4 points seat belts forces

There is a long and detailed history of seat, seatbelt, and attachment designs. Assuming you are in FAA jurisdiction, you have many Advisory Circulars to guide your work.
I take it you are not dealing with an existing "dynamic seat" (TSO C-127) otherwise you wouldn't be talking about attaching restraints to a separate monument.
Would this be a "flight attendant" seat, or something similar, in which case the same requirements may apply?

Look up GAMA-13 and the TSO C-127 for starters. The referenced data in those will keep you going for a long time.

There is a specific AC address issues relating to issues with Flight attendants 4 point harness.

Plus AC21-34 page 31 gives the shoulder harness mass / total mass split is 40%.

MarkEng512

A few basic questions/points for clarity.

Are the seat belts to be attached: (a) 100% to seat; (b) 100% to aircraft structure [IE: floor, wall and/or ceiling]; (c) 50-50% seat and acft structure???

Is the seat geometry/position fixed in-space [one-size-for-all?]... or adjustable to various degrees [adjusts to individual occupant?]. Adjustable seats add complexity to the design.

Is the seat intended for occupancy during take-off-and-landing... or only for use in-flight during specified periods? Crashworthy seating is far more complex than non-crashworthy [crew-rest-only] seating [design/analysis/testing].

May find following documents useful...

SAE AS8043 Restraint Systems for Civil Aircraft

SAE ARP4101/1 Seats and Restraint Systems for the Flight Deck

Regards, Wil Taylor

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