stabilator horns

[Russell Knowles]

Hi Zack,
I would like to add a few comments to this debate but my computer does not want to reply to so many recepients so I will mail it to you and Matt Kurke only. Please feel free to send it on if you think there would be any value.

Fellow Comanche Owners,
I would like to add my few cents worth on this topic. My greatest concern is whether we are addressing the real problem which is why are some of the stab horns cracking?
I am certainly no engineer but there are a number of reasons why a casting cracks and some of these include, wrong choice of material, excessive force [inadequately engineered part], vibration and overtorqued bolts. Most comanches do not really have really high airframe hours, my 1962 -250 has 5200hrs. [ By contrast I was flying B747's with in excess of 100,000 hours and currently fly some Airbus A340 models with 65,000 hours. I have also flown DC3's, which are certainly no strangers to vibration, with 50,000 + hrs.]
Therefore unless we can establish why some horns crack, inspecting and reconditionong these units will still not make the problem go away. Have the following been taken into consideration?
Is there a relationship between the loose tail rivets and cracked horns?
Did Piper change the designs on the many later types which use stabilators and has this problem manifested itself with those aircraft?
Could excessive play in the stab trim hinges induce stab vibration?
Could there be a relationship between the craked horns and poorly "balanced" stabilators with weight changes from re-paint etc?
Could the stab be re-manufactured with alternative material such as stainless steel?
As an interim safety measure could the stab horn be fitted with 2 or 3 steel clamps [rather like hose clips] to ensure that the horn would not separate into 2 halves in the event of the cracks extending through the entire unit?
I live in South Africa where we have only about 70 Comanches both twins and singles and to date I have not heard of any stab horn cracking problems but to be honest, I don't believe that we have had any inspections involving disassembly done over here. We also tend to have a drier climate with less temperature variations than in the US. Could this be a factor? It would be interesting to here from the Australian Tribe [with a similar climate] if they have encountered any cracked stabs.
I hope some of this may be of some value.

Regards,

Russell Knowles [South African Tribe Chief]