MRJT Additional Procedures — Page 114, Lesson 108

I want to walk you through the ETOPS fuel policy procedures that apply in-flight and the concept of critical fuel for ETOPS operations. Let's start with the in-flight replanning requirements. An operator must ensure that when a flight has to proceed along a route, or to a destination other than originally planned, the in-flight replanning procedures for calculating usable fuel include several specific components. First, you need trip fuel for the remainder of the flight. Then you have reserve fuel, which itself consists of several elements: contingency fuel; alternate fuel, if a destination alternate is required; final reserve fuel — for aeroplanes with turbine power units, that means fuel to fly for 30 minutes at holding speed at 1500 feet, which is 450 metres, above aerodrome elevation in standard conditions; additional fuel, if required by the type of operation, for example ETOPS; and extra fuel if required by the commander. Now let's move to the critical fuel concept for ETOPS. In general, an aeroplane shall not be dispatched on an ETOPS flight unless it carries sufficient fuel and oil, and in addition, such additional fuel and oil as may be required to fly to a suitable aerodrome for landing in the event of the shutdown of an engine, or in the event of airframe system failure(s) which may require diversion to an alternate. It should be assumed that this event occurs at the most critical point in terms of overall fuel and oil requirements along the planned route of flight. So for ETOPS operations, the "trip fuel for the remainder of the flight" becomes the critical fuel. That is the fuel from the most critical point, abbreviated CP, or equal time point, abbreviated ETP, to the diversion aerodrome. This is based upon a consideration of three possible events. The first event is the simultaneous failure of an engine and the pressurisation system. This is the worst scenario. In this case, you perform an emergency descent down to flight level 100 at VMO/MMO — that's maximum operating speed in knots and maximum operating Mach number — with the speed brakes extended, and then cruise to the diversion airfield at LRC speed, which is long-range cruise speed. The second event is total pressurisation failure but no engine failure. Here you also perform an emergency descent down to flight level 100 at VMO/MMO with the speed brakes extended, and cruise to the diversion airfield at LRC speed. The third event is engine failure but no pressurisation failure. In this case, descent and cruise will be initiated at the selected speeds and stabilizing level. The fuel required will be the greatest of the all-engine case and the two single-engine cases. This amount is then compared to the fuel planned to be on the aircraft at the most critical CP or ETP. If it is greater than the planned amount, then additional fuel must be uplifted before dispatch. That is the core of the ETOPS critical fuel determination.