There are three guidance methods discussed in this paper: no-gyro vectors, ASR approaches, and no-gyro approaches. For no-gyro vectors, ATC provides navigational guidance by instructing the pilot to “turn left/right” and then “stop turn” so that the pilot maintains a constant heading or a constant rate of turn based on commands from ATC. For a ‘normal’ ASR approach, ATC provides navigational guidance by giving the pilot specific headings to fly. No-gyro approaches are a combination of an ASR approach and no-gyro vectors.
There are different situations where it makes sense to execute no-gyro vectors or a no-gyro approach. One situation is when the primary heading instrument fails. Even with backup instruments in the aircraft, there may be only a magnetic compass for heading information. Other situations, such as electrical failure at night, the viewing angle of the backup instruments, high workload combined with equipment failures, or lack of proficiency using the back-up instruments may be reasons to execute no- gyro vectors or a no-gyro approach. No-gyro vectors can augment or substitute for timed turns and magnetic compass turns.
While the Instrument Rating - Airplane Airman Certification Standards (ACS) does not require an ASR or no-gyro approach, that is not a good reason to skip teaching them. The ACS does have a requirement to execute a non-precision approach with “loss of primary flight instrument indicators”. Why not go farther, and teach a no-gyro approach? During an emergency, doing something for the first time is not recommended and could have disastrous results. Successfully handling the emergency depends, in part, on successful communications between the pilot and controller and this comes from accurately practicing the procedure. This includes radar approaches.