Introduction

History

The engine failure is by nature the most feared technical failure for an aircraft. Without propulsion, especially without a suitable emergency landing area nearby, flight safety is severely compromised, particularly when there is only one engine! The first major crossings of hostile territories (sea, mountains, desert, etc.) with piston engines and the advent of commercial air transport have heightened the issue of mechanical reliability. The logical response was to increase the number of engines.r.

In the interwar period, the legendary Douglas DC-3 and its competitor the Boeing 247 opted for 2 engines. The Ford Trimotor, as its name suggests, was equipped with 3 to tackle the vast expanses of American territory. The first regular transatlantic services would amplify the issue due to the relative reliability of piston engines for these long crossings in hostile environments. This led to the peak of large seaplanes, which, in addition to being able to land on water, would be fitted with 4 engines (like the famous 314 Clipper), or even 6, with the immense Latécoère 521. The technological leap of the Second World War would see the emergence of the great piston-powered four engine aircraft (this time terrestrial), symbolised by the Lockheed Constellation and other Douglas DC-4/6/7.

By the end of the 1950s, while the advent of the jet engine had definitively eliminated piston engines from commercial transport, it did not completely resolve the issue. In the meantime, the US FAA had, in 1953, limited the maximum distance of a twin-engine aircraft from the nearest diversion airport to 1 hour of flight. The peak of four-engine jet airliners officially began in 1952 with the De Havilland Comet, followed by a large number of models (707, 747, DC-8, etc.) that are well-known, some of which still traverse the world today. At the same time, there was the alternative of tri-jets (727, DC-10, Tristar, etc.) that also bypassed the limits imposed by regulations.

The late 1970s and the oil shock marked a decisive turning point in the economic approach of airlines. Fuel became expensive, and the impact on operational costs would seriously erode profit margins. At the same time, the reliability of turbojets convinced authorities to conditionally increase the 60-minute flight limit: in 1985, TWA and its Boeing 767-200 twin-engine aircraft were allowed to operate up to 90 minutes away from the nearest airport on transatlantic flights: this was the birth of ETOPS (Extended Range Twin Operations), which the following year became ETOPS-120 minutes alongside the Airbus A310..

With an increasingly significant range, the implementation of ETOPS logically initiated the long decline of tri- and quad-jets. Indeed, with only 2 engines, it became possible to achieve satisfactory performance while making substantial savings on fuel and maintenance. Only very large aircraft such as the Boeing 747 or Airbus A340 retained the advantage of their 4-engine configuration, as the power and performance required could not yet be achieved with just 2 units. This was resolved with the advent of the Boeing 777, which obtained ETOPS-180 certification upon its entry into service, followed by 207 minutes, while being capable of carrying nearly 400 passengers over more than 14,000 kilometres. The highly advanced A340 and MD-11 saw their commercial success significantly diminished. The ultimate stretched version, the 777-300ER, which appeared in 2003, would drive the point home and gradually send the 747 into retirement within global fleets. Only the A380 has persisted beyond this point due to its size and extraordinary weight..

The latest generation of long-haul airliners has once again pushed the boundaries, with the record held by the Airbus A350, which has been granted ETOPS-370 minutes approval! This means that there are potentially no longer any routes prohibited to twin-engine aircraft around the globe, except for certain areas of the South Pacific. Additionally, it is worth noting that the ATR72-600 is the only turboprop aircraft certified for ETOPS, opening new horizons for this type of propulsion. Finally, it should be noted that the acronym ETOPS was officially replaced in 2012 by EDTO (Extended Diversion Time Operations) according to ICAO..

ETOPS certification

In real aviation, the ability to operate flights under the ETOPS regulation is subject to authorisation from the relevant authorities, usually from the country of the operator. This is based on several criteria. :

• ETOPS certification of the aircraft type

•  Track record of the operator in terms of safety and reliability

• Crew training

• Maintenance qualification

• Establishment of operational procedures

Based on the assessment of these requirements, the authority will then officially grant the ETOPS approval on the Air Operator Certificate (AOC) of the operator. This authorisation is never permanent and is constantly subject to the maintenance of the official requirements and can be revoked at any time in the event of a breach by the operator..

