Cracked Vertical Stab Bracket

How to keep the Cessna 170 flying and airworthy.

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reecewallace
Posts: 165
Joined: Tue Jan 05, 2021 1:34 am

Cracked Vertical Stab Bracket

Post by reecewallace »

On my walk around today, I noticed the main bracket which holds my vertical stabilizer has a small crack in it.

What to do? Anyone experienced this? I don't push/pull my plane by the tail, and there was no harsh landings, cross winds, or turbulence. I never spin the aircraft or stress it unnecessarily.

Any tips on replacement or what to do? Looks like p/n 0331124, but I can't find it anywhere online.

I'm assuming it needs to be replaced, but looks like a big job of removing the tail?

Thoughts?
Picture here --> https://www.pinkbike.com/photo/26250717/
- Reece
1956 Cessna 170b
Nanaimo, BC Canada
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GAHorn
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Re: Cracked Vertical Stab Bracket

Post by GAHorn »

There’s Good News…and Bad News. The Good News is…. You Found IT!

The Bad News is…. you found it is an uncommon part.

It doesn’t look like a “fresh” crack… I suspect it’s been there awhile.

You are correct in that it will require some disassembly …and that extrusion is not a readily-available part. You might try Air Repair, Inc. in Cleveland, MS as they have a large warehouse of L-19 parts. The L-19 shares many parts with the 170, especially the tail of the 170B.

662-846-0228
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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n2582d
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Re: Cracked Vertical Stab Bracket

Post by n2582d »

Reece,
-Good catch on finding the crack. I would suggest stripping the paint there to confirm that it is not just the paint that is cracked. Quite unlikely that it is just the paint but wouldn't hurt to check. If the one side is cracked it would be worth your time to strip the paint from the other one and dye-check it for cracks too.

-Do a search on this part using 0331124 in the search box. There's a lot of good information to be found in the dusty archives. One member, a metallurgist, writes about fabricating the part from titanium. If you could come up with a CAD drawing, I wonder if an online parts maker like sendcutsend.com could manufacture this fitting for you.

-Fig. 163-15 of the L-19 IPC shows this part to be 0631124. It's available from Univair.

-The subject of using the correct NAS bolts and washers here has been discussed previously. But note on the Univair L-19 part that the hole has been countersunk. I believe this is different than the C-170 fitting. (Edit: it could just be the picture that makes the hole appear to be countersunk, i.e. optical illusion.) If it is countersunk, I would follow the C-170 and L-19 IPCs and NOT use the special chamfered washer (MS20002-C5) with the NAS bolt.
Screen Shot 2024-02-19 at 5.56.10 AM.png
-The bottom rivet on your fitting seems lower than others I have seen in pictures. It will be necessary to spotface the hole to install that rivet. I wonder if this hole being lower and in the radius has contributed to the part cracking?
Gary
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c170b53
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Re: Cracked Vertical Stab Bracket

Post by c170b53 »

Not a bad situation, the rudder will have to come off, but then you’re at it. Not sure about that washer (its corroded for one) may not be a NAS (it looks too wide) but like Gary mentioned I’d clean it up first as it appears the crack/ scratch/ mark or also goes into the skin at the forward edge which doesn’t look right since its opposite to the airflow.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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cessnut
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Re: Cracked Vertical Stab Bracket

Post by cessnut »

Looks like a crack that has been fretting to me. You will more than likely need to remove the vertical stablilizer to buck that lower rivet. I do not like where that rivet is placed in the radius with a spotface. When I reskinned my vertical I considered using something like a Hilok there, but wound up installing a rivet with a custom made bar and rivet set that was turned down to a smaller diameter so as not to mar the fitting. I did inspect it carefully for cracks after riveting.
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Ryan Smith
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Re: Cracked Vertical Stab Bracket

Post by Ryan Smith »

Robert Brown in Atlanta had some, but I think I might have gotten the last one.
reecewallace
Posts: 165
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Re: Cracked Vertical Stab Bracket

Post by reecewallace »

n2582d wrote: Mon Feb 19, 2024 2:25 pm Reece,
-Good catch on finding the crack. I would suggest stripping the paint there to confirm that it is not just the paint that is cracked. Quite unlikely that it is just the paint but wouldn't hurt to check. If the one side is cracked it would be worth your time to strip the paint from the other one and dye-check it for cracks too.

