IFR flight depends upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to ...
Visual Flight Rules (VFR) are used during VMC weather, and Instrument Flight Rules (IFR) are used during IMC weather. Instrument rules can be used during VMC, but visual rules cannot be used in IMC.
A pilot gave his opinion that the Black Hawk helicopter was not looking at American Airlines Flight 5342 when he crashed.