For your information, here are the ETOPS certifications for the most common airliner types. The number of minutes represents the maximum distance an aircraft can be from a diversion airfield: ETOPS-XXX minutes.

It should be noted that to avoid unnecessary costs and constraints, airlines generally do not require an ETOPS level higher than their operational needs. For example, it would be unnecessary to have an ETOPS-330 qualification for a fleet of Boeing 787s when an ETOPS-180 certification is sufficient to cover the network. The same applies to most medium-haul aircraft (A320, B737, etc.) where the operational area does not require ETOPS certification, as is the case in Europe..

Basic principles

Without ETOPS

The regulations require a twin-engine aircraft never to stray beyond a certain flight time from an adequate aerodrome, or Adequate Aerodrome. These are considered by the operator to have satisfactory characteristics for operations (runway length, ATC, approach means, weather information, emergency services)..

The maximum allowed diversion time depends on the performance class of the aircraft, based on the maximum take-off weight (MTOW: Maximum Take Off Weight) and the number of seats (PAX).

• Classe B et C > 120 minutes

• Classe A

• • of MTOW greater than 45,360 kg OR 20 PAX or more > 60 minutess
  • if MTOW is less than 45,360 kg AND 19 PAX or less > 120 minutes

The flight duration is calculated at the cruise speed on one engine (OEI: One Engine Inoperative Speed) specific to each type of aircraft..

Flight planning programmes select a series of airfields along the route and include the TAF/METAR and NOTAM in the flight briefing.

With ETOPS

When a route cannot be fully covered by suitable airports (as shown in the diagram below), the establishment of an ETOPS planning is necessary. This involves selecting airports within the permitted radius to cover this section: the ETOPS area.

This is defined by an entry point (EET) and an exit point (EXT).

You will need to choose 2 diversion airfields along the route. These sites are referred to in this context as ETOPS En-Route Alternates..

This allows for the determination of an equitime point (ETP: Equitime point) between two airfields and the establishment of the ETOPS scenario (which we will discuss later).

Example

In this transatlantic flight plan from Warsaw to New York, a part of the route over the ocean (in yellow) is clearly not within reach of any suitable terrain (in dotted circle) within a 60-minute flight radius. The flight as it stands is therefore not authorised..

The solution is to plan for 2 ETOPS diversion airports, namely Keflavik (BIKF) and Goose Bay (CYYR). We are approved ETOPS-180 here and the circles easily cover the ETOPS portion. Before ETP-1, we would divert to BIKF, and to CYYR beyond that..

Sometimes, 2 airports are not sufficient to cover the route, as in this example of the ETOPS-120 scenario between Brussels (EBBR) and Cincinnati (KCVG). Keflavik (BIKF) covers the portion not covered by Goose Bay (CYYR) and Dublin (EIDW). Consequently, a second equal time point is created (ETP-2).

We can also add more airfields than necessary to create more diversion scenarios, like here at Prestwick (EGPK) which is not essential.

Note: ETOPS is commonly associated with over-ocean flights, but it can also apply over land when there is no suitable airfield available..

 

ETOPS regulations

Selection of ETOPS diversion airfields

In addition to being necessarily considered adequate (to be confirmed before each flight according to the NOTAMs), ETOPS airports must also be meteorologically accessible (Suitable).

The legal minimums are more restrictive than for other clearance areas (suitable or designated) and are established as follows:

An ETOPS airport must have at least ONE instrument approach (ILS, LOC, VOR, NDB). RNAV or RNP approaches cannot be considered.

Note: Some countries use specific minima, such as the United States or Canada.

The weather forecasts apply within a time window between the earliest estimated landing time and the latest estimated landing time plus 1 hour (ETA > ETA + 1 h).

Example

For Kangerlussuaq (BGSF), the reference procedure for calculating ETOPS minima is the LOC Y runway 09, which is a non-precision approach..

If we apply this calculation to the published minima for this approach, we should have a ceiling of 350ft + 400ft = 750ft, and for visibility 1200m + 1500m = 2700m.

