Seat belt locking mechanism position 1

[LVDTRVDT]

Hi everybody. I wonder if there is a regulation regarding the position of seat belt locking mechanism.

To be more clear, one of my friend mentioned about a SAFA inspection finding based on the wrong positions of seat belt locking mechanism. Inspector claimed that the mechanisms on the left hand side seats should be to the left of the seat and on the right hand side seats to the right etc.

I may confuse the details but please share your knowledge about this subject.

Thanks in advance.

 

[der8110]

Not to mince words, but it is not in the "regulations" such as 14CFR25.562 and .785, but in explanatory documents such as Advisory Circular 25-17 and industry documents like AS8049 and AS8043. Even so, it is much more custom and practice than explicit regulation.

Typically, a lift-lever buckle is oriented so it is easier for the right-handed majority, that is, pivot axis to the right side. Originally the buckle was placed at the center of the occupant, apparently early in aviation broken arms were common and a central location was desired. This was also why automotive-style pushbutton buckles took so long to appear on aircraft.

On a 3-point harness, the upper torso restraint is typically fixed at the upper outboard and lower inboard points, to take advantage of structural placement and keep the occupant towards the inside. In this case, the buckle would be on the inboard side, or right hip for left side occupants (pilot) and on left hip for right side occupants (co-pilot). (I don't want to hear about helicopters, unless they are lefties).

Another left/right consideration is side-facing seats. Crash forces can be enough to lift the lever, just on its own inertia. Typically side-facing divans have a 3-point harness, upper torso restraint over the leading shoulder and buckle at the trailing hip.

If the situation you refer to is in regards to an airline cabin, I cannot imagine an inspector being so anal about symmetry to have different seat belts on each side (OK, it might be one of the less weird findings). The airlines would not put up with two different part numbers, they'd get mixed up anyway.

Hope this helps, seat belt geometry is quite a science.

 

[LVDTRVDT]

Wow! Thanks a lot for all these valuable information. Yes I meant A/C cabin interior. I think there should be a forum section for weird SAFA findings.

 

[der8110]

a separate forum would crash the internet