Guys we've got us a mini-split so we're going to go do a leak check. Customer says that the unit has been freezing up and it defaulted out twice and it's for a little computer room which ain't much of a computer room which is a tiny little burger so we're going to scan it over see if it's leaking into the normal spots like the coil or the flares. I guess they recharged it a while back it's been a while like a couple years so it's a tiny leak if it is leaking if that's even what's wrong with it but before I disturb anything first thing I wanted to do is scan it for leaks and see if we can find something wrong with it first. So we scanned the whole thing over top back and bottom all down through here even got in here to the flare fittings I don't have anything on those. Don't have anything as far as a signal so we're going to go outside we're going to go ahead and check it and see what we got out there. I've got it back together here so let's go ahead and turn it on crank it down but the batteries are about dead and let's go up on the roof and see how the charge is because there's really no sense of spending a bunch of time if it ain't doing its job and for those new to the Mitsubishi world this little thing here once it's programmed you can take it and throw it away. It does not sense temperature all temperatures since inside the head. Common knowledge to a lot of guys out there but to anybody new you know it's something I didn't realize when I first started so I'm bringing it up now. Make sure you always strap your ladders and three rungs up. It's pretty windy up here. I had my ladder blow off before because I usually don't like strapping it but I try to do it on a routine basis now. Let's take a look at this Mitsubishi and see what we got going on. It's putting out some heat. Just doing a visual look around. I'm not seeing any oil any oil on the coil as of now. Kind of a cruddy design this one here has the whole top lift off which kind of breaks the airflow going through the coil. A great way to work on these with the covers off. So let's take a peeky and see what we got. We're running just a tad under 30 degrees which would tell me that we're probably a little low. I'm sure it's slowing down a little bit based off of it knowing that things aren't quite right. It seems to like keep itself going. If I'm reading that correctly which is really hard to see looks like three pounds one ounce possibly which I'm gonna write inside here and inside the cover so they know for later. It does look a little low. The best way to do these is pull it and weigh it in but still let's uh let's see what we can find out if we can find any leaks. All right it's pretty cool and it's like I said pretty windy up here. We uh looks like we've got are you serious? They literally got a low ambient control on this thing. This must not be a variable speed. It ain't. This is not a variable speed unit. It's no inverter drive. It's just a generic air conditioner. So they had the liquid line sensor on the discharge gas there and it wasn't even strapped. They literally just wrapped it around or just set it in there and wrapped some insulation there around it. That's it. So unhooked it. It's slowing down the motor so obviously that's starting to make a difference. Look at that. Coming up above freezing now. Imagine that right? Kind of interesting. Maybe there is no leak. Maybe it's just we've got an issue with the placement of the low ambient kit. So let's see if we can find the liquid line here and we'll move it to it and see if it starts working a little bit better. At very back corner down there and put it down and add vicinity down there or you can stick it in the coil which I don't really care for. Like I was mentioning I went ahead and got the aluminum first, wrapped it with the foam tape. Not my preferred method of how things are going but that's how we've got it. So we've got that there.  I'm going to go ahead and tap onto the discharge to kind of get an idea for where we're at on things. Usually I'm not real big on tapping these many splits but I gotta get a little bit better picture of what's going on here. So it just came on. It's running. We are starting to build up some head pressure here. You can see our condensing temperatures at 92. It's slowly building up. The fan is finally starting to kick on like it should. Generally this thing is set up I believe to hold around 100 degree liquid temperature. Now since it just came on literally we're kind of watching it before we jump to any conclusions of what we're going to do next whether we add some refrigerant or whatever. We're just going to let it run. Like I said I'm tapped onto the high side right off the discharge. It's the only place to get it. I'm able to get the cover on. This is primarily just a regular generic cheap air conditioner because it's not a variable speed compressor. It's not even a TXV system. It's literally an orifice system. It's trying to maintain that 90 some degree liquid temperature which is great. I think we might be just a touch low but like I said I don't want to jump to conclusions with 410A because it'll bite you in the butt every time. It's been running for a good probably eight to ten minutes. We're holding pretty good right at 92 degrees 32 to 33 on our suction. I don't really want to disturb it any. We could check super heat for giggles here. Since this is just a generic system this is definitely not a fancy inverter so it's all the rules of you can't do this or can't do that goes out the window. This is just a generic air conditioner at this point. Let's go ahead and get that on there and see what kind of kind of super heat we got. Well it was about 15 a minute ago and they do have an accumulator on it for a reason obviously and it's getting down there a little lower and I care to see it but it's been like that so it definitely is not overcharged.  There we go. Come on back up there to the happy lands. Don't be getting so low. There you go. Bring it on back up. Come on up. Yep she's doing pretty good. I'm gonna say we're probably fine. I'm not horribly worried about that so we're gonna probably just get her back together and get out of here. I fled my hoses all the way to the yellow which is the way I like to do it to make sure I don't get anything in the manifold trapped. So I've showed this a million times but not everybody watches me. We're dumping her back in there.  That fan blade just barely taps the shroud as you pull it off. You just got to be really careful with it. And like I said it's just an ICM controller. It looks like they've got it set correctly. It does the job. Like I said also I checked all those fittings down in there. Did not find any leaks at all. Everything looks pretty good. Contactors technically just a relay. It's all sealed. No change in anything there. We'll just leave all that go. Motor's not got really major oil or anything on it and it feels like it spins pretty freely. All right just checking our temperature drop out of it which looks like it's doing really good. So it's probably about 70 in here. It's about 28 degrees under 30 which is pretty common so that's good. We're back again.  Got a recall here but he's had it off for a while so I have a funny feeling since this is really really cold ice. Go figure. Cold ice. Ha ha. That betcha this thing's sticking on.  Let's go look and see if it's running. Here's the generic little relay they got.  Well if that's just 24 volts we're going to rip that out. We'll put a regular kind of contactor in there. That is a 120 volt coil so I'm going to put a regular contactor in there. 120 volt coil on it. It'll be a lot more reliable than this freaking thing. We have a 30 amp 120 volt here. It's sealed so we've got bug shield on it. Here's the relay. You can see it there. It's pitted pretty good. They actually used copper all the way up to it which is kind of a nice engineering there. It finally failed. We've got it hooked up here. We just basically had it mounted off the side a little bit. I made sure we had room in between here. Had to move the capacitor a little bit. Just used some self-tapping Phillips screws everything's clear and we should be good. This kind of thing happens sometimes when you know it works while you're there. It obviously opened up because it was open. I looked at it but the pads and stuff I mean you can see they're nowhere near as big as what a normal contactor is. Let's get downstairs. Well we just ran it and it got cold but the fans didn't spin because the ice is hitting it. He's just going to let it set and fall out naturally. They don't need it right now anyhow and we should be good to go.  So if you guys want to stick around I think I'm going to go ahead and just run that video right now.  They must have one person pouring it all out but you can hear it kind of the customer's complaint is it doesn't seem like it's working. They don't know if it's warm in the room. It just seems like it seems a little different. I can hear a little bit of noise out of it. We did not install this contractor put addition on the house. It's been two years they said I am going to check for oil spots. The head's right on the other side of that. Let's get into these fittings. See I wouldn't be surprised if it's like all the other ones that the fittings weren't done right. Flare fittings and that they leaked. Let's get this thing opened up. It also appears to be the guy with a hack. You can see where they use channel locks to get on there and put grooves in the brass and they use leak lock. So let's see if we can get Gage on there. At this point it's got all the signs of a leak. We're running about 300 pounds ahead which is about 95 degrees for your discharge. It's ramping up a little bit more. On something like this it runs 410A. It holds 29 measly ounces. What I would probably do is pull the charge away at end if I really have doubts on it. I did crank it up to 80 degrees to get it running at highest mode possible. It is jumping up a little bit. This is kind of a slow one. I don't like I said I don't work on Pioneer. People buy this off the wall you know. Nobody services around here and then you can't know everything about everybody's little invention. Going to pull that thing off the side of the wall there. See if we can get a sniff on the flare fittings on the back side. So we got this off and I went ahead and put a little slit in some of this stuff here just to see if we could get any sniffs out of anything and never seen that white stuff before on some sort of cloth tape or what exactly it is. Not real sure. There's no flare fittings out here so it must be on the wall.  