prompt_front: Now, answer the following question based on the text below, only give me the answer and do not output any other words.

Question: What is the problem encountered when building the fuselage sides?

Read the following text and answer briefly.

Context 1: Probably one of the most frustrating things about building experimental aircraft, especially when starting with a minimum of pre-fabricated parts, is to start building and ending up with an unexpected result  Every builder starts a new project by wanting it to go "perfectly " So when things aren't going well, especially at the beginning, the frustration can lead to an unfinished airplane 
This is the first article in a series dedicated to helping builders of the Rand Robinson KR series planes build a straight and true fuselage -- the first part of the construction process  Borrowing from modern boatbuliding techniques, focus will be on the KR-2S, but the principles apply to the entire lineup of KR-1 & KR-2 series planes 
While building the KR-2(s) a common surprise is encountered by builders when the completed fuselage sides are laid into position to form the fuselage box section  With many hours spent building the sides flat, finding the once straight longerons that now bow up from the building surface, form a most dissatisfying "banana" shape  Especially when using the preformed fiberglass parts, this curve in the top longeron is not acceptable  The builder is left wondering what went wrong and no amount of clamping or brute force forming will solve the problem to any degree of satisfaction  The problem is not the builder's fault  The solution starts by understanding the three dimensional relationship of the assembled parts being built 
First understand that the plans show the finished form of the plane  They show the "projected" form as you would expect to see it if viewing an actual plane from the top, ends and from the side  Since the sides are sloped (flared) outward, looking from the side, the distances given by measuring the profile drawing are "foreshortened" and don't give the proper shape for building the fuselage with a flat top longeron  What needs to be done is to "develop" the "true" distances and shape of the flat panel so that when it is curved into position, the longerons lay flat 
Second, understand that the dimensions called for in the plans put a twist in the sides that tends to work the panel in two directions of curvature  This twist makes the panel "undevelopable" meaning that that shape cannot be unrolled into an equivalent flat shape  This is important when laying out the side and bottom panels onto flat plywood  To illustrate this, try forming a piece of paper around a soda can  The paper can be formed flat around the can either straight or at a diagonal to it's length  It has only one direction of curvature and is by definition "developable"  Now try to form the same piece of paper around a baseball  It won't lie flat on the surface without some deformation (folding, wrinkling or tearing) of the paper  The ball has curvature in more that one direction and is a "compounded" shape  Paper (or plywood) can only be readily formed in developable shapes as opposed to aluminum or other metal which can accept in plane deformation  A developable surface is needed to lay out a curved surface when the materials used can't be deformed with any degree of in-plane strain 
Initially, the fuselage sides are laid out flat with reference to the top longeron measured to a straight chalk line  The bowing problem starts when the side panels are bent and sloped to form the fuselage box section  If the sides were not sloped (tumbled home), the section formed would be cylindrical and the longerons would lie flat  Since the sides are tumbled home, the section formed is now conical  When a conical shape is cut with a plane (building surface) not perpendicular to it's axis, the shape formed is elliptical -- exactly what happens with the top longeron  When it's built flat, bent to form a cylindrical section, and sloped to form a conical section, it takes on an elliptical shape firewall to tailstock 
This method borrows heavily from proven techniques used in the marine trades  It should be stressed at this point that although the layout procedure is not complicated, it is important to take your time  If the layout is not going well initially, start over! Better to erase layout errors now than to have them built it and cause surprises later 
Layout to ensure a fair and true fuselage starts by drawing a reference line (baseline) on the building surface  Refer to figures 2 & 3 and use a wire guide to draw a very straight baseline  About 500 lbs  Of tension should be adequate  One could use a chalk line, but we're talking airplanes here, not house framing 
The main layout difference is that the baseline isn't used as a reference for the top longeron  The baseline references the mid point of the firewall for the developed (and true dimensioned) side panel  Although the baseline will still be the reference, the top and bottom longerons will be laid separately 
Layout differences don't end there  Each of the stations (vertical members) will be laid out with a calculated separation so that when the panels are formed into position, they land on the spacing called for in the plans  Another major difference is that the bottom & side panels are applied after forming the fuselage box section  This is mainly to obtain the ability to "fair" the side and bottom surfaces and insure a straight and true shape 
Refer to figure 1 for the layout of the new developed side panel  The firewall (station a) is layed out perpendicular to the baseline  Longitudinal (station) measurements are given along the length of the baseline from the firewall  Vertical dimensions are given to reference the angle and breadths of the station at the baseline 
Notice that the top longeron is bowed outward and that the stations are spaced slightly greater than called out in the plans  When the panels are formed into the box frame section ,they will work into the dimensions specified in the plans 
Strike a centerline, longer than is needed on the building surface using a wire guide  Draw off the firewall line perpendicular to the centerline at one end 
Using the distances listed in the balloons, mark them off on the centerline  Distances are measured to the nearest sixteenth of an inch  Take time to mark them off carefully  Don't mark off the distances in a cumulative fashion  Use the firewall as a common reference 
Using the angles listed at each station, mark off a station line longer than is needed  The angles are measured to the nearest hundredth of a degree  Take time to mark them off carefully 
At each station, start by marking off each short (bottom longeron) line distance from the centerline  Use your set of trammels or beam compass for doing this  Mark the intersection of the short line with the station line 
At each station, mark off each long (top longeron) line distance from the intersection of the short line distance and the station line  Again the trammels or beam compass is best for completing this step  Mark the intersection of the long line distance with the station line 
Using the longeron as a batten, trace out the inside and outside curves of the longeron  After the batten is secure, in between each station, fasten a keeper block inside and outside to preserve the shape of the longeron taking care to avoid potential future interference with the diagonal members to be installed later  The fairing blocks can be removed or left in place if they won't interfere with building  The vertical station members and their diagonals can now be measured and positioned  Remember to refer to the plans for the material thickness direction 
After vertical and diagonal members are cut and fitted, take time to draw their outlines on the building surface to cut down on time and confusion when laying out the opposite side 
Finishing the side panel is accomplished in a manner similar to that called for in the handbook with the exception that the side and bottom skin panels will be attached later 
The next article in the series will discuss jigging and building techniques to ensure alignment and straightness of the flat built side panels  Also covered will be building a "strongback" jig to assure alignment of the side panels when they are formed into their final shape 
Part 3 in the series will cover assembly of the side panels using the jigs  Some joint details will be discussed that will ensure a stronger and more fair fuselage assembly  Also covered will be the layout & attachment of the side and bottom ply skins 
U S  Mail: Densmore Associates, inc 
ANSI "D" size, computer generated plots of all the layout drawings in this series are available from the author for $30 plus postage & handling  Full (true size) scale plots may be made available depending on demand 
"Scarfing" is the practice of splicing plywood so that short pieces of plywood can be used to span long distances  On the KR, it is required on both the fuselage skins and spar webs  The angle of the splice should be 10 to 12 degrees to maintain strength across the joint  Also, joints should coincide with structural members, such as spar webs or fuselage truss members 
This scarfer is made by mating a regular plunge router (this one costs about $50) to a table saw  Obviously, you really only need a table saw to cut the chamfer, but it does make a nice heavy table for scarfing  You could just as easily use a large work table as the base First, set the table saw for a 5 5 degree cut (for a 1:12 joint, or 6 5 degree cut for a 10:1 joint), and run a 1 x 6 through on edge to chamfer a corner on the board  Then drill the board for three router mounting holes (two are countersunk) and connect the assembly to the table saw with two 1/4 inch bolts  Use a long (2-3 inch) straight cutting bit to do the cutting  Adjust the bit so it doesn't interfere with your table top, and go to town  Keep pressure on the plywood to ensure contact with the table while you're scarfing  Make sure you feed your material from the same end as you would if you were sawing, or the router will take your plywood away from you and put a big dent in your garage door 
In the late 60's Ken Rand and Stuart Robinson were working as flight system engineers for Douglas Avionics  Ken was working as an electrical engineer, having previously worked for Sperry as an autopilots project engineer, while Stu's degree was in aeronautical engineering from Northrop University  They were two of the guys at the end of the DC-8,9, and 10 assembly lines responsible for correcting some of the nits and picks in various systems before delivery to the customer 
They both wanted to build a fast, inexpensive airplane which was also economical to maintain  Several designs were considered, and plans were bought first for the Jeanie's Teenie and then the Taylor Monoplane  The Monoplane was more to their liking, but would require some modification to fit their needs  A cooperative redesign effort ensued, with virtually no dimensions left untouched  Only the basic fuselage structure, airfoil, and powerplant were retained  The tail shape was Stu's, and came directly from the big DC-8s parked on the ramp outside his office window  The landing gear was designed by Ken, after seeing the gear on a Dewey Bird at Santa Paula airport 
Ken was killed in his KR2 a short time later while flying over Cajon Pass in what was apparently a bad weather / low fuel accident  Ken's wife Jeanette became owner of RR overnight, and stepped up to keep the plans and parts coming  Much of the engineering needs are handled by Bill Marcy of Denver, who's been helping out since early '79 
To date, almost 6000 KR1, 9200 KR2, and 760 KR2S plan sets have been sold  1200 KR2s are estimated to be flying, with 5 KR2Ss now in the air  Much of the development work done on KR's is now done by the builders themselves  KR builders tend to be innovative, which leads to some interesting modifications  Some of the mods that work eventually creep into the plans  The KR2S is a case in point  Many builders who'd heard of the pitch sensitivity and tight cabin of the KR2 began to build an enlarged version, with the length determined by the most commonly available longeron material  The result is a KR2 that is stretched 2" between firewall and main spar, and 14" behind the main spar  Higher gross weights dictated more wing area, with the new standard becoming the Diehl wing skin  Those who plan to carry passengers commonly stretch the cabin width a few inches, although 1 5 inches is the limit if you still want to use RR's premolded parts 
Mike Stearns addresses the KR Forum crowd 
This year's KR Forum featured guest speakers Mike Stearns, Steve Trentman, and Bill Marcey  Mike Stearns spoke on several topics, including the many sources for KR and homebuilding information available on the Internet  He also mentioned KRNet, the list server devoted entirely to KR aircraft, as well as several notable World Wide Web home pages  He also brought a sample of the new Rand Robinson wing skins with him, and discussed their high temperature core prepreg construction  His KR2S will receive the first set, which is currently being installed at Hinson Composites 
Steve Trentman spoke on his turbine installation  It uses a turbine engine which saw duty as an A7 attack jet starter engine  Total weight is about 85 pounds, while putting out around 90 horsepower  There is a small stockpile of these engines available from government surplus  sources  This engine can only be throttled back to 52% power, which leads to some pretty interesting landings  One inflight failure has been logged so far, with very little damage to the aircraft  More on this exciting development in next month's issue of KROnline 
Les Palmer's KR2 N202LP won Best KR2, Best Engine Installation, and People's Choice awards at the 1995 KR Gathering at Columbia, TN  After researching the KR series, and reading Neil Bingham's "A Critical Analysis of the KR2" (Jan 88 Sport Aviation), Les decided to build his as a single seater, stretched 24" in the tail, while maintaining a stock width firewall  His fuselage is made from Douglas fir, which weighs in at 4 lbs heavier than if constructed from spruce  It is skinned with 1/8" birch plywood  Spars are covered with plywoood on both fore and aft sides, ala KR2S  Diehl wing skins provide the lift  Horizontal stabilizer and elevator were stretched 7" longer on each side, while the vertical stabilizer and rudder were stretched 8" taller    The fuselage to cowling junction was made more graceful by adding 1 5 inches to the height of the firewall end of the fuselage sides 
Les's canopy is a Dragonfly, using a four linkage system to swing forward when opening  The canopy frame fits snugly into a recess in the foward deck, providing an excellent wind and water seal  The fiberglass work is exemplary 
Seating is luxurious for one 
The cowling is also a work of art, and uses NACA ducts for efficiency  Female molds were made for all the fiberglass parts on Les's plane, so he could proabably be persuaded to make more, if demand dictates  Les also machines a multitude of KR aluminum and steel parts which he now offers for sale 
The firewall was reinforced with aluminum brackets and angles bolted between the longerons in anticipation of the 200 lb Subaru EA-81 engine installation  His 100 HP Asian version is outfitted with an American Holley 5200 caburetor and manifold  It uses a PSRU of Les's own design, featuring two spur gears with a 1 69:1 reduction ratio and a toothed belt  Other than tapping the crank for larger bolts to mount the redrive, no other engine modifications were required  Also, this is probably the only air conditioned KR2 on the planet  The prop is a 60/63 Hegy 
Originally built as a taildragger, the fixed gear is made from 4130 steel tubing  Custom cast 6 00x6 aluminum wheels and steel rotors are mated with 6" Cleveland calipers for braking  An early taxi test accident damaged the main gear, and prompted Les to change to tricycle gear  Again, he designed his own fiberglass main gear, and uses a Diehl nose wheel fork with a 4130 strut and 6" wheel up front 
Early tests revealed cooling problems, which prompted a radiator move from the firewall to a lower cowling location 
The first flight was almost a disaster, as test pilot Randy Smith lost power right after takeoff  He managed a 180 with a safe downwind landing with only minor nosewheel pant damage  The culprit proved to be a spark plug with too much reach, which was quickly remedied  Subsequent flights have shown water temp to be about 210 degrees, oil temp is 220-230, and airspeed is about 180 mph 
Shopping for the Partially Built KR 
This story starts about twenty years ago when I first started looking at the KR-2 as the plane I'd like to build  The only problem at that time was a lack of money, lack of knowledge, and a lack of job stability  I liked the design, except for the low ground clearance of the retractable gear and that a KR was going to be a tight fit for me to fly 
