Zero Visibility
Zero Visibility refers to a flight condition where pilots are unable to visually distinguish the horizon, terrain, or runway environment due to weather phenomena such as heavy fog, dense rain, smoke, volcanic ash, or blizzard conditions.
Definition
Zero visibility typically occurs when reported visibility falls below 1/4 statute mile or Runway Visual Range (RVR) values fall below minimum thresholds for visual operations. Pilots must rely entirely on flight instruments, autopilot systems, and navigational aids to operate the aircraft safely under these conditions.
Importance
- Critical reliance on instrument flying (IFR) skills and procedures.
- Requires precision approach procedures (e.g., Category III ILS landings).
- Demands heightened crew coordination, discipline, and training.
Causes
- Thick fog, mist, or haze.
- Intense rain showers or thunderstorms.
- Snowstorms, blizzards, or blowing snow conditions.
- Volcanic ash clouds.
Operational Challenges
- Greater risk of spatial disorientation if instrument procedures are not followed.
- Necessity for precision approaches, such as ILS CAT II/III, with appropriate aircraft and crew certification.
- Increased potential for runway incursions and taxiing errors in low-visibility surface operations.
Example
During dense coastal fog, an aircraft attempting to land at San Francisco International Airport (SFO) may experience zero visibility conditions, requiring a fully coupled autoland system and ground-based navigation aids to complete the approach safely.
