Just curious..why are the twin Comanches not affected by the Horn AD since they have the same tail structure?

Mike

There has never been a cracked horn on a twin and they have the thicker walled torque tube.

Thanks!

Mike,

In addition to that logic, ICS volunteers Hans Neubert, DER and Dave Fitzgerald, Past Pres. with the help of many members collected data to show that 400s and Twins had different parts and zero cracks. I will be forever grateful to everyone's efforts in this regard.

I have checked my 250 stabilator a couple of times now. It has over 5000 hours on it at this time and there has been no cracking in the horn. I have often wondered as to why no cracking. I felt that my torque tube may be the reason. It is quite heavy walled unit. As I went through the inspection and talking with my IA we discussed the torquing of the through bolts of the horn. I speculated that a high enough torque could deform the tube enough to cause stress high enough to cause the horn to deform and crack. But I also feel that due to my tube being possibly a thick walled unit I have not been susceptible to such cracking. My aircraft serial number is PA24-3497. Does anyone have info on which aircraft may have been manufactured with the heavy walled torque tube?

I added the last question based on a posting I read tonight about various serial numbers on different aircraft components as they moved down the line at the factory. With this info it is possible that my single may have had a twin torque tube-horn unit installed as it moved down the line. I hope some one could check this out and get back to me.

Thanks,
Bob

I have seen two thick-walled torque tubes. One was s/n 868 and the other 14xx. The thick walled tube has a wall thickness of .19 or so.

Are the torque tubes made of the same 4130 seamless chromoly that can be bought at Spruce or are they a proprietary Piper item?

Charles,

If you use the search box in the upper right corner of this screen, you'll see a lot of info on this subject. Also suggest checking the Home Page for the reporting form and offer of help from Heritage.

My Twin is not subject to the AD so You'll want to verify - I believe the tube is proprietary.

Most folks have it done by an experienced shop. The shop I use in TX Clifton is working on one mailed it on on site every time my Twin is in for a visit.

Hope this helps.

I don't know that anyone outside of Piper knows what it is made out of, except perhaps Hans Neubert, who is no longer an ICS member, but he did some early engineering work. He does read the Airworthy Comanche forum on Delphi, if you wanted to ask him. I will say that it would take a pretty large, precision lathe to make one as Piper calls out tolerances in the tens of thousands. See Piper Service Bulletin 1160, if you haven't looked at it already.