What is the labour content for a fresh S-Tec 55X installation? I had heard about 45hours. I thought it could be double that.
@wigglyamp should know; not sure if he’s still around.
45hrs sounds about right assuming that you can buy the servo mounting metalwork and just rivet it in place.
But often you are presented with a 100 year old plane 
and have to rip out 20kg of wire, then half of the plane stops working, the customer is not happy, and you have to find some “framework” for billing for your time. The life of an avionics installer!
WilliamF wrote:
What is the labour content for a fresh S-Tec 55X installation? I had heard about 45hours. I thought it could be double that.
Will depend on whether an old autopilot needs removing, what additional options may be required (electric trim, alt pre-selector, flight director etc).
A basic 2-axis system into a clean simple aircraft such as a PA28 with no existing autopilot and space in the radio stack could be done in about 40-45 hours, but just putting a servo into a wing of a Cessna adds quite a few hours and deleting a Navomatic system can be a pain with removal of an aileron bell-crank to get the old control interconnect out.
My understanding of the altitude pre-select is that it is driven by the encoder, which is a pressure altitude to the nearest 100 feet and the pilot enters the altimeter setting to the nearest decimal value, so if the altimeter is 29.95, the pilot would enter 30.0 and 29.92 would enter 29.9. The system looks for a matching altitude to the reference once adjusted by the altimeter setting. I think the logic effectively does the equivalent of pushing the altitude hold when the selected altitude is matched. At that point, the pressure transducer output is sampled and used to maintain a constant pressure. So if the altitude wanders after the level off, the issue is probably in the transducer, but if the selected altitude varies, the issue is probably in the pre-selector or the source of the altitude from the encoder.
You may not have a problem.
Do not switch on the 55X computer simultaneously with the ST-360 preselector. First apply power to the computer, wait for RDY to appear on the display. Then turn on the ST-360.
Hope that works for you, it did for me. Although I once was an avionics technician, this was a trial-and-error discovery not based on any electrical investigation. :-)
Eric
