What charts are those Nick? The ones I have make no mention of that....
212 publishes a Critical Wind Azimuth of 40º to 135º, and says the charts are valid with relative winds up to 20 kts from any direction, with more favorable t/r control margins realized if operated outside the CW Azimuth.
The 412EP has IGE and OGE Critical Wind Azimuths, and offers IGE performance up to 35 kts in all relative wind angles up to 3K Hd, with additional control margins if operated outside the two zones.
The OGE charts have Areas A and B, the latter providing a performance benefit if operated outside the Critical Wind Azimuth areas.
Seems logical enough to me.
Just for the record, the 407 is the ship which has the 45º Area B, and the reason for it is because of the limits imposed by the conditions available during the high altitude flight testing. Additionally, Area B only comes into play in certain lateral C/G conditions above 17 kts.
[ 26 October 2001: Message edited by: CTD ]