Originally Posted by agent4573
Best practice is to install bolt heads forward, up, or out. If you deviate from best practice there should be a reason for it.
Designers have discretion for which side the head is located for many reasons including clearance to get bolt installed, ability to get nut on, and room for a torque wrench on the nut and turn the wrench. In my day job, this locates bolt head side most of the time. Clearance to moving parts can also determine head location and happens frequently in tight locations like servo linkages. Also, if fastener is on outer moldline (it sees air flow) the manufactured head (bolt head if a bolt) almost exclusively goes to the external flow side. You donít see a lot of rivet tails on outer moldline.
A reason that it makes no difference the direction of head is in a structural joint, if the nut falls off, the bolt is no longer carrying much, if any, structural load without the clamp up of the nut torqued properly and may fail as soon as any load is applied. Plus it most likely is in a location that never gets looked at in a preflight.
Where it may matter is in joints that only is loaded in pure sheer like truss structure or control system tubes and cables. Then if nut falls off maybe the bolt will stay in place long enough to be found before something bad happens. Big maybe, but if none of the above is a factor, put the bolt head up.