I'm going to go ahead and take temperature rise across this thing and see where we're at. I mean there you know it's 35 degrees out here area so I mean it's not horrible. It's definitely no hyper heat type technology I don't believe so go in there and see if we can get any sniffs on the inside unit. What temperature do you usually set it at? The last year it didn't feel like it was cold out here like it is now. I mean I've got 97 or 97 coming out and I got 77 going in. It's only 20 degrees and I'm granted it is a little cooler out but normally they can do a little better than that.  I'm going to scan this coil in here and scan the coil outside and see if maybe we have a small little leak there. You know I was checking it while it was running just to kind of let it build pressure that way if there is a leak maybe it would show up a little easier. I got nothing on the evaporator. There's a little scan out here on the condenser. Let's see if we can get anything out here. I'm thinking it could be 5-10 ounces low maybe if that and that's really small for two years worth of leak if that's even with a problem. If I don't find anything I'm going to give them the option of pulling the refrigerant charge out and weighing in or I can just add a few ounces to it and see how it does then after that which the right way is to pull it out and weigh it in. I scanned the whole thing over all deep down in here down in the compressor area on the backside front side of the coil. Didn't pick up anything. Like I said it's doggone close. From what I'm seeing here this doesn't have an electronic expansion valve. It looks like capillary tubes right there. So I'm thinking you know this thing ain't going to be super high efficient. You know I'm not usually you'd see the head down in there and I'm not seeing the servo controlled type metering device. They said go ahead and recover it and weigh it back in fresh that way we know. I don't see anything hitting on this fan blade so that rumble must just be the vibration of the compressor. When they fiber padded it down they kind of used bolts right into that concrete pad kind of pointless when they got it like that. We pulled the refrigerant out recovered it weighed in exactly the 29.5 whatever 30 ounces. I turned it up to 85 this time let's see if it does any better than what it did the last time. It should push it up to 100 capacity I would think. Just as I suspected we're at 483 area on our discharge and we're checking outdoor temp which were 43 area give or take. That's a little more along the lines of what I'm used to seeing 485 area. It's a 130 degree sat temperature there.  Maybe even be hitting up around 490 area we'll give it a little bit. 410A is always a treat always has a tendency to grow and grow that's why I'd like weighing it in I didn't want to just add refrigerant and hope that I got it where it needs it and then they have problems in cooling or vice versa when it gets warmer. We had 97 before and we're already 106 and rising 111 113 so I mean who knows they may have not got it you know they may have a little bit of a leak when they were starting it up so we at least know now we have a date and time that we we put it back to factory spec. I'm going to make a little sticker and put it on the inside of the cover so we have it for later that way we kind of know that you know at 42 degrees I had this temperature rise I had this pressure you know I don't know if that's in your book I doubt it is but it's at least gives us something. Well from what I see on the paperwork looks like we're on the right track here it's test procedure says for five minutes running its highest heat setting and its lowest cool setting for at least five minutes I was getting 109 it was a little higher at the in the beginning but it had 79 coming in so 8999 109 have almost 30 degree area for a rise it might have been better than that in the very initial beginning but you know it's monitoring temperatures all that stuff who knows what they do in their logic but it found the guy's numbers and it corresponds to what he had before it does appear we have a little bit of a leak somewhere we're going to go ahead and you know let them check it out try it out if it goes down again we'll spend more time tearing into it next time right now I don't see anything I mean if I'm not finding nothing there's not a whole lot I can do only thing I could do is yank it off the wall but I scan behind there it sounds to me like it might be down five ounces six ounces something like that and at this point you know it's working good for them so let's just try this first is what I'm going to recommend and kind of go from there you can't find it you can't find it so put today's date problems load heat pulled charge after no leaks found recharge spec 30 degree delta t at 42 degree out of air temperature I'm going to put that on the inside plus it'll be on her bill that way one of the other text comes back they'll be able to get the quick history of what was done it'll have a date there and that'll help them know what's been done in the past to kind of go from there which I would say a further deeper leak check is about all you can do


ly buildings right now, two-family buildings. Suddenly, one of those will turn over, someone will pass away, the building hasn't been maintained. It'll be torn down and a four-story building will go up there, but I'd like to see some drawings of what that will look like so people in town can see that. I really think we're overreaching here. We don't need to do that. Those aren't gonna be affordable units. There aren't gonna be six-unit buildings. Most of those lots, if you look at those lots, they're 6,000 square feet, maybe 8,000 square feet. Nobody's gonna build six units there with an affordable unit added. They're all gonna be luxury condos, so I would really ask that we take another look at that district, make it smaller, consider the three-story limit. Newton's doing sticking with two-and-a-half stories. Lexington did three stories. Let's do the same. Thank you. We're gonna go to Gordon Jamison and then Gary Goldsmith. Gary, are you? Oh, yeah, sorry. Thank you. Gordon Jamison, 163 situate, town meeting member, precinct 12, and also currently the chair of the Board of Assessors. I'm speaking in my resident precinct 12 capacity. Very quickly, I wanted to go through a few things. Yes, we need more MBTA service. The 79 needs to be restored and the 80. We give them $3.3 million a year and they keep taking stuff away from us. For those who are not familiar, the business zoning setback throughout town is zero, like in the center. Inspectional services has had a change of leadership so that concern that was raised earlier hopefully has gone away. Town meeting has passed several higher density proposals over the last several years, including mixed use zoning in the business districts. And my rhetorical question, if we only do the minimum, where do you do it? Good, I have my minute that I hope to have left. So I agree that we need transit-based smart growth. We used to talk about that in town meeting when I first joined. Smart growth along our business corridors. Now, what people don't really understand is what people can build now. So if I'm correct, along Mass Ave and parts of Broadway, the existing zoning allows four to six stories, yes or no, in general? In parts, depending on district, they can go up to five. Okay. Thank you. And then, so I think it would be helpful to come up with a map that showed the heights along there so one could understand the corridors. And then to the consultant, the capacity of the existing housing in the acreage, what is that, and what is the capacity with our existing zoning in the acreage? I don't know, we haven't done that calculation. Have it for town meeting, please. Thank you. We're going to Gary Goldsmith next, and then Kathleen Malune. Kathleen, are you still here? I don't see, so I'll pull another name while Gary's going. So hello, Gary Goldsmith, 91 Beverly Road, town meeting member of Precinct 11. There are many things that have changed in town since I moved here in 1985 and raised my family. I never expected when I moved here to be able to get beer with dinner downtown. But the town is still green, and if anything, greener, and it's a wonderful place to live. In the 38 years that I've lived here, many things have changed. And what we are doing is planning for a town what this town will look like 38 years from now. So today's 10-year-old will be 48 years old, and what will their town be like? And we are making decisions for what that town is going to be like at that time, and it's not just a question of housing. But I applaud the approach to long-term thinking as opposed to short-term thinking, which often has led to problems in a variety of things. A couple of things that I would say, one is that I appreciate the work that this committee has done. It's this project is sort of like an elephant. It depends on how you handle it, what it looks like. So you are sort of elephant handlers here. I would say that a couple of things quickly. The challenges of creating setbacks are significant. Someone said, oh, this table is like six feet. This table is eight feet. The setback of 10 feet is slightly longer than this table, maybe two feet longer than that. I think that Green Streets Arlington has approached this from the standpoint of producing more trees in Arlington. One point that has not been made is that, although we're figuring on, there's some high number of houses, but that's assuming that the houses are 1,000 square feet. That means that they are all either studios or probably not one of the edge apartments. These might be starter houses for other people. Thank you. Thank you. Oh, I have next, Elizabeth Pyle. And then after that, Beth Miloftrick. Hello, my name is Elizabeth Pyle. I'm a town meeting member from precinct eight. I would like to request that the commission put forward alternative maps showing different levels of density. It was said tonight that this particular map would call for an additional 12 to 15,000 units. I think that you should also put out a map at the 2,046 units, and then maps in the middle, 6,000, 10,000. But because of the considerable disagreement in the room about the level of density that is required, necessary or advisable here, I believe that you owe it to your constituents here in town and the residents here in town to put forward multiple alternative maps that clearly show the number of units that you're talking about. That's my first concern. My second concern is that if this map is showing 15,000 additional units, you only have 20,000 units in town right now. That's a 75% increase in the number of dwelling units in town. What does a 75% increase look like in terms of the town's ability to provide services? Have you