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Boeing Y3 As Four Engine Ultrawide Sonic Cruiser?  
User currently offline747400sp From United States of America, joined Aug 2003, 3624 posts, RR: 2
Posted (5 years 9 months 3 weeks 1 day 11 hours ago) and read 6060 times:

I was wondering could Boeing merge two of there former designs for the Y3? In 1999 Boeing had a three aisle single deck superjumbo on the design board and in 2000 they had the highspeed Sonic crusier, both designs was sheved. With the new tec of the furture, could the Y3 be a three aisle superjumbo, with four very powerful fuel effient engines, but made off the Sconic cruiser design, with the Sonic cruiser speed?

23 replies: All unread, jump to last
 
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 1, posted (5 years 9 months 3 weeks 1 day 7 hours ago) and read 6004 times:



Quoting 747400sp (Thread starter):
I was wondering could Boeing merge two of there former designs for the Y3?

They could certainly merge two (or more) former designs, but what comes out probably wouldn't be Y3. Y3 was a specific airplane from the Yellowstone study (http://en.wikipedia.org/wiki/Boeing_Yellowstone_Project). Yellowstone was a technology family. Given something like 5-10 years between the 787 and whatever comes next, it's likely that the technology will have moved on somewhat.

Quoting 747400sp (Thread starter):
With the new tec of the furture, could the Y3 be a three aisle superjumbo, with four very powerful fuel effient engines, but made off the Sconic cruiser design, with the Sonic cruiser speed?

It could be done, but fuel prices would likely dictate that it won't. The problem with going faster using technology is that, given the same technology level, the slower airplane will always be more fuel efficient. It's physically impossible for it to be otherwise. So you can never escape the tradeoff of go faster vs. burn more gas. I think you'll end up in the 787/Sonic Cruiser trade very time...we can go faster while burning the same fuel as today, or go the same speed as today and burn less fuel. Unless cost of fuel goes way down, or cost of labour goes way up, that's a pretty easy decision for most airlines.

Tom.


User currently offlineXaraB From Norway, joined Aug 2007, 210 posts, RR: 0
Reply 2, posted (5 years 9 months 3 weeks 1 day 2 hours ago) and read 5946 times:



Quoting Tdscanuck (Reply 1):
It could be done, but fuel prices would likely dictate that it won't. The problem with going faster using technology is that, given the same technology level, the slower airplane will always be more fuel efficient. It's physically impossible for it to be otherwise.

Is this always true? I read an article about the SR-71 Blackbird yesterday that stated that the aircraft actually was most efficient (miles traveled per gallon) at high Mach numbers, due to the fact that the engines would start working as ramjets instead of turbojets. I'm therefore lead to believe that any other aircraft capable of the same engine operation would become even more efficient at even higher speeds due to the way ramjets work. Am I right or wrong?

Not that this has much relevance for passenger travel anyway...



An open mind is not an empty one
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 3, posted (5 years 9 months 3 weeks 1 day 2 hours ago) and read 5941 times:



Quoting XaraB (Reply 2):

Is this always true? I read an article about the SR-71 Blackbird yesterday that stated that the aircraft actually was most efficient (miles traveled per gallon) at high Mach numbers, due to the fact that the engines would start working as ramjets instead of turbojets.

But you have to compare that to what a plane designed to travel at subsonic speeds would do. Just because a plane is most efficient at its designed speed does not equate to it being efficient. What TDSCanuck says is absolutely true; a plane designed for a lower speed will ALWAYS be more efficient (assuming equal technology) than one designed for higher speed. This is not a linear relationship, however; the cost increase for going faster increases dramatically as you approach Mach 1; and the Sonic Cruiser project was looking for ways to minimize that as much as possible. I think they were looking for an aerodynamic breakthrough; they did not find one. But what they found was that by using the same methods to go faster more efficiently they could drop the speed back and get very substantial efficiency gains. The tradeoff between speed and efficiency is very important; the faster you go the more money you can make, which is why turboprops have only been successful on short routes (turboprops are far more efficient than jets, but only at much slower speeds.) It is also why once jets appeared the airlines all ditched their recently acquired DC-7's and Connies. But Mach 1 presents a very steep efficiency penalty, and so far no aerodynamic breakthrough has lessened it. The ONLY way that faster travel than present jetliners provide will become economically viable will be if fuel becomes very cheap. What did in the SST's was fuel prices, nothing else. Before 1973 many airlines wanted Concordes, and the 2707 also had a lot of airlines interested. Doubling of fuel prices ended their prospects.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineDocLightning From United States of America, joined Nov 2005, 19727 posts, RR: 58
Reply 4, posted (5 years 9 months 3 weeks 1 day 1 hour ago) and read 5934 times:

Y3 will probably be a giant, subsonic twin with a 747 cross-section without the upper deck.

It will not have an unusual engine configuration with engines in the tail. It will not have a delta wing or BWB. It will not have staterooms for Y-class passengers. It will b a plane.


User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 5, posted (5 years 9 months 3 weeks 1 day 1 hour ago) and read 5927 times:



Quoting DocLightning (Reply 4):
Y3 will probably be a giant, subsonic twin with a 747 cross-section without the upper deck.

There is reason why the wing and tube design has maintained itself for so long. In spite of its shortcomings, every other configuration ends up having more. The BWB is the only one that has potential to replace it, but the obstacles are passenger acceptance (no windows) and stall recovery. With the acceptance of FBW the latter is easily overcome; but the first (plus evacuation difficulties) is the biggie. I don't see structural problems as being that significant; the aerodynamic efficiency gain should more than overcome the added weight needed to make a pressurized non cylindrical vessel.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineXaraB From Norway, joined Aug 2007, 210 posts, RR: 0
Reply 6, posted (5 years 9 months 3 weeks 1 day 1 hour ago) and read 5922 times:



Quoting SEPilot (Reply 3):
What TDSCanuck says is absolutely true; a plane designed for a lower speed will ALWAYS be more efficient (assuming equal technology) than one designed for higher speed. This

This is where I should have been clearer in my previous post. When both of you say "equal technology", I count engines in as well. Which is why I was wondering about these ramjets; as far as I know, you HAVE to go faster than a certain Mach number to make ramjets work at all, and I was wondering if whether my understanding that they get more efficient the faster they move is correct. If so, then ramjets would be a special case where Tdscanuck's theorem doesn't hold. I admit, it's a very narrow case and without relevancy to passenger transport, but it struck my mind while I was reading his post and thought I would ask.

Another question; the Blackbird is apparently more efficient as a ramjet than as a turbojet (probably because it was designet for high speeds). Would this be the case if it used a ramjet/turbofan (a turbofan like the ones found in newer supersonic fighters) combo? I understand this is probably related to design speed, but is there a "crossing point" within the Mach 1-5 range where it becomes so inefficient or impossible to use turbofans/jets that ram-/scramjets/rockets would be the only alternative?

Sorry to go wildly off topic...



An open mind is not an empty one
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 7, posted (5 years 9 months 3 weeks 1 day 1 hour ago) and read 5911 times:



Quoting XaraB (Reply 6):
Which is why I was wondering about these ramjets; as far as I know, you HAVE to go faster than a certain Mach number to make ramjets work at all, and I was wondering if whether my understanding that they get more efficient the faster they move is correct.

I do not believe that is the case; it would violate conservation of energy. The point is that the faster you go, the more air resistance you have to overcome, and the more energy it takes. Therefore more work is done flying at a faster speed regardless of what your propulsion is. What you are talking about is that every engine known to man has an efficiency curve, and is most efficient at a particular speed. Even if it gets more efficient as it gets faster it still has to do more work to go faster, so there will come a point where more fuel per mile is consumed to go faster. There probably is a region where the ramjet will work, but going faster will actually use less fuel. But this is only below its optimum speed; every engine/airframe combination has that. I know in my 182 that I could fly at 50-60 kts; the plane would stay in the air but if I had tried to go any distance at that speed I'm sure it would have used a lot more fuel than if I had picked up and truly flown. But I could also fly at 100-110 kts and use a little more than half the fuel as if I went at 130-135.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17044 posts, RR: 66
Reply 8, posted (5 years 9 months 3 weeks 23 hours ago) and read 5894 times:



