Sofema Online (SOL) considers the key features and transition from ETOPS to EDTO.

Introduction 

ICAO introduced ETOPS (Extended Range Twin Operations) and EDTO (Extended Diversion Time Operations) to create a unified framework for all turbine-engined aeroplanes, regardless of the number of engines.

Key Conceptual Changes

•  Expansion beyond Twin Engines: While ETOPS historically focused on the risk of losing one engine on a twin-engine jet, EDTO recognizes that for three- and four-engine aircraft, the limiting factor is often not the engine, but time-limited systems (e.g., cargo fire suppression, oxygen, or cooling).

•  The "Threshold Time": ICAO defines a threshold time beyond which an operation is considered EDTO.¹

>> Twin-engine: Typically 60 minutes (at one-engine-inoperative cruise speed).

>> More than two engines: Typically 180 minutes (at all-engines-operating cruise speed).

EDTO Definitions & Framework

• Threshold Time refers to a time range established by the State of the Operator. If this time is exceeded, the operator is required to hold a specific EDTO approval.

• Maximum Diversion Time is the maximum allowable time or range an aircraft may be from an en-route alternate aerodrome, as defined for a specific aircraft type and operator.

• An EDTO-significant system is any system whose failure or degradation could adversely affect safety during a long-range diversion. Examples include the APU, hydraulic systems, and cargo fire suppression systems.

EDTO Overview: Detailed Differences (Former ETOPS)

The shift to EDTO represents a change in philosophy from "engine reliability" to "overall system safety."

Two-Engine vs. Multi-Engine Requirements

•  Certification (Type Design): Twin-engine aircraft still require specific EDTO Type Design Approval (CMP - Configuration, Maintenance, and Procedures). For aircraft with more than two engines, ICAO does not strictly require a "CMP" document, but the operator must account for all time-limited systems.

• Maintenance: Twin-engine EDTO maintains strict "dual maintenance" prevention (e.g., not allowing the same technician to perform identical tasks on both engines). The multi-engine EDTO's focus is on selecting and monitoring en-route alternates.

•  Fuel Scenarios: EDTO introduces a Critical Fuel Scenario, requiring enough fuel to account for a simultaneous engine failure and cabin depressurization at the most critical point.

EASA SOP & Regulatory Considerations

EASA is currently transposing the ICAO EDTO SARPs (Standards and Recommended Practices) into the EU Air OPS Regulation (965/2012).

Current Status (as of late 2025)

•  Terminology: While ICAO uses EDTO, EASA still uses the term ETOPS in Part-SPA (Specific Approvals), Subpart F. However, under NPA 2023-03 and subsequent updates, EASA is aligning its definitions with EDTO to include multi-engine aircraft.

•  Operational Approval (SPA.ETOPS): An operator must hold a specific approval to operate beyond the 60-minute threshold. The EASA SOP requires a rigorous Pre-departure service check (PDSC) and an ETOPS/EDTO fuel policy.

Comparison: ICAO vs. EASA

•  Threshold Flexibility: EASA allows a threshold of up to 90 minutes for certain twin-engine aircraft without full ETOPS approval if they meet specific criteria (e.g., MTOM < 45,360 kg). ICAO's baseline remains 60 minutes.

•  Alternate Minima: EASA SOPs specify "Dispatch Minima" for EDTO alternates, which are generally higher than the landing minima (e.g., adding 200ft/800m to the published minima) to provide a safety buffer for weather deterioration during the long flight.

Relevant Considerations for Operators

•  Verification of Alternates: Crews must monitor the weather and status (NOTAMs) of EDTO alternates throughout the flight.⁶ If an alternate becomes unavailable, the crew must find a new one or re-route.

•  Reliability Tracking: Operators must track IFSD (In-Flight Shut Down) rates. If the rate exceeds the threshold (e.g., 0.02/1,000 hours for 180-min approval), the NAA may revoke or reduce the EDTO diversion time.

•  Area of Operations: This is the area within which the aircraft can fly, defined by the "circles" centered on adequate en-route alternate aerodromes.

Note: For multi-engine aircraft (3 or 4 engines), the transition to EDTO primarily impacts how you document time-limited systems. You must ensure that the most limiting system (often the cargo fire bottle duration) covers the maximum diversion time plus a 15-minute buffer.

