Seat belt mounting........

[Bob Dingley]

Marty, please don't even joke about attaching the shoulder harness to the vertical stabilizer. This is the least valuable suggestion. Its the flimsiest structure possible and someone may try it and call it an antenna.

One builder of a small open cockpit I saw has a 6 inch dowel (white pine) solidly mounted an inch or two aft of his shoulders and a touch above. The shoulder straps pass over this then run down behind the seat and attach to something way down there out of sight. Landing gear for all I know. Does not put a down force on your tender pink bod. If I could not avoid a high speed taxi into a fuel truck, this would be the one. A good, simple, light weight option. Yes, could be improved. I will go with the research over the burro crats every time.

I learn best from experience. My very first emergency was when I caught fire. I haven't flown in polyester underwear since.

[martymayes]

One builder of a small open cockpit I saw has a 6 inch dowel (white pine) solidly mounted an inch or two aft of his shoulders and a touch above. The shoulder straps pass over this then run down behind the seat and attach to something way down there out of sight. Landing gear for all I know. Does not put a down force on your tender pink bod. If I could not avoid a high speed taxi into a fuel truck, this would be the one. A good, simple, light weight option.

If he had the structure engineered and tested to ensure appropriate strength margins, great. Otherwise, it's only a "feel good" installation.

[steveinindy]

Bob, as the other crash survivability trained person on this discussion, you might have a take or more to add to an idea that struck me. Another option might be to extend the back up the seat up a couple of inches and then bring the restraints either straight back or slightly down to a more closely located and secure point than the tail. This should give the needed twenty degree clearance across the shoulders without having to resort to anything too dramatic. What is really important here is the strength of the anchorages and the angle of the shoulder straps (and, yes, there should be two of them) as they cross the collarbones and shoulder musculature.

Just out of curiosity 1600vw, have you given any thought to inclusion of inertia reels on your shoulder restraints if you don't already have them?

[steveinindy]

Otherwise, it's only a "feel good" installation.

The same can be said for a lot of certificated restraints and seat attachments honestly. When the top end of the federal standard is below even what is required for a passenger car let alone the threshold of reasonable survivability, something is- with due apologies to Shakespeare- rotten in Denmark.

[steveinindy]

He did say it might be better to have the seat belt mounted to the seat down low so the seat belt and seat stays intact incase of plane breakup.

Mounting them on the seat might actually make the strain on the seat attachments (which are often underdesigned to be brutally honest) sufficient to wrench the seat loose. I would suggest mounting the belt attachments as close to the seat as possible so if the tail snaps off, you don't lose your shoulder harnesses or have nasty injuries inflicted as the attachment wire or whatever is pulled away.

[WLIU]

For better or worse, the seat back and structure immediately behind the seat on that type of wood aircraft will not support the types of alterations that you are talking about. Seat backs in light aircraft are only expected to support the load of the pilot pushing on the rudder pedals and a little weight from the torso of an upright pilot. You can see this in TSO C-39 for aircraft seats. The seats in military aircraft use more steel and supporting structure.

The currently installed shoulder harness anchor in the Fisher is likely the only practical installation. Upgrading as discussed above likely requires throwing away the fuselage and designing a new one. Then designing new wings to support a heavier aircraft, and a bigger engine......

Of course, the best approach is to don't crash. 99.9% of recreational pilots don't.

Best of luck,

Wes
N78PS

[steveinindy]

Seat backs in light aircraft are only expected to support the load of the pilot pushing on the rudder pedals and a little weight from the torso of an upright pilot. You can see this in TSO C-39 for aircraft seats.

The mindset of that approach is quite frankly another example of what is wrong with the "official" approach to aircraft design. I am really hoping that the ASTM involvement in trying to improve the design standards will help to move us away from largely holdovers from the 1930s and other times before the broader requirements for structures were considered.

The currently installed shoulder harness anchor in the Fisher is likely the only practical installation. Upgrading as discussed above likely requires throwing away the fuselage and designing a new one. Then designing new wings to support a heavier aircraft, and a bigger engine......

It would likely be possible to redesign the seat without having to throw out everything. It could be an engineering challenge but then again why should we shy away from something because it is hard. Taking the "easy way out" is what moved us from being innovators to a group of kit assemblers many of whom had to be told by the FAA to stop using hired guns to do it for them. It is common on this forum to grouse about the "decline of the EAA" or the "new EAA" but I think we miss what has brought that about. It is not the leadership but the change in the mindset of the membership at large. The few of us who choose to speak up on here are outliers and are probably somewhat holdovers from the original era of the EAA when advancement was first, foremost and penultimate.

I don't think you would need a steel seat for this to work. The vertical loads on a seat would likely be within the range that common aluminum alloys would be sufficient. Granted, I haven't fully run the numbers for this particular approach.

Of course, the best approach is to don't crash. 99.9% of recreational pilots don't.

While I agree on that concept on it's face, I have a problem with such approaches because it is rather fatalistic and counter to the point of experimental aviation (to advance things). Based upon that approach, we should stop trying to develop new engines because they meet the 99.9% of the needs out there. We should stop crash testing cars because most people survive in the current models.

Sorry....I couldn't resist playing devil's advocate.

[WLIU]

The original poster HAS a flying airplane. Most folks would rather fly than tear their machine apart and spend months trying to make it so that it is 100% set up for handling a very unlikely event. Aviation is an exercise in compromise. So we size up the risks and decide to fly or not. It will never ever be accident free. There are too many imponderables. And even if you crash, you have more control of the outcome than you think. I have a number of friends who have had airplanes give up on them and in fact one day an acquaintance stopped me and recounted that when his engine quit, he remembered some advice that I had given him. I was surprised by that and I will offer that advice here - Never stop flying until the crunching noises stop. You are welcome to repeat that. An old aviator once said, in the days before cell phones, to crash near a telephone so you can call your base and let them know where you wound up. But we all flew old ratty ships for low budget operators in those days..... Obviously my experience is different than that of a lot of folks.

Best of luck,

Wes
N78PS

[braywood]

Interesting and important topic. I read through the document steveinindy referred to - excellent! it is full of way more info than I need (or care to understand) but has very good recommendations for basic seat, harness and cockpit design considerations. I hope to incorporate some of these in my Pietenpol!

[steveinindy]

Interesting and important topic. I read through the document steveinindy referred to - excellent! it is full of way more info than I need (or care to understand) but has very good recommendations for basic seat, harness and cockpit design considerations. I hope to incorporate some of these in my Pietenpol!

Glad to know it was helpful. If I can offer any further assistance (or references should you desire to want to read more), let me know. Is your Piet nearly complete? If so, let's see some pictures. I am not known for being a "low and slow" kind of guy but that has always been a design that I have found aesthetically charming and it would probably be really fun to fly.