From the Super Mario Wiki
The Helicopter Spin is Dixie Kong's special attack move in Donkey Kong Country 2: Diddy's Kong Quest, Donkey Kong Country 3: Dixie Kong's Double Trouble!, and Donkey Kong Country: Tropical Freeze.
Since Dixie cannot roll like Donkey or Kiddy, she uses the Helicopter Spin to attack. She can also use it to hover in the air to get across gaps and other hazardous ground objects. She can also use this to gauge her landing. When both Kongs are available and Dixie uses her Helicopter Spin to hover, Diddy/Kiddy rolls in the air, following her.
Tiny Kong, her younger sister, also uses this move in Donkey Kong 64, except she uses both of her pigtails to attack, and it is called the Pony Tail Twirl. Compared to Tiny Kong's Pony Tail Twirl, the Helicopter Spin, when used to slow descent, is used with the same button as attacking ( in SNES and Virtual Console versions, in the GBA versions). Meanwhile, Tiny's Pony Tail Twirl is used with the same button as jumping () and her attacks have the normal input ().