Quoting XaraB (Reply 6):
as far as I know, you HAVE to go faster than a certain Mach number to make ramjets work at all

Well, yes. Ramjets compress air by shoving it down the intake with the aircraft's forward motion. If the plane is going to slowly, the compression is not sufficient to support combustion.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDocLightning From United States of America, joined Nov 2005, 19727 posts, RR: 58
Reply 9, posted (5 years 9 months 3 weeks 16 hours ago) and read 5771 times:



Quoting SEPilot (Reply 5):
The BWB is the only one that has potential to replace it, but the obstacles are passenger acceptance (no windows) and stall recovery.

And airport infrastructure. Can't forget that. You would actually have to get all-new jetbridges to board the thing.

And think of the cargo implications. You would have to design an entire new set of containers.

And also, if a BWB plane were to have the same height as a 744 cross-section (which it would need to be a good cargo plane), it would carry an absurdly large number of passengers because it would be about four times as wide as a 744, which would give it a capacity probably larger than the A380. How many of THOSE is B or A going to sell? 30?

Quoting XaraB (Reply 6):
Which is why I was wondering about these ramjets; as far as I know, you HAVE to go faster than a certain Mach number to make ramjets work at all, and I was wondering if whether my understanding that they get more efficient the faster they move is correct.

Think of an efficiency curve with a maximum. Below a certain speed, the efficiency is zero because you would get zero thrust. As you increase to the designed speed of a ramjet, efficiency increases until you get to the optimum speed. As you increase beyond that designed speed, efficiency begins to fall off again until you would actually be going faster than the ramjet's exhaust velocity (which is impossible), at which point the efficiency is zero again.

It's certainly conceivable that a ramjet could be designed that would burn less fuel per mile than a current turbofan. The challenge is getting up to that speed. You would have to use turbojets, which are notoriously inefficient at lower speeds. So now you have to carry both turbojets AND ramjets, which isn't exactly a low-weight solution.

The Concorde's turbojets burned less fuel per mile than the 744 does. The problem with the Concorde was that the fuel burn per PASSENGER mile was just atrocious. And the fuel consumption at takeoff (especially with reheat) was just god-awful.

If we could figure out a way to beat the 744's fuel consumption per passenger mile on a supersonic plane, AND not have it guzzle fuel like a Scotsman in a whiskey bath on takeoff, AND not make a sonic boom that's audible on the ground, then we might have a winner.

Good luck on that.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 10, posted (5 years 9 months 3 weeks 14 hours ago) and read 5743 times:



Quoting XaraB (Reply 2):
Quoting Tdscanuck (Reply 1):
It could be done, but fuel prices would likely dictate that it won't. The problem with going faster using technology is that, given the same technology level, the slower airplane will always be more fuel efficient. It's physically impossible for it to be otherwise.

Is this always true? I read an article about the SR-71 Blackbird yesterday that stated that the aircraft actually was most efficient (miles traveled per gallon) at high Mach numbers, due to the fact that the engines would start working as ramjets instead of turbojets. I'm therefore lead to believe that any other aircraft capable of the same engine operation would become even more efficient at even higher speeds due to the way ramjets work. Am I right or wrong?

It's always true if you're using the fuel efficiency metric I was thinking of, but I wasn't very clear about which one that was.

Some engine designs, notably ramjets, but also some turbofans and turbojets, get better thrust specific fuel consumption (pounds of fuel per hour to generate one pound of thrust) as they go faster. So, in that sense, the engine is getting more efficient.

If you look at the efficiency as speed specific fuel consumption (pounds of fuel per hour per unit of speed), rather than thrust specific fuel consumption, then it always goes up with speed because the drag always goes up with speed.

Thrust specific fuel consumption is a good measure of the engine's efficiency by itself, but it doesn't tell you much about the overall aircraft because it doesn't include the thrust actually required.

