First, recording of mass values — Page 17, Lesson 18

Let’s pick this up right where the regulation leaves off — the statistical survey for passenger and baggage mass. We’ve already covered the weighing machine requirements, so now I want to walk you through the recording rules, the checked baggage procedure, and then the crucial part: how those survey results get turned into revised standard mass values that are actually safe to use in operations. First, recording of mass values. For every flight included in the survey, you must record three things: the mass of the passengers, the corresponding passenger category — that’s male, female, or children — and the flight number. So the survey isn’t just a pile of weights; each weight is tagged with who it was and which flight it came from. That tagging is what lets you later build the male/female ratio and apply the right averages. Now, checked baggage. The statistical procedure for determining revised standard baggage mass values is basically the same as for passengers, and it’s specified in subparagraph (a)1 — the same minimum sample size logic. But there are two key differences. First, the relative confidence range — the accuracy — for baggage amounts to 1 percent. Second, you must weigh a minimum of 2,000 pieces of checked baggage. So the sample is much larger in absolute terms than for passengers, and the tolerance is tighter. Now the heart of it — determination of revised standard mass values. The whole point is this: you’re allowed to use standard average masses instead of weighing every passenger and every bag on every flight, but only if that doesn’t adversely affect operational safety. So a statistical analysis must be carried out, and that analysis generates average mass values for passengers and baggage, plus other data. Here’s where the seat count comes in. On aeroplanes with 20 or more passenger seats, those averages apply directly as the revised standard male and female mass values. But on smaller aeroplanes, you must add increments to the average passenger mass to get the revised standard values. And those increments are tiered by seat count. For 1 to 5 seats inclusive, add 16 kilograms. For 6 to 9 inclusive, add 8 kilograms. For 10 to 19 inclusive, add 4 kilograms. The logic is that on smaller aeroplanes, the sample is smaller and the variability is higher, so you need a safety margin built into the standard value. There’s an alternative. On aeroplanes with 30 or more passenger seats, you may apply all adult revised standard average mass values — that’s the option to use the standard published values rather than your own survey. And revised standard average checked baggage mass values are applicable on aeroplanes with 20 or more passenger seats. So the thresholds differ: 30 seats for the adult passenger values, 20 seats for baggage. Now, the deviation option. An operator may submit a detailed survey plan to the Authority for approval, and then get a deviation from the revised standard mass value — provided that deviating value is determined using the procedure in this Appendix. But that deviation must be reviewed at intervals not exceeding five years. So it’s not a one-time approval; it has a mandatory review cycle. Next, the male/female ratio — this is critical. All adult revised standard mass values must be based on a male/female ratio of 80/20 for all flights except holiday charters, which are 50/50. So the standard assumes 80 percent male, 20 percent female — except on holiday charters, where it’s a 50/50 split. If an operator wants a different ratio on specific routes or flights, they must submit data to the Authority showing that the alternative ratio is conservative and covers at least 84 percent of the actual male/female ratios, based on a sample of at least 100 representative flights. So the 84 percent coverage and the 100-flight sample are the two hard requirements for any custom ratio. Finally, rounding. The average mass values found are rounded to the nearest whole number in kilograms. But checked baggage mass values are rounded to the nearest 0.5 kilogram figure, as appropriate. So passengers round to whole kilograms, baggage rounds to half-kilogram steps. Let me tie this together for you. The whole system is a safety valve: you survey real passengers and real bags, you compute averages, you add increments on small aeroplanes to protect against variability, you enforce a conservative male/female ratio, and you round conservatively. The result is a set of standard masses you can use operationally without weighing everyone — but only because the statistics guarantee the standard values never understate the true load in a way that would compromise safety.