Final answer:
In aviation, RVR is usually controlling over tower-reported visibility for IFR operations, as it provides a more precise measurement specific to the runway in use. However, the most restrictive measurement should always be used, and it is essential to consult current regulations and ATC.
Step-by-step explanation:
When a student asks whether RVR (Runway Visual Range) values or tower-reported visibility, such as 5SM (5 Statute Miles), is controlling, they are inquiring about aviation standards for determining the minimum visibility required for aircraft takeoff and landing operations. In aviation, RVR is the horizontal distance a pilot will be able to see down the runway from the approach end; it is used under Instrument Flight Rules (IFR) conditions. Visibility refers to the distance a pilot can see as unobstructed by fog, rain, or other meteorological phenomena.
RVR and visibility are both critical components in aviation, particularly for the safe operation of aircraft during takeoffs and landings. The Federal Aviation Regulations (FARs) and the International Civil Aviation Organization (ICAO) provide specific RVR and visibility requirements which must be met or exceeded for certain flight operations to take place. Whether RVR or reported visibility is controlling can depend on various factors including the type of operation (such as whether the aircraft is operating under IFR or Visual Flight Rules (VFR)), the equipment available at the particular airport, and the specific procedures in use.
Typically, during IFR operations, if an RVR report is available, it is controlling over tower-reported visibility. This is because RVR is a precise, instrumented measurement directly related to the ability of a pilot to land or take off from that specific runway. If RVR is not available, tower visibility may then become the controlling factor. However, there might be certain cases where the reported visibility could be more restrictive than the RVR. In such cases, the most restrictive measurement is the one that should be used.
Which is Controlling: RVR or Visibility?
To determine the controlling measure in this specific scenario, where RVR is 3/3/3 (meaning RVR is 3000 feet for all three parts of the runway) and tower reports 5SM of visibility, one would typically consider RVR to be controlling for IFR operations, unless otherwise specified by the relevant aviation regulations or authority. However, it is always essential to refer to the current aviation regulations and consult with Air Traffic Control (ATC) to make sure which reading should be adhered to.