Seat certification in all-composite aircraft 1

[Sparweb]

There's something I have noticed in the current crop of all-composite aircraft (Diamond DA-40+20 is an example) where the seats are not independent units, but fastened directly to the airframe, in fact they are molded into it to a large extent, though still removable with discrete fasteners. Instead of moving the seat to the controls, these aircraft move the controls to the pilot. They deal with adjustment issues by keeping the center column very close to the pilot and moving the foot pedals instead. In the grand scheme of things, I kind-of like this (having flown a DA-20 it's easy to get used to) and some certification issues like pilot field of view may be simplified.

So now I'm wondering how this kind of seat design would be dealt with for compliance with FAR 23.562, Emergency Landing Dynamic Conditions?
Would the aircraft manufacturer have to replicate some of the airframe in the test apparatus in order to provide suitable attachments, and reactions that respond in force and deflection that corresponds to the actual thing? How much of the airframe, and how much fidelity does it need? Could the interface loads be determined in the same way as a 4-leg seat, with load transducers?

My recent reading of the AC guidance on seat certification treats the seat as a "unit", but this assumption doesn't seem to apply to the all-composite molded-in seat pan. All the figures in the AC show seats with legs that adjust back and forth on floor tracks. Again, more assumptions that aren't the case for the molded-in seat. AC 23.562-1 provides in Paragraph 9 some descriptions of alternative test fixtures for seats that don't incorporate 4 typical legs, but avoids describing what is expected. I should also note that on this size of aircraft, some of the structure supporting this seat is the spar-carry-through, and the landing gear attachments are not far away either. There's a lot going on in that one small area of the fuselage.

This is coming up because I see a project on the horizon where I will may to understand the certification of this kind of seat, and possibly need to figure out the interface loads at the attachment points.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[berkshire]

Apparently the news article from Avweb contained some mis-information here is their correction.

https://www.avweb.com/avwebflash/news/EAA-3600-Pound-LSA-Just-a-Starting-Point-231652-1.html

B.E.

You are judged not by what you know, but by what you can do.

 

[dgapilot]

Brian,
We had two C70s at Mid Atlantic Soaring until recently. I think one sold, not sure if the other one is still in the trailer hangar or not. Haven't seen it fly in years.

The new Part 23 is a real cluster. Nobody knows how it is supposed to work. They were supposed to be working on ASTM standards much like the Light Sport rule, but to date no standards have been written. Everything is supposed to be "Risk" based now, but no guidance on how to establish a risk based certification plan. I've asked my ACO advisor, asked at DER recurrent sessions and still blank stares. Thank goodness I'm only a Vintage DER, at least I understand CAR 3, Car 4 and Aero Bulletin 7A.

 

[Sparweb]

A little note to "close" the subject, concerning the seats I was going to look at:
In the end, the designer chose to elevate the seat on legs after all. They invited me to "advise" and suggest improvements, and were not going to call on me to do more or to take responsibility. That was a relief. My inspection revealed some serious issues integrating the seat to the floor.
The nature of the floor structure under the seat legs in their aircraft, once they do get the details sorted out, will offer some energy absorption of its own. The seat pan is also extra deep, allowing for a soft cushion and a crushable block underneath it. The combined energy absorption will come from the combined crush of the block, legs, and floor beams. I do not believe the guidance gives credit for crushing of the floor structure itself, as a contribution to the crash energy absorption.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF