|ETOPS demands more strict requirements to determine an alternate aerodrome. There is a difference in
alternate aerodrome determination. Adequate aerodromes and suitable aerodromes are both used for the
same objective although usage of one another depends on specific minima and aeronautical decision
Adequate Alternate Aerodrome
An adequate alternate aerodrome is an aerodrome which is expected to be available, if required. This
means landing performance requirements on an adequate aerodrome are required to be met and the
concerning aerodrome must have the necessary facilities and services such as ATC, airport lighting,
communications, meteorological services, navigation aids, rescue and fire-fighting services and one suitable
instrument approach procedure.
Suitable Alternate Aerodrome
In ETOPS, the alternate aerodromes must comply with more strict requirements. An ETOPS aircraft may
operate in an environment where few diversion aerodromes are available. Therefore it is important to
know whether the alternate aerodromes available are well equipped with the necessary facilities. As
stated above, such an aerodrome is called “adequate”. Whether an “adequate” alternate is a “suitable”
alternate is decided prior to departure. This decision is based on the weather conditions forecast for the
adequate alternate at the Estimated Time of Arrival (ETA). An enroute adequate aerodrome is declared
- Weather forecast of the concerning aerodrome is equal or better than the ETOPS required weather
minima for a defined period of time;
- Applicable NOTAMs ensure the required enroute alternate aerodrome is and will remain available
for the same period of time;
- Surface crosswind forecasts and runway conditions are within acceptable limits to allow a safe approach
and landing with one engine inoperative.
The weather minima are set up by the national authorities of each country. Available facilities are compared
with the alternate airfield ceiling and Runway Visual Range (RVR). If more usable precision approach
facilities are present serving separate runways, the ceiling and visibility are allowed to be lower.
These planning minima are included in the operations manual and can be used for ETOPS planning.
The following table is an example (ETOPS Exposition Manual) of weather minima with one operational navigation facility which must also be included in the Aircraft Operations Manual. For every type of approach the minimum
ceiling and visibility are given.
Table 1: ETOPS weather minima
One runway with at least one instrument approach procedure
Prescribed HAT/HAA + 400 Feet
Prescribed VIS + 1.500 meters
Two separate runways (or more) with at least two separate instrument approach procedures
The higher of the two Prescribed HAT/HAA + 200 Feet
The higher of the two Prescribed VIS + 800 meters