Originally Posted by
yunje
- TAF Forecast visibility : 600m
- AIRPORT appraoch minimum : CAT 1 / VIS 800m (or RVR 550m)
Is it possible to dispatch in this case? (with one alternate airport)
It is not clear in my company regulation.
and I just wonder what ICAO/FAA/EASA ruels and others aviation workers opinion.
KingAir1978 was basically correct early in the thread.
In Europe, if the wx is below minima at destination two alternates are required (in general that is, not necessarily applicable to all operators). In the USA dispatch would be permitted with one alternate.
ICAO Annex 6 Pt 1 states that 2 alternates are required if the weather forecast is below minimums at destination. Not necessarily implemented in each country. EASA requires 2 alternates. The FAA is 1 alternate unless the weather at the alternate is "marginal" when two are required. EASA reference is CAT.OP.MPA.185. FAA reference is 14CFR 121.619 and 621.
Soncibum says:
Worst case scenario Your CMV factor is 1.0, You’re above the required RVR of 550m.
Maybe, but in Europe it is not permitted to convert the met visibility to RVR when the RVR minimum is less than 800m according to CAT.OP.MPA.110 AMC10. The implications of this rule could be discussed at length but as far as answering the OP is concerned it is a moot point because in his company:
* RVR Conversion Table Note
2. This table may not be used for landing minima determinations on Flight Planning Stage.
Furthermore...
- AIRPORT appraoch minimum : CAT 1 / VIS 800m (or RVR 550m)...
...[if] TAF visibility 600m is above appraoch minima's RVR 550m
so there is no problem, dispatch with 1 alternate
...these two things imply to me that the OP needs 2 alternates for dispatch because the forecast visibility is below the quoted Cat 1 vis of 800m and it is not permitted to convert it to equivalent RVR for the purposes of dispatch planning.