Over the past twenty years I've owned a number of planes, but still always wanted to build my own  I needed one that would fit me, my budget requirements, and have the speed and performance that I wanted  When "KITPLANES" published the article featuring Roy Marsh's new KR-2S, it was the first I had heard of any major modifications or improvements to the same old KR design  I believe that article and Roy Marsh's workmanship have probably been the greatest boon to Rand Robinson (RR) in the last twenty years  It certainly caught my eye! Here was the same design I had decided I wanted to build twenty years ago, with all of the improvements I wanted  It was sitting on fixed gear with some reasonable ground clearance  It had the capability to be built large enough to accommodate me  It has enough prefab parts available that it didn't have to be 100% scratch built if I decided to hurry the project along  And it had the speed I wanted  I knew that Roy's published speeds were probably not realistic expectations for the average KR, but after knocking around for the last three years in my Champ, anything over 90 mph seems pretty fast to me 
After purchasing the info kit and the sales video from Rand Robinson, the next step after deciding for sure to build this plane was to order the KR-2 plans and the KR-2S addendum  I finally got my plans and was putting together my first order to start the plane, when my partner in the Champ pointed out that there was a partially completed KR-2S for sale in Trade-a-plane  My initial answer was "No, I don't even want to look at it  I want to build my own from scratch " My partner insisted that for the advertised price and the fact that it wasn't too far away, I ought to at least give the guy a call and investigate it  "No, I don't think I want to buy someone else's problems," I persisted  That night I went home and crunched up some numbers on the calculator and finally came to the conclusion that for the sake of my budget for the next several years, I really should give this guy a call 
Three days later, I flew to his place about 400 miles away to take a look at his project  At this point I should probably mention that I consider myself to be fairly knowledgeable about airplane construction, although the vast majority of my experience is with tube and fabric  The rest of this article deals with what I looked for and more importantly what I missed and have had to repair in the last year since I purchased the project 
When we went to the seller's house, I found that the left wing was built using the Dan Diehl wing skins and the right wing skins were leaning against the wall inside the house  Also the canopy was in the house with the canopy covered with paper and tape  I wanted to inspect the fuselage first, so off we went to the shop 
There I found a fuselage sitting on it's gear painted in primer gray  The first step was to inspect the quality of workmanship of what could be seen as it sat  The interior of the fuselage looked as if it had been built with a great deal of care  The fit and finish of all of the interior wood was very nice  Even the gussets looked like they had been painstakingly perfectly fitted  The glass work on the turtle back also looked very precise and clean  It was evenly faired into the vertical and horizontal stabs  The tail also appeared to be well built with the exception of a depression directly over the front and rear spars in the horizontal stabs  He explained that when he moved recently, that he had shot the plane with gray primer to protect it from the weather since he wouldn't have ready access to a shop to put it in right away  It ended up sitting out in the hot south Texas summer sun for a few weeks before he got a shop rented to work in  That caused the glass (or possibly the foam inside the horizontal stab) to swell, except that it held onto the spar, so it was slightly ballooned in front of and behind the spars  His recommendation was to fill it back smooth with micro 
I also found a small linear crack in the lower left wing spar cap on the left wing stub  It appeared to be from over tightening the rear spar wing attach fitting bolts  His explanation was that the crack wasn't important because the rear spars only job is to keep the wings from folding back  I also noticed that the holes for attaching the outer wing to the wing stub were badly rounded out on the rear spar  He explained that the Diehl wing skins require the rear spar to be swept slightly more forward than the stock wings  This won't allow you to use the rear spar attach fittings from RR and that I would need to fabricate a new set of rear spar attach fittings 
I also found that the aileron bellcranks were not built or installed as per plans, but found that they looked professional  I couldn't check for function since the right bellcrank and sheeve wasn't installed, the left wing also wasn't installed, and the right wing didn't exist yet 
Next we pulled the inspection panels off of the fuselage and tail and looked at everything I could see with a good flashlight  I didn't find anything else that might be questionable about the fuselage except for a cracked elevator trim tab that was damaged when it fell off it's hanging place on the wall 
Next we spent some time going over his builders log and builders photo album  I still hadn't seen anything that would dissuade me from buying this project 
At this point it was starting to get late and my ride down needed to get airborne for the flight home  I needed to make a decision about whether I wanted this project or not, but I hadn't inspected the wings and canopy yet  I took a cursory look at the left wing and saw lots on micro built up on it and some bubbles in the leading edge, but nothing that looked seriously wrong to my amateur eye  The right wing was only a set of spars in the shop and the Diehl wing skins in the house, so there wasn't much to look at there  The canopy was wrapped in paper and tape, so there wasn't much to look at there either  I decided that even if there were serious problems in the wing that was built, I would be money ahead to go ahead and buy the project  For the advertised price, I could build a new set of wings and still be way ahead financially  We negotiated a final price, shook hands, took my ride to the airport, and started off in search of a U-haul to haul the project home 
Now, at this point, some of you are thinking about what I surely must have forgotten to inspect and why didn't I take a local A & P or EAA member along for the ride  First of all, I don't know any mechanics locally that have any experience with glass and our EAA chapter of which I am VP is woefully lacking in fiberglass knowledge  Secondly, as you will see, I missed plenty  Some by ignorance, some by just not looking close enough 
Now for a list of the problems that I found over the last year and a few of the fixes that I came up with 
I found that the lower set of rear spar attach fittings on the left rear spar were installed backwards with the longer spaced hole towards the fuselage  Since this is the same place that also had the cracked spar cap, it required a major change  Also in the same area he had drilled through the rear spar with a hole saw to create a place for the aileron cable to pass through and managed to cut out the second from the outside vertical brace in the spar  Then he chose to install the aileron bellcranks in front of the rear spar, and cut another hole through the rear spar for the aileron push rod  He also managed to cut out the outside vertical brace in the spar  Since the holes were already drilled through the spar, the choices were to either cut out that section of spar cap and scarf a new piece in, cut the whole rear spar carrythrough out of the fuselage including ruining the left lower wing skin, or do something else creative to reinforce the spar cap and install a custom built set of attach fittings 
I also found that after I built and installed the right side wing stub ribs and skin that the aileron bellcrank setup would not work as installed  The cable that crosses between the two bellcranks had a sharp uphill from the sheeve to the bellcrank in the last 12 inches on either side  This combined with the radius that the bellcranks turn caused the cross cable to pull up tight when the ailerons were pushed to either end of their travel, but allowed the cables to go very slack when the ailerons were centered  Also the Aileron pushrods needed to pass directly through the lower set of rear wing attach fittings to attach to the aileron  This whole rear spar and aileron bellcrank setup was going to either have to be redesigned or cut out and built to plans  The bottom line is that the problems I observed when I inspected this part were much more serious than expected when I had to fix it 
I decided that I had to remove the rear fittings from the left wing to be replaced with the new set that my neighborhood machinist was cutting out for me  When I put the wing on the work bench to start removing the rear fittings, I thought I had better take a closer look at the bubbles in the leading edge  I found that as I pushed on the leading edge, it delaminated between the glass lay-up on top and the upper and lower wing skin edges that were floxed together underneath  I concluded that that area had to come apart and took a belt sander to the leading edge  What I found was that the leading edge had been floxed together and glassed over, but the mold release had never been scrubbed off the leading edge of the wing  It peeled apart for rebuild quite easily 
When I got back to removing the rear spar attach fittings, I noticed that the woodwork inside the wing looked awfully dull  The reason was that the wing had been closed up without varnishing any of the woodwork  This was rectified with a small hole saw, a number of extensions and a modified undercoating sprayer 
I also found that the aluminum drain fitting in the bottom of the left wing tank had been glassed into place upside down  The tapered pipe threads were tapered the wrong way to install the draincock into the tank  Retapping the fitting the right direction seemed to be a good fix for that problem 
When I finally got around to attaching the wing to the fuselage, I found that the front spar attach fittings were badly misaligned  Although they could be forced into alignment, I didn't think I needed that kind of preload on the main spar fittings  This problem was fixed by calling on my local neighborhood machinist to build me an aligning fixture and reaming the attach holes to the next larger size and ordering the new sized bolts 
On the fuselage I found that although it had new Cleveland wheels and brakes on it, one of the brakes had a severe wobble to it  I must complement the manufacturers for taking care of that problem  One call to the Cleveland factory and they shipped me a new set of wheels and brakes even though the receipt for this set was over four years old and in the original builders name  Their only concern was that this set had never been placed in service yet 
I chose to sand the load of micro off the left wing to see what it was covering  When I got down to the glass, I found that there was no glass for the aft inch and a half of the underside of the wing in front of the aileron hinge  With the Diehl wing skins, you build the wings, then cut the ailerons out of trailing edge of the wing  He had mismeasured and cut too much material off the bottom side of the trailing edge in front of the aileron  It was filled by floxing a piece of spruce into the gap to fill the space between the back edge of the fiberglass and the aileron mount  I chose to wrap the trailing edge of that wing, and the other wing to match with a couple of lay-ups of glass 
When I sanded the primer off the aforementioned damaged trim tab, I found that the hinge was floxed to the leading edge of the foam insides of the tab, but not the glass  I also chose to wrap the front of the trim tab with a lay-up of glass 
I decided to pull the paper off the canopy and take a look at it before I'm ready to bolt it on and fly  The original builder had blown his own canopy and after some of the previous problems, I was beginning to have some concerns about not having looked it over closely enough  The canopy turned out to have been blow a little too large  It ended up with a little larger bubble for headroom, which I didn't object to  However, it had more headroom on the right side than the left  Yes, it was just a little bit lopsided  The main problem was that the canopy is stretched thin enough that it can be easily pushed in with one hand when the weather is warm   My fear was that this is just thin enough that it may decide to lay on my head or in my lap when flying on a warm day  It will have to be replaced 
I'm sure that many that are reading this could see several of the potential problems before I mentioned them, but some others may not have and I'm sure that there could have been many other problems that didn't but could have existed on this project  This is also not intended to be critical of the gentleman that started this project as many parts of it, especially the wood work are better than I could have done and much of his work is outstanding  I prefer to think that I'll end up with a better plane with his woodwork combined with my glasswork  This article is intended to feature some of the problems that you may run into in buying someone else's project 
The final question is, knowing what I have found over the past year, would I have still purchased this project  The answer is yes, but primarily because the price was right in that I am still money and work ahead of where I would be if I had started the project from scratch  There are a few things that I would have done differently, but nothing that I can't live with  Although I won't be able to say that I built it all from scratch, I have built and rebuild enough of the plane that I should have no problem qualifying under the 51% rule 
You can send comments directly to the author via e-mail at "jscott@LANL GOV" 
Here is an brief explanation of how I built my turtledecks  The jig was constructed from scrap plywood and a few 1x4s that I ripped into stringers  I made two temporary bulkheads from the plywood, one for each end  Remember the forward bulkhead needs to be shaped in a way that will closely match the aft end of your canopy frame  Make an aft bulkhead by placing a straight edge at the top of your forward bulkhead and the trailing edge of your horizontal stabilizer  This will give you an idea of how tall your aft bulkhead needs to be  As far as location, I placed my aft bulkhead just forward of the lower/front of my vertical fin  I constructed the jig on the fuselage, it is glued together with automotive bondo 
After the bulkheads were bondoed to the fuselage I used the stringers that I ripped from the 1x4s and bondoed them to the bulkheads  This gave me a male form to cover with thin plastic or posterboard  I stapled two layers of posterboard to the jig(thin plastic would work better)  The posterboard wraps down two inches onto the fuselage  After I was satisfied with the way it looked, I then covered the entire thing with duct tape (fiberglass will not stick to duct tape) On top of this I wetout one layer of tri-ply cloth (22oz) that I had left over from an earlier project, and one layer of 8oz  bid  Remember to mask off your fuselage so you don't get epoxy on it  If you are not familiar with composite lay-ups, you should plan on razor cutting your lay-ups 4 to 6 hours after wetout while the lay-up is still soft enough to cut with a razorblade 
After the lay-up cured (2 or 3 days) it was removed from the jig, and the jig was removed from the fuselage and discarded  (be careful, the bondo sticks very well to the spruce, you could splinter your wood during removal) I now have a fiberglass skin that tends to hold the shape of the jig but is still flexible enough to work with  I made two bulkheads out of 1/4 last-a-foam (AS&S) using the plywood formers from the jig as a guide  I covered these foam bulkheads with one 8oz layer of glass on each side, with a glass to glass edge on the bottom  After cure these bulkheads were bondoed into place (to the fuselage)and the fiberglass skin was pulled down tight and floxed to the bulkheads  When the flox cured the bondo joints were broken, again being careful not to harm the wood  The turtledeck was removed from the fuselage and 2 inch tapes added to the bulkheads inside and out 
At this point the turtledeck looked great and only weighed about 5lbs  but I noticed you could deform the skin by pushing hard on the outside  So I flipped the turtledeck over and from 1/4 inch last-a-foam, I cut two inch wide strips that would run the entire length, forward and aft inside the turtledeck  In effect these would act as composite stringers, I made enough of these two inch wide strips to make up three stringers  One down the center (sort of a backbone) and one on each side of the "backbone" half the distance to the edge of the turtledeck  I sanded the edge of the foam so that when covered with a layer of bid @ 45degrees there would be a nice transition from the turtledeck skin up onto the foam and then back onto the turtledeck I scuff sanded and glued the foam stringers in with micro  I covered the foam stringers with one layer of 8oz bid @ 45degrees 
Context 2: \section{Introduction}
\label{sec:Intro}

