California firefighting helicopter collision caused by pilot flying too high and making rapid descent, NTSB reports

radio problems - of course

https://www.msn.com/en-us/news/us/california-firefighting-helicopter-collision-caused-by-pilot-flying-too-high-and-making-rapid-descent-ntsb-reports/ar-AA1Mrv1o

probably 99% of wildfire air to air comms are simplex

gonna guess that some FDs use repeaters or TRS - like LAFD or LA
County or San Diego County or Orange County CA or East Bay Regional
Parks - maybe even Cal Fire does some air to air on Command repeaters
at times