For any particular airplane configuration, the drag always goes up with increasing speed. As a result, the required thrust always goes up with increasing speed. And the thrust increase is bigger than the efficiency increase, so your fuel flow per mph always goes up as you increase speed.

Caveats:
-For *really* low Reynolds numbers (very slow flows and/or very small objects) this might not be true due to viscous effects
-The drag *coefficient* can drop with increasing speed...this happens for golf balls when the flow goes from laminar to turbulent, or to a lot of aircraft as they get through the transonic regime. However, since the dynamic pressure scales with speed squared, the drop in drag coefficient still corresponds to an increase in drag (just a slower increase).

Quoting XaraB (Reply 6):
Another question; the Blackbird is apparently more efficient as a ramjet than as a turbojet (probably because it was designet for high speeds). Would this be the case if it used a ramjet/turbofan (a turbofan like the ones found in newer supersonic fighters) combo? I understand this is probably related to design speed, but is there a "crossing point" within the Mach 1-5 range where it becomes so inefficient or impossible to use turbofans/jets that ram-/scramjets/rockets would be the only alternative?

As you increase speed, your optimal powerplant shifts from turboprop to turbofan to turbojet to ramjet to scramjet to rocket.

A rocket actually works equally well at any speed, but you pay a huge weight penalty for packing your own oxidizer so you only want to use it when you don't need long duration or you need to go really fast when all the other options won't work..

You always want maximum bypass for efficiency. At turboprop has the highest bypass you can get (basically 100%) so you use that first. However, the mass flow is so large that the velocity change across the prop is small, so you can't go that fast. Switching to a turbofan buys you some more speed because the fan duct improves the aerodyanmics enough that you can get the fan exit speed basically up to Mach 1. As you go faster still, you need supersonic exhaust, which means a convergent/divergent nozzle (the exhaust coming out of the combustor of a turbo-anything has to be subsonic). This means combining the core and bypass flows in the nozzle, so you start to shrink the fan to keep the exhaust pressure up to power your nozzle. Eventually your bypass ratio drops all the way to zero, and you've got a turbojet.

At this point, you're going so fast that you don't actually need a turbocompressor (or the turbine to power it)...you can use shock compression in the nozzle. Now you've got a ramjet. However, you still need to decelerate the air to subsonic speed for the combustor, which limits how fast you can get it going again at the exit. If you want to go faster than that, you need to keep the air supersonic through the engine...a scramjet.

Tom.


User currently offlineNomadd22 From United States of America, joined Feb 2008, 1866 posts, RR: 0
Reply 11, posted (5 years 9 months 3 weeks 13 hours ago) and read 5727 times:

The Blackbird was more efficient at high speeds because the ramjet type engine was grossly inefficient at low speeds. It used so much fuel to take off it was often refueled as soon as it got to KC135 operating speed. The purpose of the movable cone in front of the intakes was almost always misunderstood. It sounds counter intuitive, but it was there to speed up the airflow so the engine could function at low speeds. It did it by funneling air from a large area into a smaller area to speed it up. The variable intake was the reason they bought Ben Rich into the program, and got him started with Skunk Works.


Andy Goetsch
User currently offlineXaraB From Norway, joined Aug 2007, 210 posts, RR: 0
Reply 12, posted (5 years 9 months 3 weeks 8 hours ago) and read 5679 times:

Thanks for a lot of informative replies, guys! I always enjoy reading what knowledgeable people have to say!


An open mind is not an empty one
User currently offlineSCAT15F From United States of America, joined Feb 2007, 402 posts, RR: 0
Reply 13, posted (5 years 9 months 2 weeks 6 days 23 hours ago) and read 5583 times:

As I recall, the BWB would have a cruise speed of at least mach .88, and maybe mach .9; It could be a "near-sonic" cruiser.

User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 14, posted (5 years 9 months 2 weeks 6 days 19 hours ago) and read 5512 times:



Quoting DocLightning (Reply 9):
And airport infrastructure. Can't forget that. You would actually have to get all-new jetbridges to board the thing.