If the required accessibility window is between 13:00 and 15:00 UTC, the TAF forecasts during this period indicate a visibility of more than 10 km and a ceiling of 9000 ft. We are therefore authorised to select BGSF as the ETOPS alternate in our scenario.

Establishment of critical scenarios

The planning of a flight under the ETOPS regime involves not only selecting diversion airfields but also calculating the fuel and time required in the event of a diversion to one of these airports.

These calculations are based on each equitime point (ETP) for 3 operational conditions:

• Engine failure > optimal FL

• Depressurisation > FL100

• Engine failure + depressurisation > FL100

The scenario requiring the most fuel is the critical scenario (Critical Fuel Scenario). This refers to the fuel needed to fly from the departure airport to the ETOPS alternate airport in the most critical scenario. The ETP involved is the critical point (Critical Point)..

Note: All flight times for ETOPS scenarios are calculated at cruise speed on one engine (OEI).

Fuel policy

According to the regulations, the minimum block fuel required does not differ from a non-ETOPS flight and corresponds, as a reminder, to the following total:

• Taxing

• Trip

• Contingency

• Alternate

• Final Reserve

However, it sometimes happens that the fuel required to execute the critical scenario is greater than the trip fuel. In this case, an additional fuel supplement must be added to make up the difference..

 

ETOPS Flight planning

The operational flight plan (OFP: Operational Flight Plan) must contain the ETOPS scenario data where applicable. For this, it is necessary to use complex planning software such as SimBrief (free) or PFPX (paid), for example.

CIt is for this reason that we will see how to insert an ETOPS scenario into a flight using the two most popular simulation software. Our flight will be as follows:

Nantes (LFRS) to Montréal (CYUL)

Airbus A310-300 / ETOPS 120 minutes

Shannon (EINN)/Kelfakiv (BIKF)/ Goose Bay (CYYR)

With PFPX

After calculating the flight, if the suitable airports do not cover the entirety of the route, PFPX requires creating an ETOPS scenario (EDTO setup). In the Advanced tab, you must then select the available scenario for the type of aircraft (here EDTO 120).

Then, it's up to us to choose the diversion airports. We then see the 120-minute circles displayed gradually.re.

When the entire ETOPS section is covered, PFPX will then suggest calculating the flight (Compute Flight).

Once the flight is calculated, the ETOPS scenario will be displayed in the OFP. It includes the following in order:

•  Lthe coordinates of the entry and exit points(ETOPS ENTRY/EXIT).

•  The required accessibility time windows for each ETOP airportS.

•  The diversion scenarios (3 for each of the 2 ETP).

La The Route Chart provides an overview of the flight and notably includes the ETOPS circles as well as the points (entry/exit/equal time).

With SimBrief

Comme avec PFPX, il faut accéder à la partie ETOPS de la page de préparation. On choisit ensuite le scénario (Target Scenario).

You must first enter the first and last airfields in their respective boxes (Entry/Exit Airport), then insert all the ETOPS airports of the scenario. Click on Validate. The green validation message will appear if the circles adequately cover the entire ETOPS portion. You can then generate (Generate Flight) the OFP.

Note: In Simbrief, only the OFP in UAE format (Emirates model) generates a complete ETOPS scenario. Other formats generally provide a simplified briefing that includes only the points (ETP, ENT, EXT). Therefore, it is necessary to select the correct version from the menu (OFP Layout)..

The OFP presents a different layout, but it contains the same information as its counterpart PFPX. The 3 scenarios are here designated by letters (1D, 1E, 2D). Notably, there is the addition of very interesting information: the comparison of the required weather minima within the time window (ETOPS WX/MIN) with the forecasts (MET WX DC) for each ETOPS alternate airport (Ceiling/Visibility).

On the map, there is also an overview of the route. The large circles represent a radius of 120 minutes of flight, while the small ones correspond to 60 minutes..

Finally, the alternate airports are automatically mentioned in the ATC flight plan:

References

-The Doc 10085, Extended Diversion Time Operations (EDTO) Manual, the official ICAO standards.

-A course published by the ICAO with many illustrations.

-The ETOPS regulation of EASA for its european application.

- The latest developments from ETOPS towards l’EDTO.