The correct answer is b — Page 101, Lesson 121

Let's start with the question about maximum structural landing mass. The correct answer is b. the undercarriage could collapse on landing. Here's the reasoning: the maximum structural landing mass is the heaviest the aircraft is certified to land at, based on the strength of the landing gear and the airframe structure. If you exceed it, the undercarriage—the landing gear—may not be able to absorb the impact of touchdown, and it could collapse. That's a structural limit, not a performance one. Option a is wrong because exceeding landing mass doesn't prevent takeoff—that's a different limit. Options c and d are wrong because exceeding the structural limit causes damage regardless of whether you're within the regulated or performance-limited landing mass. The structural limit is absolute. Now, the second question is a full mass and balance calculation using the MRJT1 data from CAP 696. Let's work through it step by step. We have the following data: - PLTOM = 62,800 kg — this is the Performance Limited Take-Off Mass, the maximum take-off mass allowed by performance considerations. - PLLM = 54,200 kg — the Performance Limited Landing Mass, the maximum landing mass allowed by performance. - DOM = 34,930 kg — the Dry Operating Mass, the mass of the aircraft ready for service but without traffic load and fuel. - Taxi fuel = 250 kg — fuel used for taxiing before take-off. - Trip fuel = 9,250 kg — fuel for the planned flight. - Contingency and holding fuel = 850 kg — reserve fuel. - Alternate fuel = 700 kg — fuel for the alternate destination. We need to calculate the maximum allowable traffic load — the mass of passengers, baggage, and cargo that can be carried. First, let's find the total fuel on board at take-off. That's the trip fuel, contingency and holding fuel, and alternate fuel added together: 9,250 + 850 + 700 = 10,800 kg. But wait — the taxi fuel is burned before take-off, so it's not part of the take-off mass. The take-off mass includes the DOM, the traffic load, and the fuel at take-off, which is the 10,800 kg we just calculated. So the take-off mass is: DOM + traffic load + 10,800 kg. This must not exceed the PLTOM of 62,800 kg. So: 34,930 + traffic load + 10,800 ≤ 62,800. That gives: traffic load ≤ 62,800 − 34,930 − 10,800 = 17,070 kg. Now, we also have a landing mass limit. At landing, the fuel remaining is the contingency and holding fuel plus the alternate fuel, because the trip fuel has been burned. That's: 850 + 700 = 1,550 kg. The landing mass is: DOM + traffic load + 1,550 kg. This must not exceed the PLLM of 54,200 kg. So: 34,930 + traffic load + 1,550 ≤ 54,200. That gives: traffic load ≤ 54,200 − 34,930 − 1,550 = 17,720 kg. Now, the maximum allowable traffic load is the lower of the two limits, because we must satisfy both the take-off and landing constraints. So we take 17,070 kg. But wait — the question says the aircraft is loaded with maximum fuel of 20,100 L at an SG of 0.78. Let's check that. The fuel capacity is 20,100 litres, and the specific gravity is 0.78. The mass of fuel is: 20,100 × 0.78 = 15,678 kg. But the fuel we calculated for the trip, contingency, holding, and alternate is only 10,800 kg. So the maximum fuel of 15,678 kg is more than what's needed for this flight. The question says "maximum fuel" — but the fuel actually used for the flight is the trip, contingency, holding, and alternate fuel. The taxi fuel is additional, but it's burned before take-off. Hmm, let me reconsider. The question says "loaded with maximum fuel of 20,100 L at an SG of 0.78." That means the tanks are full. So the total fuel on board at take-off is 15,678 kg. But the taxi fuel of 250 kg is burned before take-off, so the fuel at take-off is: 15,678 − 250 = 15,428 kg. Wait, but the trip, contingency, holding, and alternate fuel are the fuel required for the flight. If the tanks are full, the fuel on board is 15,678 kg, which is more than the 10,800 kg required. So the extra fuel is just carried as additional weight. Let me redo the calculation with the actual fuel on board. At take-off, the fuel is 15,428 kg (after taxi). So the take-off mass is: DOM + traffic load + 15,428 ≤ 62,800. That gives: traffic load ≤ 62,800 − 34,930 − 15,428 = 12,442 kg. At landing, the fuel remaining is the fuel on board minus the trip fuel burned. The trip fuel is 9,250 kg. So the fuel at landing is: 15,428 − 9,250 = 6,178 kg. But wait — the contingency, holding, and alternate fuel are reserves. If the flight goes as planned, only the trip fuel is burned. So the fuel at landing is 15,428 − 9,250 = 6,178 kg. The landing mass is: DOM + traffic load + 6,178 ≤ 54,200. That gives: traffic load ≤ 54,200 − 34,930 − 6,178 = 13,092 kg. Now, the maximum allowable traffic load is the lower of the two: 12,442 kg from the take-off limit, and 13,092 kg from the landing limit. So the answer is 12,442 kg, which is option b. Let me double-check the fuel at landing. The fuel on board at take-off is 15,428 kg. The trip fuel is 9,250 kg. So after the trip, the fuel remaining is 15,428 − 9,250 = 6,178 kg. That includes the contingency, holding, and alternate fuel, which are 850 + 700 = 1,550 kg. So the fuel at landing is 6,178 kg, which is more than the reserves, meaning there's extra fuel. So the take-off limit is the binding constraint, giving 12,442 kg. The correct answer is b. 12,442 kg. Now, let me also mention the other numbers in the options: 13,092 kg is the landing-limited value, 16,370 kg and 16,842 kg are not correct for this scenario. So, to summarize: the maximum structural landing mass question — answer is b, undercarriage collapse. The MRJT1 calculation — answer is b, 12,442 kg. Let's move on.