Unless otherwise specified, how should aircraft bolts be installed?

The correct approach to installing aircraft bolts is to position the bolthead upward or in a forward direction. This practice is essential for several reasons. First, having the bolthead in this position helps to ensure that if a failure occurs, it is more likely to happen at the bolt shank, rather than at the bolthead. This helps maintain the integrity of the structure being secured, as the shank can absorb more stress without causing catastrophic failure.

Moreover, installing the bolthead upward facilitates proper inspection and maintenance access, allowing personnel to easily check the tightness and condition of the bolts without needing to manipulate the assembly excessively. This orientation also reduces the risk of foreign object ingestion or interference, which is particularly crucial in high-velocity environments like aircraft engines.

In contrast, horizontal or downward installations could increase the risk of loosening due to vibration and may complicate maintenance efforts. Therefore, the upward or forward positioning is consistent with aerospace standards for safety and efficiency.