talked to the Capital Planning Committee? Have you addressed this with the demographer of the school department? The answer, though, that was on your website that says that there's been a decrease in elementary school enrollment, doesn't cut it in terms of what is likely to occur here with influx of people of different ages coming in with new housing being developed. So the new high school is sized for 1,700 students. A 75% increase in town, if that translates, that's an additional 1,250 students. All right, thank you. So these impacts need to be addressed before you make this level of change. Thank you. Yep, Beth Milofchuk and then Kristen Anderson. Beth Milofchuk, 20 Russell Street, town meeting member precinct nine. I think the plans presented are predicated on a functioning public transportation system, which we know we don't have. Or it hasn't been presented in an adequate way to me to see that this is about affordability or school teachers being able to buy million dollar condos. I will not be able to vote for this plan. I will be unlikely to vote for anything beyond just a straightforward compliance to see how that gets applied. And I think that every single project the town takes on should be looked at through a lens of climate breakdown. Wearing climate breakdown, we have the hottest summer in a year that's going to be the coolest year for the next four years. We're facing the loss of the Gulf Stream by 2025. So please go back to the drawing board. Please listen to the remarks tonight from Liz Pyle, from Elizabeth Card Jones, from Susan Stamps. We need 15 foot setbacks. We need shade trees so people can walk to the store. And the retired folks and the elderly going to appointments are not gonna ride their bicycle. Thank you very much. Thank you. We have Kristen Anderson next and then Charles Foskett. Is Charles here? Oh, he is there. Okay, yep, thank you. Kristen Anderson, I live at 12 upland road west and I'm a town meeting member. And I wanna thank especially Uteel for the good work that they've done and also the working group and the planning department as well as the ARB. I run a business in the Heights and the plan that we see before us now includes protection for all businesses in the commercial zones, both industrial and business. Local businesses provide services, products and jobs to the community which makes Arlington a better place to live and I am extremely in favor of a plan that protects our businesses. So thank you for that. The other thing that I wanted to say is that I think that we really do need to have 15 or 20 foot setbacks for trees. In addition to being a town meeting member, I am a co-founder of Save the El Wife Brook and two of the things that we are interested in are water quality of the El Wife Brook but we're also interested in, I'm also interested in other water bodies including Mystic Lake and the Mill Brook, Spy Pond, Hills Pond and if we have trees that will help to drink up some of this storm water, it'll take rain water and keep it from turning into a pollutant. Additionally, I'm very concerned about flooding and I think that if we have more trees and room for green storm water infrastructure that it will help reduce flooding and so thank you very much. I hope that you'll take those things into consideration and again, thank you for protecting our businesses. Thank you. We have Charles Foskett and then Carol Kowalski. Thank you, Charlie Foskett, precinct 10 and member of the finance committee and thank you to the working group for the tremendous effort that you've put in to get us where we are today. However, I'm concerned about where we are today. I think this capacity issue is a very serious one and I can't imagine that you would bring this before town meeting without a detailed financial analysis of what the cost that a taxpayer is. The school committee has asked for another seven to eight million dollars in the next couple of years which is coming as part of an override request in the fall and that's roughly at the same time contemporary with the town meeting that this subject will come up at. This is, in my view, this is a plan that the capacity cannot be afforded by the taxpayers in Arlington and I think that right now we're in a situation where we have mostly residential citizens paying 93% of the taxes and if we increase the density by another 10%, 20%, 30%, whatever the number is, we need to know what it costs. So I would ask that you're not bringing this before town meeting without a detailed financial analysis. Thank you. Thank you. We have Carol Kowalski next and then after that Stephen Wilde. Carol Kowalski, 182 Situate Street. I wanna thank the working group for all your hard work. I wanna thank Matille and I wanna thank the board. I heard Mr. Revillac say that it's either in the commercial districts or in residential and I want you to open your minds please to the possibility that there are and have been for a long time. I had the privilege of working for the town as planning director for several years and we looked at a lot of these sites that were crying out to be redeveloped and they're of substantial size and they're outside of the core of the commercial districts. 28 Mass Ave should really be considered for inclusion, for example. These are sites that for years, 30 years I've been thinking and I'm not the only one who's been thinking that could be a beautiful gateway to our town. There are lots of properties in Arlington in these proposed districts that might be in a flood zone but they're not no-build areas and there are ways to do it. That could be a fantastic site. 28 Mass Ave, also 30 Mystic Street. 30 Mystic Street is a massive parking lot and a 50-year-old office building and it's recessed down so it's sighted in a way where I wanna keep going because I, so please take a look at that. That's, it's crying out, it's perfectly smart growth. Also, the Greater Boston Motorsports Block stand across the street from it, stand in front of Jimmy's, look at it and say, oh my gosh, it almost looks like an apartment building and say to yourself, why isn't that included? What are we, we do not have a split tax rate. And I don't think, two other quick things, I don't think we're sure we should maybe look at what it would cost but these properties will pay taxes and new multi-family development is more valued and gives us more revenue than depreciated 50-year-old commercial buildings that we struggle to tenant right now. I don't think, I know we don't, I work as a professional planner, we don't have a commercial development market. So the Greater Boston Motorsports, 37 Broadway, Friday, 2 p.m., anyone who wants to meet with me, I'll help you walk those sites and I'm also walking the districts and I recommend that you do the same thing. Thank you so much. You're the time, thank you. We have Stephen Weil and then Joe Zeph. Joe Zeph, Stephen Weil. Okay, I have Ratnakar Vallani. Vallanki, yep, great. Hi, Ratnakar Vallanki, 21 Adams Street. I'm in one of those orange areas and I welcome this plan and I thank all the working group members who have put in their effort and volunteered for this. Now, a few things, right? I know a lot of speakers before me have said that higher density is not good, but I just would like to reiterate that higher density saves much more green space than it saves, than it uses, sorry. Higher density is also more financially sustainable and in addition to that, right, in addition to the sustainability argument, I would like to also extend and say that this is also one step, one good step, forward towards protecting an owner's right to decide how best to use that property. Not my words, these are the words just as John Paul Stevens, Supreme Court, and it continues the opinion saying which we've forgotten, this right we've forgotten. This is enshrined in English common law which we've forgotten since the 1926 ruling of the court. Now, coming to another topic which is what I originally wanted to make. Now, the Section 3A guidelines that were outlined by the Attorney General of the Commonwealth also say that the multi-family zoning district should be in areas that are safe, accessible, and convenient access to transit stations for pedestrians and bicyclists, right, keywords for pedestrians and bicyclists. Now, we know that in the proposed Mass Ave and Broadway corridor, we know that there's no bike lane on Broadway and the bike lane is pretty much non-existent on Mass Ave, right, I would like to request the working group members to consider having separated or protected bike lanes on both Broadway and Mass Ave because not just because clearly Section 3A guidelines require that because one could say that we'll be in breach of that without safe access, but more importantly, it's probably the, yeah, thank you. Thank you, we're out of time. Matthew, I think you had something from earlier that you wanted to circle back to. Yeah, a clarification. It was suggested that the number of units that the modelist is estimating, 12, 15,000, is in addition to existing units, that is not the case. That number is as if all of those parcels, all those blue and orange areas were completely vacant and people were building as of right. So I just want to get that clarification out there. Thank you. Next I have Juliette Furman and then after that, Brian McBride. Juliette Furman, right, Brian, you're up then. And after Brian, we'll have Steve Macalco. Hi, good evening. This is Gordon Macalco. Yeah, I'm Brian McBride, I live at 36 Eastern Avenue. I'm a member of the Conservation Commission and a member of the Open Space Committee. Tonight I'm speaking as a member of Green Streets Arlington. So my job, I know everyone's tired. My job is to try to convince you all that we shouldn't submit this plan with 10 feet of setback. I think that's a terrific mistake. And the reason of that is setback is very important for your experience of the streetscape. When we look at the table model plus two feet, I guess here, that's not enough of a setback to really have a green space. It's not enough for the tree warden to plant a tree that's sustainable. So consider that when you've got a higher temperature in 25 years, when we've got five or six-story buildings along Mass Ave, when we've got people using the subway, or sorry, the bus and waiting for the bus on the street, we're trying to drive engagement with community members to knit the community together, right? The setback, although it seems like a trivial kind of architectural number, is really important for how we envision our future community. It's the trade, when we look at increased density, but we try to build in a pleasant living and walking environment and something that's in sync with our habitat. So I really