Dropping Fire Retardants by Helicopter and Its Application to Wildfire Prevention near Electrical Transmission Lines

Abstract

Dropping fire retardants by helicopter can effectively reduce the intensity of wildfires. This study proposes a test plan for spraying different fire retardants from a helicopter bucket fire extinguisher. In this study, pure water, 10% Class AB flame retardant, 0.3% gel flame retardant, 10% Class A flame retardant, and 10% Class A flame retardant + 0.6% guar gum were each added to the bucket fire extinguishing device and sprayed on 4-layer, 6-layer, and 12-layer wood cribs. The radiation intensity, mass loss, and temperature were used as indicators to compare the burning intensity of the fire field and the difference in fire field combustion intensity after the wood cribs were ignited 1 h after natural air drying. The results showed that flame retardancy could be ranked from high to low as follows: 10% Class A flame retardant + 0.6% guar gum > gel flame retardant > 10% Class A flame retardant > Class AB flame retardant > pure water. During the long-term high temperature and drought period in Hunan Province, China, from August to September 2022, a field application showed that dropping fire retardants by helicopter effectively reduced the intensity of wildfires and avoided transmission line trips due to the wildfire, which reduced the number of ground personnel required when fighting large-scale forest fires.