they themselves cannot take it, or give it to themselves. |
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#69 |
Scholar
Join Date: Jun 2010
Posts: 103
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__________________
"It couldn't be that all the pious people are liars, couldn't be an artifact of confirmation bias, a product of groupthink,a mass delusion , an emperors new clothes style fear of exclusion" Tim Minchin "Thank you god" |
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#70 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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More on the shortcomings of the previous design and testing regime, and the new design:
Initial Tests of Battery by Boeing Fell Short |
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A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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#71 |
Penultimate Amazing
Join Date: Nov 2002
Location: Directly under a deadly chemtrail
Posts: 19,794
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__________________
What a fool believes, no wise man has the power to reason away. What seems to be, is always better than nothing. 2 prints, same midtarsal crock..., I mean break? |
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#72 |
Penultimate Amazing
Join Date: Nov 2002
Location: Directly under a deadly chemtrail
Posts: 19,794
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__________________
What a fool believes, no wise man has the power to reason away. What seems to be, is always better than nothing. 2 prints, same midtarsal crock..., I mean break? |
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#73 |
Philosopher
Join Date: Apr 2007
Posts: 6,848
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Having the new batteries able to vent gases outside the plane sounds like a major rework; surely you can't just punch a hole in the fuselage and seal a tube to it that leads to the battery containment? Wouldn't you then have a whole bunch of new concerns, like temperature & pressure variations, water ingress & icing, robustness & resilience, etc. ?
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Simple probability tells us that we should expect coincidences, and simple psychology tells us that we'll remember the ones we notice... |
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#74 |
Penultimate Amazing
Join Date: Nov 2002
Location: Directly under a deadly chemtrail
Posts: 19,794
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__________________
What a fool believes, no wise man has the power to reason away. What seems to be, is always better than nothing. 2 prints, same midtarsal crock..., I mean break? |
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#75 |
Director of Hatcheries and Conditioning
Join Date: Jul 2002
Location: Waiting for the pod bay door to open.
Posts: 38,610
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They haven't found the root cause of the battery failures, so they are effectively going to mitigate the effects of a fire more effectively, and make the battery design more robust. This may be enough to get them flying again, but it's going to take longer than weeks to get that fully tested and certified. Perhaps Boeing was using '787' time to make the claim.
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Continually pushing the boundaries of mediocrity. Everything is possible, but not everything is probable. For if a man pretend to me that God hath spoken to him supernaturally, and immediately, and I make doubt of it, I cannot easily perceive what argument he can produce to oblige me to believe it. Hobbes |
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#76 |
Critical Thinker
Join Date: Jan 2009
Posts: 348
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Yeah...that wont be too big of a deal. There is already holes and tubes and vents all over that thing. Adding another likely wont be too big of a deal.
Very surprised it has taken this long. I sill think they should have redesigned for dual batteries types. Lithium as well as the more common Lead/acid. That would have given them massive flexibility in the future. |
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#77 |
Philosopher
Join Date: Apr 2007
Posts: 6,848
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__________________
Simple probability tells us that we should expect coincidences, and simple psychology tells us that we'll remember the ones we notice... |
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#78 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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There's some more details and pictures here:
Boeing Discloses Fixes for Lithium-Ion Batteries
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A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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#79 |
a carbon based life-form
Join Date: Nov 2005
Posts: 39,049
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#80 |
Penultimate Amazing
Join Date: Jan 2003
Posts: 22,755
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It's not necessarily contradictory. The enclosure may serve two or more functions, not just one.
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A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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