Excessive wear in the shoulder area of an aircraft tire indicates what condition?

Excessive wear in the shoulder area of an aircraft tire is indicative of underinflation. When a tire is underinflated, the sidewalls are not able to support the load properly, causing the tire to flex more at the shoulders. This increased flexing leads to higher friction and heat generation in that area, resulting in accelerated wear. As the tires make contact with the runway, the portion of the tire that bears the weight becomes more pronounced due to the lack of appropriate air pressure, thus wearing down the shoulders more rapidly than the center of the tread.

In contrast, other conditions like overinflation would typically cause the tire to wear more in the center of the tread rather than the shoulders, since excess pressure pushes the tire's contact patch to be narrower and reduces sidewall flexing. Normal wear would reflect an even distribution of wear across the entire tread surface, and improper alignment would usually lead to uneven wear patterns that are not specifically concentrated on the shoulder areas. Thus, recognizing the signs of underinflation through shoulder wear is crucial for maintaining tire longevity and aircraft safety.