Some of you may rememeber this autothrottle unit. I never had a pitot, got mine 2nd hand. I'm wondering what the pitot setup consisted of. 1/8" or 5/32" K&S tube and silicone fuel line, right?

It was not some fancy pitot/static deal with orifices and all that, was it?

it was just a piece of tubing, no static line.

However, I would STRONGLY recommend against using this in a turbine powered model. JPO tested a number of these a while back and what was discovered was that when the unit starts to reduce the throttle it takes 100% of your throttle control away. If you need or want to reduce throttle more you cannot. If you have an emergency and need to shut the engine down you cannot (if you are using a single channel control). This was reported to the AMA and they removed the unit from the list of approved means to keep under 200 mph. This all went away with the rules changes that took place over 10 years ago.

If you have a turbine under the control of a Gasper ECU, then you can get a proper airspeed limiter that will do the job. Gasper and Todd at Dreamworks carry them, and it interfaces to the ECU as intended.

Dan

My complaint about that unit on my old Hotspot was that when it detected that I hit 200 mph, it did not gently reduce the power a bit to keep from exceeding 200, it just chopped the throttle! The first few times I hit the limit at airshow center and I heard "PHHHEEEEEWWWWWWWWW", I about crapped my underwear!!! I finally figured out what was happening and ripped that unit out immediately and used the eyeball method of speed control thereafter. Worked great.

During the testing we determined that it had a 10 mph band. At 190 it started to throttle back and continued a linear ramp down till you hit 200, so you could punch through the band pretty fast in a dive. It is concevable that if a model could hit 200 straight and level that the unit would take control and keep control untill the pilot did something to slow the model down below 190. Another interesting feature is that if you do the setup backwards the unit works backwards; hit 200 and it would hold the throttle wide open.