What is the likely consequence of not applying the fill coat correctly?

Not applying the fill coat correctly can lead to improper UV protection for the fabric covering on an aircraft. The fill coat serves as a vital layer that not only fills in the weave of the fabric but also enhances its protective qualities against ultraviolet (UV) rays. Without a properly applied fill coat, the underlying fabric is more vulnerable to UV degradation, which can result in premature deterioration, weakening the material over time. This degradation can lead to a range of issues including reduced strength and durability of the fabric, ultimately compromising the safety and performance of the aircraft.

The other potential consequences, while relevant to aircraft fabric covering, do not directly address the primary function of the fill coat in relation to UV protection.