Fin Inspection Panels BC12D

[Scott]

Hi All

I made two Fin (elevator bellcrank access) covers, one left and one right that are basically a mirror image of each other. Once I installed the right one I realized the relief for the elevator doesn't need to be as large because there is no trim shaft on the right elevator.

Question: anyone know the original BC12D configuration ie are the access panels the same left and right or is the gap behind the right elevator tube closed up?

Sorry don't have a decent photo. Will get one later
thanks
S

[Guest]

Re: Fin Inspection Panels BC12D

Hi Scott,

I had a bunch (3 or 4) of used ones in a spare parts box about a year ago and I think they were all identical.

Of course I may have had all lefts or all rights but I suspect not.

If I was manufacturing them I would not incur the cost or making two P/N's maybe they thought the same way?

Perhaps pre-war and post-war are different since they are the same on LH and RH?

Dave R

[3Dreaming]

Re: Fin Inspection Panels BC12D

I have never seen a difference between left and rights.

[astjp2]

Re: Fin Inspection Panels BC12D

Dont forget there is an AD on those covers...for the elevator hardware rubbing. Tim

[Scott]

Re: Fin Inspection Panels BC12D

Dont forget there is an AD on those covers...for the elevator hardware rubbing. Tim

Thanks Tim
I believe it was caused by over tightening a through bolt that went through both covers. Seems like an accident waiting to happen to me. Mine didn't have a through bolt and still doesn't but there is good clearances, especially with the larger than necessary cutout.

[Hank Jarrett]

Re: Fin Inspection Panels BC12D

All I have seen are the same size, except for mine which I made slightly taller so the screw points can't hit the bell crank (the cause for the inspection). The inspection and use of a shorter screw was a really stupid solution to the problem. Seems like every time you check an airplane, the short screw isn't in the right hole! Just make the cover and hole a bit taller and the screws aren't in the arc of the crank.

Hank

If you come across a mine field, do you go around, clear the mines or wear armored boots. I guess the FAA likes big boots.

[3Dreaming]

Re: Fin Inspection Panels BC12D

The AD was not about the bellcrank hitting the screws. It came about because the top bolt in the bellcrank was rubbing on the inside of the plates because they were pulled to tight together by the through bolt. The top bellcrank bolt wore a groove on the inside of the plate, and finally the end of the bolt popped through locking the elevator full down.

[Guest]

Re: Fin Inspection Panels BC12D

Thanks Tom.

Any ideas about why the tru-bolt was included in the design. It seems that it may not be necessary.

Dave R

[3Dreaming]

Re: Fin Inspection Panels BC12D

Thanks Tom.

Any ideas about why the tru-bolt was included in the design. It seems that it may not be necessary.

Dave R

I do not.

[LostnSpace]

Re: Fin Inspection Panels BC12D

My 46 BC12D doesn't have a thru bolt, but I've seen a couple that did and inside the two side panels was a tube that the bolt went thru to hold the panels out a ways, there were washers at the end of the tube to keep the edge of the tube away from the panels

[Scott]

Re: Fin Inspection Panels BC12D

Not sure but I think the original inspection cover frames were plastic and not very rigid. The through-bolt was perhaps a way to keep the fabric and panel from "ballooning" out potentially contacting the elevators. Or maybe it was just a way to hold the panels in the absence of a decent frame.

Anyway I took a couple of photos of the left and right side. Look normal to you guys?
thanks
S

[Guest]

Re: Fin Inspection Panels BC12D

Looks normal to me except for missing thru bolt and I don't recall a screw at the aft most lowest location on mine.

I coped your image and added a red dot at the approx. location of the thru bolt. Actual location may be a bit lower.

I am thinking that the thru bolt stops the narrow aft section of the fairing from ever popping out and jamming the elevator in the down position. There may be an old bulletin on that, not sure.

The screws that hold the fairing to the fabric originally screwed into a plastic perhaps acetate template. Those templates can crack or holes get big and the crews pull out that could leave the aft most narrow piece come off the surface and interfere with elevator.

I circled what I am calling the narrow aft most piece in blue.

Dave R

[Hank Jarrett]

Re: Fin Inspection Panels BC12D

Anyone have a photo of the through bolt? I have never seen one. I know i look at those covers on every pre-flight and have never found anything loose back there. It might be nice to see any info anyone has on the incident that caused the inspection in the first place. Sure sounds like what I was told the inspection was is wrong. Can someone post the actual inspection here? I think there was a copy in the old newsletters, but that isn't a very good source for official inspections!

Hank

[3Dreaming]

Re: Fin Inspection Panels BC12D

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/DD69D721A88A2F9586256A56006C8112?OpenDocument

[Scott]

Re: Fin Inspection Panels BC12D

Thanks Dave
I fabricated panel frames from 2024 T3. 032" and included a tab at the bottom for two extra screws at the bottom, one aft which is the one you see and one at the forward lower corner under the stab. I also wrapped the fabric around the frame and fastened it to the fuselage tubes with polytak.

In total this was my "suitable means" of ensuring the panels can't interfere with the elevators.

Here's a pic of the frame