PRECIPITATION STATIC

PRECIPITATION STATIC

Precipitation static, often referred to as P – static, occurs when accumulated static electricity is discharged from the extremities of aircraft. This discharge has the potential to create problems for the instrument pilot. These problems range from the serious, such as erroneous magnetic compass readings and the complete loss of very high frequency ( VHF ) communications to the annoyance of high – pitched audio squealing and St. Elmo’s fire. figure above.

Precipitation static is caused when an aircraft encounters airborne particles during flight ( e.g., rain or snow ), and develops a negative charge. It can also result from atmospheric electric fields in thunderstorm clouds. When a significant negative voltage level is reached, the aircraft discharges it, which can create electrical disturbances. This electrical discharge builds with time as the aircraft flies in precipitation. It is usually encountered in rain, but snow can cause the same effect. As the static buildup increases, the effectiveness of both communication and navigation systems decreases to the point of potential unusability.

To reduce the problems associated with P – static, the pilot should ensure the aircraft’ s static wicks are properly maintained and accounted for. Broken or missing static wicks should be replaced before an instrument flight. Figure below.