EDTO and ETOPS

The one-hour circle

You drive a car with two engines, and one quits. You can go on with the other, but you want a garage close by.

A twin jet over the ocean is that car. Chennai to Perth is mostly water.

So the first rule is simple. A twin stays within one hour of an airfield, flying on one engine in still air.

With a one-engine speed of 400 kt, that is a 400 NM circle round each field. This is the threshold.

Distance = one-engine TAS × time

Draw the straight line to Perth. Part of it leaves the circles.

To fly that part, a twin needs special approval. That is ETOPS, extended-range twin operations. ICAO’s newer name, for two or more engines, is EDTO: extended diversion time operations.

Doc 10085 is ICAO’s EDTO manual. For three and four engines, you may also see LROPS.

ETOPS: twins. EDTO: the ICAO name, for two or more turbine engines.

The approval

An approval stretches the time. 90, 120, 138, or 180 minutes from an adequate field.

At 180 minutes the circles reach right across the ocean. Now the route is inside them.

Now the one sentence the paper asks. An aeroplane under the 180-minute ETOPS rule may be up to 180 minutes flying time from a suitable airfield, in still air, with one engine inoperative.

A time. On one engine. In still air, ISA. From a suitable field.

Which speed? A twin: one engine inoperative. More than two engines: all engines operating.

And the threshold time itself is set by the State.

The words

This lesson is part of the Navigation plan. See plans

Before it may leave

This lesson is part of the Navigation plan. See plans