The death of a Utah wildland firefighter during the Mendocino complex fire was determined to have been from a slurry retardant drop by a 747 that was too low to disperse properly and hit the ground full force, on top of firefighters working underneath. The impact dropped large trees, one of which fell on the firefighter and killed him. A tragic accident. The lead plane FAC that was leading the 747 through the drop run didn't notice mildly upsloping in the hilly terrain at the drop site, which would have placed the normal drop altitude for the 747 from a few hundred feet AGL, to only about 100' AGL, too low for the heavy slurry to disperse to a mist, and instead hit the ground in it's heavy undispersed form. 3 other firefighters were injured also.
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Firefighter's Mendocino Complex death caused by retardant drop from low-flying 747
Story here:
Firefighter's Mendocino Complex death caused by retardant drop from low-flying 747