True, but I think that would come if the airlines really wanted it. But your point about cargo containers is well taken; the bottom line is that the infrastructure requirements of a BWB are vastly different than for current planes, and considering the vast amount of capital required to accommodate them in addition to the cost to design and build them, it probably won't happen. But we can still dream.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineStarglider From Netherlands, joined Sep 2006, 678 posts, RR: 44
Reply 15, posted (5 years 9 months 2 weeks 6 days 19 hours ago) and read 5509 times:



Quoting Nomadd22 (Reply 11):
The Blackbird was more efficient at high speeds because the ramjet type engine was grossly inefficient at low speeds.

The SR-71 had turbojets. The airflow through the ducting around the turbojets at cruising speed acted, in conjunction with the tubojets somewhat like ram jets.

Quoting Nomadd22 (Reply 11):
The purpose of the movable cone in front of the intakes was almost always misunderstood. It sounds counter intuitive, but it was there to speed up the airflow so the engine could function at low speeds. It did it by funneling air from a large area into a smaller area to speed it up.

I disagree. The spikes (or cones as you call them) are automatically locked in the forward position for ground operation and flight below 30,000 ft. They are unlocked above this altitude, but remain in their forward position until Mach 1.6. They do not have a regulating function at low/subsonic speeds but move aft above Mach 1.6 to control/reduce the intake throat area, thereby controlling the shock waves and the "terminal shock" inside the intake in conjunction with the centerbody bleed and bypass door position. The spike throat has a maximum intake area in the forward (low speed) position. The intake duct behind the throat increases in size/area toward the engine compressor face slowing down the airflow, it does not reduce in size to a smaller area as you claim. At low speeds airflow is controlled by the centerbody bleeds, depending on airspeed, sucking in air or bleeding air as required.

Starglider


User currently offlineDocLightning From United States of America, joined Nov 2005, 19727 posts, RR: 58
Reply 16, posted (5 years 9 months 2 weeks 6 days 17 hours ago) and read 5465 times:



Quoting Tdscanuck (Reply 10):
As you increase speed, your optimal powerplant shifts from turboprop to turbofan to turbojet to ramjet to scramjet to rocket.

You forgot "conveyer belt" before turboprop.  duck 

To be perfectly honest, I am very doubtful that there will be a Y3. My guess is that the 787 will be Boeing's last plane. They can't possibly make money off of that plane now and so if they aren't profitable anymore, what is Boeing going to do with BCA?


User currently offlineNomadd22 From United States of America, joined Feb 2008, 1866 posts, RR: 0
Reply 17, posted (5 years 9 months 2 weeks 6 days 14 hours ago) and read 5433 times:



Quoting Starglider (Reply 15):
I disagree. The spikes (or cones as you call them) are automatically locked in the forward position for ground operation and flight below 30,000 ft. They are unlocked above this altitude, but remain in their forward position until Mach 1.6. They do not have a regulating function at low/subsonic speeds but move aft above Mach 1.6 to control/reduce the intake throat area, thereby controlling the shock waves and the "terminal shock" inside the intake in conjunction with the centerbody bleed and bypass door position. The spike throat has a maximum intake area in the forward (low speed) position. The intake duct behind the throat increases in size/area toward the engine compressor face slowing down the airflow, it does not reduce in size to a smaller area as you claim. At low speeds airflow is controlled by the centerbody bleeds, depending on airspeed, sucking in air or bleeding air as required.

I wasn't trying to show off my expert opinion. Just paraphrasing the guy who designed those inlet cones. Ben Rich said that people always assumed differently, but the main purpose of those cones was to increase the intake air velocity by funneling it. It's been a while since I read Skunk Works, and he didn't write it for engineers, so I'll have to defer to you on the rest.



Andy Goetsch
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 18, posted (5 years 9 months 2 weeks 6 days 14 hours ago) and read 5426 times:



Quoting DocLightning (Reply 16):
To be perfectly honest, I am very doubtful that there will be a Y3. My guess is that the 787 will be Boeing's last plane. They can't possibly make money off of that plane now

How do you figure? They've sold 900+ frames...even the most gloomy and pessimistic predictions of program progess, cancellations, etc. aren't going to drop that below breakeven.

