MRJT Additional Procedures — Page 120, Lesson 111

I want to walk you through the MRJT Additional Procedures section, starting with ETOPS. ETOPS stands for Extended-range Twin-engine Operations Standards — it’s the set of rules that allows a twin-engine aircraft like the MRJT to fly routes where it might be more than a certain time away from a suitable diversion airfield. The key reference here is CAP 697, pages 72 to 75, and specifically Figures 4.7.1a and 4.7.1b. Those two graphs give you the Critical Fuel Reserve for Long Range Cruise, or LRC. One graph is for one engine inoperative — that’s the engine failure case — and the other is for all engines operative at the Critical Point. The Critical Point, or CP, is the point along the route where, if you lose an engine, you’re equally far from your departure and destination airfields in terms of time. The Critical Fuel Reserve is the amount of fuel you must have at that point to safely reach a diversion airfield under the worst permitted conditions. If this reserve is greater than the fuel you had planned to have at that point, you must increase your total fuel load accordingly. Both graphs are built on the same set of common parameters. Let me list them carefully. First, there’s a pressurization failure — you lose cabin pressure. Second, you perform an emergency descent to 10,000 feet, then level cruise at 10,000 feet. Third, you do a 250 KIAS descent to 1,500 feet over the airfield — that’s 250 knots indicated airspeed down to 1,500 feet above the field. Fourth, you have 15 minutes of holding at 1,500 feet, then one missed approach, approach, and land. Fifth, there’s a 5% allowance for wind errors — that’s a safety margin built into the fuel calculation. Now, the One Engine Inoperative graph also includes Auxiliary Power Unit (APU) fuel burn. The APU is a small turbine engine in the tail that provides electrical power and pneumatic air — for things like air conditioning — when the main engines aren’t running or can’t supply enough. So the one-engine-inoperative graph represents the worst case scenario: simultaneous engine failure and pressurization failure. That’s why the APU is started in flight — to compensate, in part, for the loss of the power plant’s ability to provide essential electrics and pneumatics. Below each graph, you’ll find corrections for two conditions: temperatures hotter than ISA — that’s International Standard Atmosphere — and icing conditions. These corrections adjust the fuel reserve for non-standard conditions. Let’s look at the examples to see how this works in practice. Example 1: An aircraft at a weight of 48,000 kg suffers an engine and pressurization failure simultaneously. The forecast conditions at FL100 — that’s flight level 100, or 10,000 feet — are +5°C and a 50 kt headwind for the 850 NM distance from the Critical Point to the diversion airfield. You need to calculate the LRC Critical Fuel Reserve. The answer is on page 121. Example 2: Same details, but assuming pressurization failure only — so all engines are still operative. Again, answer on page 121. Example 3: An aircraft at 50,000 kg has an engine and pressurization failure simultaneously. The forecast is icing conditions at FL100, -15°C, and a 60 kt tailwind for 750 NM from the CP to the diversion airfield. Calculate the LRC Critical Fuel Reserve. Answer on page 121. Example 4: Same details, but pressurization failure only. Answer on page 121. Now let’s move to the next topic: Area of Operation – Diversion Distance, which uses CAP 697 Figure 4.7.2. The area of operation is defined as the region within which the operator is authorized to conduct ETOPS. The key rule is: the distance to the diversion airfield from any point along the route must be flown within the approved time, using the single-engine cruise speed, assuming still air and ISA conditions. So you don’t get credit for tailwinds or warmer temperatures — it’s a conservative, worst-case assumption. The maximum diversion distance used to establish the area of operation can be obtained from this chart. Here’s the method: enter the chart with the appropriate speed and weight at the point of diversion. Select the appropriate time — that’s the approved ETOPS diversion time, like 120 minutes, 135 minutes, 150 minutes, or 180 minutes. Then read off the maximum diversion distance. Example 5 gives you a table to fill in. You have different speeds — like Mach 0.70 with 280 KIAS, Mach 0.74 with 290 KIAS, and so on — and diversion weights in thousands of kilograms. For each combination, you need to find the diversion distance for approved times of 120, 135, 150, and 180 minutes. The answer is on page 121. So in summary: the Critical Fuel Reserve graphs tell you how much fuel you need at the Critical Point for the worst-case diversion. The Area of Operation chart tells you how far you can be from a diversion airfield, given your speed, weight, and approved ETOPS time. Both are essential for planning an ETOPS flight.