encourage the committee not to submit a plan with 10-foot setback. Please look at 15 or 20 per the tree warden, and let's make this a win-win. We need the housing, we need the green streets. Thank you very much. Thank you. I have Steve McAlcay, and then I think we have a clarification for a circle back and something. Good evening, Steve McAlcay, 17 Russell Street. I am a member of the Historical Cultural Resources Working Group, working on implementing the town master plan. Also chair of the Arlington Historic District Commission. With my Historic District Commission just a couple of comments. One was mentioned that the current plan avoids Historic Districts. I mentioned to Claire earlier, and I just want to reiterate to the full committee that it's still, the map is drawn up now, still covers half of one of our Historic Districts. So I hope that gets resolved. But that brings up another point. I've looked at other communities, Brookline, it's which other places, Belmont, all of them have had representatives of cultural and historical resources as part of the committee thinking more broadly about meeting housing goals, but doing that in a way that's compatible with all the other community objectives. And I just encourage Working Group to be, to do more outreach to other folks to learn about those things. Because I feel that there hasn't been a lot of outreach here. I commend all the work that the Working Group has done, but I think they are working in a very compressed time environment. And that leads to my first question. I understand we're doing that because of the need to meet the gas ban. I understand there's only 10 communities in Massachusetts that will be able to be involved with that. If Arlington does not, as I understand it, the next towns that would be included in that group would be Somerville and Boston. Is that correct? They are on the list, yes. Oh, sorry? They're on the list, they're on the waiting list. So if Arlington does not do it this November and does not participate in the first phase of that ban, Somerville will make it the opportunity to be part of that group. They may. It's contingent on the state's decisions, but they are in line, so they can't comply. So just from an environmental perspective, if you want the biggest bang for the buck. Six more seconds. Biggest bang for the buck. I don't know why that short-term thing is driving our effort to do something that's really, really complicated in a short period of time. Mr. McCauske, you're actually passed by now 20 seconds. Sorry. One last question. Can you put all these Q&A up on an FAQ for people to get, is everyone's leaving tonight? The whole thing is recorded. David, your time is over. I think, David, you also had some other things from earlier that you wanted to, something you wanted to clarify. I do. We've had a lot of conversations about environmental concerns tonight, and just quickly show our hands how many people know who Bill McKibbin is. How many people know who Bill McKibbin is? Majority of the room, Bill McKibbin, world-renowned environmental activist. He is from Lexington. You may not know that piece, and he wrote a piece in the New Yorker of all places when MBTA communities passed in Lexington celebrating their accomplishment and chiming in, not just on the environmental front, but from the equity perspective, that this is a very valuable thing to do that addresses the climate crisis, and does so in a just way. So I have to say I support Bill's decision to do that and his position in that way. I want to say that there are things that we need to look to beyond zoning to really realize the things that we're discussing tonight. So we can get to those in a subsequent conversation, but I think the more meaningful piece for tonight is that MBTA communities is a zoning by-law. We can work on other kinds of compliance with promoting public transit, et cetera, in other venues. There are other ways to meet those goals, and I think you will find that the town is very receptive to accomplishing those goals. There are some things within the zoning code that we may also change in order for them to apply to MBTA communities, and one of those things is the site development standards mentioned earlier broadening that to not just apply to the districts where they currently apply, but to have public shade trees required in your development, redevelopment, large additions, et cetera, you get a public shade tree in addition to the context that I just described. So there are ways within and without zoning that we can accomplish a number of these things, and I really welcome the conversation about this because it engenders further conversation about how we get to those goals. So just a clarification that there are some things that we can apply within zoning that have bearing on much that we've discussed and others that we want to pursue, perhaps as soon as springtown meeting, and we're open to having those conversations. Thank you. Chris Loretty is next, and then I'll pull another name with Chris. Narissa Smoger. Thank you, Chris Loretty, 56 Adams Street, town meeting member precinct seven. I think the map should have names instead of numbers, and I would call this one the shit on East Arlington map. As someone who lives in that area, you really are concentrating particularly on Broadway, and I find it astounding that people are claiming that this isn't keeping with the neighborhood. The south side of Broadway is predominantly two family homes of two and a half stories, and you're gonna be building or allowing a by-right six-story, 60-foot building five feet from my property line, and I'm supposed to think that's fitting for the neighborhood? Well, I'm sorry, I don't. I appreciate the efforts of the committee, but I think you kind of missed the boat on the location of these zones. What I was hearing in the previous public meetings is people wanted to spread it out, put it near Alewife. You haven't even covered most of the bus routes. Why are you concentrating only on Broadway and Massachusetts Avenue? It's kind of clear to me that the committee was more interested in listening to themselves than in listening to the public, and so a couple of requests I'd like to make is I think it's gonna be necessary to do a substitute motion at town meeting. I'd like to know, either from the committee or staff, what support you will give people in making the substitute motion to ensure compliance with the MBTA Communities Act? Will you allow the use of UTL? Will you allow the use of the model? Will you encourage DHCD to pass judgment on any substitute motion so that town meeting will know the alternative is an acceptable plan? And finally, I think the whole idea that this is gonna create affordable housing is just delusional. I don't need academic studies. All I need to do is walk down the street into my neighborhood and see what happens when two family houses, typically owned or occupied with one unit rented out, are sold to developers and then sold as condos for a million dollars. Thank you. Thank you. We have Narissa Smoger, and then after that, Dorothy Gosling. Dorothy, are you? Okay, you're gonna, Narissa and then you. Yeah, I just wanted to make sure. Go ahead, sorry. Hi everyone, it's okay. It's my first meeting. Thank you to the committee. I really appreciate the work that's gone into this clearly. I'm new to Arlington. I'm on 30 Temple Street. I have some concerns about this plan as is. While I admire the spirit of the plan, I feel like there are some aspirational aspects without the safeguards to ensure smart implementation of the plan. For example, we want, I bite to work today and then I took the train and the bus home. It took me over two hours to get home. I don't see that changing when we have more people that need to be relying on this type of transportation. What can we do to make this experience better for more people? I think the way that this plan is outlined is as others have said, it's a big bang all at once potentially, even though we don't expect that, it could be. And I feel like we're giving a lot away for free in a way. Again, what can we as a community gain from this, aside from the diversity of people in more affordable housing or housing that's available? What other programs can we tap into and kind of use this as leverage potentially? I also want to urge the committee to think about who's most harmed. I think we thought a lot about who can benefit most from this, but who is most harmed with this implementation? And one group of folks that come to mind are town employees and people that we want to actually be able to afford to live in the town that they work in. For example, our school teachers who will have a ton of burden put on them by the more children that they'll have to be teaching when we have more folks joining our lovely town. So I'm not sure if the committee's considered how we might think about our town employees, school teachers and that sort of, that group of people who would be critical to the backbone of a healthy community and what we might do to support them a little bit more. Thank you. Thank you. We have Dorothy Gosling next and then Elaine Crowder. Elaine, oh yeah, I said Elaine. Dorothy Gosling, Sixth Wyman Terrace. Who is most harmed and what is the worst that can happen? I moved here from Seattle, Capitol Hill. They changed the district zoning 10 years ago and all of the things that they're talking about with developers, I saw it happen in my neighborhood that is no longer a neighborhood. The developers, I'm concerned we're giving the developers a carte blanche. I think the committee's done a great job but I also think the input has been very, very helpful. We, my neighborhood ended up with all different size buildings and I just wanna say, let's open our minds, what are other options? There's an article in the New York Times a month ago in Vienna how large units are people love living there and they stay there forever. They do little apartments that are group places with small living spaces. Maybe that works for elderly people. The boomers are eventually gonna be giving up their large houses. People with young kids are gonna be moving in. I've got two grandkids in my two family. So let's really think about, open our minds and not just do what we've always done and double down on multifamily housing that we've already got on the east side. Great, we have Elaine Crowder next and then after that, Linda Hansen. Linda's still here, let me help you. Elaine Crowder, precinct 19 to Glenbrook Lane. We've heard about the difficulty of public transportation that people are experiencing in Arlington and about difficulties in particular, getting to L-Wife. We've also heard concerns about the treeless canyons that might result down Mass Ave and about the heat islands that might result without the ability to host street trees. I'm from Arizona, I know what 110 and 115 degree pavement feels like when it slaps you in the face when there's no tree or shade. It seems that the idea of spreading a bit beyond the current map, it seems I've heard that the bike path corridor has not been considered for part of this, is that correct? Claire, do you wanna talk about what things have been considered? Not intentionally, I think that when we were, or when the working group, and again, I don't wanna speak too much for the working group, but the bike path was not intentionally removed. I believe that what we were doing was focusing again on the transportation corridors where the transit is, but point is well taken that the bike path is a form of transit. And the bike path is not only a form of transit, but it goes to L-Wife. Correct. Which is, I believe the bike path is also owned by MBTA, is that correct? Which means that it is directly within the purview of an MBTA plan, I would think. So it seems like a good solution to begin to think in terms of spreading it a little bit away from a six-story mass app corridor and reducing a bit.  