S-TEC autopilot servo -- quality product?
Some months ago I got a brand new S-TEC autopilot, system 60-2 with all bells and whistles (GPSS, autotrim, altitude preselect, etc.). Don't ask me what I paid for it and how many alternatives I had...
The other day after flying to Paris, leaving the airplane there for 2 days (up to 33°C) I wanted to fly back and noticed that the autopilot would no longer operate the pitch axis. It would not notice the error (diagnostics pass) and when engaged happily block my trim wheel. Great!
So next trip is to the shop that installed it. The "computer" (what a euphemism for this 1970s analog circuit rubbish) was diagnosed to be fine so the servo was removed which is quite a job involving a slim employee climbing all the way inside the tailcone with hardly any air to breathe.
The servo was opened and what a surprise! It has a little motor which has a cog mounted onto its shaft. The cog is held in place with a little shear pin pressed through a hole in the cog and shaft. That pin has fallen out with the shaft rotating freely.
When the aircraft was parked in Paris at 33°C, the metal expanded and by intelligent choice of metals, the shaft expanded more than the pin which just fell out (the shaft was probably by coincidence positioned with the pin vertical).
S-TEC in their effort to even maximize their obscene margins no longer consider the servos to be field serviceable and no longer make spare parts available to its dealers. Every issue means sending the servo to Texas and (in case out of warranty) pay an obscene fixed price repair fee. Luckily my dealer still had some spare parts in stock including the shear pin and the repair was done in 10 minutes.
I find it totally amazing what crap quality companies like S-TEC deliver. The servos are very expensive and everything is certified, the company, the production, the product, its application in a given plane etc. They build the stuff exactly like they have been doing for 30 years and it's full of this "proudly made in USA" bull**** while it's just very very poor quality. Such a simple product and after 30 years of producing it, it's hard to believe.
Sorry, had to get this off my chest. I have no problem with products failing but I have a problem paying obscene amounts of money for what is clearly the result of poor build quality and sloppy quality assurance.
Last edited by achimha; 2nd Aug 2012 at 08:44.