Create a new “Flight Duration” firework effect in your game/editor/tool (or duplicate an existing “Flight Duration” effect preset).
Set the firework’s “Duration”/“Flight Time” parameter to 3 seconds.
Set the “Initial Velocity”/“Launch Speed” so the projectile reaches the desired height within the 3-second flight window.
Set “Gravity”/“Drag” to match the motion you want during the 3-second flight.
Ensure the “Explode/Detonate” trigger is tied to “time elapsed” (or set the detonation time to 3.0s).
Configure the “Explosion”/“Burst” to occur at the end of the flight (at 3.0s), not on impact.
Verify the particle/sound timing so the explosion visuals and effects start at 3.0s.
Save the effect as a reusable preset named “Flight Duration 3”.
Test in play mode/preview and adjust velocity/gravity slightly until the explosion consistently occurs at ~3 seconds.