Is Johnny Pacheco's main instrument the flute?

Numerous. Scads of it. For instance: Claude Debussy: Syrinx - La Flute De Pan - Flute Solo Composed by Claude Debussy (1862-1918), edited by Ernst-Gunter Heinemann. For flute (unaccompanied)....

a flute is a woodwind instrument

it is a wind instrument dumbo

The Flute is a Melodic instrument, in a Concert Band it can be heard playing the melody along with many solos. In a Orchestra, it can be heard doubling the Violins an octave higher, or playing Solos.

Woodwind because it was originally made of wood, and you use wind to play it. E.g: Clarinet, and Oboe Calum, 12