The exchange interactions control the magnetic order and properties of a vast number of materials
\cite{White2006Dec}
and lead to many fascinating phenomena, such as various types of the Kondo effect 
\cite{Kondo,NozieresBlandin,Pustilnik_Glazman} 
Double quantum dots (DQDs), and in general multi-impurity systems, constitute
a convenient and controllable playground,
where nearly as much different exchange mechanisms compete with each other to
shape the ground state of the system 
\emph{Local exchange} between the spin of a quantum dot (QD)
and the spin of conduction band electrons gives rise to the
Kondo effect \cite{Kondo,Hewson_book}  
\emph{Direct exchange} arriving with an additional side-coupled QD may destroy it or lead to the 
two-stage Kondo screening \cite{Pustilnik_Glazman,Cornaglia,Granger,ZitkoBonca,ZitkoPRB2010,Ferreira} 
In a geometry where the two QDs contact the same lead, conduction band electrons 
mediate the \emph{RKKY exchange} \cite{RK,K,Y}  The RKKY interaction competes
with the Kondo effect and leads to the quantum phase transition of a still debated nature
\cite{Doniach,Jones,Affleck,Bork,Neel,KondoRKKYexp,Hans,Hans2,Fabian} 
Moreover, in DQDs coupled in series also \emph{superexchange} can alter the Kondo physics significantly
\cite{Zitko_2QDEx,Sela} 

Recently, hybrid quantum devices, in which the interplay between various magnetic correlations
with superconductivity (SC) plays an important role, have become an important direction of research
\cite{hybridQDs,SCspintronics}  In particular, chains of magnetic atoms on SC surface have proven 
to contain self-organized Majorana quasi-particles and exotic spin textures
\cite{Braunecker,Klinovaja,Vazifeh,Yazdani},
while hybrid DQD structures have been used to split the Cooper pairs coherently into two entangled 
electrons propagating to separated normal leads \cite{CPS1,CPS2,CPS4,CPS5,CPS9} 
The latter is possible due to non-local (\emph{crossed}) Andreev reflections (CARs),
in which each electron of a Cooper pair tunnels into different QD, and
subsequently to attached lead  Such processes give rise to an exchange mechanism \cite{Yao},
that we henceforth refer to as \emph{the CAR exchange}, which can greatly modify
the low-temperature transport behavior of correlated hybrid nanostructures 

The CAR exchange may be seen as RKKY-like interaction between
two nearby impurities on SC surface \cite{Yao} 
The effect can be understood as a consequence
of spin-dependent hybridization of the Yu-Shiba-Rusinov (YSR)
states \cite{Yu,Shiba,Rusinov} in SC contact,
caused both by the overlap of their wave functions
and their coupling to Cooper-pair condensate 
This process is the most effective when the YSR states 
are close to the middle of the SC gap, {\it e g } in the YSR-screened phase \cite{YSRscreening} 
The mechanism presented here is essentially the same,
yet in the considered regime can be understood
perturbatively without referring to YSR states,
as a consequence of the non-local pairing induced by SC electrode  
In particular, the presence of YSR bound states close to the Fermi level 
is not necessary for significant consequences for the Kondo physics, 
as long as some inter-dot pairing is present  


The proximity of SC induces pairing in QDs \cite{RozhkovArovas,Buitelaar} 
and tends to suppress the Kondo effect if the superconducting energy gap $2\Delta$ 
becomes larger than the relevant Kondo temperature $T_K$ 
\cite{Buitelaar2002Dec,adatomsSC,Kondo_vs_SC1,Kondo_vs_SC2,Zitko_Kondo-Andreev,Zitko_S-QD-N,IW_Sau,YSRscreening} 
Moreover, the strength of SC pairing can greatly affect the Kondo physics in the sub-gap transport regime:
For QDs attached to SC and normal contacts, it can enhance the Kondo effect
\cite{DomanskiIW,KWIW,part1}, while
for DQD-based Cooper pair splitters, it tends to suppress both the $\mathrm{SU}(2)$ and $\mathrm{SU}(4)$ Kondo effects \cite{IW_Kacper} 
Our main result is that the non-local pairing induced by superconducting 
proximity effect, which gives rise to CAR exchange, can be the sole cause of the Kondo screening 
Moreover, relatively small values of coupling to SC, $\GS{}\ll U$, are sufficient for the effect to occur 
This is in contrast to the DQD system considered in Ref ~\cite{part1},
where only one of the quantum dots is proximized, such that 
CAR exchange cannot arise,
and the Kondo physics becomes qualitatively
affected only for $\GS{}\sim U/2$ %


\begin{figure}[bt]
\centering
\includegraphics[width=1\linewidth]{Fig1 png}
\caption{
		 (a) Schematic of the considered system  Left/right (L/R) lead
		 is coupled to the first quantum dot (QD1), while superconductor
		 is attached to both QD1 and QD2 
		 (b)-(d) illustrate an example of direct spin exchange:
		 spin-up electron from the initial state (b) hops to the other QD (c) and spin-down electron 
		 hops back (d)  Note, that the final state is in fact the same singlet state, 
		 only with opposite sign 
		 (e)-(g) show an example of process contributing to crossed Andreev reflection (CAR) exchange 
		 A Cooper pair from SC approaches DQD (e) and two singlets of the same charge 
		 are formed (f), before the Cooper pair is re-emitted (g) 
		 (h)-(j) present an example of RKKY process: an electron scattered off
		 one QD (h) mediates the spin exchange towards the other (i), before it is finally scattered
		 off there, too (j) 
		 }
\label{fig:system}
\end{figure}


In this paper we discuss the CAR-induced Kondo screening in a setup comprising T-shaped DQD
with normal and superconducting contacts, see \fig{system}(a) 
We note that despite quite generic character of CAR exchange,
and its presence in systems containing at least two localized electrons
coupled close to each other to the same SC bath,
to best of our knowledge CAR-induced screening
has hardly been identified in previous studies
\cite{CPS1,CPS2,CPS4,CPS5,CPS9,IW_Kacper,IW_Sau,Zitko_Josephson,Zitko_S2QD,Martinek2017} 
In the system proposed here [\fig{system}(a)], its presence is evident 
Moreover, CAR exchange magnitude can be directly related to the relevant energy scales, such as the Kondo 
temperature, which provides a fingerprint for quantitative experimental verification of our predictions  

The paper is organized as follows  In \Sec{model} we describe the considered system 
and present the model we use to study it  In \Sec{scales} the relevant energy scales are estimated
to make the discussion of main results concerning CAR-induced Kondo effect in \Sec{main} more clear  
Finally, the influence of effects neglected in \Sec{main} are presented in the following sections,
including CAR exchange interplay with RKKY interaction (\Sec{RKKY}), particle-hole asymmetry (\Sec{asym}),
couplings asymmetry (\Sec{x}) and reduced efficiency of CAR coupling (\Sec{coef})  In summary,
the effects discussed in \Sec{main} remain qualitatively valid in all these cases 
The paper is concluded in \Sec{conclusions} 


