Help identifying validity of seat design or unauthorized "modification"

[AeroCapture]

I recently discovered after some investigation that my 1946 Talyorcraft BC-12D has a hard mounted seat in-place of the canvas seat as well as what appears to be a less than effective seat belt harness arrangement. (See photos below)

Any advise as to whether or not this seat and seat belt arrangement was ever officially used by the manufacture would be greatly appreciated.

This is how I received the aircraft from the IA (who is a Taylorcraft owner as well) that brokered the sale, did the pre-buy inspection, subsequent annual and signed the aircraft off as airworthy.

Thanks, Lyle Jansma

[Robert Lees]

Re: Help identifying validity of seat design or unauthorized "modification"

If he signed it off as airworthy, it must be so.

Best not say too much.

Rob

[Guest]

Re: Help identifying validity of seat design or unauthorized "modification"

If he signed it off as airworthy, it must be so.
Best not say too much.

Rob

ha! That's a funny one Rob. When I got my t-craft it had a number of things signed off that were not airworthy that cost the man his IA and rightfully so. One item was an incomplete cable swage on elevator cable, one squeeze instead of three.

Is there documentation for the alteration? What does it say? Is it a field approval? STC?

That is not a factory installation. I never saw a seat belt installation like that one. It looks odd to me but it is hard to figure out what is there from a few pictures. Based on what I think I see it looks all wrong to me but your paperwork search might cause me to eat those words.


Dave

[AeroCapture]

Re: Help identifying validity of seat design or unauthorized "modification"

Dave,

After reviewing the records CD that I received from the FAA, there is no paperwork showing any approved modifications to the seat or seat belts. Could it be expected that something like this should have been identified in the pre-buy inspection and subsequent annual performed by the IA. If so, my next question would be, is this something that should be reported?

- Lyle

[Robert Lees]

Re: Help identifying validity of seat design or unauthorized "modification"

There are two 1946 Taylorcraft in the UK imported from the USA with a similar but different "hard seat" installation. Not legal here and not legal when they were exported from the USA in the late 80's. They should not have received FAA export Certificates of Airworthiness.

Yet all three of these aircraft were "signed off" and therefore all legal from the paperwork sense.

Go figure.

(one of the UK ones has since been corrected back to factory original)

[Guest]

Re: Help identifying validity of seat design or unauthorized "modification"

Dave,

After reviewing the records CD that I received from the FAA, there is no paperwork showing any approved modifications to the seat or seat belts. Could it be expected that something like this should have been identified in the pre-buy inspection and subsequent annual performed by the IA. If so, my next question would be, is this something that should be reported?

- Lyle

Lyle,

I assume that there is no log book entry for this or other aircraft records that you possess for this. Is that correct?

It is not a major alteration, see italicized text below. It may not be a violation. However it does not meet its type design data and the rule for airworthy is in part that it meets it type design and/or its properly modified condition. So whoever did the annual should have noticed this. If you find a log entry of this alteration then maybe all is well. If not then you got a sloppy annual regarding this item.

All it takes is a log entry or better stated an aircraft records entry for this kind of change.

However there is often debate and disagreement about what exactly constitutes a major alteration so no doubt that some will disagree about sentence above.

More importantly based on what I think that I see the is a bad mod. Here is why. It looks like both sides of the belt for an occupant can pull from the rear and outside corner of the seat, thus crushing the pelvis or abdomen when the occupant is thrown forward. Am I correct about this or do I see it wrong?

Taylorcraft made a wire frame truss to fit in that area and it prevented that crushing load. I think that one could achieve that same result bay adding two more cable.

Dave

Appendix A to Part 43—Major Alterations, Major Repairs, and Preventive Maintenance

(a) Major alterations—(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:

(i) Wings.

(ii) Tail surfaces.

(iii) Fuselage.

(iv) Engine mounts.

(v) Control system.

(vi) Landing gear.

(vii) Hull or floats.

(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.

(ix) Hydraulic and electrical actuating system of components.

(x) Rotor blades.

(xi) Changes to the empty weight or empty balance which result in an increase in the maximum certificated weight or center of gravity limits of the aircraft.

(xii) Changes to the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, de-icing, or exhaust systems.

(xiii) Changes to the wing or to fixed or movable control surfaces which affect flutter and vibration characteristics.

[AeroCapture]

Re: Help identifying validity of seat design or unauthorized "modification"

Thanks Dave for your explanation on this,

I have seen the 337 for the seat belt modification located here http://taylorcraft.org/docs/seat%20belt%20mod1.pdf on the tech resources page and I am hoping to adopt this for my aircraft as well .