-Do a search on this part using 0331124 in the search box. There's a lot of good information to be found in the dusty archives. One member, a metallurgist, writes about fabricating the part from titanium. If you could come up with a CAD drawing, I wonder if an online parts maker like sendcutsend.com could manufacture this fitting for you.

-Fig. 163-15 of the L-19 IPC shows this part to be 0631124. It's available from Univair.

-The subject of using the correct NAS bolts and washers here has been discussed previously. But note on the Univair L-19 part that the hole has been countersunk. I believe this is different than the C-170 fitting. (Edit: it could just be the picture that makes the hole appear to be countersunk, i.e. optical illusion.) If it is countersunk, I would follow the C-170 and L-19 IPCs and NOT use the special chamfered washer (MS20002-C5) with the NAS bolt.
Screen Shot 2024-02-19 at 5.56.10 AM.png-The bottom rivet on your fitting seems lower than others I have seen in pictures. It will be necessary to spotface the hole to install that rivet. I wonder if this hole being lower and in the radius has contributed to the part cracking?
Thanks for all the info.

Will the L-19 bracket fit my 170b?
- Reece
1956 Cessna 170b
Nanaimo, BC Canada
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GAHorn
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Re: Cracked Vertical Stab Bracket

Post by GAHorn »

Reece, while this does not apply in EVERY comparison between models, … notice that the 170 PN is 0331124 and the L-19 PN is 0631124

Cessna Part numbers are related to Drawing numbers…and the last Five digits reference that drawing…the first two digits refer to model applicability.

This is just more indication they are actually the same part. As mentioned earlier, the L19 and the 170B share many common parts, especially in the wings and tail.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
reecewallace
Posts: 165
Joined: Tue Jan 05, 2021 1:34 am

Re: Cracked Vertical Stab Bracket

Post by reecewallace »

GAHorn wrote: Wed Feb 21, 2024 12:11 pm Reece, while this does not apply in EVERY comparison between models, … notice that the 170 PN is 0331124 and the L-19 PN is 0631124

Cessna Part numbers are related to Drawing numbers…and the last Five digits reference that drawing…the first two digits refer to model applicability.

This is just more indication they are actually the same part. As mentioned earlier, the L19 and the 170B share many common parts, especially in the wings and tail.
Thank you for this! A lot easier for me to order the L-19 brackets than search or have some made for my 170b.

I'll order and install them, then update the forum here once I confirm they fit.
- Reece
1956 Cessna 170b
Nanaimo, BC Canada
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n2582d
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Re: Cracked Vertical Stab Bracket

Post by n2582d »

How would you sheetmetal gurus drill the holes in this fitting? It's obviously critical that the holes be accurately drilled. No room for a strap duplicator. As this fitting sandwiches the skin, the holes can't be backdrilled. The only way I see is to make a jig using the removed fitting to accurately locate the holes for the new fitting.
Vertical Attach Fitting.png
Gary
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cessnut
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Re: Cracked Vertical Stab Bracket

Post by cessnut »

I can think of several ways that would get the job done. A drill jig would be a good option. If a guy has access to a milling machine, mounting it up and mapping the holes along the x and y axis relative to the base would be a very accurate method.
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c170b53
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Re: Cracked Vertical Stab Bracket

Post by c170b53 »

Aside from location, I think all the holes need to be reamed to size to avoid another crack.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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ghostflyer
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Re: Cracked Vertical Stab Bracket

Post by ghostflyer »

People often think what have I done to have this component fail. I do not push on the tail etc. But what have the previous owners have done ?
Nobody knows . This is why a very close 100hrly inspection should be carried out . i still do the required SIDS inspections. I have been lectured that spinning is allowed in the utility category . Back in 1950 when new maybe and even then Cessna had reservations about that manoeuvre. I treat my airframe as a 74 year old lady. Respect and dignity . There is numerous areas of concern in the airframes these days due to unannounced failures.
reecewallace
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Re: Cracked Vertical Stab Bracket

Post by reecewallace »

What's the jury's verdict on whether or not I use a chamfered washer?

The old cracked Cessna brackets on the tail are countersunk and had the washers on them.

The new brackets I ordered are the L-19 bracket and are also countersunk.

Should I follow the 170b IPC and not use the washer?
- Reece
1956 Cessna 170b
Nanaimo, BC Canada
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GAHorn
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Re: Cracked Vertical Stab Bracket

Post by GAHorn »

The subject was discussed at length: viewtopic.php?p=103245&hilit=Vertical+s ... et#p103245

(no washer)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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