Hi Jinx Only the VERY expensive AC used in airlines have speed control - and they are turbo jets/fans. Speed control with the prop pitch will not work either, as the change in RPM to maintain airspeed will be very big indeed. All CS props has a min/max angle that the blades will deflect. Low reving AC engines - like Lycoming, Continental et al - have not been built to change speed quickly like a car engine. It might be different with the small screamers like Rotax and co. Two factors contribute to the speed of an AC engine - manifold pressure, and the RPM setting. Changing either of these will affect the other. And then you have to decide at which speed you want to set the cruise - Indicated Air Speed, True Air Speed, or Ground Speed - which will be a different calculation all together. I have some tech info on this from my CP course which I can let you have if you are interested. Regards Chris Albrecht ----- Original Message ----- From: "Jinx" To: Sent: Thursday, 13 June, 2002 02:48 Subject: [EE]: Airplane cruise control I've been asked to look at a cruise control for a single- engined light plane. I got the request via an intermediary, who doesn't know a lot of details except that (1) the micro should maintain the sensor input at 200Hz by (2) sending a DC pulse to a pitch-control servo on the propellor It seems "simple" enough, under ideal conditons anyway, but if any of the licenced pilots on the list have any comments I'd be glad to hear them. There will be real life factors to take into consideration, eg buffeting, plane loading, time needed to change pitch etc Also, I have my hourly rate of course, and have a rough idea what time is involved in the initial stages at least, but have no idea what a commercially available unit costs. Possibly the enquirer can't afford a unit off the shelf, I don't know. Any ideas ? I'd just like to know whether I'm hundreds or thousands of dollars off-beam. As there could be a small run follow up, it would be nice to know I could actually get a reasonable return -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.