To correct Hamrah's post - it is an 'adequate' airfield that is required, not 'suitable'. 'Suitable' or 'ETOPS Adequate' is the term used in ETOPS planning. This requires weather considerations, 'adequate' does not (apart from met services).
I'm not sure there is a 'definition' of 'adequate' in EUOPS (that I can find!), but this is one I have used for a long time:
"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."
Mind you, all the above does not rule out commonsense!
Just to confuse the (ETOPS) issue, Boeing now say
"A noteworthy change is the addition of the term "ETOPS alternate airport," which is an adequate airport (i.e., one appropriate for the airplane type) that meets the stated requirements for planned diversion use and is listed in the certificate holder's operations specifications. The weather conditions at these airports are checked at dispatch or flight release, and again in flight, to determine whether they are at or above the operating minimums specified for a safe landing and can thus serve as an alternate for that flight. "
ETOPS alternate" thus replaces the former ETOPS term "
suitable airport," which denoted an alternate airport that was both above required weather minimums and available for diversion use. Under the new ETOPS rule, "
suitable" no longer has an ETOPS-specific meaning. Therefore, where it appears in the new ETOPS rule, it is to be interpreted only according to its broadly accepted everyday meaning."
So there!