\section{Model}
\label{sec:model}

The schematic of the considered system is depicted in \fig{system}(a) 
It contains two QDs attached to a common SC lead 
Only one of them (QD1) is directly attached to the left (L) and right (R) normal leads,
while the other dot (QD2) remains coupled only through QD1 
The SC is modeled by the BCS Hamiltonian, 
$H_{\mathrm{S}}=\sum_{\mathbf{k}\sigma}\xi_{\mathbf{k}}a_{\mathbf{k}\sigma}^{\dag}a_{\mathbf{k}\sigma}-\Delta\sum_{\mathbf{k}}(a^\dag_{\mathbf{k}\uparrow}a_{-\mathbf{k}\downarrow}^{\dag}+a_{-\mathbf{k}\downarrow}a_{\mathbf{k}\uparrow})$,
with energy dispersion $\xi_{\mathbf{k}}$, energy gap $2\Delta>0$ and $a_{\mathbf{k}\sigma}$ annihilation operator 
of electron possessing spin $\sigma$ and momentum $\mathbf{k}$  The coupling between
SC and QDs is described by the hopping Hamiltonian 
$H_{\mathrm{TS}}=\sum_{i\mathbf{k}\sigma}v_{\mathrm{S}i}(d^\dagger_{i\sigma}a^{}_{\mathbf{k}\sigma}+h c )$,
with $d^\dagger_{i\sigma}$ creating a spin-$\sigma$ electron at QD$i$  The matrix element 
$v_{\mathrm{S}i}$ and the normalized density of states of SC in normal state, $\rho_{\rm S}$, 
contribute to the coupling of QD$i$ to SC electrode as $\GS{i} = \pi \rho_{\rm S} |v_{{\rm S}i}|^2$  
We focus on the sub-gap regime, therefore, we integrate out SC degrees of freedom lying outside the energy gap \cite{RozhkovArovas} 
This gives rise to the following effective Hamiltonian,
$H_{\mathrm{eff}}=H_{\mathrm{SDQD}}+H_{\rm L}+H_{\rm R}+H_{\rm T}$, 
where 
\begin{eqnarray}
H_{\rm SDQD} 	& = & 
				\sum_{i\sigma} \varepsilon_{i} n_{i\sigma} 
				+\sum_{i} U n_{i\uparrow} n_{i\downarrow} 
				+U' (n_1-1)(n_2-1) 
				\nonumber\\
				&+&\sum_\sigma t(d^\dagger_{1\sigma}d^{}_{2\sigma} + h c ) 
				+J \vec{S}_1\vec{S}_2
				\nonumber\\
				&+&\sum_{i} \!\!\left[ \Gamma_{{\rm S}i} (d^\dagger_{i\uparrow} d^\dagger_{i\downarrow} \!+\! h c )
				+\Gamma_{\rm SX} (d^\dagger_{i\uparrow} d^\dagger_{\bar{i}\downarrow} \!+\! h c ) \right]
	\label{H_DQD} 
\end{eqnarray}
is the Hamiltonian of the SC-proximized DQD
\cite{IW_Kacper,Walldorf2018Feb}, with QD$i$ energy level $\varepsilon_i$,
inter-site (intra-site) Coulomb interactions $U'$ ($U$),
inter-dot hopping $t$, and CAR coupling $\GS{\rm X}$ 
$n_{i\sigma}=d^\dagger_{i\sigma}d^{}_{i\sigma}$ denotes the electron number operator 
at QD$i$, $n_i=n_\uparrow+n_\downarrow$, and $\bar{i}\equiv 3-i$  
Our model is strictly valid in the regime where $\Delta$ is the largest 
energy scale  Nevertheless, all discussed phenomena are
present in a full model for energies smaller than SC gap 
Moreover, by eliminating other consequences of the presence of SC lead,
our model pinpoints the fact that the non-local pairing is 
sufficient for the occurrence of the CAR exchange 
The presence of out-gap states shall result mainly in additional broadening of DQD energy levels,
changing the relevant Kondo temperatures 
We note that the procedure of integrating out out-gap states neglects the 
RKKY interaction mediated by SC lead and other possible indirect exchange mechanisms%
 \footnote{
 Note, that by RKKY interaction we mean only such an effective exchange, 
 which arises due to multiple scattering of a single electron or hole, see \fig{system}(h)-(j) 
 Other mechanisms leading to the total indirect exchange are considered separately 
 In particular, in the large gap limit, exchange described in Ref ~\cite{Yao} is in fact reduced to
 the CAR exchange, and additional antiferromagnetic contribution would arise for finite gap 
 }  
To compensate for this,
we explicitly include the Heisenberg term $ J \vec{S}_1\vec{S}_2$ in
$H_{\rm SDQD}$, with $\vec{S}_i$ denoting the spin operator of QD$i$
and a Heisenberg coupling $J$ substituting the genuine RKKY exchange 

The normal leads are treated as reservoirs of noninteracting electrons,
$H_{r}=\sum_{\mathbf{k}\sigma}\varepsilon_{r\mathbf{k}}c^\dagger_{r\mathbf{k}\sigma}c^{}_{r\mathbf{k}\sigma}$,
where $c^{}_{r\mathbf{k}\sigma}$ annihilates an electron of spin 
$\sigma$ and momentum $\mathbf{k}$ in lead $r$ ($r={\rm L,R}$) with the corresponding energy $\varepsilon_{r\mathbf{k}\sigma}$ 
The tunneling Hamiltonian reads,
$H_{\rm T} = \sum_{r\mathbf{k}\sigma} v_{r} (d^\dagger_{1\sigma}c^{}_{r\mathbf{k}\sigma} + h c )$,
giving rise to coupling between lead $r$ and QD$i$ of strength $\Gamma_r = \pi \rho_r |v_r|^2$,
with $\rho_r$ the normalized density of states of lead $r$ and $v_r$ the 
local hopping matrix element, assumed momentum-independent 
We consider a wide-band limit, assuming constant $\Gamma_r=\Gamma/2$
within the cutoff $\pm D = \pm 2U$ around the Fermi level  

For thorough analysis of the CAR exchange mechanism and its consequences
for transport, we determine the linear conductance between the two normal leads from
\begin{equation}
G = \frac{2e^2}{h} \pi \Gamma \int \left[ -\frac{\partial f_T}{\partial\omega} \right] \mathcal{A}(\omega) {\rm d} \omega ,
\label{G}
\end{equation}
where $f_T$ is the Fermi function at temperature $T$,
while $\mathcal{A}(\omega)$ denotes the normalized local spectral density 
of QD1 \cite{fn1} 
Henceforth, unless we state otherwise, we assume a maximal CAR coupling, 
$\GS{\rm X} = \sqrt{\GS{1}\GS{2}}$ \cite{IW_Kacper,Walldorf2018Feb},
$\GS{1}=\GS{2}=\GS{}$ and consider DQD tuned to the particle-hole symmetry point, 
$\varepsilon_1=\varepsilon_2=-U/2$  However, these assumptions are not crucial for the results presented
here, as discussed in Secs ~\ref{sec:asym}-\ref{sec:coef} 

\section{Estimation of relevant energy scales}
\label{sec:scales}

Since we analyze a relatively complex system, let us build up the understanding of its behavior starting
from the case of a QD between two normal-metallic leads, which can be obtained in our 
model by setting $t=\GS{}=J=U'=0$  Then, the conductance as a function of temperature, $G(T)$, grows
below the Kondo temperature $T_K$ and reaches maximum for $T\to 0$, $G(T\!=\!0)=G_{\rm max}$ 
At particle-hole symmetry point, the unitary transmission is achieved, $G_{\rm max}= G_0 = 2e^2/h$;
see short-dashed line in \fig{G-T}(a) 
An experimentally relevant definition of $T_K$ is that at $T=T_K$ 
$G(T)=G_{\rm max}/2$  $T_K$ is exponentially small in 
the local exchange $J_0 = 8\Gamma / (\pi \rho U)$, and is approximated by
$T_K \approx D \exp[-1/(\rho J_0)]$ \cite{Hewson_book} 

The presence of a second side-coupled QD, $t,U'>0$, significantly enriches the physics of the system 
by introducing direct exchange between QDs, see \fig{system}(b-d) 
In general, effective inter-dot exchange can be defined as energy difference between 
the triplet and singlet states of isolated DQD, 
$J^{\mathrm{eff}} = E_{S=1} - E_{\rm GS}$  Unless $U$ becomes very large, superexchange can be neglected
\cite{Zitko_2QDEx} and $J^{\mathrm{eff}}$ is determined by \emph{direct exchange}, $J^{\mathrm{eff}}\approx 4t^2/(U-U')>0$ 
When the hopping $t$ is tuned small \cite{CPS1}, one can expect $J^{\mathrm{eff}}\lesssim T_K$, which 
implies the two-stage Kondo screening \cite{Pustilnik_Glazman,Cornaglia} 
Then, for $T \ll T_K$, the local spectral density of QD1 serves as a band of width $\sim T_K$ for QD2 
The spin of an electron occupying QD2 
experiences the Kondo screening below the associated Kondo temperature
\begin{equation}
T^* = a T_K \exp(- b T_K / J_{\rm eff})
\label{Tstar}
\end{equation}
with $a$ and $b$ constants of order of unity \cite{Pustilnik_Glazman,Cornaglia} 
This is reflected in conductance, which drops to $0$ with lowering $T$, maintaining characteristic 
Fermi-liquid 
$G\sim T^2$ dependence \cite{Cornaglia}; see the curves indicated with squares 
in \fig{G-T}(a)  Similarly to $T_K$, experimentally relevant definition of $T^*$ is that 
$G(T\!=\!T^*) = G_{\rm max}/2$  Even at the particle-hole 
symmetry point $G_{\rm max} < G_0$, because the single-QD strong-coupling fixed point 
is unstable in the presence of QD2 and $G(T)$ does not achieve $G_0$ exactly,
before it starts to decrease 


The proximity of SC gives rise to two further exchange mechanisms that
determine the system's behavior  First of all, the (conventional)
\emph{RKKY interaction} appears, $J \sim \GS{}^2$ \cite{RK,K,Y}  
Moreover, the \emph{CAR exchange} emerges as a consequence of finite $\GS{}$ \cite{Yao}  
It can be understood on the basis 
of perturbation theory as follows  DQD in the inter-dot singlet state may absorb
and re-emit a Cooper pair approaching from SC; see \fig{system}(e)-(g)  As a second-order
process, it reduces the energy of the singlet, which is the ground state of isolated DQD 
A similar process is not possible in the triplet state due to spin conservation 
Therefore, the singlet-triplet energy splitting $J^{\mathrm{eff}}$ is increased (or generated for $t=J=0$)  
More precisely, the leading ($2$nd-order in $t$ and $\GS{}$) terms
in the total exchange are 
\begin{equation}
J^{\mathrm{eff}} 	\approx 	J + \frac{4t^2}{U-U'+\frac{3}{4}J} + \frac{4\GS{}^2}{U+U'+\frac{3}{4}J} 
\label{Jeff}
\end{equation}
Using this estimation, one can predict $T^*$ for finite $\GS{}$, $t$ and $J$ with \eq{Tstar} 
Apparently, from three contributions corresponding to:
(i) RKKY interaction, (ii) direct exchange and (iii) CAR exchange, only the first may bear a negative (ferromagnetic) sign 
The two other contributions always have an anti-ferromagnetic nature 
More accurate expression for $J^{\mathrm{eff}}$ is derived in Appendix~\ref{sec:downfolding}
[see \eq{A_J}] by the Hamiltonian down-folding procedure  The relevant terms differ 
by factors important only for large $\GS{}/U$  
Finally, it seems worth stressing that normal leads are not necessary for CAR exchange to occur 
At least one of them is inevitable for the Kondo screening though, and two symmetrically coupled 
normal leads allow for measurement of the normal conductance 


It is also noteworthy that inter-dot Coulomb interactions
decrease the energy of intermediate states contributing to direct exchange 
[\fig{system}(c)], while increasing the energy of intermediate
states causing the CAR exchange [\fig{system}(f)] 
This results in different dependence of corresponding terms in \eq{Jeff} on $U'$ 
As can be seen in \figs{G-T}(b) and \ref{fig:G-T}(c), it has a significant effect 
on the actual values of $T^*$ 

\begin{figure}
\includegraphics[width=1\linewidth]{Fig2 pdf}
\caption{(a) Linear conductance $G$ as function of $T$ calculated for 
		 $\varepsilon_1=\varepsilon_2=-U/2$, $\Gamma=U/5$, $U'=U/10$ and different situations, 
		 as indicated  The quantity $\xi\equiv\sqrt{\GS{}^2+t^2}$ is fixed 
		 for different curves drawn with the same dashing style 
		 Note the logarithmic scale on both axes 
		 %
		 (b) Points show $T^*/T_K$ calculated by NRG from curves in subfigure (a)  
		 Lines present the fit to \eq{Tstar} with $J^{\mathrm{eff}}$ obtained from \eq{Jeff} 
		 %
		 (c) The same as (b), only for $U'=0$ 
		 %
		 (d) and (e) show the residual conductance $G_{\mathrm{min}} \equiv G(T \!=\! 0)$ as a function of
		 $\GS{}$ for $t=0$ (denoted "CAR") and $t=\GS{}$ (denoted "Both")  
		 Dotted line is a guide for eyes  $U'=U/10$ in (b) and (d) and $U'=0$ in (c) and (e) 
		}
\label{fig:G-T}
\end{figure}

\section{CAR exchange and Kondo effect}
\label{sec:main}

To verify \eqs{Tstar}-(\ref{Jeff}) we calculate $G$ using
accurate full density matrix numerical renormalization group (NRG) technique \cite{WilsonNRG,Weichselbaum,FlexibleDMNRG,fn2} 
We compare $U'=0$ case with experimentally relevant value $U'=U/10$ \cite{Keller2013Dec} 
While for two close adatoms on SC surface RKKY interactions may lead to prominent consequences
\cite{Klinovaja}, the conventional ({\it i e } non-CAR) contribution should 
vanish rapidly when the inter-impurity distance $r$ exceeds a few lattice constants \cite{RKKYrange,SC_RKKY}  
Meanwhile, the CAR exchange may remain significant for $r$ of the order
of coherence length of the SC contact \cite{Yao}  Therefore, we first neglect the conventional RKKY coupling and analyze its consequences in Sec ~\ref{sec:RKKY} 

