are you studying for your atpl exams do you need a little bit of help with mass and balance if so you come to the right place to help with this technical little subject hi i'm grant i'm a first officer based here in the uk for a major uk airline i've been flying jets for five years with two different airlines and i'm here to guide you through mass imbalance in a plane and easy to understand format with some real-world examples from my own experiences in this first class we're going to be covering the unit conversions that come up all the time in math and balance and help play our foundations for the rest of the course okay so starting first we have our conversions now very annoyingly there are two sets of units in aviation imperial and metric unfortunately they are used interchangeably so we need to understand some basic conversions for distance mass and volume the conversions are standardized by iko which is the international civil aviation organization and that is all laid out in a document called annex 5 which is a very very interesting document the easiest to understand is distance and in mass and balance specifically the distances are usually quite small so we deal with meters and feet so one meter equals three point two eight eight and if we want to go from one to the other we either divide or multiply by three point two eight for example 25 meters if we were to get that into feet we would multiply by 3.28 and come up with a value of 82 feet this is a good point to do an error check we know that feet are the smaller of the distances because there are 3.28 of them in every meter so therefore there should be more feet than there are meters that means we have to multiply and we get 82. simple the next unit to talk about is mass for every kilogram we have 2.205 pounds so if we want to get from kilos to pounds we multiply by 2.205 and pounds to kilos we do the inverse so for example 200 pounds what does that equal in kilograms we know that kilograms are the larger of the two because there are 2.205 pounds in every kilogram therefore there should be fewer kilograms than there are pounds and that means we divide let's do we divide by 2.205 and we come up with an answer of 90.703 kgs so we've done that error check already in our calculation we know that kilos are the larger so there should be fewer of them than pounds now something important to touch on is the concept of weight versus mass if you've done physics in school or anything like that you'll know the weight is technically a force so it's measured in newtons but if somebody asks you how much you weigh you don't say i weigh 150 newtons you realistically talk about highway 90 kgs or 200 pounds so the same logic applies in aviation most of the time they're used interchangeably but there can be some cases where things will be given as forces and other things will be going in mass and you have to convert them all into the same either force or mass equivalent now this is a very easy thing to do we just use the g constant which stands for the acceleration due to gravity and in aviation we use the figure 9.81 meters per second squared so if we have a weight of 150 kgs sorry a mass of 150 kgs and we want to know the weight we multiply by 9.81 and come up with our answer 1471.5 next unit of measurement to talk about is volume volume is measured in three ways in aviation we have liters imperial gallons and u.s gallons so an imperial gallon is equal to six 4.564 liters and a us gallon is equal to three point seven eight five liters those are the two conversions that we need and if we want to convert from u.s gallons to imperial gallons we'll convert to liters first and then come back from liters into the appropriate um gallon so if we do one of those examples i'll show you how it works if we have 5 us gallons and we want to know what it is an imperial gallons first of all we go to liters we know that there are more liters so we need to have more than five therefore we must multiply so times by 3.785 come up with an answer in liters which is 18.925 that's our midpoint and then we want to go back to imperial gallons we know there are going to be fewer imperial gallons as they are bigger than meters therefore we have to divide so i take that 18.925 divide divided by our conversion which is four point five six four and we come up with an answer which is four point one four seven imperial gallons to summarize one meter equals 3.28 feet 1 kilogram equals 2.205 pounds one imperial gallon is equal to 4.56 liters and one us gallon is equal to 3.785 liters you