I used to be a design engineer for an aircraft seating manufacturer .. long time ago, now, so the memory probably is a bit hazy and the rules may well have changed a tad.
passenger seats must be able to withstand a 16g dynamic loading.
Depends on the class of aircaft. Helicopters are the highest due to the typical prang having a high vertical velocity component.
Going back a long way (DC3, for instance) the design restraint was only 6g forward. This later changed (still a static load) to 9g .. with an overload requirement for seat attachments.
Later on, motor vehicle dynamic standards were introduced which really increased the work required in testing. End result is that, for later designs, the occupant has a very high level of crash survivability.
I am struggling to find a reference for maximum loading for passenger seats.
The design loads are in the FARs and cited standards. As far as I am aware, there is no limit regarding what the operator might put in the seat, passenger wise. Generally, if freight is seat loaded, the restriction is to the 170lb/77kg seat design load.
In the modern era of extremely obese travellers, am I missing something?
Not at all .. pick a seat row with the skinny occupants and you will maximise your survivability .. presuming that the seats behind don't separate from their attachments and take you out anyway ...
Are seat anchors, rails and seat belts so strong that it is a moot point?
The current dynamic design standards provide a very high level of crash survivability for occupants. The various attachment load capabilities are included in the various design standards if you fancy searching them out.
Even the older static standards provided pretty good survivability. Probably, the main deficiency was the ability of the seat to retain anchorage security with deformation in a crash .. this was one of the main changes when the dynamic tests came in. Another, especially important in helos, was to limit the maximum spinal loads .. current helos are only able to meet that with seats incorporating vertically controlled deformation, usually with interference attachment structures which let the seat settle downwards in a controlled manner.
170 lbs or 77 kg does seem very light, but I guess that might be an average of who might be in the seat row?
Just an old line in the sand ...
I seem to recall back in the day (Andes Crash) that all the seats ended up piled up at the front and injured or killed many.
As above, the static design standards didn't look at restraint under crash deformations. Seat departure was not uncommon.
Perhaps the increased 16g loading has mitigated that somewhat?
Not so much the inertial requirement as the requirement for the restraint to work in the sled test with pre-misalignment of the seat attachment structure.
I believe that the R44 has this weight published, but yes it would be interesting to know.
Helo (current) seating is to a much higher restraint than 14g .. I'd have to look it up but something in excess of 30g comes to mind. Certainly, and especially for helos, heavier occupants will materially decrease the survivability, especially regarding spinal injuries ...
I expect most come done to the cargo load limits per square (x) but what is the area of the chair over the floor area? most are on tracks that do not give a surface area.
Anchoring seats directly to the floor went out when 6g increased to 9g. If you have a look under the floor, you will see some heavier beams to which the seats are anchored. Nothing to do with floor limits.
The 170 or 77kg is the standard weight per passenger for loading unless you actually weigh the passengers.
170lb goes back a long ways to a report on US Army personnel in North America. I have a copy tucked away somewhere but not to hand .. sometime in the 40s as I recall. Obviously, not overly pertinent to today's fatties ... (did I mention that I am finally getting around to losing some weight ?)
In Oz, there has been some discussion on categories, as on smaller aircraft, there is a larger risk of overloading..
The CAAP is based on a study by John Klingberg, when he was with CASA. His report goes back to the 80s, as I recall .. again, I have a copy but not immediately to hand. John reviewed NHMRC statistical data and came up with the results in the CAAP. For whatever reasons, which annoyed many of us, the Authority took forever and a day to implement John's results.
If you are in Canberra, John (now retired) probably would trade a coffee or two for a briefing on his study.
Main thing to take home is that there is a statistical problem with small sample numbers (ie small aircraft). Large aircraft have the statistical lumps and bumps smoothed out somewhat ...
The US studies would be similar to John's but not based on Australian population statistics as was his.
So if I weigh 60 kg and my 3 fellow bench sitters weigh on average 110 kg, what is my protection level?
Somewhat reduced ... the usual asymmetric test loading will provide some comfort ..
What is the maximum allowable seat loading for the 4 seats mounted on the 2 seat rails at 4 small points?
The standard provides a line in the sand, not an all points guarantee. Asymmetric testing will provide some comfort.
I wouldn't worry too much about the anchorages .. for current standard seats, they are pretty good. Keep in mind that the rails, themselves, are supported by comparatively massive beam structures. One consideration is that the rails need to be anchored by structural screws at minimum pitch (normally 1") to protect against local rail bending .. local deformation can then let the button out .. which is why the better anchorages don't have round buttons alone.
The only time I've seen a max load stipulated was for an EMS stretcher, and the general opinion of pilots was that was down to the crane wire strength used to lift the stretcher to the door for loading.
The stretcher design would have been addressed as a combination of berth and freight requirements. Probably a 9g plus anchorage overload requirement.
Probably not limited by the wire, I suggest, multistrand steel cable is pretty good.
The GA8 has several
The original design chief for the GA8 is a PPRuNe poster so he may be along sometime with a comment or two ..