A rescue operation was launched on Sunday after the man crashed at the site above Hundred House near Llandrindod Wells in Powys.
Firefighters, paramedics and mountain rescue teams were called to the scene at about 2pm.
The pilot was flown to the University Hospital of Wales in Cardiff with head, leg and pelvic injuries.
Mid and West Wales Fire and Rescue said crews were called in to help from Ammanford in Carmarthenshire, Pontardawe in the Swansea Valley, and Aberystwyth, Ceredigion, along with Powys firefighters from Llandrindod and Builth.
The pilot was stabilised at the scene by Helimed flying doctors from the Emergency Medical Retrival Service, while rescuers struggled for nearly three hours to free him from tree branches.
The man was eventually winched onto a coastguard rescue helicopter, before being taken the 65 miles to Cardiff for emergency care.