Horn inspection

by **Paul Eckenroth** » Thu May 15, 2008 11:33 pm

I'm in for annual. Having the horn inspected. Would like to know ave. hrs. req. if all goes well.

Thanks, Paul

by **Paul Yoon** » Sun May 18, 2008 5:00 am

I just had my horn checked. It was a pretty easy inspection. Took the stabilator off and had the horn out before I even left the shop. Took a bit to get it inspected and probably half a day to put it back together.

by **Hansmeister** » Thu May 22, 2008 6:47 pm

In my case, had the stabilator, torque tube assenbly, and horn off, in 5 hours time. Performed a dye penetrant inspection. Putting it back together takes a little longer, since you will want to re-pack the bearings and maybe prime and paint a few of the items.

DON'T FORGET TO RADIUS THE INTERSECTION WHERE THE COUNTERBALANCE ARM HOLE INTERSECTS THE MAIN BORE. USE INCREASING GRADES OF SANDPAPER, ENDING UP WITH 600 GRIT. THE COUNTERBALANCE TUBE DOES NOT NEED TO BE REMOVED TO DO THIS.

Picture of mine before installation, attached.

by **Paul Eckenroth** » Thu May 22, 2008 7:11 pm

Thanks Hans. The horn is about to be slid off the torque tube. Bearings were shot. The tech wants to remove the balance arm to inspect and I told him that I heard of damage in removing the arm because it's a pressed fit. He says he has done it before and didn't even need to use heat on the horn. Just two guys pulling and a twist. I told him to hold off until I got expert advise. You being one and any others willing to chime in are welcome. Also, is dye check sufficient or should other NDT's be done? Will have him radius the bore. Torque tube has expected corrosion but is treatable.

Cheers, Paul

by **Hansmeister** » Fri May 23, 2008 4:06 am

Dye penetrant is easy and it works. The alternative method is eddy current.

I do not recommend removing the counterbalance arm unless there is clear evidence by one of the two methods above that cracking has occurred.

If your mechanic insists, then special tooling will be needed. Two different styles of extractors are shown. One by Eric Paul, and the other that Mark Wilson & I made. In either case, the horn is removed by restraining the counterbalance tube in a press, and the 2000 pound push pushes the horn off.

Extreme care is required for the alignment and re-insertion of the tube back into the horn. The tube is placed in a freezer, and the horn is boiled in water. You will have about 5 seconds to get everything in alignment.

by **Paul Eckenroth** » Fri May 23, 2008 1:17 pm

by **Dan Johnson** » Tue Sep 02, 2008 9:22 pm

by **IO720** » Wed Sep 17, 2008 5:30 pm

by **Matt Kurke** » Thu Sep 18, 2008 1:59 am

by **John Moore** » Tue Apr 28, 2009 3:52 am

Don't know if anybody is still keeping count, but have just inspected the horn on my '69 PA30 C. TT 4167 hours. No cracks. Horn had been off before but intersection of the bores hadn't been radiused - that inspection would have been 9 or 10 years ago at least (before any awareness of the problem). Also checked the rudder hinges at the same time and no cracks either.

John Moore

by **Hansmeister** » Tue Apr 28, 2009 4:08 am

we're still keeping track of the inspections, but it has been erratic. Good to see another one passed the test.

The general sense is that only the early models have been cracking, 1958 through 1961, predominately.

by **Don Oltman** » Wed Apr 29, 2009 1:36 am

Hans;
Forgot to post on my friends 58-250 who is 47 serial #'s later than me. It made a believer out of him when he saw mine so approx: 8 months ago he pulled his. Cracked but not as bad, just down the back between the holes. Flew the whole thing to Webco and they handled it. My IA pulled the horn on the 58-250 that was chewing on my tail in the factory 1 month ago, cracked the same way. I'm beginning to think the early forging's were not very good at all. There's 4 58 models on my field, all 250's and so far 3 were cracked. The other guy knows about all three but not sure when that one will come off. Anyway, we're just doing what we're supposed to do, replace bad parts and go on.
Don

by **JIMICS2452** » Wed Apr 29, 2009 12:51 pm

My '60 250, SN 1668 finished the tail inspection with no cracks in the horn and only very light corrosion in the area of the stabilator mounting bolts on the torque tube. The trim dum had .035" of play. I sent it to Webco for repair. The bearings also needed to be replaced. I chamfered the hole radius per Hans' recomendation.

Total Time on the airframe is 5650 hours.

Times to do the inspection are approximate:
Remove the torque tube assembly from the aircraft - 4 Hrs
Clean and dissassemble assembly, including removal of the horn - 3 Hrs
Inspect horn and trim drum- 1.5 Hr
Assemble horn and torque tube assy - 2.5 Hr
Install Torque tube assy and trim dum and check rigging - 5 Hr

Tip on removing the horn (from Matt Kurke) - Use a heat gun, no open flame. The horn practicaly fell of the tube. I put it back on the same way. No pressing required. Leave the counterbalance arm alone. The area of concern can be seen with it in place.

Many thanks to Hans and Matt for advise on this project.

Jim Hiatt

by **T210DRVR** » Mon May 04, 2009 2:41 am

Hans, I'm fairly new to Comanches but vaguely aware of the torque tube issue. I have a '58 180 Comanche. We haven't done the inspection yet. Is there any indication that the 180 HP Comanche suffers from the problem to the same extent or less than the 250?

by **Hansmeister** » Mon May 04, 2009 2:59 am

Please submit the questionnaire form checking off the Have Not Inspected box. When you do inspect, submit another one with your findings.

Based on the data that we have seen, the 1958 to 1962 single models have been the most common.

It would be worth your while to have the inspection done.

Horn inspection

Horn inspection

horn

Horn

Who is online