I am still at a loss for the welded in angle iron that constitutes the rear base of the aluminum seat that came with my aircraft. I would assume that an installation such as this must be covered by point VIII as it would be welded to the airframe.

Would you agree? - Lyle

[Guest]

Re: Help identifying validity of seat design or unauthorized "modification"

I think that Tim's installation is done in such a way that he continues to use that wire frame that I referred to. Recently someone else was looking for one of those so there is a thread on the sight that you can search for that talks about how to obtain and replace one.

Sadly I tossed about 3 of them earlier this year assuming that since some wires were bent that no one would ever want them. Never throw anything away .

It looks to me like that angle iron is bolted to the bottom of the wooden door frame. Is that correct? Even though it is (if it is) I think that you are correct and that I missed something; viii covers bracing and the change that you have does alter bracing for the seats. Good catch I failed to see that! So it should have been a major alt. with a 337.

I have to say that I am still having trouble "seeing" the big picture regarding how it all goes together. Where to the cushions go? What do the cushions look like? ...

Dave

[N96337]

Re: Help identifying validity of seat design or unauthorized "modification"

I'd think it'd need a 337 too....that's a fairly major mod in my opinion. I used to live over there Lyle, who's Tcraft is this....and who signed it off???
John

[AeroCapture]

Re: Help identifying validity of seat design or unauthorized "modification"

Here are a few additional images to demonstrate how the substitute seat is installed.

[Robert Lees]

Re: Help identifying validity of seat design or unauthorized "modification"

Lyle, it would appear that someone has essentially replaced the sling with a hard aluminium pan. That is not my concern.

In your first picture above (IMG_4218) (and also seen in your previous IMG_4214) I can see that the centre harness [shared by both occupants] appears to have wires to the lower aft fuselage longerons, and not to the forward longerons (as if only half of the original X-brace exists). Also, the outside harness seems to be attached to the rear doorpost extension member.



Furthermore, in your post of yesterday, here's your original IMG_4214 picture:



And my annotations, 1 to 3:




First of all: my notes on my Item 1:



Then on my Item 2:



And then on my item 3:





I'm going to bow out of this discussion at this point, but not without saying that if I owned this aircraft, I should like to have a competent inspection of this harness system.

From what I can see (albeit from photos only) I would not like to be involved in an accident in that aircraft where my life (and that of passengers) could depend upon the seat harness keeping my torso attached to my legs.

Rob

[Guest]

Re: Help identifying validity of seat design or unauthorized "modification"

Rob,

You are right on.

Super job with the pictures. We are noticing the same thing but your pictures really bring it out.

Earlier I had said "More importantly based on what I think that I see the is a bad mod. Here is why. It looks like both sides of the belt for an occupant can pull from the rear and outside corner of the seat, thus crushing the pelvis or abdomen when the occupant is thrown forward. Am I correct about this or do I see it wrong?"

Your pic's show that to be true.

I wondered about that door frame/angle iron joint. It's more nearly clear in your picture views. I suspect that a cable goes from the longeron joint where the wire frame had been attached thru the angle iron and thru the door frame wood and terminates on that "D" fitting for the cable. It's not good. It lacks a lot more than a mere 337 form.

At the very least the wire frame should be re-installed.

Dave

[AeroCapture]

Re: Help identifying validity of seat design or unauthorized "modification"

Rob, Dave, John,

I really appreciate your insight and it confirms what I expected. I really have a challenging situation on my hands here.

This is my first aircraft, I am a student pilot and I purchased this aircraft, N95333, with the intent of using it for my training.

Needless to say, the IA that brokered the deal, was supposed to have conducted a pre-sale inspection and perform an annual stumbled in fulfilling his responsibilities in certifying my aircraft as airworthy.

The IA cited that his qualifications for being able to objectively conduct those three tasks could be based on the fact that he was a Taylorcraft owner himself.

I have owned the aircraft of just over a year now and only seen it fly 3 times. My first experience buying an aircraft has been a bitter pill to swallow to say the least.

Again, Thank You for your help. I helps to prove that I am only inexperienced, not stupid.

[PA1195]

Re: Help identifying validity of seat design or unauthorized "modification"

Not a mechanic here so take it FWIW. It appears to me that the side cables are attached at the rear clevis along with the companion center belt, and merely routed outside of the baggage area around the frame members. If it were mine I'd follow Tim's 337 as far as the cabling and attachments design for the lap belts (component specs plus dual common attach points for the center belts), and add shoulder harness assemblies per the 337 provided or similar. I have both in my T-Craft. I'd leave the sling seat as is unless the I/A has a better idea.