Thank you. We have Linda Hansen and then Amy Goldstein. Amy. Hi, good evening, Linda Hansen, 11 Webster Street, Precinct 9, Orange Zone. I wanna start by thanking the committee for the work done to date and the work that you still have in front of you and the staff as well who've worked really hard on this. I wanna start off by saying that I see the MBTA communities as an opportunity to increase the amount and types of housing we have in Arlington. I think that's a good thing. And I also just hope that we can use this opportunity to increase the kind and amount of affordable housing in any way we can. That's actually, I'm very interested in that. I have a clarifying question though, maybe for Claire. There are two, there's blue and orange zones. Can you just re-clarify the heights that you have proposed in this plan? There was like a six, four, three on a slide. You mentioned something about stepping down, something about two and a half. If you could just quickly reiterate that, I'd appreciate it. Sure, I'm happy to do that. So essentially what we're looking at is the Mass Ave and Broadway Corridor Sub-District, which are properties with frontage on Mass Ave and Broadway. By right, allowable would be four stories with plus two stories for ground floor commercial plus one story for affordable housing above and beyond our inclusionary zoning. So the maximum height on Mass Ave would go to six stories, maximum height on Broadway, five stories. In the neighborhood multifamily district, properties within 350 feet of Mass Ave and Broadway, we figured that was roughly three parcels, four stories by right, with a 10 foot front setback, 10 on the sides, 20 in the rear. We have not yet contemplated bonuses for a neighborhood multifamily district. So to be clear, in the orange zones, three parcels back, four stories by right. That's correct. Without any additional bonus opportunities. That's correct. And did you consider, I'm curious to why you... Miss Anton, I know. Two, okay. I know, two minutes is hard. Okay, I'll email it. Thank you. Great. Next, it was Amy Goldstein. Okay. Then I have Julia Mayrak. Hi, Julia Mayrak, 438 Mass Ave, property owner, business owner in town. Thank you for all the work you've done. Great ideas. My only suggestion or request is that you do not exclude all the commercial and all the industrial. By doing that, you have excluded the largest parcels in town. If you wanna get the density out of the neighborhoods, then allow some building on the larger parcels in town. These are the parcels that are most attractive to a developer.  But if you have a nice big piece of land that's in a smart growth area that's on Mass Ave or on Broadway that's next to grocery stores that next to the school that fits all your smart growth criteria, that's desirable to a developer. It'll be profitable, it'll be something that could actually get built. I fear that if you leave all the commercial and the industrial zones out and leave all the large parcels out, that you may hit the letter of the law, but you won't actually get what you want, which is some serious development. And so I would just encourage you to include some larger parcels of land. Thank you. Thank you. Next I have John Warden. Mr. Warden. Oh, would you like us? Thank you. Have you heard all right? Yeah, John Warden, tell me you remember Precinct 8 Jason Street. I'd like to mention a couple of statistics. One, Arlington is the 12th densest community in the state. I just mentioned in the state. We have already done our share to house people. And the other 11 communities that are more dense than us of all cities at Brookline all have substantial industrial, commercial, retail, whatever businesses that pay taxes that don't use services. We don't. We have 5% in that in those categories. That means all the burden of taxes falls upon the residents and the homeowners. The statistics show that each new resident on average brings in half as much in new taxes as they do require for services. So we're digging a hole and we're gonna dig it deeper. I call upon the, and the third thing I'd like to say, the statute itself, read the statute, section 3A, chapter 40, 48. It talks about the half mile zone around near a transit, adjacent to a transit station. Doesn't say anything about all these other zones spread throughout the town. That is the creation of the bureaucrats in Boston who I think must be obviously deeply in bed with developers. I call upon the committee, the working group, to craft a plan that follows the minimum possible compliance with the law, the law, and let's struggle it. The laws, one thing, the regulations, which could be tipped in court, is another. Mr. Warden, you've reached your two minutes. Let me, please just wrap up. I call upon the committee to craft something that's- Mr. Warden, I'm sure you appreciate the difficultness of the job that I'm doing right now. And we've hit, you've hit your two minutes. Two minutes is a lot of love. I understand. Two minutes is a tough time. Two minutes is not enough time. I've waited for two hours to speak here. I understand. And I think you should protect the residents, the homeowners of our area. We're on to Paul Bradford, please. It's the most important thing you should do. We're on to Paul Bradford next. Paul Bradford, no. We are very close to the end here. I appreciate everybody's patience. Oh, Carol, we already did Carol Kowalski. Oh, you must have put two in. Yeah, Doug Greenfield. Amy Slutsky. And the winner of the prize here is Alan Jones. So Alan can talk until town meeting starts. Thank you to all of you. I actually watched the video of the last meeting you had and I thought, I'm so proud to live in this gorgeous, fantastic town that is progressive, thinking about sustainability, people, equity and all of those important things. And I also am really thinking, oh, Amy Slutsky, I am town meeting member precinct 17. And I live at one Mortimer Place, the 130 unit building overlooking the Schwann Mill complex right on the bike trail. So I appreciate that a lot. So my main point, I'm really sorry because I so appreciate the work that you guys have done really, truly. With that said, I would love it if you, number one, reopen the survey because I'm someone who just woke up to the importance of this issue really late as you can see, really late. I think that would be a fantastic thing to do. And number two, I think it would be really great to put a copy of one of the maps in a gigantic banner across Mass AF. I'm a member of Arlington Chapter Mothers Outfront and we are all about the climate breakdown and trying to do what we can. And number one, I love the reminder of a 15 foot setback. Every time I walk by that horrendous building, I don't know when it lives here, there. Right next to stop and shop, I thought, what were they thinking? This is so not Arlington. Trees, yes, and protected roofs for solar panels. I don't know if we're gonna have windmills in Arlington, but at least we can do solar panels. What else did I want to say? We've hit, you've hit your two minutes. Perfect, thank you. All right, Alan Jones. And that is our last slip. Alan Jones, one Lehigh Street, and I know I'm gonna request that the board consider a number of things, which I know we probably can't require, but maybe can be incentivized. First is setbacks on the front that are larger than the 15 feet I know you're gonna land on. 20, 25 feet, so big enough for a real shade tree. I would mention that if you look at the butt-oddly buildings next to the high school, if you push them back 25 feet, put a couple of big sugar maples in front of them, they'd look a whole lot better. We wouldn't have to stare at them all the time. Easements for public access to those 15-foot front setbacks in the form of tiny parks, maybe a bench or two, a trash can, maybe a little table, a big shade tree as a refuge for hot pedestrians and cyclists. Planning and maintenance of landscaping with native trees, shrubs, and other perennials, particularly if they're in one of the wildlife and pollinator corridors that we're planning. Green parking lots with at least 50% shade tree canopy or a photovoltaic over the top and permeable pavement, reducing the size of open parking lots using structured or underground parking inside the building footprint incentives for that, and in large projects, significantly more green space than necessary. All of these things are about more natural green space, managing stormwater, reducing heat islands. The possibly most important is to make sure we're not building second-class buildings so that our new neighbors don't have to live on hot, treeless, second-class streets. It's a matter of equity, thank you. Thank you. Thank you so much to everybody for your patience this evening. It's been wonderful to hear from so many different people. Thank you to all of our panelists, to all of the staff who have made this possible. Thank you to the working group members who have been working very, very, very hard. I've been proud to be the chair of this. Thank you. Not a little bit of applause, but... So for folks who are watching the livestream at home or are watching the recording later, if you want to send, share your feedback or your questions with the committee, MBTA communities at, oh, and I always forget, is it town.arlington.ma.us? Did I get that right? Yes, okay. You can send your feedback to there, and we will get that to the committee. Thank you again for a very late evening and we appreciate your time. Thank you.


