Now, there's an alternative — Page 114, Lesson 104

I want to walk you through the definitions that underpin ETOPS — Extended Twin Operations. This is a critical set of rules for any twin-engine aircraft flying long overwater or remote routes, and the definitions here are the foundation you'll use for diversion planning and fuel calculations. Let's start with the core definition. Extended Twin Operations — ETOPS — are those operations intended to be, or actually, conducted over a route that contains a point further than one hour's flying time, in still air, at the normal one-engine-inoperative cruise speed, from an adequate aerodrome. So the key threshold is one hour at a specific speed with one engine out. That "in still air" part means we're not accounting for wind — it's a pure distance-in-time measure. Now, there's an alternative. When a Threshold Distance has been agreed with the Authority — that's your national aviation authority — then all non-ETOPS flights shall remain within that threshold distance of an adequate aerodrome. So if you're not operating under ETOPS rules, you must stay within that agreed distance. The default threshold time is 60 minutes, which I'll come back to. Next, the ETOPS Segment. This is the portion of an ETOPS flight that begins when the aeroplane is first more than the threshold distance from any adequate aerodrome — that point is called the ETOPS Entry Point — and ends when the aeroplane is last more than the threshold distance from any adequate aerodrome — that's the ETOPS Exit Point. So the ETOPS segment is the part of the route where you're beyond that one-hour or threshold-distance boundary from any suitable diversion airfield. Everything inside that segment is governed by special planning and fuel rules. Now, what speed are we talking about? The Normal One-engine-inoperative Cruise Speed. An operator — that's the airline — shall determine a speed for the calculation of the maximum distance to an adequate aerodrome for each two-engine aeroplane type or variant operated. This speed must not exceed VMO — that's the maximum operating speed, a structural limit. The speed is based upon the true airspeed that the aeroplane can maintain with one engine inoperative under certain conditions. The excerpt references EU-OPS 1.245 (b) for the full determination of this speed. Importantly, this speed is only intended to be used to establish the maximum distance from an adequate aerodrome — it's not your normal cruise speed, it's a planning figure for diversion distance calculations. Finally, the Threshold Time is 60 minutes. That's the default. Before granting an extension to that threshold time — say, going to 120 or 180 minutes — the Licensing Authority considers several factors: the propulsion system reliability record, the modification and maintenance programme, flight dispatch requirements, training evaluation programme, operations limitation and specifications, operational validation flight, and continuing surveillance and engine reliability monitoring. So an extension is not automatic; it's granted only after a thorough review of the aircraft's and operator's capability. Let me tie this together with the figures available. shows the all-engine Point of Equal Time, or Critical Point, which is related to these diversion concepts. continues that illustration. These diagrams help visualise where the ETOPS entry and exit points sit relative to adequate aerodromes and the threshold distance. So in summary: ETOPS applies when your route takes you beyond one hour at one-engine-inoperative speed from a suitable airfield. The threshold time is 60 minutes by default. The ETOPS segment is the portion of the flight between the entry and exit points beyond that threshold. And the speed used for planning that distance is a specific one-engine-inoperative cruise speed, not exceeding VMO, determined by the operator.