Does the Skyfall cheat disable trophies and achievements?

Yes. Activating any cheat disables Trophies and Achievements for the current play session. Reload your save without using cheats to re-enable them.

//GTA V · Player Effects

Skyfall

Teleport into the upper atmosphere.

SKYFALL

Press ~ (tilde) to open the console, then type the code and press Enter.

PlayStation

Press in sequence on the controller (quick, no pause).

Xbox

Press in sequence on the controller (quick, no pause).

Hurls the player straight up into the sky. Bring a parachute (or Invincibility) for a survivable landing.

Effect · Player launched into the sky.

What does the Skyfall cheat do in GTA V?: Hurls the player straight up into the sky. Bring a parachute (or Invincibility) for a survivable landing.
Does the Skyfall cheat disable trophies and achievements?: Yes. Activating any cheat disables Trophies and Achievements for the current play session. Reload your save without using cheats to re-enable them.