What type of approach is used when devices like ACLS, TACAN, and ICLS are not operational?

When devices like Area Navigation (ACLS), Tactical Air Navigation (TACAN), and Instrument Carrier Landing System (ICLS) are not operational, a non-precision approach is the correct method used. Non-precision approaches rely on pilotage and navigation aids that do not provide vertical guidance, typically involving either a visual reference or basic lateral navigation guidance.

In situations where advanced systems are inoperative, non-precision approaches may utilize navigational aids for lateral positioning, allowing pilots to position the aircraft effectively for landing without the assistance of precision instruments that would otherwise provide more detailed guidance, like glide slopes or decision altitudes. This approach is vital for maintaining safety and operational efficiency under circumstances where aircraft systems are limited.

The other options represent different methods that are typically used under conditions where precision instruments are available or functioning, such as precision approaches that provide detailed guidance for both lateral and vertical alignment during landing or visual approaches that depend on sufficient visual references.