Let us look at how we can get the limit on the thrust to weight ratio from the constraint on the mist approached gradient. As we can see from the table, the specified value of mist approach gradient is 2.1 percent. This happens at the maximum landing weight of 165608 kilograms under sea level ISA conditions. So once again, this is the constraint, the formula for constraint on the mist approach gradient, only thing is I have inserted the term MA wherever there is mist approach and MAG stands for the mist approach gradient. Now here any stands for number of engines which is 2, L by D MAG is the L by D of the aircraft in the mist approach configuration. As you know during the mist approach, the flaps are in the approach configuration. So they are at a higher angle than in takeoff and the landing gear is down. So from the aircraft data related to this particular aircraft, we have got this number of 0.1135. So the delta CD because of the deflection of flaps and the landing gear is a very large number 0.1135 and the requirement on the mist approach gradient as specified is 2.1 percent. Let us now calculate L by D in the mist approach just like we did it for the previous case of second stage climb gradient. The procedure is identical, only the numbers will change slightly. So the steps are very similar. First we calculate the atmospheric parameters during MA. In this case, we do not have to do this step because the mist approach is happening under ISA conditions. So therefore, we already know the values of density and temperature and sonic speed under ISA conditions. Then we calculate the Mach number of the aircraft because once you know the speed and the sonic speed, you can get the Mach number. Once you get the Mach number, then you can get the Oswald efficiency. Once we have the Oswald efficiency, we can get the induced drag coefficient. Once we have the induced drag coefficient, we can get the total drag coefficient. We already know the lift coefficient. So therefore, we can get the L by D and let us do these steps for Boeing 787 now. It is specified that the mist approach occurs at sea level ISA conditions. So therefore, the parameters of the atmosphere are very well known. T is 288.16, rho is P by RT which is 101325 divided by 287 into 288.16. Although all of us know this value, but still it makes sense to calculate it. The number comes out to be 1.225 kg per meter square. The sonic speed will be obtained by a root of gamma RT for these standard values. Once again, this number is known to us, but still it is important for us to calculate it and assure ourselves that we are on the right track. Now the value of sigma will be equal to 1 because rho and rho naught are the same in this case. Now to calculate the Mach number, we first use the fact that the V stall landing as specified in the requirements is 102 knots EAS at ISA. Now under ISA conditions at sea level EAS is equal to TAS because sigma is equal to 1. Therefore A and also we have just calculated that A is equal to 340.27. So just convert the value of speed 102 knots into meters per second by as I said multiplying 1852 divided by 3600 or simply multiplying by 0.514444. Now during missed approach, we assume that the speed is not 1.2, but 1.3 times V stall. So that will come as 1.3 times 52.47. Pause the video and please calculate this value. The value is 68.2 meters per second. And hence since we know the value of VMA and we also know the value of sonic speed A, we can get the Mach number by taking a simple ratio. Please pause the video calculate the value. The value comes out to be 0.20. Once we know the Mach number, we can calculate the asphalt efficiency factor using the information that is available already using the same formula that we have used earlier for the value estimation of the value of E during the second stage climb. So calculate the value of E missed approach. Please pause the video here and calculate the value by this simple expression. The value comes to be 0.7276. So with this we can now get the induced drive coefficient in missed approach. So we know the value of CL max landing at 2.66 is specified in the aerodynamic data and we have just calculated the value of asphalt efficiency in the missed approach EMA as 0.7276. We know that in missed approach condition the stall velocity is 1.3 times V stall. Hence CLMA will be CL max landing by 1.69. Please calculate this value. It will be 2.66 by 1.69 that is 1.574. Once the value of CL is known, therefore you can get the induced drive coefficient because now we have all the information we have CL missed approach and we have the value of aspect ratio 10.58 and E missed approach 0.7276. So by including these values inside the formula, now you can pause the video and calculate the value of CDI MA. The value comes out to be 0.0997. Moving ahead, now you can calculate the lift to drag ratio in the missed approach. For this we know from the previous calculations the value of CDI SSC and CL missed approach. And now we also know that we have to add additional term because of the extra drag of the flaps and the landing gear during this condition. So CDO plus CDI thus Lyd will be CL missed approach by CDI MA and that will be 6.965. Let us look at the T by W missed approach. For that we insert the corresponding values of T, W and L by D and the gamma in the formula. Now we have already been given by the requirements that the missed approach gradient is 2.1 percent and we know that this aircraft Boeing 787-8 has 2 engines. The L by D missed approach has been calculated previously as 6.965. So therefore, once you insert these numerical values in the expression, it becomes very easy for us to calculate. So pause at this stage and calculate the values. We see that the value of T MA by W MA has to be more than 0.3291 during the missed approach condition. But remember that the missed approach condition occurs during landing whereas we are interested in the value of T by W under the C level static conditions and for maximum takeoff weight.  So to get the value of missed approach T by W limitations at C level static conditions and max takeoff weight, we just reproduce from the previous slide the values that we know. We also know that the thrust during missed approach is equal to thrust at the C level condition because the missed approach constraint is supposed to be met at C level conditions and also we can assume that the weight of the aircraft during the missed approach is almost equal to the weight at landing. So keeping these 2 in mind, we can first calculate the value of beta which is the ratio of weight of the aircraft during the missed approach condition and the max takeoff weight. These 2 numbers are known to us and hence it can be easily estimated. Please pause the video and calculate this ratio. The ratio turns out to be 0.7668. So now we know that TSL by WTO is equal to TMA by WMA into beta. So you just multiply this number by beta and you will get the value TSL by WTO missed approach will be more than or equal to 0.2524. This is one mistake which many students make they forget to convert the values obtained for a constraint to the standard conditions of C level static thrust and weight of the aircraft at takeoff. So be very careful. Let us see how this maps into the constraint diagram as a line because the constraint was directly on T by W there is no role of W by S here. So therefore, this will appear as a horizontal line in the graph as shown. So we also arrive at an interesting conclusion that the thrust to weight ratio of the aircraft cannot be less than 0.2524 from the constraint on the missed approach gradient. Let us look at the constraints that depend on wing loading alone. In our table of constraints there are three such constraints the one on takeoff stalling speed, landing stalling speed and the landing ground roll. So let us see how these three appear in the constraint diagram. So since they depend on W by S alone it is clear that they will appear as vertical lines. First let us look at the limit on wing loading from the constraint on takeoff stalling speed. As per the specified requirements the value has to be 71 meters per second equivalent air speed or less at the max takeoff weight under C level conditions but under ISA plus 15 conditions. This is the requirement which you have to meet. The formula that we will use is very straightforward. We know that lift is equal to weight during a 1g stall. So from there you can easily get an expression between the wing loading required versus the density of the air at takeoff condition, the maximum value of CL at takeoff condition and the specified value of stalling speed square. So let us see how this constraint can be incorporated. First of all there is a specified requirement that the V stall should be less than 138 EES which I have already converted 2 meter per second. Now previously we have already calculated that the density of air at ISA plus 15 at C level is 1.1646 kg per meter cube and we also know from the data that CL max of the aircraft at takeoff conditions is 1.91. So therefore you can get the value of the stall speed at ISA plus 15 conditions. And once we obtain the value we just have to insert the numbers in this formula which means we have to replace rho takeoff by 1.1646, CL max takeoff by 1.91 and V stall takeoff by 72.82. Pause at this stage and calculate the value of wing loading required. We see that the wing loading has to be less than or equal to 5897.7 Newton per meter square. This is what you get by directly inserting the numbers in this formula. But remember that the answer you get would be in Newton per meter square which has to be converted into kg per meter square so that we can by dividing with G so that we can have consistent units in our constraint diagram. So with this let us see how the constraint line appears on the diagram because of takeoff stalling speed. As I said it will be a vertical line which is stationed at 601.37 kg per meter square and the area on the left of this line is going to be feasible because the wing loading cannot be more than this number it has to be less than or equal to this number. So the area on the right of this line is infeasible on the left is feasible. Moving on let us look at the limit imposed on wing loading from the constraint on landing stalling speed. Here the requirement is to calculate at the landing weight at sea level ISE conditions there will be no need to convert the densities we can use the standard sea level values and the units are also the value is specified as 52.46 it was 102 knots EAS which can be converted to meter per second using a simple formula. Once again we will use the standard formula just like we used for the takeoff condition the only difference is that we will put subscript land for wing loading density CL max and V stall. So let us see how this number pans out this is the requirement which I am repeating here for ease in memory CL max at landing is given as 2.66 from the aerodynamic data for this aircraft. So you have a simple expression and now if you substitute in it the values you get 1.225 in place of row land CL max land is replaced by 2.66 and V stall land by 52.46. So pause at this stage and please do the