![stec 50 autopilot hold altitude problems stec 50 autopilot hold altitude problems](https://slideplayer.com/slide/4491963/14/images/15/ALTITUDE+HOLD+(ALT).jpg)
Obviously lots of wasted energy used in trying to maintain altitude. The TAS ranged from 83.9 kts to 95.6 kts. Using altitude hold the altitude excursions between the highest and lowest was about 20 feet (10 up and 10 down). The altitude excursions between the highest and lowest was about 150 feet. Also there was a small fuel savings but I couldn't calculate it precisely. I found that the difference was a speed advantage of 1.8 Knots in using IAS to maintain cruise flight. The indicator was actually between the two- 10 feet. My previous 20 feet estimate was linked to the "20" being the next numeric above and "80" the next number below the "000". The altitude changes were in fact 10 feet above and 10 feet below the selected altitude. I flew the airplane again and made a more accurate calculation to see if flying in IAS mode is advantageous over the altitude hold mode.
![stec 50 autopilot hold altitude problems stec 50 autopilot hold altitude problems](https://www.euroga.org/system/1/user_files/files/000/046/618/46618/3200afa84/large/20200520_141454.jpg)
I was more concerned about getting to my destination so I didn't do any comparison runs.Īgain, this is off the point but it seems to me that fluctuating pressure indications cannot be cured by an autopilot adjustment. Something I wasn't able to determine is if this method results in a faster airspeed in cruise. Obviously you can still use the "NAV", "TRACK", or "Heading" mode in addition. The reason to set the altitude bug well above or below your desired cruise altitude is that if you ever intercept it during the ups or downs the autopilot will capture it and cancel the "IAS" mode and go to altitude hold instead.
STEC 50 AUTOPILOT HOLD ALTITUDE PROBLEMS PLUS
The airspeed is maintained very accurately, much more so than during the plus or minus 20 feet using altitude hold. Most of the time altitude was within plus or minus 50 feet. The gains or losses are small and mommetary. Primarily due to me not paying attention over a 10 or 15 minute period. Even in turbulence I was rarely more than within 200 feet of my desired altitude. Set your power at whatever you normally cruise at and then adjust the airspeed bug or power to maintain that altitude. Then set the airspeed bug to whatever your airplane will normally cruise at. Then select "IAS" just as you would if you wanted to climb or descend. Once at cruise altitude set the altitude bug well above or below your desired altitude. Quite by accident I discovered that using the "IAS" mode works great for use in either smooth or turbulent air in maintaining cruse altitude/pitch. In very smooth air it isn't too noticeable but in turbulent air the changes in attitude and airspeed are much greater. Each "up" cycle includes a loss of airspeed and RPM and a gain of airspeed and RPM going down. The cycle is up 20 feet and then down 20 feet. My Dynon autopilot maintains altitude within plus or minus 20 feet.