The main results are presented in \fig{G-T}(a), showing the temperature dependence of $G$
for different circumstances  
For reference, results for $\GS{}=0$ are shown, exhibiting 
the two-stage Kondo effect caused by \emph{direct} exchange mechanism 
As can be seen in \figs{G-T}(b) and \ref{fig:G-T}(c), an excellent agreement of $T^*$ found from NRG calculations and \eq{Tstar} 
is obtained with $a=0 42$ and $b=1 51$, the same for both $U'=0$ and $U'=U/10$  Note, 
however, that $J^{\mathrm{eff}}$ is different in these cases, cf  \eq{Jeff},
and $U'$ leads to increase of $T^*$ 

Furthermore, for $t=0$ and $\GS{}>0$ the two-stage Kondo effect caused solely by the \emph{CAR
exchange} is present; see \fig{G-T}(a) 
Experimentally, this situation
corresponds to a distance between the two QDs smaller than the superconducting coherence length,
but large enough for the exponentially suppressed direct hopping to be negligible 
While intuitively one could expect pairing to compete with any kind of magnetic ordering,
the Kondo screening induced by CAR exchange is a beautiful example of a superconductivity
in fact leading to magnetic order, namely the formation of the Kondo singlet 
This CAR-exchange-mediated Kondo screening is our main finding 
For such screening, \eq{Tstar} is still fulfilled with very similar 
parameters, $a=0 37$ ($a=0 35$) and $b=1
Context 3: Transport Aircraft for IAF - Page 67 - Bharat Rakshak
Transport Aircraft for IAF
Re: Transport Aircraft for IAF
Postby abhik » 17 Nov 2014 05:55
+1, Air India recently sold their entire fleet of Boeing 777s 
afaik the A330 MRTT does not make any structural mods or add anything internally in cargo or passenger cabin  it just relies on the intrinsic 110 tons of fuel  external refueling pods are added and internally the control station and cameras for the operator i guess 
so its a easy conversion from a passenger layout to the AAR mode - mostly ripping out the passenger cabin of all extra stuff and retuning the FCS for any changes in COG 
this should have been pursued years ago
the IL78 adds a palletized drum tank system inside its cargo bay due to paucity of intrinsic fuel but it can be removed and a/c converted back to cargo hauling or send off to russia for Phalcon structural mods if we want it that way  they will however need to change engines to PS90 as they have the old engines
http://www airplane-pictures net/images     7/5616 jpg
the RAF is already gone that route in 2011
http://www defensenews com/article/2011     -Refuelers
LONDON - Airbus Military has delivered the first of 12 A330-200 airliners due to be converted into in-flight refueling planes for the British Royal Air Force by Cobham Aviation Services 
The aircraft, part of an order of 14 jets, will be modified with aerial refueling pods and other equipment at Cobham's newly refurbished facility in Bournemouth, England  The first two aircraft have already been converted by Airbus in Spain 
The multirole tanker aircraft are being provided to the RAF under a private finance initiative service deal led by Airbus parent EADS 
Seven of the planes will be operated full time by the RAF  The remainder will be available for lease in the third-party market, with the proviso that they can be returned to British military service to meet any surge in demand 
All of the aircraft, to be known as the Voyager in RAF service, will be fitted with two wing-mounted refueling pods, while half the fleet will also be fitted for, but not necessarily with, a center-line mounted unit  The refueling units are being supplied by Cobham 
The first aircraft will become operational in a passenger and freight transport role by the end of this year to start relieving pressure on the RAF's hard-pressed assets 
Despite the increasing fragility of current RAF in-flight refueling operations, the new capability is not contracted to start being used in this role until 2015 
All 14 Voyagers are scheduled to be available for RAF operations by the middle of the decade  The A330 will replace the increasingly ancient Tristar and VC-10 refuelers now in service 
Push the 6 Il-476 from refueler to AEW duty  Phalcon them up
Not sure if that is a good path to follow  For one they all should be sent to pasture in about 8 years  Then if the are to be phalconed up - the requires major structural changes  Not worth that cost 
Whatever happened ot the two new ones that were supposed ot be ordered?
the IL78 can be easily converted back to IL76 cargo hauling  only the fuel tank inside cargo bay needs removal   infact that was even mentioned in initial days as swing role fuel/cargo 
Postby Cybaru » 17 Nov 2014 07:55
I am talking about the new il78 that we ordered recently in refueling role  Sorry for the mix up  They are the same platform, that I why i used 476 or 76 to identify it 
777 carries more internal fuel than the A330  We suck!
From the KC-777 program 
http://www globalsecurity org/military/     kc-777 htm
"the KC-777 would be 209 feet long with a wingspan of 212 feet, 7 inches  That's the same size as the 777-200LR commercial jet  The KC-777 would be able to carry far more fuel, cargo and passengers than either the KC-767 or the Airbus A330 tanker  The KC-767 offers more operational flexibility, while the KC-777 would be better suited for long-range strategic missions in which more cargo needs to be delivered  The KC-777 would be able to carry more than 350,000 pounds (160,000 kilograms) of fuel and offload more than 220,000 pounds (100,000 kg) of it on a mission of 500 nautical miles (900 kilometers)  On the other hand, the KC-767 can lift off with more than 200,000 pounds (90,000 kg) of fuel and offload more than 130,000 pounds (60,000 kg) in a similar mission  The KC-777 would be able to deliver 200 percent more fuel after flying 1,000 nautical miles than older Air Force KC-135s  The KC-777 could carry up to 37 pallets of cargo, compared to the 19 pallets for the KC-767 "
Postby Cosmo_R » 18 Nov 2014 04:31
Viv S wrote: From Ajai Shukla's article -
HAL points out that, since each Avro flies barely 350 hours every year, most of them have a residual life of about 80,000 hours  In a request for information (RFI) released on August 15, HAL has proposed replacing the aircraft’s engines (Rolls Royce Dart) with “modern fuel efficient engines” 
So, the IAF's Avros have a residual life of 228 years at the current rate of usage  Ain't life grand?
At zero up time, it could reach infinity 
Relax Cy  Kc777 has no client  Usaf is going with kc767 and almost everyone else with a330 
We don't have the number of heavies and long missions of usaf else I would say convert an124 
KC777 will be extremely expensive given the demand/backlog for the 777 and the 777x  Any buyer would have to virtually pay for the increase in capacity 
I think the 767 production line is closed  so the proposed KC767 Boeing is supposed to deliver 18 by 2017  that can be managed from mothballed and cargo hauler airframes on the market 
but to meet the final order of around 180 will they not have to open the production line unless such a huge number were available on the market?
I do get the spider feel this program again will be cancelled in favour of a in-production plane like the 777X ?
I wasn't suggesting we get the KC777  All I was doing was comparing what possibly the 777 could offload compared to A330  It carries 171000 liters of fuel versus 130000 liters that the A330 carries  If we had older 777s in stock, we could have quite easily converted them to this config  The cost to us would be miniscule just the refurbishing cost vs acquiring a new type 
Singha wrote: I think the 767 production line is closed  so the proposed KC767 Boeing is supposed to deliver 18 by 2017  that can be managed from mothballed and cargo hauler airframes on the market 
The Line is open, they have a backlog of around 50 (All Fed ex), with Fed Ex placing a small order this year  The Pegasus order is for all new builds, and so will the follow on order  The only reason for any nation to buy the 767 tanker is going to be because of the ability to hard bargain with Boeing given that the commercial future of the 767 is dead  This also allows a potential buyer to purchase cheap spares from the open market, or club its logistical and inventory purchase with that of the USAF  Other than that and perhaps availability (which would be doubtful once USAF pushes through a larger order) there is really no technical reason to purchase the this tanker over the A330 which by all accounts is a superior tanker in addition to being a much much better airliner in general 
IAI is doing conversations for the 767 and its called the 767 MMTT
http://www iai co il/sip_storage/FILES/1/38471 pdf
Cybaru wrote: I wasn't suggesting we get the KC777  All I was doing was comparing what possibly the 777 could offload compared to A330  It carries 171000 liters of fuel versus 130000 liters that the A330 carries  If we had older 777s in stock, we could have quite easily converted them to this config  The cost to us would be miniscule just the refurbishing cost vs acquiring a new type 
The cost of converting a commercial airliner to a tanker, certifying it and running a full fledged test program is by no means small  There is absolutely no justification for that sort of cost over and above the capability that that A330 provides  If it were a certified and tested conversion, that would be a different matter 
Postby Kartik » 21 Nov 2014 12:27
Cybaru wrote:
Why? If the airframe can handle more flight hours, why not?
because it is a very very old airframe as is  Maintenance spares won't be available easily even as of now, then imagine how it'll be 20-30 years from now   and as things stood anyway, the HS-748 offered very little in terms of payload and range versus a C-295 class aircraft  The C-295 offers a very credible light transport, whereas the HS-748's role in the IAF was more akin to a transport trainer and for communication duties with little operational use  Having seen a dozen or so HS-748s parked at Vadodara airport all through my childhood, I never once saw one in the air  They just seemed to be stored out in the open  Upon asking an IAF transport pilot who was my friend's father, he remarked "zyaada kaam ke nahi hain yeh" 
Why would you expend more capital on what is essentially an obsolete airframe, even if theoretically it had not yet reached its service life? You'd have to re-engine it, put new avionics on board and even that wouldn't suffice for para dropping requirements  it was operationally never suitable for para dropping, which is an important mission for transport aircraft and had deficiencies in hot and high climes as well 
Unfortunately, the 748 was never meant to be a military transport  At the request of IAF, its door was enlarged to enable larger cargo items to be loaded and to allow para dropping without hitting the tail plane



ground_truth: The longerons bow up from the building surface, forming a "banana" shape.

prompt_front: Now, answer the following question based on the text below, only give me the answer and do not output any other words.

Question: What is the effect of the proximity of superconductivity on the Kondo effect?

Read the following text and answer briefly.

Context 2: 51$ ($b=1 50$) for $U'=0$ ($U'=U/10$),
correspondingly; see \figs{G-T}(b-c) 
Moreover, as follows from \eq{Jeff}, $U'$ reduces CAR exchange, and therefore diminishes $T^*$ 
For the same values of $J^{\mathrm{eff}}$, the dependence of $G(T)$ for $t=0$ and $\GS{}>0$ is hardly different 
from the one for $\GS{}=0$ and $t>0$ for $T\geq T^*$ (results not shown) 
However, $G(T)$ saturates at residual value $G_{\mathrm{min}}$ as $T\to 0$ only for finite
$\GS{}$, which at particle-hole symmetry makes $G_{\mathrm{min}}$
the hallmark of SC proximity and the corresponding CAR exchange processes 
From numerical results, one can estimate it as
\begin{equation}
G_{\mathrm{min}} = \frac{e^2}{h} \cdot c \, \frac{\GS{}^2}{U^2} 
	\qquad {\scriptstyle (\GS{1}=\GS{2}=\GS{})} ,
\label{Gmin}
\end{equation}
with $c\approx 2 25$, barely depending on $U'$ and getting smaller for $t>0$  
This is illustrated in \figs{G-T}(d-e), where the dotted line corresponds to \eq{Gmin} with $c=2 25$  

Lastly, in \fig{G-T}(a) we also present the curves obtained for $t=\GS{}$ chosen such, 
that the quantity $\xi=\sqrt{t^2+\GS{}^2}$ remains the same 
in all the cases 
This is to illustrate what happens when \emph{both} (direct and CAR) exchange interactions are
present  \fig{G-T}(c) clearly shows that $T^*$ remains practically unaltered for $U'=0$ 
The comparison with \fig{G-T}(b) proves that in this case it practically does not depend 
on $U'$  The enhancement of direct exchange is compensated by the decrease of the CAR one  
On the contrary, $G_{\mathrm{min}}$ decreases for larger $t$ below the estimation given by Eq ~(\ref{Gmin}), 
as can be seen in \figs{G-T}(d-e)  