The sling is a sling. I might ask an I/A about supporting the red angle piece from the crosstubing above at the junction of it's two angled supports to carry additional downloads, and maybe with a lower post to the fuselage crosstube below. Let it all carry the loads and deform in a crash. Tim has also done a seat mod via 337 for the same plane (N3572T) that has the cable anchors for the belts (see below).

As far as the occupant(s) fate in an abrupt stoppage, providing the torso/pelvis is properly held, the main concerns in accidents I've observed are the legs and arms being thrown forward due to momentum, and the head area subject to forward or side impact with the airframe or panel. A shoulder harness and wearing a helmet can help, but if the main torso is secured that's about all you get for protection short of a harness airbag (which are becoming available). If the plane drops with a vertical vector then additional seat compression can occur. I'm not prepared to debate the relative strength of the Taylorcraft OEM seat versus other Field Approved designs.

Aerocapture/Lyle. Don't despair and note this Taylorcraft N3572T: I'd access the records for this aircraft (http://aircraft.faa.gov/e.gov/ND/), copy the Field Approvals via Form 337, and discuss in a polite but firm mode with the I/A about applying for similar before you invite the FAA into the process. Allow the I/A to help work to make it all better. The work done involves the cable seat belt anchor and aluminum seat mods also available in the Taylorcraft Owner's Club tech resources. You should also request the FAA's records on CD for your plane as well, and compare them with the prior registered ownership, logbooks, and paperwork transferred to you at purchase.

In my experience these "alterations" are more common than realized. Once done by "person or persons unknown" they can become part of the undocumented history of the aircraft and often several annual inspections will be completed before the work or paperwork comes to question. The problem then becomes one of correcting the aircraft records either via part removal or approval. Per FAR 91.403 the owner is responsible for airworthiness as well as maintaining records (See also for further clarification: http://www.faa.gov/regulations_polic...h-8083-19a.pdf) so it becomes a shared responsibility in maintaining airworthiness.

Gary

[Mark Bowden]

Re: Help identifying validity of seat design or unauthorized "modification"

Lyle, Welcome to learning to fly, especially in a Taylorcraft. Glad you are part of the group, your intuition is correct.

I agree with the other guys on the things that are wrong on how stuff is bolted up and modified. I would be concerned about more than just the belts. Every mod changed how occupant loads are supported and distributed, not in a good way. However, it appears all fixes are straightforward. I think too, from earlier comments and Rob's photo work it appears that each lap harness is cabled to the single outer frame corner attach point with the outer belt cable running behind the side lining and coming through the rear door frame and L angle that supports the rear of the seat.

The original design of the belt attachment is for each occupant's belt load to be transmitted into opposite corners of the lower fuselage frame via the original spider X-wires and rod. The spider can also transmit loads to the forward frame corners where the strut and gear attach if pulled such a direction. As it is now, modified, the load for each occupant goes to only one point, vs. 2-4 points.

The original sling wraps around the upper cross tube. That tube supports the seat loads through the down angled tube that crosses the door opening, down to the frame for the gear and struts and also straight down to the rear frame corners where the belt attaches. It makes a two leg A-frame load path.

Importantly an L-angle of similar size is NOT the same as a tube in stiffness and ability to carry load across the span of the seat and can't support the same occupant load. As modified, the L-angle is now only supported by fuselage frame at only one point…the door frame to that small tube going to the corner where the belt attaches.

Also worrisome is, as modified, it is now just a bench seat and without a sling there is no support for your back. That hinged seat back panel will let you slide out of the seat backwards because the seat back isn't secured to the upper cross tube.

Is there a liner for the baggage compartment? The problem is that it has holes that can let FOD (foreign object debris) out into the fuselage where it can them jam up flight controls. Two, the flight control cables are exposed so whatever you put in the compartment can rub on the cables and either damage them or jam them.

The part that isn't straight forward is the IA missing this and then "what else" was missed. While it can be hard to find a new A&P/IA to work with on vintage fabric airplanes that would appear to be in order.

I would echo the others and not fly her until repaired but it is all fixable. I think a new sling is $100-150, get that L-angle out of there. Do the harness cable mod on the Foundation Site like you mentioned. Close up your baggage compartment and whatever else a better A&P/IA resource finds. It looks like you have a shoulder harness, better check it is installed properly too. There is FAA policy and an AC that shoulder harnesses can be a log entry/minor alteration for old aircraft.

Mark