Collapsible Seat Mount ????

[asra]

HelpIn my recent near vertical impact, my seat mount bent approx 10mm down. How strong do should they be??? Should they be designed to collapse down in a vertical impact, or is it better to mount the seat on thick impact absorbing material.Any suggestions would be appreciated.Ross B

[Tim]

G'day Ross,"The seat and its supporting structure must be designed for the maximum occupant weight and for the maximun load factors corresponding to the specified flight and ground conditions including emergency landing conditions.Load factors are - Upward 4.5, Forward 9.0, Sideways 3.0 and Downward 4.5"These figures are from the Two Seat light Gyroplane Requirements, but will soon carry over to all gyros.If you have a seat tank, you must include it (full of fuel) in the calculation. ie. yourself plus the tank and fuel, multiplied by 4.5Regards TimTim McClure

[asra]

TimThe two seat standard states[blue]G 561 General(a) The gyroplane, although it may be damaged in emergency landing conditions, must be designed as prescribed in this paragraph to protect each occupant under those conditions.(b) The structure must be designed to give each occupant every reasonable chance of escaping serious injury in a crash landing, when proper use is made of belts and harnesses provided for in the design, in the following conditions:Each occupant experiences ultimate inertial forces corresponding to the following load factorsirection Load FactorUpward 4.5Forward 9.0Sideward 3.0Downward 4.5These forces are independent of each other and are relative to the surrounding structure.(c) The supporting structure must be designed to restrain, under loads up to those specified in sub-paragrap (b) of this paragraph, each item of mass that could injure an occupant if it came loose in a minor crash landing.(d) For a gyroplane with the engine located behind an occupants seat, the engine mounting structure must be able to restrain the engine, propeller and any other items supported by the engine mounting structure, when they experience an ultimate inertial force in the forward direction corresponding to a load factor of 15.(e) Fuel tanks, fuel lines, oil tanks and oil lines must be capable of retaining their contents under the inertial forces of (b) without rupture.So the question is at a load factor of 4.5 downward, what am I aiming to achieve. Do I need a seat mount that can withstand this amount of force without permanent deformation, or a seat mount that will suffer permanent deformation and absorbe energy and thus offer a higher level of occupant protection???I am also considering some thick padding on the seat to provide some additional impact protection. Any thoughts on what type of padding would be helpful.RegardsRoss B

[asra]

Hi Ross,I'm no expert at all on seat padding, and most other things [] but have been aware of considerable discussion in my previous aviation activities.These links on seat cushions may be of interest.http://www.bl.uk/about/annual/pdf/casestudy5.pdfhttp://www.dg-flugzeugbau.de/sich-details-e.htmlDave

[Tim]

Ross, my interpretation would be up to 4.5 without permanent deformation. Over that it may collapse.Covered in section G 785.Tim McClure

[asra]

Ross: Your seat collapses 10 mm (Thanks Good you use METRIC UNITS!!)in your recent "Near etical impact".Your gyro descent to a near constant velocity in order of 6 Mts/sec. This is equivalent to drop it from 2 meters.To disipate the impact in a 4 G'limit, you must absorb the impact in a 0,5 mts of deformation. This include: tires, flex of axe, seat cushion and your rump!!The progresive and "Not Quick Returning" deformation will protect you. This is ensured in the landing train with hidraulic dampers. In your seat with a long memory foam and a collapsible support you develop in your seat. Only need more travel, for the next time.Have a nice 2005.Edgardo MaffíaBuenos Aires - Argentina

[NiqueNaque]

Ross,A guide may be to examine what G forces your body can withstand. John Evans may have access to this info.Happy New year.Nick.

[asra]

Gentleman: Patty Wagstaff uses to support 9 G's in his rump, at least 10 years ago.I hope the back of Ross is a bit less cushioned, so you must put a correction factor of 0,8.Happy new year!!Edgardo Maffia - Buenos Aires - Argentina

[asra]

I understand that Tim's interpretation is correct, furthermore while I haven't any Gz guidline limits at my fingertips, the ones quoted by Ross from the 2 seat standard are apporopriate. People vary considerably in their Gz tolerance, both on their tolerance before GLOC [Gz loss of consciousnes] and before actual injury occurs. I was pleased when I wrecked the old VW in a vertical descent from 20' [about 7 metres to you Edgardo] in that assorted things broke, but I was able to walk away, even the old fibreglass seat tank ruptured. It seems that one of our major concerns for pusher aircraft should be engineering the engine mounts to comply with the requirement for resistance to a X 15 force from the engine mass, or in a tandem machine the rear seat occupant.John EvansThink logically and do things well, think laterally and do things better.

[asra]

I am a little confused by this thread. Lets say I want to secure a seat 300mm from the keel. Given a material like 20mm X 20mm X 3mm 6061 angle. What sort of design would provide the Direction Load Factors (Upward 4.5, Forward 9.0, Sideward 3.0,Downward 4.5) that are required? Short of destructive testing how is this worked out? An example picture of design that complies or a drawing would be great if anyone has one.Dave