Final answer:
RNAV systems can be used to follow conventional routes without dependence on ground-based aids (Overlay Procedures), fly parallel tracks to maintain route structure (Parallel Routes), create en route alternatives, and substitute for out-of-service navigational aids during approach procedures.
Step-by-step explanation:
The question you've asked pertains to four ways Area Navigation (RNAV) systems can be utilized even when a specific navigational facility has been designated as required. Once known as 'Random Navigation', RNAV is a method of navigation that allows an aircraft to fly on any desired path within the coverage of ground- or space-based navigation aids or within the limits of the capability of self-contained aids, or a combination of these.
Here are four ways RNAV can be used in such scenarios:
- Overlay Procedures: RNAV systems can be used for overlay procedures, where conventional routes defined by ground-based navigational aids are flown using RNAV, thus not strictly relying on the out-of-service aid.
- Parallel Routes: RNAV can enable aircraft to fly parallel tracks alongside traditional airways when the related ground-based aid is not operational, maintaining route structure without the facility.
- En Route Alternatives: When a navigation aid is unavailable, RNAV can be utilized to create alternative routes that safely maintain the intended flight path without direct reliance on the aid.
- Approach Procedures: In the case of approaches where a specific navigational aid is required, RNAV can substitute for the facility by creating a GPS-based or DME/DME fix that ensures the approach path is adhered to, provided the aircraft is equipped with the necessary certified RNAV system.
RNAV systems give pilots the flexibility to navigate effectively, even when navigational facilities are not available or out of service.