While analyzing the results concerning $G_{\mathrm{min}}(\GS{})$ plotted in \figs{G-T}(d-e) 
one needs to keep in mind that $G_{\mathrm{min}}$ is obtained at deeply cryogenic conditions  To illustrate
this better, $G(\GS{})$ obtained for $t=0$ and $T=10^{-6}U$ is plotted with solid line 
in \fig{3}  Clearly, for weak $\GS{}$ the system exhibits rather conventional (single-stage)
Kondo effect with $G=G_{\mathrm{max}}\approx 2e^2/h$, while QD2 is effectively decoupled ($G_{\mathrm{max}}<2e^2/h$
in the proximity of SC lead \cite{KWIW})  Only for larger values of $\GS{}$
the CAR exchange is strong enough, such that $T^*>T$ and the dependence $G(\GS{})$ continuously 
approaches the $T=0$ limit estimated by \eq{Gmin} and presented in \figs{G-T}(d-e) 

\section{CAR-RKKY competition}
\label{sec:RKKY}

\begin{figure}
\includegraphics[width=0 98\linewidth]{Fig3 pdf}
\caption{Linear conductance $G$ vs  $\GS{}$ calculated
		 for $t=0$, $\Gamma=U/5$, $U'=U/10$, finite $T=10^{-6}U$
		 and different values of RKKY coupling $J$, as indicated  
		 Inset shows QD1 spectral function $\mathcal{A}(\omega)$ as a function of energy $\omega$
		 for points on $J=-0 1U$ curve, indicated with corresponding symbols 
		}
\label{fig:3}
\end{figure}

Let us now discuss the effects introduced by the conventional RKKY interaction 
We choose $t=0$ for the sake of simplicity and
analyze a wide range of $\GS{}$, starting from the case of anti-ferromagnetic 
RKKY interaction ($J>0$)  Large $J>0$ leads to the formation of a molecular singlet in the 
nanostructure  This suppresses the conductance, unless $\GS{}$ becomes of the order of $U/2$, 
when the excited states of DQD are all close to the ground state  This is illustrated 
by double-dotted line in \fig{3} 
Smaller value of $J>0$ causes less dramatic consequences, namely it just increases $J^{\mathrm{eff}}$ according
to \eq{Jeff}, leading to enhancement of $T^*$, cf  \eq{Tstar}  This is presented with
dot-dashed line in \fig{3} 

The situation changes qualitatively for ferromagnetic RKKY coupling, $J<0$ 
Then, RKKY exchange and CAR exchange have opposite signs and compete with each other 
Depending on their magnitudes and temperature, one
of the following scenarios may happen 

For $J^{\mathrm{eff}} > 0$, {\it i e } large enough $\GS{}$, and $T<T^*$, the system is in the 
singlet state due to the two-stage Kondo screening of DQD spins  $G(T\!=\!0)$ is reduced 
to $G_{\mathrm{min}}$, which tends to increase for large negative $J$; see dashed lines in \fig{3}  
In the inset to \fig{3}, the spectral density of QD1 representative for this regime is plotted 
as curve indicated by triangle  It corresponds to a point on the $J=-0 1U$ curve in the main 
plot, also indicated by triangle  The dip in $\mathcal{A}(\omega)$ has width of order of $T^*$ 

For finite $T$, there is always a range of sufficiently small $|J^{\mathrm{eff}}|$, where QD2 becomes effectively
decoupled, and, provided $T<T_K$, $G$ reaches $G_{\mathrm{max}}$ due to conventional Kondo effect 
at QD1  This is the case for sufficiently small $\GS{}$ for $J=0$ or $J=-0 01U$, and in the narrow
range of $\GS{}$ around the point indicated by a circle in \fig{3} for $J=-0 1U$ (for $J=0 01U$, 
the considered $T$ is close to $T^*$ and $G$ does not reach $G_{\rm max}$)  The conventional Kondo effect manifests itself with 
a characteristic peak in $\mathcal{A}(\omega)$, as illustrated in the inset in \fig{3} with line denoted by circle 

Finally, large enough $J^{\mathrm{eff}} < 0$ and low $T$, give rise to an effective ferromagnetic coupling of DQDs 
spins into triplet state  Consequently, the underscreened Kondo effect occurs 
\cite{Mattis,NozieresBlandin} for weak $\GS{}$ and, {\it e g }, $J=-0 1U$; 
see the point indicated by square in \fig{3} 
This leads to $G=G_{\mathrm{max}}$ and a peak in $\mathcal{A}(\omega)$, whose shape is significantly different from the
Kondo peak, cf  the curve denoted by square in the inset in \fig{3}  



\section{Effects of detuning from the particle-hole symmetry point}
\label{sec:asym}

\begin{figure}
\includegraphics[width=0 98\linewidth]{Fig4 pdf}
\caption{
         (a) Linear conductance between the normal leads $G$ as a function of temperature $T$
         for parameters corresponding to \fig{G-T}(a) with $\xi=U/10$, and additional curves for finite 
         detuning from particle-hole symmetry point, $\delta_1=-\delta_2$, 
         and two values of $\xi=\sqrt{t^2+\GS{}^2}$, as indicated in the figure 
         (b) $G_{\mathrm{min}} \equiv G(T \!=\! 0)$ as a function of QD1 detuning $\delta_1$ for different
         exchange mechanisms, $\xi=U/10$ and $\delta_2=\pm\delta_1$ (as indicated) 
		}
\label{fig:asym}
\end{figure}

At PHS $G_{\mathrm{min}}=G(T \!=\! 0)=0$ in the absence of superconducting lead, making $G_{\mathrm{min}} > 0$ a hallmark
of SC-induced two-stage Kondo effect  However, outside of PHS point $G_{\mathrm{min}} > 0$ even in the case of 
the two-stage Kondo effect caused by the direct exchange  
Exact PHS conditions are hardly possible in real systems, and the fine-tuning of the QD energy
levels to PHS point is limited to some finite accuracy 
Therefore, there may appear a question, if the results obtained at PHS are of any importance for the
realistic setups  As we show below --- they are,
in a reasonable range of detunings $\delta_i=\varepsilon_i +U/2$ 

In \fig{asym}(a) we present the $G(T)$ dependence in and outside the PHS, corresponding to 
parameters of \fig{G-T}(a)  
Clearly, for considered small values of $\delta_1=\delta_2=\delta$, 
$G_{\mathrm{min}}<10^{-3}e^2/h$ for direct exchange only, while $G_{\mathrm{min}}$ in the presence of a superconductor is 
significantly increased and close to the PHS value  Furthermore, for $|\delta_1| \sim |\delta_2| 
\sim \delta$, the residual conductance caused by the lack of PHS, $G_{\mathrm{min}} \approx e^2/h \cdot (\delta/U)^2$,
which is a rapidly decreasing function in the vicinity of PHS point, as illustrated in \fig{asym}(b)
with lines denoted by a square  Evidently, in the regime $|\delta_i| < 0 01U$ the residual conductance
caused by SC is orders of magnitude larger, leading to the plateau in $G_{\mathrm{min}}(\delta_1)$ dependence,
visible in \fig{asym}(b) 
Taking into account that the realistic values of $U$ in the semiconductor quantum dots are rather 
large, this condition seems to be realizable by fine-tuning of QD gate voltages 

Lastly, let us point out that while in the presence of only one exchange mechanism, \emph{CAR} or
\emph{direct}, $G_{\mathrm{min}}(\delta_1)$ dependencies depicted in \fig{asym}(b) are symmetrical with respect
to sign change of $\delta_1$, for \emph{both} exchange mechanisms the dependence is non-symmetric  

\section{Effects of asymmetry of couplings to superconductor}
\label{sec:x}

\begin{figure}
\includegraphics[width=0 98\linewidth]{Fig5 pdf}
\caption{
		 (a) Linear conductance between the normal leads, $G$, as a function of temperature, $T$,
		 for parameters corresponding to \fig{G-T}(a) with $\xi=U/10$, for different values 
		 of asymmetry coefficient $x$ [see \eq{xGS}], in the presence of \emph{CAR} exchange only 
		 %
		 (b) The second-stage Kondo temperature $T^*$ normalized by $T_K$ as a function of $x$, 
		 calculated with the aid of NRG (points) and a fit to \eq{Tstar} (lines) 
		 with $J^{\mathrm{eff}}$ from \eq{Jeff} 
		 %
		 (c) The zero-temperature conductance $G_{\mathrm{min}}$ as a function of QD1 coupling to SC lead, $\GS{1}$,
		 compiled from data obtained at different circumstances (as indicated in the legend)
		 for different $x$  Dotted line corresponds to \eq{Gmin2} with $c=2 25$ 
		}
\label{fig:x}
\end{figure}

Similarly to PHS, the ideal symmetry in the coupling between respective QDs and SC lead is hardly possible
in experimental reality  As shown below, it does not introduce any qualitatively new features 
On the other hand, it decreases the second stage Kondo temperature, which is already small, therefore,
quantitative estimation of this decrease may be important for potential experimental approaches 
To analyze the effects of $\GS{1}\neq\GS{2}$, we introduce the asymmetry parameter $x$ and extend
the definition of $\GS{}$,
\beq
x = \frac{\GS{1}-\GS{2}}{\GS{1}+\GS{2}}, \quad \GS{} = \frac{\GS{1}+\GS{2}}{2} 
\label{xGS}
 \end{equation} 
Note, that even for a fixed $\GS{}$, the actual CAR coupling $\GS{\rm X}=\GS{}\sqrt{1-x^2}$ decreases
with increasing $|x|$, which is a main mechanism leading to a decrease of $T^*$ outside the $x=0$ point
visible in \figs{x}(a) and (b)  To illustrate this, the curves corresponding to \emph{both} exchange
mechanisms were calculated using $x$-dependent $t=\GS{\rm X}$ instead of $t=\xi/\sqrt{2}$  
Therefore, $\xi$ was generalized for $x\neq 0$ by setting $\xi=\sqrt{t^2(1-x^2)^{-1}+\GS{}^2}$ 
Clearly, in \fig{x}(b) the curves for different exchange mechanisms are very similar and differ mainly 
by a constant factor, resulting from different influence of $U'$; see \Sec{scales}  
The magnitude of $T^*$ changes is quite large, exceeding an order of magnitude for $x=\pm 0 5$ 
and $\xi=U/20$  Moreover, $T^* \to 0$ for $x\to\pm 1$  Consequently, for strongly asymmetric
devices one cannot hope to observe the second stage of Kondo screening 

A careful observer can note that the $T^*(x)$ dependency is not symmetrical; note for example different 
$T^*$ for $x=\pm 0 5$ in \fig{x}(a)  This is caused by the dependence of the first stage Kondo temperature
$T_K$ on $\GS{1}$ \cite{part1,DomanskiIW},
\beq
\widetilde{T}_K(\GS{1}) = T_K \cdot \exp\!\left( \frac{\pi}{2} \frac{\GS{1}^2}{\Gamma U}\right) 
 \end{equation} 
Here, $T_K$ is, as earlier, defined in the absence of SC, while $\widetilde{T}_K$ is a function 
of $\GS{1}$, such that $G(\widetilde{T}_K) = G_{\rm max}(\GS{1})/2$ in the absence of QD2  
As $\widetilde{T}_K$ grows for increasing $\GS{1}$ (or $x$), $T^*$ decreases according to \eq{Tstar}  
Its $\GS{}$ dependence can be accounted for by small changes in the coefficients $a$ and $b$ in \eq{Tstar}, 
as long as $x$ is kept constant  

To close the discussion of $T^*(x)$ dependence let us point out, that in \eq{A_J} 
there appears a correction to \eq{Jeff} for $x\neq 0$  However, it is very small due to additional
factor $\GS{}^2/U^2$ in the leading order  Its influence on curves plotted in \fig{x}(b) is hardly visible 

In turn, let us examine the $x$ dependence of the $T=0$ conductance $G_{\mathrm{min}}$  As can be seen 
in \fig{x}(a), it monotonically increases with $x$, as it crosses $x=0$ point  In fact, \eq{Gmin}
can be generalized to
\beq
G_{\mathrm{min}} = \frac{e^2}{h} \cdot c \, \frac{\GS{1}^2}{U^2} ,
\label{Gmin2}
 \end{equation} 
with $c\approx 2 25$ (indicated by a dotted line in \fig{x}(c))  Note that $G_{\mathrm{min}}$ is proportional to 
$\GS{1}^2=(x+1)^2 \GS{}^2$, instead of simply $\GS{}$, cf  \eq{Gmin}  The values of $G_{\mathrm{min}}$ obtained
from all analyzed $G(T)$ dependencies for different $x$ have been compiled in \fig{x}(c) 
It is evident, that \eq{Gmin2} is approximately fulfilled for all the considered cases 

