EDTO Explained: Extended Diversion Time Operations from Scratch
EDTO stands for Extended Diversion Time Operations. It is the ICAO name for flights that go far from airports where they could land after an engine failure or another serious problem. It replaced the older term ETOPS, which covered twin-engine aeroplanes only.
Why EDTO exists
ICAO requirements for extended range twin-engine operations (ETOPS) have been in place since 1985. They let twin-engine aeroplanes fly routes across oceans and remote areas, far from the nearest airport, provided safety is protected in two ways: designing reliable engines and critical systems so that a diversion is unlikely, and protecting any diversion that does become necessary through the aeroplane's design, the operator's procedures and the choice of alternate airports.
EDTO in ICAO Annex 6
The rules are in Annex 6, Part I, section 4.7, with guidance in the attachments and in ICAO Doc 10085, the Extended Diversion Time Operations Manual. The Annex applies to aeroplanes with two or more turbine engines. Unless the State of the Operator has given a specific approval, such an aeroplane may not operate on a route where the diversion time to an en-route alternate aerodrome exceeds a threshold time set by that State.
Key terms
- Threshold time: the range, expressed in time, set by the State of the Operator to an en-route alternate aerodrome. Any time beyond it needs an EDTO approval. Several States set it at 60 minutes for twin-engine aeroplanes.
- Diversion time: the time to fly from a point on the route to an en-route alternate aerodrome, calculated in ISA and still air conditions. For aeroplanes with two engines it uses the one-engine-inoperative cruise speed. For aeroplanes with more than two engines it uses the all-engines-operating cruise speed.
- Maximum diversion time: the largest diversion time allowed by an operator's approval, for example 120, 180 or more minutes. National authorities also describe extensions of 15 percent, giving figures such as 138 minutes (120 plus 15 percent) and 207 minutes (180 plus 15 percent).
- En-route alternate: an aerodrome where the aeroplane can land if a diversion becomes necessary while en route. The departure aerodrome may also serve as one.
What the operator has to do
- Establish, for each proposed route, a list of adequate en-route alternate aerodromes. Requirements include, but are not limited to, at least one approach aid and a minimum rescue and firefighting category of 4.
- Decide the diversion time required and the one-engine-inoperative planning speed.
- Plan the EDTO en-route alternates, the equal time points, the critical fuel scenario and any time-limited systems.
- Make arrangements to obtain weather data for the EDTO en-route alternates.
Who approves it
The State of the Operator grants the approval. Authorities look at the aeroplane's design and reliability and at the operator's procedures, and each State publishes its own circular. According to Doc 10085, there are no additional maintenance or certification requirements for aeroplanes with more than two engines. The FAA still uses the term ETOPS in Advisory Circular 120-42B, which also covers polar operations. Always use your own State's rules.
This is an overview for learning. It is not a substitute for Annex 6, Doc 10085 or your authority's requirements.
FAQ
Is EDTO the same as ETOPS?
EDTO is ICAO's newer term and covers all turbine-engine aeroplanes with two or more engines. ETOPS is the older term for twin-engine operations, and some States, such as the United States, still use it.
Does EDTO apply to aeroplanes with four engines?
Annex 6 applies to aeroplanes with two or more turbine engines, with the diversion time for more-than-two-engine aeroplanes calculated at the all-engines-operating cruise speed.
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For training and reference only. Check official sources before any real flight.