What is the standard inside downwind spacing reference for no flap configurations?

The standard inside downwind spacing reference for no flap configurations is the outside edge of the wing. This reference helps pilots maintain proper separation from the runway during the downwind leg of the traffic pattern. By using the outside edge of the wing, pilots can visually gauge their position relative to the runway, ensuring they are correctly aligned for an approach, while also accounting for how the aircraft behaves without the influence of flaps.

Using the outside edge of the wing as a reference provides consistency in spacing and allows pilots to effectively manage their altitude and speed throughout the landing pattern. It helps maintain awareness of their position in relation to the runway environment and assists in achieving the desired landing profile. Other references, such as the wingtip or aircraft nose, may not provide as accurate a reference for this specific configuration, thus making the outside edge of the wing the appropriate choice for this scenario.