Enroute Alternate Weather Requirements

[Jimmy Do Little]

on a non ETOPs route for a twin engine operation what's the weather requirements for an enroute alternate airport

Does the following help?

3.4.6 Alternate Airports

1. An aeroplane shall not be released unless the required take-off, destination and alternate airports, including en route alternate airports to be used in the event of a system failure which requires a diversion, are listed in the operational flight plan, (e.g. on board copy of computer flight plan).
2. Suitable en route alternates are also required to be identified, listed and provided to the crew with the most up to date information (e.g. airport data, facilities, weather, etc.) as part of the dispatch release for all cases where the planned route of flight contains a point (Note: appendix "B" includes the word "no" a this point) more than 60 minutes flying time at the approved one-engine-inoperative cruise speed from an adequate airport. Since these en route alternates serve a different purpose than the destination airport and would normally be used only in the event of an engine failure or the loss of a primary airframe system, an airport may not be listed as an en route alternate unless:
   1. The landing distances required as specified in the Aircraft Flight Manual for the altitude of the airport, for the runway expected to be used, taking into account wind conditions, runway surface conditions, and aeroplane handling characteristics, permit the aeroplane to be stopped within the landing distance available as declared by the airport authorities and computed in accordance with the applicable regulations;
   2. The airport services and facilities are available and adequate for the operator's approved approach procedure(s) and operating minima for the runway expected to be used;
   3. The latest available forecast weather conditions for a period commencing one hour before the established earliest time of landing and ending one hour after the established latest time of landing at that airport, are equal to or exceed the authorized weather minima for en route alternate airports in appendix B; (Standard Alternate Requirements).
   4. For the same period, the forecast cross wind component for the intended landing runway, including gusts, is less than the maximum permitted cross wind for a single engine landing. Where no single engine demonstrated cross wind value exists, 80% of the all engine demonstrated value will be used.