The transition from ETOPS to EDTO (Extended Diversion Time Operations) within the ICAO framework represents a shift from "engine-centric" safety to "system-centric" safety. As of late 2025, EASA has significantly updated its regulatory material (Revision 23 of Easy Access Rules for Air OPS) to align more closely with ICAO Annex 6, Part I.

ICAO Annex 6 vs. EASA SPA.ETOPS: The Comparison

While ICAO uses EDTO for all aircraft with two or more turbine engines, EASA retains the term ETOPS in Part-SPA but has expanded its scope to include multi-engine aircraft (formerly under LROPS - Long Range Operations).

Key Technical Differences

Feature	ICAO Annex 6 (EDTO)	EASA Part-SPA (ETOPS/LROPS)
Terminology	EDTO (Extended Diversion Time Operations)	ETOPS (Extended-range Twin/Multi-engine Ops)
Threshold (Twin)	60 minutes (1-engine speed)	60 mins (Baseline) or up to 90 mins (Special cases)
Threshold (3+ Eng)	180 minutes (All-engines speed)	180 minutes (Alignment in progress via RMT.0392)
System Focus	Emphasis on Time-Limited Systems (TLS)	Focus on ETOPS Significant Systems (Group 1 & 2)
Cargo Fire Suppression	Diversion time must not exceed fire bottle duration - 15 mins	Stringent "TLS" audit required for multi-engine
Fuel Policy	Critical Fuel Scenario (Scenario 1-3)	Same (EASA AMC-20 Appendix 4)

 

Detailed Differences: Former ETOPS vs. New EDTO

The "Old ETOPS" was primarily about the reliability of the engine (IFSD rate). The "New EDTO" treats the aircraft as a holistic set of survival systems.

1. The "Time-Limited System" (TLS) Constraint

Historically, a four-engine aircraft (like a B747 or A380) could fly almost anywhere without special approval. Under EDTO, if that aircraft is more than 180 minutes from an alternate, it must prove that its systems—specifically cargo fire suppression and emergency oxygen -  can last for the duration of the longest possible diversion.

•  Buffer Requirement: ICAO requires a safety buffer (usually 15 minutes) beyond the maximum diversion time for TLS.

•  EASA SOP: Operators must now include a "TLS Duration" table in the OM-B (Part B) of their Operations Manual.

2. One-Engine Out vs. All-Engines Operating

•  Twin-Engine (ETOPS): The threshold is calculated at the one-engine-inoperative (OEI) cruise speed.

•  Multi-Engine (EDTO): The 180-minute threshold is calculated at the all-engines-operating (AEO) cruise speed in ISA still-air conditions.

Relevant Considerations for EASA SOPs (2025 Updates)

Under the latest EASA ED Decision 2025/001/R and RMT.0392, the following SOP considerations are critical for flight crews and dispatchers:

Operational Planning & Dispatch

1. En-route Alternate Suitability: Alternates are not just "adequate" (runway length/services); they must be "suitable" (weather above dispatch minima at the estimated time of use).
2. Weather Buffers: EASA requires specific weather increments (e.g., +200ft ceiling and +800m visibility) for planning an EDTO alternate, providing a margin for deterioration during long-range segments.
3. Critical Fuel Scenarios:

>> Scenario 1: Engine failure at the most critical point.

>> Scenario 2: Simultaneous engine failure and depressurization.

>> Scenario 3: Depressurization only (usually the most fuel-intensive due to low-altitude drag).

Maintenance (The "Double Maintenance" Rule)

For twin-engine ETOPS, EASA maintains a strict ban on "identical maintenance actions" being performed on both engines by the same person during the same check. While multi-engine EDTO is more lenient, SOPs now require a Post-Maintenance Verification Flight or specific ground runs if any "Significant System" was disturbed.

Verification of TLS (Time Limited Systems)

Before dispatching a flight beyond 180 minutes (for a 4-engine jet), the dispatcher must verify that the cargo fire suppression capability (determined by the number of bottles/discharge rate) matches the planned diversion time on that specific airframe.

Next Steps

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