Tail Bulkhead

[Mike Myers]

I'm wondering if anyone out there has had experience replacing the aft tail bulkhead that holds the torque tube assembly on. During my first annual with my PA24-180 (I bought it last November), we have discovered mine is cracked and bent, probably from a tail strike in the past. I've been working with Aircraftman in California who built a new bulkhead. The problem is, it doesn't fit! It seems to be too big. However, if we hold the 2 pieces together (the old and the new bulkhead), everything seems to line up in terms of holes, etc. but when we have to shoe horn it into the tail of the airplane, it throws all the holes off.

After several phone calls back and forth with Aircraftman, I am sending both the old and new bulkheads back and they said they would build a new one for me. I'm just afraid it will be the same size and I will have the same issues with it not fitting correctly.

Does anyone out there have any experience replacing this bulkhead, and if so, have you had the same issue? My understanding is the 180 had a slightly smaller bulkhead then the 260, but Aircraftsman said they used the jig for the 180. I also should mention the skin on the tail is straight, and no evidence that it might be bent as well.

This is turning into a big headache, and my plane has already been down for 2 months. I'm hoping someone out there could give me some advice so I can have this thing back in the air ASAP! I've attached a couple pictures of the old bulkhead so everyone knows what I am talking about. I will upload pictures of the new bulkhead not fitting correctly hopefully later today. They are on my mechanics phone and he is going to email them to me.

Thanks,

Mike

[Pat Donovan]

Hi Mike,

Just my two cents here, but I suggest that if you can get the current size replacement bulkhead in, then it is the right size. Second, since Comanche's were built before CNC and pre-drilling, I would not be surprised that only some pieces had holes and the mating item was match drilled. Soooo, you might consider telling Aircraftman to not drill holes where they had to mate with an exterior skin or an interior existing part; you can match drill those after placing the bulkhead in position.

Alternately, if the holes were NOT too far off, you could have them drill undersize and then you follow up with the correct size.

In either case, you would need to drill from the old material and not the new bulkhead to obtain the correct positioning.

Let us know what happens.

PatD

[Clarence Beintema]

Hi Mike,

I've never changed one in my shop but as the tail section is a tapered cone it would make sense that it would be a challenge to fit. The old one being damaged may have come out much easier that the new rigid one fits in.
Sorry that I have no suggestions other than care and patience.

Clarence

[Mike Myers]

Thanks for the replies. I've attached another photo of the new bulkhead sitting in place. As you can see it's physically too big, but when you match it up to the old bent bulkhead, it seems like it should fit. When we shoe horn it in place, it puts about a quarter inch gap in the skin.

[JMH23]

Mike,
I have not replaced a bulkhead, but in your first post, the photo shows some deformation and bending of the bottom skin, probably due to the tail skid hitting hard. Were you able to straighten the skin after you removed the damaged bulkhead? A 1/4" gap on the skins on the circumference of the bulkhead is not much and could be due to any gaps between the skins and the flange of the bulkhead. Have you tried to use a small nylon ratchet strap wrapped around the skins over the bulkhead flange to see if you can close up the gap?

Joe Hand
N9023P

[Mike Myers]

Thanks for the info Joe. We in fact did put a strap around the skin to line the holes up. In fact, we out about 300lbs of weight hang down from the tail hook and put 2 straps around the tail. We drilled out most of the rivets along the top skin on both sides to make more room. We were successful in getting the holes on one side of the tail to line up, but the other side was still a quarter inch off. Only thing we can thing of is the taper on the trim piece is too aggressive making the bulkhead to big. I shipped the original and the new bulkheads back to Aircraftsman and they should have received it Friday. I will probably call on Monday and see if they have had a chance to play with the two pieces and see what they come up with for ideas. I have a feeling I'm going to have to call around to salvage yards and see if I can find a used one. Which will lead me to my next question, does anyone recommend a good salvage yard or know someone piecing out a 1959 180? This is my first airplane I've ever owned so I'm learning about these kinds of places as I go.

Mike

[9089P]

Hi Mike,

Don't wish to interfere but are you limited to a 180 for a used replacement?

Good luck, Don

[JIMICS2452]

According to the parts manual there are 2 different part numbers used in 180's and 250's for the aft bulkhead-
20479-00 PA 24-180 with S/N 24-1 thru 24-3284 and PA24-250 with S/N 24-1 thru 24-2843

20479-12 PA-180 with S/N 24-3285 and up, and PA24-250 with S/N 24-2844 and up

260's use 20479-15

There is no hint in the manual as to the differences.

[9089P]

Thanks Jim,

So if I understand, either a 180 or 250 will work provided it falls in the correct period of bulkheads. Most likely an early one in this case.

Don

[Mike Myers]

That's interesting Jim. Aircraftsman told me they have built around 30 of these in the past (considered owner produced part) and said they have never had them not fit. I wonder if the differences in serial numbers is a slightly larger bulkhead, although with mine being 928, you would think I would fall into the majority of the common Comanche size, it's definitely something to bring up to them when I talk to them.


As for keeping it strictly to a 180, I guess I need it keep my search to a part number of 20479-00 and it doesn't matter if it's from a 180 or 250.

This is all great info everyone! Thanks again!

Mike

[9089P]

Hi Mike,

This is a guess but I doubt the outside dimension of the bulkhead was changed. That is based solely on observation and could be entirely wrong.

Don

[Mike Myers]

Well, finally some good news. Seems as if the bulkhead was 1/16 of an inch off in 3 different places which doesn't sound like much, but enough to cause me issues. Aircraftsman said they are going to build a brand new mold and build a another new bulkhead. Hopefully this one will slide into place.