Strut Attach Inspection

[BenD]

I'm currently in my first annual on my '47 BC-12D. Struts were replaced in 2013 with Wag-Aero new sealed units and logbook entry states that 2008-09-18 was complied with by inspection at that time. Current IA says there is no evidence that inspection was completed since no evidence of cut and repaired fabric exists. Plane was last recovered in 2000. Never on skis or floats. He wants to conduct the inspection. Would there have been any way for the inspection to have been completed without seeing patches? Where would the patch be? On the bottom or the sides?

[waltermrich]

There is a service bulletin, to inspect the strut attach cluster where the step is located , looking for corrosion in the tubing it must also be an AD as you IA is mentioning it, It is a one time event, do a forum search and you will find the information, or someone here will chime in. Its not a big deal to do. But you need to cut some fabric

[BenD]

There is a service bulletin, to inspect the strut attach cluster where the step is located , looking for corrosion in the tubing it must also be an AD as you IA is mentioning it, It is a one time event, do a forum search and you will find the information, or someone here will chime in. Its not a big deal to do. But you need to cut some fabric

Thanks. I have the docs, but I'm unclear what fabric has to be cut. Looking at the pics in the SB, it looks like the borescope inspection can be done without cutting.

[PA1195]

I've had mine done twice since it flys on skis and floats. A minimal amount for nearby fabric was removed and left off. The mechanic looked at the fitting and tubing from the outside and inside of the fuselage plus scoped the innards. It had been epoxy primed so nothing was corroded but we sprayed the innards with Corrosion-X anyway. I'll re-post the SB in case others haven't seen it.

Gary

[3Dreaming]

I'm currently in my first annual on my '47 BC-12D. Struts were replaced in 2013 with Wag-Aero new sealed units and logbook entry states that 2008-09-18 was complied with by inspection at that time. Current IA says there is no evidence that inspection was completed since no evidence of cut and repaired fabric exists. Plane was last recovered in 2000. Never on skis or floats. He wants to conduct the inspection. Would there have been any way for the inspection to have been completed without seeing patches? Where would the patch be? On the bottom or the sides?

There may not be a need to remove much fabric. It depends on how the covering was done. Post a picture of the fitting for a more informed opinion. Tom

[BenD]

There may not be a need to remove much fabric. It depends on how the covering was done. Post a picture of the fitting for a more informed opinion. Tom

[Hank Jarrett]

When I first heard of the fuselage strut/gear attach cluster it looked like a good idea to watch it regardless of if it was required. I made a set of small wrap around covers for the area and look at it at every annual. I find a LOT of dirt and debris every time so I feel like it was a good idea and it sure makes it easier to clean trash that collects there out. I have a couple of small plywood pieces inside and the machine screws go through the covers into "T" nuts on the plywood. Only weighs a few ounces and provides great access to the cluster.

Hank

[PA1195]

The metal inspection cover is a good mod Hank. Maybe also would be a piece of clear polycarbonate fastened to a suitable glued-on to the fabric support like used for round inspection rings.

We know what and why the SB and AD were generated. Old story. I'm still trying to figure out what floats and particularly skis have to do with that fitting other than that's how the subject aircraft was equipped when the accident occurred. It rains on wheel only planes just as much and water can follow the lift struts to that fitting as well. Salt water corrosion is another matter but that's not mentioned.

Another source of stress I suggest is the step bolted to that fitting. Over the years bearing the body's weight during ingress and egress must have some effect I would think. I don't use the steps as there's other easier ways for me to get in and out.

Gary

[N96337]

Yeah, I agree on the step...I always wondered how much it stressed that area.
Ben, it doesn't look to me like yours has been done and even if it was, it isn't in compliance with the specs in the service bulletin paragraph 2... "2. Remove any aircraft fabric that is attached to the actual lower wing strut attach fitting. Use a
razor to carefully cut and remove the fabric from the lower fuselage longerons up and around
the strut attach fitting, leaving a minimum 1/2” gap around the strut attach fitting. Take care
not to scratch the protective coatings or primer (see photo #1).
If you look at photo 3, it shows pretty plainly what they're looking for. From what i can see in your picture, unless the plane was recovered after the Bulletin, it's not been done, or at least not been done properly. That being said, I'd be totally amazed if you find anything behind that fabric. So as an IA, I'm in agreement with your IA. If it was in my shop, I'd set up an inspection cover like Hank posted. That looks really nice and it's a great way to get crap out of the are, like he says!
Good luck,
John

[Robert Lees]

Most of us know that the original issue was corrosion caused by water retention in cotton fabric, that was somehow wrapped in and amongst that cluster of Dave Wiley's Taylorcraft.Cotton retails moisture very effectively (which is why it's not good for insulating clothing).

I have seen close-up photos of the failed fitting...it was corroded more that 50% through, giving credence to CG Taylor's excellent design. I agree with Hank that it was always a good idea to inspect around there anyway (anyway, it's a requirement of both FAA and EASA regulations to inspect all structural members at 100hr or annual inspections).

I'm still trying to figure out what floats and particularly skis have to do with that fitting other than that's how the subject aircraft was equipped when the accident occurred. It rains on wheel only planes just as much and water can follow the lift struts to that fitting as well

Do aircraft on floats not sit "flatter", such that water/moisture might collect at that point? (Like you, I'm bemused about skis, however!)

Rob

[PA1195]

Yes Rob they do sit flatter on floats and can be tipped side to side more when parked. Perhaps some of the water ingress is internal (?) to the fuselage via wing root leaks then flows down to tubing and whatever. For example on some planes and maybe Taylorcraft water enters the wing's root via any small openings (the fairings aren't a weather seal) and can collect-pool in low spots. Eventually corrosion can start in those locations along the longerons and various fittings.

Also pilots on floats or muddy airfields have wet boots and water plus debris runs off onto the floor and seeks a low spot to later collect. The gear attachments subject to the AD are at the L and R rear of the floor boards and subject to contamination from inside the cockpit. Planes with inside covering may be harder to inspect than mine that's exposed.

The hardware and struts to that fitting aren't weather sealed though they could be somewhat better by applying Paralketone or similar. Same for the internal cavities the inspection requires.

Gary