Quoting DocLightning (Reply 16):
so if they aren't profitable anymore, what is Boeing going to do with BCA?

Even if the 787 turns out to be a money looser, that certainly doesn't mean BCA wouldn't be profitable. The 737 and 777 (and 767) are certainly profitable. 747-8 might be, might not....but it's not such a big program that BCA will rise or fall on the 747-8. There's enough money coming in from the profitable lines to keep BCA an ongoing entity and, eventually, all those 737's and 777's are going to need replacing.

Tom.


User currently offlineNomadd22 From United States of America, joined Feb 2008, 1866 posts, RR: 0
Reply 19, posted (5 years 9 months 2 weeks 6 days 12 hours ago) and read 5403 times:

With Boeing's experience of trying to build a completely new plane in a completely new manner still smarting, I wouldn't be surprised if they took a conservative approach to the Y3, and built what was pretty much a 787 big brother. They say that the efficiencies of CFRP barrels don't scale down to 737 size too well. Maybe that means that they'd be even better in a larger plane. Something about 12" larger than the 777 for acceptable 10 across, with enough weight and aerodynamic improvement to fly with about the same thrust engine as the 90-115.
I haven't seen much wrong with the 787 concept and design. Just the execution. I'm not sure if the Dreamlifter could be widened a couple of feet so they could produce a 787 type Y3 the way they're doing it's little brother, but after spending so much trouble getting the Dreamliner method wrung out, it would seem safest to avoid changing everything around for the next one.



Andy Goetsch
User currently offlineStarglider From Netherlands, joined Sep 2006, 678 posts, RR: 44
Reply 20, posted (5 years 9 months 2 weeks 6 days 1 hour ago) and read 5312 times:



Quoting Nomadd22 (Reply 17):
I wasn't trying to show off my expert opinion. Just paraphrasing the guy who designed those inlet cones. Ben Rich said that people always assumed differently, but the main purpose of those cones was to increase the intake air velocity by funneling it. It's been a while since I read Skunk Works, and he didn't write it for engineers, so I'll have to defer to you on the rest.

My reference in reply 15 is a copy I have of the SR-71 flight manual. The manual provides detailed information about the engine and has a figure with airflow patterns. The same figure can be found here:

http://upload.wikimedia.org/wikipedia/commons/0/02/SR71J58.png


Regards,
Starglider


User currently offlineNomadd22 From United States of America, joined Feb 2008, 1866 posts, RR: 0
Reply 21, posted (5 years 9 months 2 weeks 5 days 23 hours ago) and read 5283 times:



Quoting Starglider (Reply 20):
My reference in reply 15 is a copy I have of the SR-71 flight manual. The manual provides detailed information about the engine and has a figure with airflow patterns. The same figure can be found here:

Ok. Before I sound even more stupid (If possible) I ordered another copy of the book I read 10 years ago to refresh my aging memory as to the details of controlling the degree and position of that inlet shock.
Unless the Y3 uses SR-71 engines, I guess I've drifted a tad off topic. Sue Tdscanuck. He's the one that got me interested in this stuff again. Damn troublemaker.



Andy Goetsch
User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 22, posted (5 years 9 months 2 weeks 5 days 21 hours ago) and read 5266 times:

Last year I plyed with the idea it would become a tripple aisle <500 seater, 2.5 engined aircraft. Henry Lam did some great graphics.

http://www.airliners.net/aviation-forums/tech_ops/read.main/209330/1/
http://nl.youtube.com/watch?v=CVWQ5h5UOfk&NR=1


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 23, posted (5 years 9 months 2 weeks 5 days 19 hours ago) and read 5226 times:



Quoting Nomadd22 (Reply 21):
Sue Tdscanuck. He's the one that got me interested in this stuff again. Damn troublemaker.

If that's the worst thing I get sued for, I'm going to consider this a good year!

Tom.


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