EU-OPS 1 - Extract — Page 12, Lesson 10

I want to walk you through the regulatory heart of mass and balance — EU-OPS 1. This is the rulebook that governs how an operator must handle the load on every single flight. Let's start with OPS 1.625, which is titled "Mass and balance documentation." The core requirement is in paragraph (a): an operator must establish mass and balance documentation prior to each flight. That documentation must specify the load and its distribution. So it's not just "how heavy are we" — it's also "where is that weight sitting." The whole point of this document is to let the commander determine that the load and its distribution are such that the mass and balance limits of the aeroplane are not exceeded. In other words, the document has to be good enough that the captain can check, before take-off, that the aircraft is within its certified limits. Now, the accountability chain. The person who prepares the mass and balance documentation must be named on the document. Then there's a separate person — the one supervising the loading of the aeroplane — and that person must confirm by signature that the load and its distribution are in accordance with the documentation. So you have a named preparer and a signing supervisor. Finally, the document must be acceptable to the commander, and the commander's acceptance is indicated by countersignature or equivalent. So three layers: prepared, supervised and signed, then accepted by the captain. There's a cross-reference here — OPS 1.1055(a)12 — which is the operational part that ties into this, but the key point for now is that chain of accountability. Paragraph (b) says an operator must specify procedures for last minute changes to the load. That's a real operational scenario — a passenger shows up late, cargo gets swapped at the door — and the rule requires a defined procedure for handling that change safely. Paragraph (c) gives flexibility: subject to the approval of the Authority, an operator may use an alternative to the procedures required by paragraphs (a) and (b). So the regulator can approve a different method, but it must be approved. Now let's move to Appendix 1 to OPS 1.605, which is titled "Mass and Balance — General." This is where the detail on how you actually determine mass lives. Section (a) is about determining the dry operating mass of an aeroplane. First, weighing. New aeroplanes are normally weighed at the factory, and they're eligible to be placed into operation without reweighing — provided the mass and balance records have been adjusted for any alterations or modifications. So if you modify the aircraft, the records must be updated to reflect that. There's a specific rule for transfers between operators: if an aeroplane is transferred from one operator with an approved mass control programme to another operator with an approved programme, it need not be weighed prior to use by the receiving operator — unless more than four years have elapsed since the last weighing. So four years is the trigger. Then, periodically, the individual mass and centre of gravity position of each aeroplane must be re-established. The maximum interval between two weighings must be defined by the operator, and it must meet the requirements of OPS 1.605(b). So the operator sets the interval, but it has to comply with the regulation. Now here's the interesting part — there are two ways to re-establish mass and CG. Either by weighing, or by calculation — but calculation is only allowed if the operator can provide the necessary justification to prove the validity of the method chosen. And calculation is triggered by specific thresholds: whenever the cumulative changes to the dry operating mass exceed ±0.5% of the maximum landing mass, or the cumulative change in CG position exceeds 0.5% of the mean aerodynamic chord. So two triggers — a mass trigger and a CG trigger. Note the units: 0.5% of maximum landing mass for mass, and 0.5% of mean aerodynamic chord for CG position. Then we get to fleet mass and CG position. For a fleet or group of aeroplanes of the same model and configuration, an average dry operating mass and CG position may be used as the fleet mass and CG position — but only if the individual aeroplanes' dry operating masses and CG positions meet the tolerances specified in subparagraph (ii). And there are additional criteria in subparagraphs (iii), (iv), and (a)3 that also apply. The excerpt cuts off right at the start of those tolerances, but the principle is clear: you can average across a fleet only when the individual aircraft are close enough together that the average is safe. Let me show you the flow of this on the figure — it lays out the documentation chain and the weighing logic visually. So to tie it together: OPS 1.625 gives you the documentation and accountability requirements for every flight, and Appendix 1 to OPS 1.605 gives you the underlying rules for how you establish the dry operating mass and CG in the first place — weighing at the factory, the four-year transfer rule, periodic re-establishment, the ±0.5% triggers for calculation, and the fleet averaging concept with its tolerances. That's the regulatory skeleton of mass and balance.