EDTO Approval and Dispatch Requirements Explained

EDTO has two layers: the operator must first be approved, and then every flight must meet dispatch requirements. This guide covers both, using ICAO guidance as summarised by SKYbrary and a national advisory circular as a worked example. Your own State's rules always apply.

Threshold time

The threshold time is not an aircraft limit. It is a safety criterion for flying long distances from adequate en-route alternates. Flying beyond it is EDTO and needs an approval. In Singapore's rules, for example, the threshold is 60 minutes for an aeroplane with two turbine engines and 180 minutes for one with more than two. The FAA's guidance uses the same figures for ETOPS: a point farther than 60 minutes from an adequate airport for two-engine aeroplanes, and farther than 180 minutes for passenger aeroplanes with more than two engines.

Approval levels

Flights beyond the threshold can be approved at different levels: up to 90 minutes, beyond 90 and up to 180 minutes, and beyond 180 minutes, with fifteen percent increases for specific routes. As an example of progression, Singapore's circular considers 120 minutes after 12 months of operating experience on the same airframe and engine at 60 minutes, and 180 minutes after 12 months at 120 minutes. It allows up to 138 minutes (120 plus 15 percent) and, case by case, up to 207 minutes (180 plus 15 percent). Operators without that experience follow a longer accelerated approval.

What an applicant has to show

The routes covered, and EDTO maintenance procedures including engine condition, in-flight shutdown and oil consumption monitoring.
For each route, a list of adequate en-route alternates, the diversion time needed and the one-engine-inoperative planning speed.
A system for obtaining flight plan data: en-route alternates, equal time points, the critical fuel scenario and time-limited systems.
Weather data for the alternates, reliable communication with the operator, an EDTO minimum equipment list, EDTO procedures manuals and training for crews and ground staff.

A State normally ensures that the maximum diversion time does not exceed the most limiting EDTO-significant-system time in the aircraft flight manual, which for many aeroplanes is the cargo fire suppression system.

Dispatch requirements for each flight

The required en-route alternates are identified.
The crew has up-to-date information on them, including operational status and weather, and can get updates in flight.
Two-way communication with the operator's control centre exists, and conditions along the route are monitored.
The intended route does not exceed the approved maximum diversion time.
Aircraft systems, including the relevant minimum equipment list items, are serviceable.
Communication and navigation facilities are available, fuel requirements are met, and performance information for the alternates is available.

Planning principles

If an engine fails, the aeroplane must be able to proceed to and land at the nearest en-route alternate, in terms of least flying time, where a safe landing can be made. For a failure of an EDTO-significant system the same applies, unless continuing the flight causes no substantial loss of safety. Before the flight goes beyond the threshold time, the alternates must be re-evaluated, and conditions during the time they might be needed must not be below the applicable aerodrome operating minima.

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FAQ

Is the threshold time an aircraft limit?

No. It is a criterion for when an EDTO approval is needed. The limit that applies to a flight is the maximum diversion time in the operator's approval.

Why does the cargo fire suppression system matter?

It is often the most time-limited EDTO-significant system, and a State normally does not approve a maximum diversion time beyond the most limiting such system in the flight manual.

More guides

For training and reference only. Check official sources before any real flight.