Page 1 of 1
Cracked Vertical Stab Bracket
Posted: Mon Feb 19, 2024 5:01 am
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/
Re: Cracked Vertical Stab Bracket
Posted: Mon Feb 19, 2024 11:31 am
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
Re: Cracked Vertical Stab Bracket
Posted: Mon Feb 19, 2024 2:25 pm
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.
-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?
Re: Cracked Vertical Stab Bracket
Posted: Mon Feb 19, 2024 5:38 pm
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.
Re: Cracked Vertical Stab Bracket
Posted: Mon Feb 19, 2024 6:00 pm
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.
Re: Cracked Vertical Stab Bracket
Posted: Mon Feb 19, 2024 9:12 pm
by Ryan Smith
Robert Brown in Atlanta had some, but I think I might have gotten the last one.
Re: Cracked Vertical Stab Bracket
Posted: Tue Feb 20, 2024 8:36 pm
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?
Re: Cracked Vertical Stab Bracket
Posted: Wed Feb 21, 2024 12:11 pm
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.
Re: Cracked Vertical Stab Bracket
Posted: Wed Feb 21, 2024 5:16 pm
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 03
31124 and the L-19 PN is 06
31124
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.
Re: Cracked Vertical Stab Bracket
Posted: Fri Feb 23, 2024 6:19 pm
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.
Re: Cracked Vertical Stab Bracket
Posted: Sat Feb 24, 2024 1:14 am
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.
Re: Cracked Vertical Stab Bracket
Posted: Wed Feb 28, 2024 11:21 pm
by c170b53
Aside from location, I think all the holes need to be reamed to size to avoid another crack.
Re: Cracked Vertical Stab Bracket
Posted: Sat Mar 02, 2024 2:40 am
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.
Re: Cracked Vertical Stab Bracket
Posted: Sat Mar 09, 2024 7:38 am
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?
Re: Cracked Vertical Stab Bracket
Posted: Sat Mar 09, 2024 12:13 pm
by GAHorn