number. We find that the value is 4483.8 Newton per meter square or 457.2 kg per meter square. So this is a much stricter limit but remember again this is at landing so it has to be converted to the values corresponding to W takeoff. So W takeoff by S is what is our on the constraint line. So during landing condition it is supposed to be less than 457.2 and we know that the takeoff weight is 215971 and W land is 165608 specified. So we can calculate the value of beta which we got in the last expression also as 0.7668. So with this beta you can easily estimate what will be the value of WTO by S at landing. It will be W land by beta land by S if you want to convert W land to WTO and since both are in the denominator you can get it as W by S landing by beta landing. So we know these values insert the values pause the video and try to get the constraint limit as shown. So get this number this number is going to be less than 596.24 kg per meter square. So it turns out that the landing stalling speed constraint is slightly more harsher than the constraint due to the takeoff stalling speed but that is only for this particular example it is not a general statement. So once again we see that the line will map on the constraint diagram as a vertical line with the area on the left of the line as feasible and the area on the right as infeasible. Moving ahead let us look at the third constraint which depends only on W by S that is the landing ground roll. The requirements specify that the ground roll should be less than 621 meters at maximum landing weight of 165608 kg under sea level ISA conditions. So for that we will use this particular formula. If you are not familiar with this formula I would request you to go back and look at the video of clips of the lecture on constraint analysis for transport aircraft where all these formulae have been explained. So this formula will be used by us. So the specifications are that the atmosphere is ISA the altitude is sea level and the required distance is less than 621 meters. The aerodynamic data is that the CL max is 2.66. We have to assume a few values in this case we do not assume any afterburner therefore alpha is equal to 1. We assume that the operations are from some standard airports therefore the mu roll is going to be 0.4. Since the thrust force you know at landing is such and also just after landing during the ground roll we put the spoilers therefore we can assume that the lift at landing is completely killed and hence we also neglect the drag at landing. So and the sea level condition density is 1.225. So with this what we need to now do is just calculate beta. Beta is already known actually as 0.7668 we have done it just a few minutes ago. So we can just remember that value. So this is the formula that I mentioned. Now if you look at neglecting the values of D land and L land then the formula simplifies and with a simple rearrangement of W by S on the left hand side you can see that it is just a formula in terms of landing distance S land density CL land and mu roll and beta. So inserting these values we can calculate the W by S constraint. So please pause and insert the values we all know these values from the last slide. So the number turns out to be less than 624.6 kg per meter square. So it is interesting to note that the landing ground roll constraint is not really that harsh in this case. And also please remember that we have not worried about converting it to take off conditions because already in the formula we have included those parameters in the form of beta. So therefore the constraint because of the landing ground roll turns out to be 624.6 kg per meter square and appears as a vertical line with the area on the left being feasible and area on the right being infeasible. So this is how we looked at the constraints that depended only on W by S. Let us look at constraints that depend on both W by S and T by W. There are two such constraints in our table. The first one is the constraint due to the residual climb rate at cruise conditions and the second is the balance field length. So let us see the first one the one which is a constraint due to the climb rate at cruise. This particular requirement is 2.2 meters per second or 429 feet per minute which is to be calculated when the aircraft is just at the beginning of the cruise and the altitude is the cruising altitude of 37000 feet or 11278 meters under ISA conditions. For this we will use this master equation and if you have if you do not understand this equation or if it seems very unfamiliar to you I would request you to go back and have a look at the video clips of the lecture on constraint analysis for military aircraft because we have used master equation mostly in that particular application. But we will use it also for the current requirement. So in this in this large expression which relates the TSL by WTO and WTO by S for several operating conditions, we notice that the climb rate is actually DH by DT. So we are given the value of DH by DT and we have to calculate the link between or the relationship between relationship between TSL and WTO by S for we have to calculate the relationship between TSL by WTO and WTO by S for a given value of DH by DT and the other parameters will be obtained from either the known value or from the specified constraints. Let us see how it is done. So the data for this requirement is that the ROC is 2.2 meters per second under ISA conditions since it is a level flight n is equal to 1 and also it is a study flight. So therefore, there is no acceleration. So the aircraft is in a study level flight. The cruise Mach number is 0.85 and the cruise altitude is 37,000 feet or 11 to 78 meters. And we have obtained some information about the fuel consumed in the warm-up, take out, take off, climb, etc. So through that we come to know that the aircraft weighs approximately 203457 kg. When it comes in at the beginning of the cruise, the condition at which this climb rate is to be estimated. There are some values which we will assume. First of all, we will assume that the takeoff weight of the aircraft is 215971. This is given in the aircraft data. We also know from the aerodynamic information that the CDO of this aircraft is 0.01277. The wing aspect ratio is 10.87. And from the engine data, we come to know that the value of alpha at this cruise Mach number is 0.1789. And we have also calculated earlier that the value of the Oswald efficiency at cruise Mach number is 0.6961. So with this information, we now have to calculate few parameters which are required in the master equation. These are the induced drag coefficient K1, the value of aircraft weight ratio beta, the cruise speed and the dynamic pressure during cruise. These can be straightaway calculated using standard formula. Let us see how it is done. First of all, for the induced drag factor, it is actually 1 upon pi AR into E. So A wing is known, ECR is known. So pause the video and calculate the value. This value turns out to be 0.04207. The next information we need is beta, which is the ratio of the weight of the aircraft at the cruise condition or beginning of the cruise divide by the weight at the maximum takeoff condition or the maximum takeoff weight. This also can be easily calculated. The number is 0.9421. Then the cruise velocity at the cruising altitude can be obtained either by a numerical calculation or you can also pick it up from the ISA table because it is an ISA condition and that number is 0.3494 kg per meter cube. We can also calculate the temperature at the cruising altitude and the value of sonic speed. The temperature we all know, temperature at cruising altitude is already known because it is a standard value, it is 216.66 at an altitude between 1125 kilometers under ISA conditions. And hence the value of sonic speed can be easily calculated as root of gamma RT, where gamma is 1.4, R is 287 joules per kg degree Kelvin and T is 216.66 degree Kelvin. So with that the value comes out to be straight away as 295.05. Now since we know the value of cruise Mach number and now we know the cruise, the sonic velocity at cruise conditions, you can calculate the value of V and once you know V, you know rho and you know V. So half rho V square is Q, please pause the video and calculate these two numbers. So VCR is 0.85 into 295.08 or 250.8 and QCR is half into rho into V square, which if I would request you to pause and calculate comes out to be 1120.6 kg per meter square. So we now have all the numbers that we need k1, beta, V, CR, Q and HCR, which we need in the master equation. So we can go ahead. The master equation is written there on the top of the screen. So we know that dV by dt is 0 therefore the last term will vanish. We know that dH by dt is 2.2 and V is 250.8. So with that you can actually substitute the values and you can get a long expression and here what we have done is we have inserted the values of beta, alpha, Q, CD0, k1, N, V and dH by dt in the expression. So this can be easily solved. In fact, if this turns out to be an expression like TSL by WTO is equal to this whole constant, this whole number divided by WTO by S and then this whole number divided by into W by S plus a constant C which will be the terms outside the bracket, these terms and these terms. So I think we should pause the video at this stage and calculate the values of these three constants A, B and C. The values come out to be as shown on the screen. Now with these values you can replace now in this equation. So you will get relationship between TSL by WTO because you can put A here, you can put B here, you can put C here and for various numerical values of WTO by S ranging from 300 kg plus meter square to 650 kg by meter square, you can see how it pans out into the diagram. So this constraint on climb rate at cruise depends both on WTO by S and TSL by WTO, therefore it will come up as a line in the constraint diagram. So if you draw this line in the constraint landscape, we see that it appears as a curved line with the area below the line as being infeasible. Moving ahead to the last constraint which is on balance field length, the requirement given is that the balance field length should be 2 weight, 1, 2 meters at maximum takeoff weight and under sea level and IC plus 15 conditions. For this we are going to use the takeoff parameter as explained in the textbook by Daniel Rehmer. So the takeoff parameter is a parameter that is obtained from a graph and from there you can get a direct link between T by W and W by S. Let us look at the constraint on takeoff balance field length. This is an image taken from the famous textbook by Dan Rehmer which shows the correlation between various types of takeoff distances and the takeoff parameter. So we know from our specifications that the BFL has to be 9 to 25 feet at IC plus 15 and the data is that there are only 2 engines in this aircraft. So with that if you proceed from the Y axis with 9 to 25 feet and hit the line for BFL or balance field length for twin engine jet aircraft, you can go down and obtain the value of takeoff parameter as 233 pounds per square feet. This has to be converted into SI units and after that the value of sigma at IC plus 15 has already