Finally, it seems noteworthy that the normal-lead coupling asymmetry, 
$\Gamma_{\rm L}\neq \Gamma_{\rm R}$, is irrelevant for the results except for a constant factor
diminishing the conductance $G$ \cite{KWIWJB-asym} 



\section{The role of CAR efficiency}
\label{sec:coef}

\begin{figure}[tb]
\includegraphics[width=0 98\linewidth]{Fig6 pdf}
\caption{Linear conductance between the normal leads
		 $G$ as a function of coupling to SC lead, $\GS{}$, for indicated values of RKKY exchange $J$
		 and the efficiency of CAR processes reduced by factor (a) $\mathcal{C}=0 9$ and (b) $\mathcal{C}=0 5$ 
		 Other parameters as in \fig{3} 
		 Insets: QD1 local spectral density $\mathcal{A}(\omega)$ as a function of energy $\omega$
		 for points on $J=-0 1U$ curve, indicated with corresponding symbols 
		} 
\label{fig:C}
\end{figure}

Up to this point we assumed $\GS{\rm X} = \sqrt{\GS{1}\GS{2}}$, which is valid when the two 
quantum dots are much closer to each other than the coherence length in the superconductor 
This does not have to be the case in real setups, yet relaxing this assumption does not 
introduce qualitative changes  Nevertheless, the model cannot be extended to inter-dot 
distances much larger than the coherence length, where $\GS{\rm X}\to 0$ 

To quantitatively analyze the consequences of less effective Andreev coupling we define the 
CAR efficiency as $\mathcal{C} \equiv \GS{\rm X} / \sqrt{\GS{1}\GS{2}}$ and analyze $\mathcal{C} < 1$
in the wide range of $\GS{1}=\GS{2}=\GS{}$ and other parameters corresponding to \fig{3}  
The results are presented in \fig{C} 

Clearly, decreasing $\mathcal{C}$ from $\mathcal{C}=1$ causes diminishing of $\GS{\rm X}$, and consequently of CAR 
exchange  For a change as small as $\mathcal{C}=0 9$, the consequences reduce to some shift of the 
conventional Kondo regime, compare \fig{C}(a) with \fig{3}  Stronger suppression of CAR may, 
however, increase the SC coupling necessary to observe the second stage of Kondo screening caused
by CAR outside the experimentally achievable range, see \fig{C}(b)  Moreover, the reduced $T^*$
leads to narrowing of the related local spectral density dip, while the
increased critical $\GS{}$ necessary for the observation of the second stage of screening leads to the
shallowing of the dip  This is visible especially in the inset in \fig{C}(b) 


\section{Conclusions}
\label{sec:conclusions}

The CAR exchange mechanism is present in any system comprising at least
two QDs or magnetic impurities coupled to the same superconducting contact
in a way allowing for crossed Andreev reflections 
In the considered setup, comprised of two quantum dots in a T-shaped geometry 
with respect to normal leads and proximized by superconductor,
it leads to the two-stage Kondo
screening even in the absence of other exchange mechanisms 
This CAR induced exchange screening is characterized by a residual 
low-temperature conductance at particle-hole symmetric case 
We have also shown that the competition between CAR exchange and RKKY
interaction may result in completely different Kondo screening scenarios 

The presented results bring further insight into the low-temperature
behavior of hybrid coupled quantum dot systems, which hopefully could be verified
with the present-day experimental techniques 
Moreover, non-local pairing is present also in bulk systems such as non-$s$-wave superconductors 
The question if an analogue of discussed CAR exchange may play a role there
seems intriguing in the context of tendencies of many strongly correlated materials
to possess superconducting and anti-ferromagnetic phases 


\begin{acknowledgments}
This work was supported by the National Science Centre in Poland through project no 
2015/19/N/ST3/01030 
We thank J  Barna\'{s} and T  Maier for valuable discussions 
\end{acknowledgments}





Context 3:  However, to load a jeep in it, a 30-ft long ramp was required  The jeep would drive in and insert its front wheels into the aircraft  Then it had to be manually lifted and turned to get it in  Unloading it was just as difficult  Para dropping of troops or cargo even from the aircraft with the enlarged door was considered too dangerous with the risk of hitting the tail plane  The aircraft's performance at hot and high airfields was hopelessly inadequate  Eventually IAF acquired the tail-loading An-32s which were powered specifically for IAF's need for operating in the Himalayas 
BRF article -Avro in IAF service
Now unless you want to overcome all these through a costly, time consuming engineering re-design program, that too without access to original documents since this airplane was designed in the 1960s, there is no question of keeping them going for another 40 years  By which time the original design would be over 80 years old and with no one on earth but the IAF as an operator and HAL as the agency supporting it  Hardly a situation anyone would want 
abhik wrote: +1, Air India recently sold their entire fleet of Boeing 777s 
Only 5 of the Boeing 777-200LR, to Etihad Airways, which IMO was a bad decision  they could have reconfigured the airplanes with just 2 classes and continued to fly them to the US, non-stop 
The remaining 3 777-200LR were offered for lease but are still a part of AI's fleet since they didn't find any takers  This particular model hardly sold much and was developed for ultra-long range flights  it was the least successful 777 model and clearly AI goofed up on the configuration by going for these in place of the 300ER  The economics however didn't make too much sense for AI eventually 
there are 13 777-300ER as a part of their fleet ahd their economics is much better 
Govt  to decide tomorrow on whether to go ahead and allow the IAF to verify the technical details of the C-295 bid by Tata-Airbus instead of scrapping the tender due to single vendor situation 
The government will decide on Saturday whether to press ahead with the Rs 13,000 crore mega project for the private sector to supply 56 medium transport aircraft to the IAF despite only a single bidder, the Tata-Airbus consortium, being in the fray 
Though the defence acquisitions council (DAC) chaired by Manohar Parrikar will take the final decision, MoD sources on Tuesday said the "emerging dominant view" is that green signal should be given to the crucial project designed to promote Indian private sector's entry into the domestic aerospace arena with foreign collaboration 
"The Tata-Airbus technical and commercial bid is a credible offer submitted in a competitive environment  The other seven contenders backed out for one reason or the other," said a source 
IAF has now sought the clearance of the DAC -- the first such meeting to be chaired by Parrikar after becoming defence minister on November 10 -- to begin technical evaluation of the C-295 aircraft offered by Airbus Defence & Space and Tata Advanced Systems 
Though it has become a single-vendor situation, the DAC can approve it if it wants as per existing procurement procedures  Of the eight foreign aviation majors that got the global tender, American Boeing and Lockheed-Martin as well as Brazilian Embraer said they did not manufacture the class of aircraft being sought by IAF 
Refusing to take part in the tender, Russian Rosoboronexport said it wanted a fresh design and development project  Antonov of Ukraine wanted yet another extension of the bid submission deadline due to the ongoing conflict in Crimea  Swedish Saab said it had shut down its assembly line for such aircraft 
Then, Alenia Aermacchi was linked to Italian conglomerate Finmeccanica, which has been slapped with "a partial ban" after the infamous VVIP helicopter scandal  "All this left only the European consortium Airbus  The DAC will have to take a call since re-tendering may lead to the same situation," said the source 
Incidentally, it was the Modi government's first DAC in July -- then headed by Arun Jaitley - which revived the Avro replacement project after it was put on hold by the UPA-2 regime last year due to strong opposition from the powerful PSU lobby and ministers like Praful Patel, as reported by TOI earlier 
Apart from the critical need to encourage the private sector to enter defence production in a big way, especially in the aerospace arena where Hindustan Aeronautics enjoys a monopoly, its felt the defence PSU's order books are already overflowing with projects 
Fingers crossed  Hopefully sense will prevail 
Why was lr got? Er is capable of Dubai to sfo nonstop 
Lr is overkill unless we want Delhi to Peru  
Singha wrote: Why was lr got? Er is capable of Dubai to sfo nonstop 
they wanted it for non-stop routes from India to the west coast of the US  But with fuel prices going higher and with the lower seat count on the 777-200LR, the seat mile costs grew too high  A 3 class configuration only made matters worse  A higher density configuration with more economy class seats and just 12-15 Business class seats would have been better perhaps, especially if they didn't have very high First Class load factors 
LR and ER is better if you want to have a better payload down below for long haul  Ultimately, the best bet is going to come form the 787's that take a fewer people (so you can do the longer routes) with still a competitive CASM, and the B and F class folks will pay good money for newer aircraft 
Postby Kartik » 04 Dec 2014 12:55
Lets see if there is any forward movement on the stalled MTA project once Putin arrives in New Delhi
Major defence deals to be signed during Putin-Modi summit
In this connection, it is expected that during the summit, Russia and India may ultimately resolve several long-delayed agreements on military-technical cooperation projects between the two countries and sign them finally for their implementation  These agreements, above all, include joint Fifth Generation Fighter Aircraft (FGFA) project and joint development of Multi-role Transport Aircraft (MTA) 
A final deal on FGFA for production has been delayed because the Indian Air Force (IAF) did not approve the design and work-share  Now Russia has reportedly agreed that the jet would be a two-seat design, not a one-seater  India’s work-share would also be increased from18 percent to 25 percent, and even up to 40-50 percent in the near future, in view of the steady development of the Indian aviation industry 
Defence and SecurityAccording to the agreement, India’s stealth air-to-air missile “Astra” along with Indo-Russian BrahMos supersonic cruise missile will be mounted on the FGFA 
The preliminary design agreement on FGFA had been signed in 2010 between Indian HAL and Russian Sukhoi Design Bureau to build the jet for the use by both countries  The final design contract was to be signed in July-August 2012  But the deadline has already passed  According to the Indian media reports, under the programme, India is expected to build 200 fighter jets at the cost of $30 billion 
FGFA is not the only Indo-Russia joint project  The two countries also signed an agreement on the joint development of MTA in 2007, based on Il-214 Russian plane  The cost of the $600 million project is being equally shared by the two countries  The MTA, when developed, will have ready market for 205 aircraft - 45 for the Indian Air Force, 100 for the Russian Air Force, and 60 more for exporting to friendly countries  The international market for MTA is estimated at 390 planes  Under the agreement, thirty percent of the annual production of planes could be exported to third countries 
The MTA was expected to go in service with the Russian and Indian Air Forces in 2015  But the project faced a number of problems, delaying the development of the MTA  The project got into rough weather after India felt there was nothing much for Indian engineers and scientists to do in the design and development of the MTA 
However, all the issues related to the project were resolved with the Russians when the HAL undertook to carry out design and development of its work-share of MTA at Aircraft R&D Centre at Bangalore  Russian Ilyushin Design Bureau and the Irkut Corporation and HAL are participating in the project  The first flight is expected to take place in 2017-18 
The MTA would replace the AN- 32 aircraft being used by the IAF  It will be used for both cargo and troop transportation, para-drop and air drop of supplies, including low-altitude parachute extraction system 
BrahMos missile exports a challenging proposition
Another key deal expected to be signed during the summit, is for the development of “BrahMos mini missile” by the Indo-Russian joint venture BrahMos Aerospace which manufactures supersonic cruise missile  BrahMos’ new CEO Sudhir Mishra recently said he was hopeful that a deal to develop the mini version of the missile will be signed during Putin’s summit with Modi 
“We are hoping to sign a tripartite agreement between DRDO, NPOM lab and BrahMos Aerospace during the planned visit of Russian President in December,” Mishra said 
He said that the new missile will have a speed of 3 5 mach and carry a payload of 300 km up to a range of 290 km  In size, it will be about half of the present missile, which is around 10 metres long  The missile can be integrated with different platforms, including submarines and FGFA  It is planned to be inducted into service by 2017 
Modi-Abbott to upgrade defence ties
A new dimension:
In a first, India and Australia will also set up a mechanism to discuss “synergies in integrating defence system”, including research and development cooperation on integrating defence equipment that both countries currently purchase, for example, U S’s C-17 Globemaster III, according to officials 
^^That report about MTA is fishy  First it says that India has nothing to learn from an existing design (duh) and then says the issue has been resolved  How? Next it says India's need is 45 planes to replace over 100 An-32s  It also speculates about the export potential which may be nonexistent unless we sell it for peanuts 
This is a scam which only aims to create screwdriver jobs at HAL, stall any attempt to introduce private players into the aviation market and continue the Russian gravy train  My fear is the Russkies have our testiments in a firm grip with key components of Brahmos, nuke subs, Su30mki etc and we may be jerked around 
(They need to be more definitive about "MTA" - Multirole vs  Medium)
The Indians had not selected an engine (among other things) for the MTA with the Russians  Perhaps that has been resolved now 
On export numbers, IIRC, it was the responsibility of Rosoboronexport  ?????
Kartik wrote: The MTA would replace the AN- 32 aircraft being used by the IAF  It will be used for both cargo and troop transportation, para-drop and air drop of supplies, including low-altitude parachute extraction system 
Pardon my ignorance  The Avro and An-32 have different upgrade paths  How are the replacements for these venerable aircraft different in terms of use cases in IAF  Cannot one platform replace both these types? (Either MTA or C-295)
In this case, I feel they should have just gone with screwdrivergiri (production tech) and got to market first  There is no jet-powered transporter in this range! Just license produce the IL-214 with the PD-14M, glass cockpit and a state-of-the-art COTS avionics computer 
In my view, it was a low hanging fruit, which they completely messed up! They could have learnt on how to adopt the plane for the 160-200 seater 
indranilroy wrote: They could have learnt on how to adopt the plane for the 160-200 seater 
Yes, the MTA project should fold the Avro, An-32 and the regional transport role and become a conversion project rather a development one  The driving numbers will come from the regional transport (thousands in India itself) rather than the Avro or medium transport roles (max 300 between them)  This changes the ball game and introduces all kinds of possibilities  But I'm pretty sure that the Il-214/MTA is not the way to go because it will take a decade or more to arrive  A good possibility was another Antonov, the An-148 but it has some mechanical glitches apparently besides being bogged down in the Ukraine mess  Maybe the Russians can "relocate" the aircraft to Russia? The other possibility is the BAe-146 which is ironically another Avro  We should remember that both the HS-748 "Avro" and An-32 were regional airliners that were converted to military use, not the other way around  HAL or a private firm will pick up a lot of experience in the conversion process itself 
The Sukhoi Superjet is already in production/orders,with over 100+ for Russian and intl  customers



