A bright sunny day, but a persistent stratiform cloud blocks the view of the runway when approaching the minimums. Or even worse, more than sufficient visibility, but a thick cloud layer extends below CAT 1 minimums and Low Visibility Operations (LVO) are not (yet) activated… A go-around seems imminent while the weather forecast and ATIS information may not have caused you to expect this course of action.
This is why we put together brief guidance with mitigating measures that could help crews operating into any airport, where a ceiling/vertical visibility is not considered when deciding on the type of operations.
An approach in instrument meteorological conditions (IMC) may only be continued below the appropriate minimum if the required features of the landing runway, the runway or the approach lights are in sight at these minimums. The required visibility assures that the lights are within a distance from the pilots’ eyes that it is physically possible to see them.
If, however, clouds with a base at or below the CAT 1 minimum are present at the position where the aircraft reaches the CAT 1 minimum, the density of this phenomenon might well prevent the crew from acquiring enough cues to be able to continue the approach.
When LVO have been activated, a CAT 2 or even CAT 3 approach could be executed, enabling the crew to descend to a lower height over ground, permitting them to descend below cloudbase and identify the appropriate lights or features of the landing runway.
The commencement of Low Visibility Operations may be based solely on the prevailing visibility, irrespective of any cloud ceiling of vertical visibility. In the conditions described above, this might lead to an increased number of go-arounds as in the absence of LVO flight crews might be expecting CAT 1 conditions in their approach preparation.
Last but not least, pilots should always remember that it is within the commander’s authority to refuse any given approach and even divert to an alternate airport, if the overall risk for an approach is considered excessive.