Return-Path: Received: from mail.his.com ([205.177.25.9]) by truman.olsusa.com (Post.Office MTA v3.5.1 release 219 ID# 0-52269U2500L250S0V35) with ESMTP id com for ; Thu, 25 Feb 1999 07:41:14 -0500 Received: from hk53 (pm9-186.his.com [205.252.121.186]) by mail.his.com (8.8.5/8.8.5) with SMTP id HAA17152 for ; Thu, 25 Feb 1999 07:43:00 -0500 (EST) Message-ID: <001f01be60bb$fcbf5120$ba79fccd@hk53> Reply-To: "Avionics Systems" From: "Avionics Systems" To: Subject: Autopilots Date: Thu, 25 Feb 1999 07:40:11 -0500 X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> There are several factors that contribute to proper autopilot operation. The first is correct installation, good clutch torque settings, bridle cable tensions, etc. Autopilots track well in heading mode (heading bug in D.G. or HSI because when you rotate the heading bug, an error signal is sent to the autopilot, which turns the aircraft until the error is resolved, then it flies the aircraft holding that error signal at zero. When you couple an autopilot to a VOR, the autopilot is slaved to the same left-right signal from the nav receiver that drives the vertical needle in the VOR indicator. Therefore, anytime the VOR needle even twitches to the right or left (a common situation, particularly when near the VOR), the autopilot will twitch right or left, causing the poor tracking you described. Some autopilots have a "Soft Mode" which dampen the response to the VOR input, reducing the problem somewhat. Coupling the autopilot the the GPS will provide probably the smoothest tracking of all. Enroute, the GPS is tracking to a fixed point in space, so there is no right-left deviation. No matter how close you are to your selected waypoint, the autopilot should track smoothly. All panel-mount GPS receivers provide the left-right outputs required to drive an autopilot. >From practical experience, a correctly-installed S-Tec autopilot in a Lancair will fly the airplane like it's on rails. David Buckwalter Avionics Systems