been calculated it is 0.9502. So let us look at how this constraint can be calculated. So the takeoff parameter is parameter defined as W by S divided by sigma CL max takeoff by T by W. So by rearrangement you can get a link between T by W and W by S. Sigma CL max takeoff and TOP are known. CL max is specified by the aerodynamic data. Sigma and TOP have already been calculated. So T by W can be obtained simply as W by S divided by 3 constant terms or the expression is T by W is equal to A times W by S. So I think you can pause the video and calculate the value of A. A turns out to be 4.8 410 power minus 4 and with this you can get various combinations between W by S and T by W as shown. So this pans up into the constraint diagram as a straight line and this line the area below this line is infeasible and the above the line is feasible. So now let us look at how do we plot the constraint diagram by suppurposing all the constraint lines one by one. First let us look at the constraint that depend on T by W alone which are the second stage climb gradient and the mist approach gradient. These are appearing as horizontal lines. The first one is SSCG and the second one is MAG. So for this problem we see that the mist approach gradient is more severe than the second stage climb gradient of constraint. Then let us look at the constraint that depend on W by S alone. There were 3 constraints in our diagram takeoff stalling speed, landing stalling speed and landing ground roll. These will appear as vertical lines. So the first one is the one on stall takeoff. Then the next one is on stall at landing and the third one is because of the landing ground roll. Area on the left of these lines is feasible. So we notice here that the constraints because of the stalling speed at takeoff and at landing ground roll are weaker than the constraint on the stalling speed at landing. Finally let us look at the 2 constraints that depend on both W by S and T by W which are the climb rate at cruise and balance field length. These will appear as curves or lines in the constraint diagram. The first one that we bring here is the line due to the climb rate which is a curved line and the next one is the constraint due to the landing due to the balance field length. So the intersection of all these lines this is the final constraint diagram. So this area above this purple line and on the left of this red line this is going to be the feasible area because the area below this line is infeasible the area on the right of this line is infeasible. So therefore this area is the one which is the feasible area. So now moving on let us see how do you find the design point. This is obtained by taking the intersection of the most critical constraints which is as shown in the screen 596.6 kg per meter square and T by W of 0.291. The design point will be taken slightly above and slightly on the left of this constraint this intersection point because of the requirement to give some margin for growth of the aircraft and for changes in the design as the analysis procedure progresses. So it is always good to give some margin. So what I have done is I have given little bit of margin on the left hand side and little bit margin on the vertical side. So the design point. Now let us see how far we are from reality. Let us just check. So this is our constraint diagram and the values that are given in piano for Boeing 787 are 600 and 0.28. So what we see is that we are very much near the values which are available in piano. So it shows that our constraint analysis calculations is very much near reality. Hope your calculations were matching with these. Thanks for your attention.


So before jumping into the topic just a quick survey, how many of you are familiar with using containers in production? Like, how many of you have services running in containers? So this topic is about how to secure or how to make container environment more safer, considering that containers share the same kernel on the server. So this is one attempt or method to make those containers run in a safe or run safely. So today the containers, as I said before, they share the same kernel on the host or they're on the same VM, they basically they share the same kernel. There are these technologies, namespaces, say comp and app armor and few others, technologies provided by the kernel. They provide a barrier protection between the containers. But container isolation is actually, we can say that is as strong as the kernel. And if, for example, the kernel is compromised and the barriers between the boundaries between the containers can disappear, meaning we lose the isolation between containers as soon as the kernel is compromised. So this concept or this talk is about how we can make the kernel safe or how we can protect the kernel and make it safer. So this is like kernel protect itself. Yeah, we can do that and I'll talk about it now. What is it about? So this kernel protection is the idea is to protect kernel resources, like, for example, Intra Biscuit tables or any other kernel resource that needs to be, that should not be modified or need to be tampered with. We can protect those resources by making those, for example, some kernel resources are only read-only, maybe like something like const or IDT or system descriptor tables. And also processor state, for example, with Intra, there is something called control registers. So once the kernel sets the control register during its init, then those registers should not be tampered with or manipulated again. So with this method or idea, we can help monitor any changes to the kernel resources or processor state. And how this one helps, as I said, this helps monitor and protect the system resources. And for that matter, any range of kernel memory, if it deems to be protected, we can protect or monitor that resource. And with this idea, also, we can extend the CPU features. For example, older platforms will not have the newer security features. So we can provide those newer features on older platforms using this concept. And all this we can achieve without any minimal modifications to the kernel. These are examples of system resources. So now we'll come to how it is done. So this idea revolves around using VTX, using virtualization technology. In terms of Intel, it is VTX. So the idea is to run the Linux or the host OS in guest mode so that we can leverage the advantages, meaning isolation and security features available in virtualization for Linux, that is host OS. We specify policies for protecting the resources, meaning I'll go over it in the next slide. The idea is to use a thin hypervisor, possibly an extension to KVM, to handle this protection kernel protection. So this is about the policies. So we can mention the asset, meaning, for example, let's say IDT. We can say IDT to be monitored and how we want to protect the IDT. It should not be written to, so we can say read only. And for example, if there is an attempt by some malicious software or some exploit in the kernel, changing the IDT, we can monitor it and we can terminate that attempt. So concluding where we are now, we have a functional POC to switch the Linux into guest mode, running Linux into guest mode. And right now we are adding code for implementing the policies that I mentioned in the previous slide. And we are planning to submit patches into the community sooner. I'm well ahead of time. So if there are any questions, I can take them. Anything that has virtualization? I think a lot, VTX. Do you use VTX for Intel, yeah? Let me just show you, yeah. No, the patches, this is not public yet. So we are planning to make them soon. So guest mode, specifically in Intel terms, we are using non-root mode in VTX. So when you run a processor in non-root mode, you get to take, you can basically use the features like EPD or VMCS. If you are aware of VMCS in Intel VTX, if a processor is executing certain instructions, you can trap them and check them whether it is valid or not. It's pretty much the same because we are making the interrupts and IO instructions, all of them pass through. So if there are any interrupts or if there are any IO instructions, they kind of run without being trapped into root mode. KVM is just, the idea is to use KVM as an extend KVM to implement the operations that needs to be done in root mode. We kind of use extend KVM module to handle those operations. It can be any other hypervisor. KVM is just one way to do it. Well, we need something, some module, kernel module to intercept those operations in the root mode. So we need something that executes in root mode. Yeah, a module in the host operating system. Any other questions? This is like done once after init. For example, once the boot is complete. Oh, it's kernel init, not the processor init. Once the kernel is booted and once, for example, before you start running any application, you can switch, make this active and then you are done. And then the only thing you can do at runtime is specifying policies. Like what you need to protect, how you want to protect. That can be done at runtime.


There are three common ways to estimate the amount of bad debt expense to be recorded under the allowance method. They are the percent of sales method, percentage of receivable method, and the aging of accounts receivable method. We will learn about the aging of receivables method in this short video. The aging of receivables method is sometimes called the balance sheet approach to estimating bad debt expense because it focuses on the balance sheet account allowance for doubtful accounts. The method calculates what the adjusted balance in the allowance for doubtful accounts should be. Then we record bad debt expense to make that balance correct. Usually this method starts with a table. We age our invoices because the collectability of older accounts are less than recent accounts. In this example, you can see that the total amount of accounts receivable is $17,500, but we have classified that into four subtotals based on aging. Then we use historical bad debt rates for each of those aging columns. Then we multiply the aged columns, the totals by the historical rate to determine how much of each classification we think we won't collect. The total of these becomes the amount of accounts receivable we think we won't collect, and that should be the balance in the allowance for doubtful accounts. So in this example, we think the balance in the allowance for doubtful accounts should be credit of $825. $825 is not the amount of adjusting entry, however. Let's look at this example. If the allowance for doubtful accounts had an unadjusted credit balance of $500, then the adjusting entry amount required to bring this balance to $825 is a debit to bad debt expense and a credit to the allowance for doubtful accounts for an additional $325. Sometimes you will see an example like this. If we've written off more accounts than expected, we could temporarily have a debit balance in the allowance for doubtful accounts. In this case, we have an unadjusted debit balance of $800. In order to make this account a credit balance of $825, we need to debit bad debt expense and credit the allowance for doubtful accounts for $1,625.