ground_truth: It tends to suppress the Kondo effect.

prompt_front: Now, answer the following question based on the text below, only give me the answer and do not output any other words.

Question: Besides the Boeing C-17, what other transport aircraft is the IAF considering for acquisition?

Read the following text and answer briefly.

Context 3:  It is ideal for regional transport,perfect for flights to smaller Tier-2/3 cities from metros  If we really want a regional jet this is the fastest way toi go,we can set up a manufacturing unti here for the same at an HAL unit 
Postby shaun » 05 Dec 2014 15:24
Its an international projects, with components outsourced from different international vendors   Over 30 foreign partnership companies are involved in the project and partly financed by Italy 
Sukhoi is good for passenger use but wont be suitable for military, rough field use  The shoulder wing jets like the An-148 have slower speeds and better ground clearance  The Bae-146 was usedby Druk Air in Bhutan so it should do OK in the ALGs  If we don't fold our requirements then we should go with something like the Superjet which we will at least be able to make in India and also modify to stretched versions  Unless we have a clear path to operational clearance within 10 yrs for the RTA project vetted by our top industrial houses, it is pie-in-the-sky and should be dropped  The RTA will be big enough to keep 2-3 factories humming and leapfrog our capabilities  If we don't get our act together almost immediately, we will miss the boat, just like our trainer fiascos 
I don't think Superjet fits into our scheme of things  We should think as a country and see to it that our programs don't trample on each other 
First, the more certain ones:
1  Mahindras NM5 and Airvans can care of the low-cost but sturdy 5,8,10 and 18-seater section 
2  Saras had such great potential for being the high performance 14-18 seater  But I have almost given up on it  This section will most probably be taken up by the Tata-built Do-228 NG 
3  We should standardize the C-295 as the Avro/An-32 replacement and create a 70-80 seater variant out of it 
And then the more wishful ones:
1  If the RTA is going to be a jet, then make it a 100-130 seater  I don't expect the first prototype to take the sky before 2025  I feel it is too big of a jump where we don't even have a base  With LCA, at least we were at least license producing other fighters 
4  Building on the IL-214, the MTA was on a more sure footing  But, I can't see how the first prototype can to take to the sky before 2019(more than 10 years since MTAL was formed)! If the transport plane materializes, then one can imagine making a civilian 150-200 seater version of the same  But this program needs a push  Will Putin's visit be able to galvanize this into the next symbol of Indo-Russian cooperation  Probably not!
Postby GeorgeWelch » 12 Dec 2014 23:39
http://www ctvnews ca/canada/defence-de     -1 2144472
The Defence Department intends to purchase a Boeing C-17 Globemaster III, a large military transport plane that comes with a price tag of just under $200 million, CTV News has learned
It's difficult to get a good count, but by some sources, if this and the 4 Australia planes go through, there will only be 5 left 
X-Posting from FGFA thread 
Despite Putin’s visit, two pacts on military aircraft still in doldrums
President Vladimir Putin may have come and gone but stalemate largely persists over two key long-pending India-Russian defence projects, the fifth-generation fighter aircraft (FGFA) and military multirole transport aircraft (MTA) 
The deadlock over the MTA, which were initially envisaged to gradually replace IAF's ageing fleet of the medium-lift AN-32 aircraft, seems to be much more serious  India now wants to ascertain the cost viability of the twin-engine transport aircraft in comparison to similar planes available in the market 
There are also questions about the MTA's "predicted timelines for delivery" as well as its failure to meet the high-altitude requirements, which need to be answered before India even thinks of inking the full-scale contract for the project, said sources 
Postby Gyan » 13 Dec 2014 12:29
indranilroy wrote: I don't think Superjet fits into our scheme of things  We should think as a country and see to it that our programs don't trample on each other 
1  Mahindras NM5 and Airvans can care of the low-cost but sturdy 5,8,10 and 18-seater section  Righto
2  Saras had such great potential for being the high performance 14-18 seater  But I have almost given up on it  This section will most probably be taken up by the Tata-built Do-228 NG  We need future extended variants of presurrized aircraft like 30 seater Saras and say 30 seater unpressurized Do-328 NG 
3  We should standardize the C-295 as the Avro/An-32 replacement and create a Civilian turboprop pressurized cabin 70-80 seater variant out of it 
1  If the RTA is going to be a jet, then make it a 100-130 seater  Agreeeeeed I don't expect the first prototype to take the sky before 2025  I feel it is too big of a jump where we don't even have a base  With LCA, at least we were at least license producing other fighters  Though I think that we should participate in Russian MS-21 and also the wide body follow on 
4  Building on the IL-214, the MTA was on a more sure footing  But, I can't see how the first prototype can to take to the sky before 2019(more than 10 years since MTAL was formed)! If the transport plane materializes, then one can imagine making a civilian 150-200 seater version of the same  Though I think that we should participate in Russian MS-21 and also the wide body follow on  But this program needs a push  Will Putin's visit be able to galvanize this into the next symbol of Indo-Russian cooperation  Probably not!
Absence of any specifics on Sukhoi Superjet, MS-21, Wide body aircraft, Mi-38, MRTA, FGFA, even after Putin visit is very disappointing 
FlightGlobal- Boeing sitting on 8 unsold C-17s
By: Dan ParsonsWashington DCSource: Flightglobal com
This story is sourced from Flightglobal com 12 hours agoBoeing has sold two more C-17 transports to an undisclosed customer, but it will likely end the year with eight unsold white tails 
There are 10 Boeing C-17 airlifters in various stages of assembly at the company’s Long Beach, California, production facility 
Two of the aircraft are spoken for by an unnamed customer, Boeing says  Boeing is trying to sell off the other eight white tails, which will be the last produced before the factory is shuttered sometime in the summer of 2015 
The 279th – and final – C-17 fuselage will be mated to its wings in January or February, programme spokeswoman Tiffany Pitts tells Flightglobal  The operation is California’s last remaining aircraft production line and the lone widebody military aircraft production line in the USA, according to Boeing 
At least two countries – Australia and Canada – have publicly announced an intention to purchase a C-17, though neither factor into Boeing’s future planning, Pitts says  Until contracts are finalised, the number available remains eight, she says  The Royal Canadian Air Force already has four C-17As, according to Flightglobal’s World Air Forces 2014 directory 
Canadian news outlets reported earlier in December that the air force would buy one C-17 with money left over at the end of 2015 
Australia is further along with its bid to purchase C-17s  The US Defense Security Cooperation Agency in November announced Australia was approved to buy up to four C-17s and support equipment for $1 6 billion 
Boeing has plans to store any unsold C-17s following closure of its production line, Pitts says 
“I’m hoping they all will be sold before then, but we’ve had plans in place for a very long time to store and maintain the aircraft if that doesn’t happen,” she says 
the IAF will need to factor in the demand vs availability of C-17s and stock up with a follow-on order quickly  The initial plan to have 16 C-17s may not fructify, considering that there are just 8 left now, with Australia having announced plans to buy 4 more 
why are they closing the line if it has demands ???
Real estate sales tactics probably  Buy now last 8 3bhk flats Saar 
krishnan wrote: why are they closing the line if it has demands ???
It requires 3 years lead time to order raw materials/parts from all of its sub-vendors  All current firm orders have been fulfilled, and no new orders have come  Anticipating a need for a few more aircrafts, they produced 10 extra (self-funded) units before production winded down  Bottom line is they don't make money keeping an idle plant around with all its employees and infrastructure  At most what they will likely do is keep a limited infrastructure around for a few more years in case a bunch of new orders come  They can then see if it makes business sense to re-open the plant 
Postby Aditya_V » 17 Dec 2014 12:19
Wish this can be brought to the notice of Journos/ Poster when slamming LCA/ Arjun and other indigenous projects  If there are no orders there will be no efficiency 
Dec 10, 2014 :: Russia launches Il-76MDM upgrade programme
Russia's Ilyushin has started to upgrade a first Russian Air Force (VVS) Ilyushin Il-76MD 'Candid' military transport aircraft to Il-76MDM standard, company officials have told IHS Jane's   The main features of the upgrade include refurbished engines and upgraded avionics 
The modernisation is being conducted at the VVS's Military Transport Aviation (MTA) maintenance facility based at the Ilyushin division in Zhukovsky city near Moscow 
A senior Ilyushin official told IHS Jane's that the upgrade of the first aircraft will be finished in 18 months  Subsequent aircraft will take less time to complete the process, however  When the modernisation is finished the initial Il-76MDM will undergo state trials  The upgrade process for subsequent aircraft will begin when the trials programme is completed 
IHS Jane's was previously told by a VVS senior official that the modernisation of 41 MTA Il-76MDs is planned by 2020  While the Il-76MDM upgrade retains the old D-30KP engine (compared with the PS-90A engine equipping the new Il-76MD-90A/Il-476), the modernisation effort should match the aircraft's onboard electronics with those of the newbuild Il-76MD-90A  This and other efforts mean the cost of modernising the Il-76MD to Il-76MDM is only a third of that of a newbuild Il-76MD-90A 
The existing D-30KP engines are to be enhanced to increase their service life  The overall aircraft's service life will be extended by 15 years 
The upgrade works are planned to be conducted in an aviation repair factory or in the MTA's aircraft maintenance facility  As a result, the Ulyanovsk-based Aviastar-SP plant, which is building the Il-76MD-90A, is not involved in the Il-76MD to Il-76MDM modernisation programme 
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ground_truth: The IAF is considering the acquisition of the Airbus A330 MRTT (Multi-Role Tanker Transport) besides the Boeing C-17.