Hi,
•For Category II and Category III operations, transmissometer systems are strategically located to provide RVR measurements associated with three basic portions of a runway:
*
•− the touchdown zone (TDZ),
•− the mid-runway portion (MID), and
•− the rollout portion or stop end.
•For Category II operations the TDZ measurement is required, and for Category III operations the TDZ and MID measurements are mandatory. But for CAT III
* *operations with the lowest weather minima, the three measurements are normally required by FAA.
*
•For CAT III without DH JAR OPS 1 requires only one RVR measuring point on the runway.
VISUAL REFERENCES
* * *CAT II Operations
*
•− a segment of the approach light system,
•− the runway threshold,
•− the touchdown zone.
* CAT III Operations
*
•In CAT III operations with DH, the condition required at DH is that there should be visual references, which confirm that the aircraft is over the touchdown zone. Go around is mandatory if the visual references do not confirm this.
•CAT III without DH ( CAT IIIA FAIL OPERATIONAL -CAT3 DUAL)
*
* * For this category of operation, the decision to continue does not depend on visual references, even though a minimum RVR is specified. It is nevertheless good airmanship to confirm aircraft position with available visual references. However, the decision depends only on the operational status of the aircraft and ground equipment. If a failure occurs prior to reaching the AH, a go-around will be made. A go around must nevertheless be performed if the autoland warning is triggered below AH.
LOW VISIBILITY TAKEOFF (LVTO)
•Takeoff with RVR less than 400m is considered as LVTO by JAR OPS 1.
•The maximum RVR at Takeoff is quite independent of the aircraft type and aircraft equipment except for very low RVR.
•The Takeoff minima is mainly determined by the airport installation (runway lighting system, RVR measurement system, ...).
*
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•When weather conditions are more severe than the landing minima, a takeoff *alternate is normally required:
*
* * − within one hour for twins
* * − within two hours for quads
* * − within the maximum approved diversion time for aircraft qualified for ETOPS, but not more than 2 hours (JAR OPS).
* *Above time is determined at the one engine inoperative speed.
*
•Additional requirements are as follows:
*
* * − Low Visibility Procedures are in force
* * − High intensity runway centerline lights spaced 15m or less and high intensity edge lights spaced 60m or less are in operation
* * − The 125m RVR value has been achieved for all of the relevant RVR reporting points
* * − Flight crew members have satisfactorily completed training in a simulator approved for this procedure.
I hope this helps.
Regards
Toby320
